From lee.stanford@eclipsys.com Tue Apr 22 19:29:28 1997 Received: by csres2.cropsci.ncsu.edu (5.61-AIX-1.2/1.0) from [192.41.32.161] with SMTP id AA117852 (for rdkeys, from lee.stanford@eclipsys.com/lee.stanford@eclipsys.com); Tue, 22 Apr 97 19:29:28 GMT Received: from smtp.eclipsnet.com ([199.250.158.26]) by eclipsys.com (8.8.5) id NAA06545; Tue, 22 Apr 1997 13:29:52 -0600 (MDT) From: lee.stanford@eclipsys.com X-Authentication-Warning: eclipsys.com: Host [199.250.158.26] claimed to be smtp.eclipsnet.com Received: from ccMail by smtp.eclipsnet.com (ccMail Link to SMTP R6.00.01) id AA861741148; Tue, 22 Apr 97 15:32:51 -0500 Message-Id: <9704228617.AA861741148@smtp.eclipsnet.com> X-Mailer: ccMail Link to SMTP R6.00.01 Date: Tue, 22 Apr 97 12:26:58 -0500 To: Subject: glowbugs digests 16 - 20 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="simple boundary" Status: O --simple boundary Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Attached files glowbugs digests 16 through 20 --simple boundary Content-Type: text/plain; charset=US-ASCII; name="GLO-POR0.016" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="GLO-POR0.016" GLOWBUGS Digest 16 Topics covered in this issue include: 1) Soldering Book by "Tony Stalls (K4KYO)" 2) Re: Soldering Book by "Deane D McIntyre" 3) Simple XMTR's using 6T9 tubes by "Deane D McIntyre" 4) Re: Simple XMTR's using 6T9 tubes by "Tony Stalls (K4KYO)" 5) Regen Recvr Feedback Control by EricNess@aol.com 6) Re: Regen Recvr Feedback Control by Bob Roehrig 7) tube needed by Bob Roehrig 8) Re: tube needed by artdeco@bway.net 9) GOODIES FOR GRABS III RESULTS by David Stinson <72227.1640@compuserve.com> 10) Xmt'g Tube Manual by Jeffrey Herman ---------------------------------------------------------------------- Date: Sat, 11 Nov 1995 22:38:01 -0500 (EST) >From: "Tony Stalls (K4KYO)" To: GLOWBUGS Subject: Soldering Book Message-ID: I picked up a great book on soldering, SOLDERING ELECTRICAL CONNECTIONS, NASA SP-5002, at the Government Printing Office store in Washington a few years back. It is THE most complete short work on the subject I've seen anywhere. Topics covered are hand soldering (32 pages), automatic machine soldering (2 pages), termination of shields by soldering (3 pages), lacing of cable trunks (6 pages), solder characteristics (2 pages), and solder cracking problems (13 pages). I thought I was pretty good at soldering and until I saw this. I didn't know anything about soldering! ;-) Anyway, this is a 1967 publication and I've had it a long time, so I don't know if this is still available. I have a message out to our friend Larry Mills at NTIS, but I haven't heard back from him. I'll also check with the GPO bookstore the next time I cross the Potomac. Of course we can have Kinkos make some up if there's enough interest. Stay tuned... 73, Tony K4KYO ------------------------------ Date: Sat, 11 Nov 1995 21:27:28 -0700 >From: "Deane D McIntyre" To: glowbugs@theporch.com Subject: Re: Soldering Book Message-ID: <9511120427.AA43596@ds1.acs.ucalgary.ca> In message writes: > > I picked up a great book on soldering, SOLDERING ELECTRICAL CONNECTIONS, > NASA SP-5002, at the Government Printing Office store in Washington a few > years back. It is THE most complete short work on the subject I've seen > anywhere. (Much Deleted) Another good book on this subject is Solder....its fundamentals and usage, by Clifford L Barber, published by the Kester Solder Company. My edition, the second, was published in 1961. I have no idea as to if Kester has a more recent edition available. This 84 page book covers solder, solderinf fluxes, and soldering methods in detail. It has a short chapter on soldering the new printed circuit boards, including the new wave soldering technology...... 73, Deane D McIntyre VE6BPO dmcintyr@acs.ucalgary.ca ------------------------------ Date: Sat, 11 Nov 1995 21:54:02 -0700 >From: "Deane D McIntyre" To: glowbugs@theporch.com Subject: Simple XMTR's using 6T9 tubes Message-ID: <9511120454.AA27698@ds1.acs.ucalgary.ca> Gang: A couple of week ago Jeff, NH6IL asked if anyone had built the 6T9 rig that was featured in the early 1970's ARRL handbook. The 6T9 is a 12-pin Compactron tube containing a low mu triode and a pentode. The orginal purpose of this tube, if my memory is correct, was to serve as a combined audio driver/audio output stage in television sets, or as a compined vertical osc/vertical output stage. However, I have never seen a television set that used a 6T9. The Handbook 6T9 rig Jeff mentioned is a 10 watt xmtr, using the triode section as an xtal controlled oscillator driving the pentode output stage. I do not have the article in front of me, but I believe that this xmtr was primarily intended for 80/40 operation, however the possibility of operation on 160 or 40 was pointed out. Anyhow, the good news is that 6T9's are cheap, only oabout $2 or so NIB from Antique Electronic supply. I ordered a couple, and they arrived a few weeks ago. Today, I came across a 1969 Handbook, and they have a circuit for a 15 watt CW/AM 160 metre rig that uses two 6T9's and a 12AT7. As in the rig discussed above, one 6T9 serves as the xtal contolled oscillator/ output stage. The 12AT7 is a speech amplifier, which feeds the triode section of the second 6T9, ehich in turn feeds the modulator 6T9 pentode section. As 6T9's are so cheap this sounds like an interesting project. I am sure that it would run on 80/40 as well. Has anyone built this beast? Plate voltage required was 275, about right for an old TV power transformer based supply.... 73, Deane D McIntyre VE6BPO dmcintyr@acs.ucalgary.ca ------------------------------ Date: Sun, 12 Nov 1995 01:32:19 -0500 (EST) >From: "Tony Stalls (K4KYO)" To: Multiple recipients of list Subject: Re: Simple XMTR's using 6T9 tubes Message-ID: On Sat, 11 Nov 1995, Deane D McIntyre wrote: > The Handbook 6T9 rig Jeff mentioned is a 10 watt xmtr, using the triode > section as an xtal controlled oscillator driving the pentode output stage. > I do not have the article in front of me, but I believe that this xmtr was > primarily intended for 80/40 operation, however the possibility of > operation on 160 or 40 was pointed out. Anyhow, the good news is that > 6T9's are cheap, only oabout $2 or so NIB from Antique Electronic supply. > I ordered a couple, and they arrived a few weeks ago. > > Today, I came across a 1969 Handbook, and they have a circuit for > a 15 watt CW/AM 160 metre rig that uses two 6T9's and a 12AT7. As in > the rig discussed above, one 6T9 serves as the xtal contolled oscillator/ > output stage. The 12AT7 is a speech amplifier, which feeds the triode > section of the second 6T9, ehich in turn feeds the modulator 6T9 > pentode section. As 6T9's are so cheap this sounds like an interesting > project. I am sure that it would run on 80/40 as well. Has anyone built > this beast? Plate voltage required was 275, about right for an old TV > power transformer based supply.... I have both of the articles in front of me and RF section in the the single-band, 160 meter rig in the 1969 ARRL handbook is almost identical to the 160-20 meter (it uses plug-in coils) CW rig Jeff mentioned. It looks like adding the 160 only rig's modulator would be a piece of cake. As it the 6T9 only draws 80 ma. plate current, the little rig could probably be powered by some receiver's power supplies. 73, Tony K4KYO ------------------------------ Date: Sun, 12 Nov 1995 02:22:14 -0500 >From: EricNess@aol.com To: glowbugs@theporch.com Subject: Regen Recvr Feedback Control Message-ID: <951112022214_104308609@emout05.mail.aol.com> Greetings GlowBugs, I'm new to this list so please forgive me if I cover old material. I am in the process of building the "Red-Hot Radio" described in Sept. 95 CQ mag. The circuit is a very familiar one except for the feedback control. The feedback in this circuit is controlled by a 1K pot placed in parallel with the tickler winding. At this time I can't comment on how well the circuit works since I still have a few holes to drill before I can start wiring. This brings up my question. What is the best way to control the feedback in an Armstrong style regen receiver? I am most familar with the plate voltage technique but I have seen schematics using screen grid control, throttle caps, and varimeter (sp?) coils. Any comments? Eric, WD6DGX ------------------------------ Date: Sun, 12 Nov 1995 09:47:44 -0600 (CST) >From: Bob Roehrig To: EricNess@aol.com Cc: Multiple recipients of list Subject: Re: Regen Recvr Feedback Control Message-ID: On Sun, 12 Nov 1995 EricNess@aol.com wrote: > Greetings GlowBugs, > snip > > This brings up my question. What is the best way to control the feedback in > an Armstrong style regen receiver? I am most familar with the plate voltage > technique but I have seen schematics using screen grid control, throttle > caps, and varimeter (sp?) coils. Any comments? > Hi Eric -I have a problem with the idea of using a pot in an RF circuit like that. I have not seen the article you mention but I have heard of using a pot across the tickler winding. I prefer a pot to vary the DC voltage, or the throttle condenser method. 73 de Bob, K9EUI ------------------------------ Date: Sun, 12 Nov 1995 11:20:40 -0600 (CST) >From: Bob Roehrig To: Boatanchors , glowbugs Subject: tube needed Message-ID: I am looking for a type 1232 tube. This is a loktal type used in the front end of a Zenith console I am restoring. I am unaware of any equivalents, if there are any. Thanks & 73 de Bob, K9EUI (broehrig@admin.aurora.edu) ------------------------------ Date: Sun, 12 Nov 1995 15:58:58 -0500 (EST) >From: artdeco@bway.net To: glowbugs@theporch.com Subject: Re: tube needed Message-ID: <199511122058.PAA21359@nico.bway.net> Bob Roehrig wrote: >I am looking for a type 1232 tube. This is a loktal type used in the >front end of a Zenith console I am restoring. I am unaware of any >equivalents, if there are any. The 1232 is available from Antique Electronic Supply, 6221 S. Maple St.,Tempe Arizona 85283, for $4.30. Their catalog does not list any other tube as a possible substitute. Phone number is 602-820-5411. Request their catalog if you don't already have one... it's full of goodies for restoring old radios. Carl Ratner artdeco@bway.net ------------------------------ Date: 12 Nov 95 17:33:24 EST >From: David Stinson <72227.1640@compuserve.com> To: mailing list , Subject: GOODIES FOR GRABS III RESULTS Message-ID: <951112223323_72227.1640_EHM173-7@CompuServe.COM> Stephanie has done the dirty name-drawing deed in Goodies for Grabs III. Since you can't blame me, and no one here is so crude as to cuss-out a little 9-year-old girl, I feel mighty safe...(dodging tomato). Here are the lucky new owners of all these teenie treasures (or trivial trash, depending on your personal tastes). Anything unclaimed goes GFG IV. If you're on the list, email me your mailing address, even if you've written before. It helps with my archiving. Return of postage is requested. If you'd like to return-mail a BC-610 or something, it would be pretty cool but isn't neccessary. Collins-Made and Marked Tube Shields: Roy Morgan Collins KWM-2/51S1 power-volume control knob: Jeff Anderson Collins/Heath 9-11 pin plugs. One set each go to: Greg Wasik Mike KB9VU@aol.com Drake AC-4 female Cinch-Jones connector. One each to: RF Buchanan Greg Parsons NIB Tubes: (2) 866As: Jon Schumacher (5) 6AK5, (4) 6DK6: Jerry Dries (1) 43: Stan Gilstrap Bird 43 Wattmeter Slugs ( found another): Mike n1ist@netcom.com Bill Smith AB6MT NOS Replacement electrolytics. WARNING: REFORM BEFORE USE!!! Three lots went to: Hal Waite Wai Kei Leung Phil Mills, AB5TH Drake W4 wattmeter manual with cards: Jack Giehl WB8BFS Astatic Model 331 Mobile Mike: Don Merz N3RHT Twenty non-ham freq FT-243 crystals One each of two lots: Eric Ness, WD6DGX Ken Harrison DM-64 Dynamotor with base: Pasquale Lombardi That's it for this time! Please email me your addr so I can shoot you the goodies; return postage requested. If you missed-out, don't worry. I'm constantly finding this stuff so GFG IV is only a few months away. 73 DE Dave Stinson AB5S/7 72227.1640@compuserve.com ------------------------------ Date: Sun, 12 Nov 1995 14:00:38 -1000 >From: Jeffrey Herman To: Glowbugs List , Subject: Xmt'g Tube Manual Message-ID: Where could I get a copy of an (RCA?) transmitting tube manual, including a substitution index? Anyone have a copy for sale? My 1991 ARRL Handbook doesn't have much in the way of a tube reference guide. My '95 edition has even less data. My '72 edition is 2500 miles away. Jeff NH6IL ------------------------------ End of GLOWBUGS Digest 16 *************************  --simple boundary Content-Type: text/plain; charset=US-ASCII; name="GLO-POR0.017" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="GLO-POR0.017" GLOWBUGS Digest 17 Topics covered in this issue include: 1) Re: Xmt'g Tube Manual by "Tony Stalls (K4KYO)" 2) Zenith's 1232 tube by "Blake Dietze" 3) 6AG7s and more... by mjsilva@ix.netcom.com (michael silva) 4) re:Regen Rcvr Feedback Control by UofSstudent 5) Re: 6AG7s and more... by af852@rgfn.epcc.Edu (William R Colbert) 6) correction! re:regen rcvrs... by UofSstudent 7) Re: 6AG7s and more... by Bob Roehrig 8) Re: 6AG7s and more... by mjsilva@ix.netcom.com (michael silva) ---------------------------------------------------------------------- Date: Sun, 12 Nov 1995 19:48:06 -0500 (EST) >From: "Tony Stalls (K4KYO)" To: Jeffrey Herman Subject: Re: Xmt'g Tube Manual Message-ID: Hi Jeff, Antique Electronic Supply lists a reprint of the RCA Transmitting Tube Manual TT-5, 316 pages, their stock number B-676, for $12.95. 602-820-5411 (no toll free number except for fax - 800-706-6789) Good luck & 73, Tony K4KYO ------------------------------- On Sun, 12 Nov 1995, Jeffrey Herman wrote: > Where could I get a copy of an (RCA?) transmitting tube manual, including > a substitution index? Anyone have a copy for sale? > > My 1991 ARRL Handbook doesn't have much in the way of a tube reference > guide. My '95 edition has even less data. My '72 edition is 2500 miles > away. > > Jeff NH6IL > ------------------------------ Date: Mon, 13 Nov 95 8:24:34 CST >From: "Blake Dietze" To: Subject: Zenith's 1232 tube Message-ID: The 1232 tube which Zenith (and others) used in the early 1940's may be substituted with a common 7G7 octal. I concur with Mr Ratner, The Antique Electronic Supply Catalog is a worthwhile addition to your reference materials. The following was included as an attachement. Please use UUDECODE to retrieve it. The original file name was 'ATTRIBS.BND'. ------------------------------ Date: Mon, 13 Nov 1995 12:08:07 -0800 >From: mjsilva@ix.netcom.com (michael silva) To: glowbugs@theporch.com Subject: 6AG7s and more... Message-ID: <199511132008.MAA07138@ix4.ix.netcom.com> I happened to see a message over on AOL where somebody is selling NOS 6AG7s for $3 each, or 10 for $25. For those who don't know this tube, it's an early video driver tube (octal) which apparently is the ideal oscillator tube, and was the main tube used for this job for maybe twenty years in amateur designs. The normal price for these seems to be about $6, so this is a good deal (I've already ordered mine). Build up a 6AG7 - 6L6 rig and you've got an instant classic. It turns out that the "somebody" selling the tubes is Pat Bunn of 624 Kits, and he mentioned that he's considering putting together some tube kits if there's enough interest, so if any of you have some ideas you may want to bend his ear. His e-mail address is PBUNN624@aol.com, and his phone number is 803-583-1304. 73, Mike, KK6GM ------------------------------ Date: Mon, 13 Nov 1995 14:51:26 PST >From: UofSstudent To: glowbugs@theporch.com Cc: jfw121@duke.usask.ca Subject: re:Regen Rcvr Feedback Control Message-ID: I built a number of regenerative receivers in the last several years, some from v ery old Radio News publications, others from my own creation. A well built regen rcvr is quite stable and should approach the sensitivity of a superhet. The secret is to use low loss coils. The best approach considering cost, would be to use the thickest wire for the job, and wind it on a coilform that has ridges on it, or pe rhaps an open air coilform with support being a few strips of plastic holding the thing together. These forms are either easy or hard to find, depending where you look. I was able to find alot of these forms, both 4pin and 5pin while visiting Vancouver to some radio-electronic shop up on West Broadway about 5 years ago. Haven't run across any since. If you have some great, because once the coils are built for whatever frequencies you wish they can be reused in any other radio you happen to build. For stability, once you have tested the coils and they are to your satisfaction, ie: the radio works hot-damn, sparingly GLUE the coil onto the form with a dabs of speaker cement or what have you, and let dry. You don't want to change characteristics as you plug and unplug the coils! Second point in the homebrew construction is to use a metal chassis. Forget about the glorious breadboard creations with mother's crusty breadboard, unless you buy a nice 6 x 10 piece of the finest oak you can find and have it prepared to the glossiest finish you can get. I have built a couple of these using a real bakelit e panel, but everytime you bring your hand to a circuit that's tettering on the bri nk of instability, you either go into annoying regeneration or else you lose your selec ted frequency because of body capacitance.(Actually, some very old commercial radios from the 1920's had a stick about 6-8" connected to the tuning knob so that the user didn't have the aforementioned problem.) It looks very nice for your projec t display case, but not very practical. Stick with a metal chassis, you can always slap on a bakelite front panel when everything works and you won't have the nasty capacitance to annoy you. Point Three: Use a bus between the ground connection on the coil and the ground connection (cathode) on the tube socket (we are using tubes I hope!). This will n ow be the 'common grounding point'. Every single ground connection including a ground wire from the chassis mounted tuning capacitor will have a lead going to this grounding point. Your "B-" plate supply voltage will also make a connection here, as will the ground binding post for your outside ground. This ensures that there will be no ground loop. The chassis will be grounded from the variable capacitor bolted to the chassis, and will not be used for a convenient path to ground. These three points are necessary for the stability of a ,by nature, unsta ble circuit. Once the receiver is stable, it's ease of operation and user enjoyment become apparent. Now, on with the tubes: What tube to use? Well, if you are building a set and you would like to replicate the looks or performance of a 1920's type regen receiver, there are a number of triode tubes that you could use for both the regenerative detector and the following stage[s] of audio amplification. Technically, you coul d use *any* triode with varying degrees of success as long as the plate and filamen t voltages are right, but the tried and true consists of these: uv201,uv201a,ux201,ux201a,cx201a,'01a,'01b,'01c, ux112,12,ux112 -these need 5 volts for the filament using either 6volts and a rheostat, or else build yourself a solidstate 5volt powersupply like the type used for logic circuits. The negative side of the +/- powersupply could be used for grid bias wh en your plate voltage exceeds 67 volts for the audio amplifier, when using these tubes. They will work in both the rf and af circuit. The tubes without the 'a' dr aw about 1 amp at the rated voltage, but they sure throw a pretty light to dine by. The tubes ending with 'a' draw 1/4 amp each, and the tubes with a 'b' and 'c' draw 1/ 8 and 1/16 amp repectively at the rated voltage which is great for portable battery use, but you can't tell what tubes are lit except in pitch darkness. There are other tubes specifically designed for portable battery use in this era such as wd11 for 1.5 volts and others, but they are rare, costly, filaments aren't rob ust, and generally don't work as good as these tubes mentioned. (note: If you have a wd11 with a good filament, I would gladly trade for a ux201a to make my radiola play like original again! Will also accept ux199's for trade or sale...) Here are the later tubes circa early 1930's, which were designed for battery use and have very low filament current. - ux230, '30, 30 for both rf and af. 4 pin tubes use 2volts filament (rheostat and 3volts) . A similar tube with same characteristics as this one is the 1H4 with 8 pin octal base. - ux231,'31,31 for af output, 4pin tube uses 2volts filament. - 19. this tube is a dual triode, ie. 2tubes in one shell, 6pins, 2 volts. With this tube, you only need one tube for a 2 tube set. Many circuits built using this tube... Several 1.5 tubes fit in this category such as 1G4, and other 8 pin tubes. For best performance, I found that I would want to steer away from triodes altogether, and use pentodes. These are the oldtimer's equivalent to FET's used today. This means that they have higher input impedances than triodes, making them less of a short across the coil therby improving the Q of the coil, thus mak ing the tuning sharper than with a triode in the same circuit. Other advantages are t hat the output of the tube is isolated from the input of the tube capacitance wise because of the screen grid being at ground potential, is inbetween the grid and plate. This adds to the stability of the circuit among other advantages beyond th e scope of this reply. Thirdly, a pentode tube has greater gain than a triode . As a result the output is greater, and the feedback can be less, or, can be more loose ly coupled to the input,leaving the Q of the coil higher than in a triode circuit. F ourthly, a pentode is WAY easier to control than a triode when tettering on the brink of regeneration. What are the choice methods of control? In a triode circuit, you can control feedback using from best to worst, capacitance from feedback loop (tickler) to ground. Have the capacitor's rotor or frame at ground potential so body capacitan ce doesn't figure into the equation. Use a metal front panel. Next best, use a varia ble tickler coil rotating inside the main coil. Lots of commercial radios of the 1920 's used this method probably because it was cheaper than including extra tuning capacitors. You can vary feedback by changing tube characteristics by varying either the plate or filament voltage. The downside of varying plate voltage is th at you will want maximum efficiency from a triode circuit. This means you will want in the neighborhood of 45 volts on the plate for the tubes stated in the rf section. If you have less, your efficiency drops. Why then, obtain maximum efficiency for regeneration at less than 45 volts when you can get maximum efficiency and a louder signal using 45 volts and one of the previously stated methods for regeneration? Some very early radios using straight non-thoriated tungsten, such as the 1 amp variety, varied filament voltage to change the tube's characteristic s thus varying feedback, but this isn't stable particularily when battery potential drops and so on. The plus side to using triodes is that the circuit is so simple you can slap one together while the wife is at bingo. Yes, and 2000 ohm d.c. resistance as measure d on you multimeter is a must if you want to match the output impedance of these tubes for maximum efficiency. There are lots of them still out there. A quick visit to the local junque treasures store last week revealed 4 more for my collection at 5 bucks a crack. Bring your ohmmeter to check for continuity. Price drops dramatically when all that is good are the shell and headband. Don't worry: with a 2 tube triode set using 201a's and 45 volts, with a 10 foot antenna, and n o ground, I am able to pick up Radio Australia around 9 or so Mhz at 9:30 pm with a volume so loud that I am able to listen to it with an old pair of Baldwin type C headphones laying on the worktable. If you build a few, you soon expect a level o f performance from your radios and you will tinker with minute adjustments with the coils and such to replicate a known standard of performance. In my location, Saskatoon, this is a test of that standard. So pentode tubes are choice. Methods of pentode control are many but the best from experience is using screen grid control,using whatever voltage you can get t o the plate, anywhere from 90 up to 250volts, the higher the better. Have a 50k pot in series with 250k resistor of a couple watts across the plate voltage, and take th e tap of the pot going to to the grid2 of the pentode. Have a .1 ufd capacitor acro ss the pot arm and ground to eliminate scratch when varying voltages. There are many forms of regeneration stated for pentodes, they all seem to work equally good as long as the feedback is set up for maximum regeneration when the screen voltage is around 30 volts. This gets maximum volume (detection) from this circuit. Properly constructed, one pentode will give roughly the same results as the 2tube triode combo. One pentode for rf such as a 6sk7, 6sj7 and the like, coupled with a 6v6,6F6, or 6L6 will provide ample volume for a loudspeaker. I currently use such a homebrew rcvr using a 6v6 and 6sj7 built on a 8 x 12 chassis which slides into a wooden case complete with powersupply and speaker, on my nighttable. Great for listening to another country's perspectives. Depending on the project and whether you have tools to work with metal, a receive r should take a day or so to get/find parts (varies on your resources and location) , an evening to place the parts on the chassis to figure out where each should be, if there is room for other parts, etc., then (gulp) carefully drill and punch all th e holes in that 7 dollar shiny chassis., and finally mount your parts. Next day should be one of connecting and soldering. You should have a radio that sort of works. Use the following evening to take out the bugs. This means you may have to replace or remove some turns on your coil for maximum efficiency. you may have to use another gridleak resistor of a different value, you may want to try other tubes. Maybe some are newer than others? You may want to extend the testing over through several nights, as from experience, once the radio works better and bette r, you actually find yourself sitting back having a smoke and getting interested in the program you're listening to while testing... When this happens,unplug the iron, you are done. I hope this reply answered some of your questions regarding feedback control with the homebrew set you are considering to build. You will not be disappointed with a properly constructed regen set. Good Luck!! ------------------------------ Date: Mon, 13 Nov 95 13:58:45 MST >From: af852@rgfn.epcc.Edu (William R Colbert) To: glowbugs@theporch.com Subject: Re: 6AG7s and more... Message-ID: <9511132058.AA10881@rgfn.epcc.Edu> There was also early articles using the 6ag7 in a linear amp. I think W6BLZ (now W6XM), Ed Marriner, writing for CQ had one up and running in the early 50's with an output of a couple hundred watts. This tube is probably similar to the 5763 in its capability and it sure would be nice to see a "new" old kit line available. Ray, W5XE, El Paso, Tx ------------------------------ Date: Mon, 13 Nov 1995 15:09:11 PST >From: UofSstudent To: glowbugs@theporch.com Subject: correction! re:regen rcvrs... Message-ID: The plus side to using triodes is that the circuit is so simple you can slap one together while the wife is at bingo. Yes, and 2000 ohm d.c. resistance as measure d on you multimeter is a must if you want to match the output impedance of these tubes for maximum efficiency. There are lots of them still out there. A quick ... There is an error here that I never picked up before I sent this. This blurb shou ld have read.... You will need a 2000 ohm pair of headphones for the triode regen radio. Yes, and 2000 ohm dc. resistance is a must, if you want to match the output impedance of the tubes to these headphones for maximum efficiency.... Sorry 'bout that folks! ------------------------------ Date: Mon, 13 Nov 1995 15:54:11 -0600 (CST) >From: Bob Roehrig To: William R Colbert Cc: Multiple recipients of list Subject: Re: 6AG7s and more... Message-ID: On Mon, 13 Nov 1995, William R Colbert wrote: > There was also early articles using the 6ag7 in a linear amp. > I think W6BLZ (now W6XM), Ed Marriner, writing for CQ had > one up and running in the early 50's with an output of a couple > hundred watts. Yes, I remember a 6AG7 linear using 4 tubes that ran about 200 watts. You had to tune up real quick! They only seemed to operate properly if the paint started flaking off from the heat :-) Bob, K9EUI ------------------------------ Date: Mon, 13 Nov 1995 14:54:06 -0800 >From: mjsilva@ix.netcom.com (michael silva) To: glowbugs@theporch.com Subject: Re: 6AG7s and more... Message-ID: <199511132254.OAA28650@ix5.ix.netcom.com> Bob, K9EUI, wrote: >Yes, I remember a 6AG7 linear using 4 tubes that ran about 200 watts. >You had to tune up real quick! They only seemed to operate properly >if the paint started flaking off from the heat :-) Wow, and I do mean WOW! And these are 9 watt tubes! Did anybody ever run a Novice gallon using 6AU6s? :) Ray is correct, the 6AG7 fits in with the 5763 and 12BY7 as the oscillator tubes of choice for the entire post-war era. The other two seem to be getting rather pricey these days. 73, Mike, KK6GM ------------------------------ End of GLOWBUGS Digest 17 *************************  --simple boundary Content-Type: text/plain; charset=US-ASCII; name="GLO-POR0.018" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="GLO-POR0.018" GLOWBUGS Digest 18 Topics covered in this issue include: 1) re:Regen Rcvr Feedback Control by UofSstudent 2) regens - a couple comments by Bob Roehrig 3) Re: regens - a couple comments by "Tony Stalls (K4KYO)" 4) More on choke versus capacitor input filters by "Barry L. Ornitz" 5) 6AG7 circuits by af852@rgfn.epcc.Edu (William R Colbert) 6) Re: regens - a couple comments by mjsilva@ix.netcom.com (michael silva) 7) Re: More on choke versus capacitor input filters by Bill Turner 8) 6AG7s and more... by Duncan Cadd 9) Re: 6AG7s and more... by "Tony Stalls (K4KYO)" 10) FS Tubes by dmedley@indirect.com (David Medley) 11) Power supplies L-C ? by kellymed@tmxbris.mhs.oz.au (Murray Kelly) 12) Re: Power supplies L-C ? by Bob Roehrig ---------------------------------------------------------------------- Date: Mon, 13 Nov 1995 18:10:00 PST >From: UofSstudent To: glowbugs@theporch.com Subject: re:Regen Rcvr Feedback Control Message-ID: On Mon, 13 Nov 1995 14:35:32 -0700 (MST) James P. Rybak wrote: > From: James P. Rybak > Date: Mon, 13 Nov 1995 14:35:32 -0700 (MST) > Subject: re:Regen Rcvr Feedback Control > To: UofSstudent > > Dear Michael: > > Your discussion on building regen rcvrs is very useful. It has been a > while since I have built a regen. Which 2 or 3-tube regen circuit do you > recommend for producing a reasonably sensitive and fairly fool-proof > rcvr? After I get a little practice in putting these together, I will > tackle the more complex circuits. Are there any old QST or Radio News > articles which you particularly recommend? > > Thanks. > > Jim Rybak W0KSD I think you were referring to my article, Jim. Yes, there are old Radio News articles around. The ones I have from 1923-1928, the heydey of radio, have several schematics each issue. They all tend to be electrically the same. In all cases, there is positive feedback from the plate to the grid, either from interelectrode capacitance,external capacitance, or by inductance. They will all oscillate, but what you want is stability. From experience, for triodes, varying regeneration via regeneration capacitor is the best bet for reasons stated in the article. The frames of the capacitors are at ground potential, reducing stray capacitance when you reach for a knob. The circuit according to Hugo Gernsback, publisher of that rag, is called the modified Reinhardt circuit. Other sources of interest may be the Dorle Radio construction series. These were originally published in the early 1930's and used parts salvaged from the neutrodyne and other sets five years previous. They offer a step by step guide to the construction of their sets, the first one being the famous '2 tube Dorle' with a 12000 mile range. Perhaps... Today, these 10cent books are being reprinted with a 95% authenticity at a somewhat inflated price compared to the original. Last I checked in 1991 they could be found at Lindsay's Books, and also at Antique Radio Supply, in Tempe,AZ. There are a number of pentode circuits out there as well. ARRL published a collection of beginner projects back in the 1960's when I was still a kid. I can't remember the title, (maybe someone out there knows..), but I remember that there was a circuit featuring a 6u8 which is a pentode/triode combo. It used the pentode as the regen detector, and the triode as the af stage. It also ran on house current, using a little power transformer salvaged out of undoubtedly a $1 vtvm clunker found at a garage sale. I would opt for the pentode circuits if you aren't recreating a "classic". Unless you are using the third tube for added af amplification, usually a triode before the pentode output stage, Then it would appear you want an input or extra rf stage. There might be a few good reasons for doing this, principally so that you don't radiate. But hey, everything seems to radiate these days- your tv, computer, other hams tuning their xmittrs up and down the band, etc, . By putting in the rf amp stage, you have added to the complexity of both construction and operation of your radio. Remember, all stages will have to track, follow each other up and down the band, unless you tune with 3 hands: two for the 2 tuning controls, one for regeneration. If you wanted to go for 3 tubes and two tuning capacitors WITHOUT regeneration, try the standard 3 tube superhet. This circuit would be far more stable because the nature of the IF difference frequency keeps the oscillator stage away from the input stage. A circuit like this with separate osc and ant capacitors is about as complex as the regen with an rf stage. Also, you can wind the coils yourself. You'd need at least three: ant, osc, and if input. Cheat and use a variloopstick for an if coil tuned to the high end of am band, and your difference frequency may be comparable to some superhet kits of the 1960's. Just have it shielded. Someone asked about variometers in the plate. Well, as any ham knows if you have a tuned input with a tuned output to that same frequency, due to interelectrode capacitance of the tube, you have oscillations. detune the plate, and oscillations cease. Replace the tuned input ie: the coil and the variable capacitor, with a crystal that the output variometer tunes across, and presto! You have a vintage transmitter!! Just key the plate voltage. Those simple 1920's regen radio circuits never cease to amaze. Actually according to radio news (1923),in one of the issues, they said for fun, force the regen radio to oscillate, put a carbon telephone mike in the plate circuit in series with the plate battery where the headphones would be, and speak to your next door neighbor. A diagram was provided for the necessary hookups. This also was before the 1927 radio regulations came into effect. I'll bet radio was sure fun in those days. I hope this provides the answers sought. 73's! james whiskeyjack, VE5JFW ------------------------------ Date: Mon, 13 Nov 1995 19:24:21 -0600 (CST) >From: Bob Roehrig To: glowbugs Subject: regens - a couple comments Message-ID: When I was a student at VTI I built a regen using a 6SN7 (regen stage & audio stage). It was just for 160/80/40 meters and worked like a charm in the dorm. I used the bed spring for an antenna and the first station I worked using a 50 watt rig & that regen rcvr was in California on 80 CW. I also got to thinking about years before that (sometime in the 40's) I had a 2 tube regen put out by the local Boy Scout store. I think it used a 1T4 and a 3V4. Anyway, it had several plug-in coils and worked really well. Used a 90V "B" battery I think. I put it in a cardboard box and had it in the basket on my bicycle, using a surplus 12 foot whip for an antenna. The set was either designed by Philmore or Meissner and was a kit. I think my dad got more of a kick out of assembling it than I did since he had made several BC TRF sets in the 20's. Golly, I am just going to have to build a "new" regen again......... 73 de Bob, K9EUI ------------------------------ Date: Mon, 13 Nov 1995 20:58:23 -0500 (EST) >From: "Tony Stalls (K4KYO)" To: Bob Roehrig Subject: Re: regens - a couple comments Message-ID: On Mon, 13 Nov 1995, Bob Roehrig wrote: > I also got to thinking about years before that (sometime in the 40's) I > had a 2 tube regen put out by the local Boy Scout store. I think it used > a 1T4 and a 3V4. Anyway, it had several plug-in coils and worked really well. > Used a 90V "B" battery I think. Hi Bob, You reminded me that Antique Electronic Supply has a reprint of the 1937 Hammarlund Short Wave Manual that has a number of (excuse me) really neat-o project receivers including a one tube (type 30) receiver, "A Boy Scout's Receiver" built by Scout Robert Crockett of Pelham, New York (NOT "NY"... New York!). It's a great time warp book! 73, Tony K4KYO ------------------------------ Date: Mon, 13 Nov 1995 21:17:45 -0500 (EST) >From: "Barry L. Ornitz" To: wrt@eskimo.com Cc: Glowbugs Mailing List Subject: More on choke versus capacitor input filters Message-ID: Continuing the ongoing saga of the choke input versus capacitor input for power supply filters, I would like to provide several additional arguments that might convince Bill, W7LZP, that his understanding of choke input filters is lacking. My first approach will be practical rather than pedantic for those who do not want to get into the mathematics. Once again I apologize for the length of this post. This argument is simply that a Single Sideband Suppressed Carrier amplifier is no different that an AM or CW transmitter as far as power supply requirements go. The current draw from the power supply will vary at an audio rate exactly as if the power supply were powering a class AB1, AB2, or B (or even a switching class D) stage. In all of these cases, what is needed is a relatively constant supply voltage. A properly designed choke input filter can and does meet this requirement. Is Bill saying that all of the older classic amateur rigs, AM and CW, had power supplies that supplied constant current rather than constant voltage? They virtually all used choke input filters. What about broadcast transmitters? How can you argue with standard practice? Bill appears to be confused about the energy storage in a choke. A capacitor stores electric charge but an inductance stores a magnetic field. Kevin Pease, WB0JZG, is correct when he says: We must keep in mind that inductive kickback is what inductance is all about. The higher the inductance the more the kickback. The choke stores a magnetic field and that energy is used to fill in the 0 voltage portion of the 120 HZ Pulsating DC. Actually the choke supplies energy from its collapsing magnetic field whenever the input voltage is less than the output voltage. The critical inductance I discussed in the previous post is the value needed to maintain current flow from the transformer, through the diodes, into the choke for the full half cycle. Bill seems to be confused by the properties of an inductor when used as a relay. From his post: Barry is correct of course about cost, size and weight, but I stand by my original comment about the rapidly varying current draw and the "inductive kick" phenomenon. Inductive kick is familiar to anyone who has powered a relay coil from DC. When the power is removed from the coil, the stored energy in the field attempts to maintain the existing current flow (which it can't) and the result is a sudden voltage spike across the coil. Nearly all designers place a reversed-polarity diode across the coil to absorb the spike. When the power is removed from the coil of a relay, its magnetic field collapses generating a voltage across the coil in an attempt to maintain the coil current. In fact, the inductance does a damn good job of this - to the point of generating enough voltage across switch contacts for them to arc, or for the collector of a transistor to "punch through" to the emitter. Placing the reversed polarity diode across the coil does provide a current path but there is NO spike generated when the diode is there. The presence of this diode actually slows down the response of the relay since the coil current continues to decay after the switch is opened. [In the real world, the diode has a finite turn-on time so there may be a minuscule spike. Diode capacitance and the distributed capacitance of the coil usually prevent this.] A resistive or resistive-capacitive snubbing network may be used instead of the diode. This will turn the relay off faster since the resistance provides an additional way for the energy in the magnetic field to be dissipated as heat. With a perfect diode (no forward resistance), all of the stored energy in the relay's inductance will be dissipated by the coil resistance. However a power supply is quite different electrically from a switch turning off a relay coil. As the input voltage to the choke drops, due to the collapsing magnetic field of the choke, the transformer and the rectifier still supply current to the choke. If the inductance is greater than the critical inductance, this current will continue to flow over the entire half cycle. As the next half cycle begins, the other rectifier in the full-wave center-tap circuit begins supplying current to the choke which replenishes its magnetic field. At no point in the entire cycle is the current to inductance totally switched off. [In circuits that use controlled rectifiers (SCR, Triacs, SCS, etc.), where the turn-on of the rectifier is delayed until partially into the cycle, a bypass ("commutating" or "freewheeling") diode is needed to supply the choke current. This diode not only clamps the output to zero while the inductively maintained current flows, it also allows the thyristors to turn off.] Bill postulates the following scenario: In a power supply, the same effect will happen if a choke is supplying a constant current and the load is suddenly removed (or varied, as with SSB). The difference in a power supply is that the voltage spike is absorbed by the output filter capacitor instead of a diode. Since the voltage on the capacitor cannot change instantaneously either, you have a LC circuit. The damping will depend on the value of the output resistance. My point is that if the capacitor has to be there anyway, why bother with the choke? As an illustration, imagine a power supply with a very large inductance choke and little or no output capacitance. For SSB, it simply wouldn't work. The reverse situation -- big capacitor and little or no choke would work fine. The reason for that is that a power supply for an SSB transmitter should be a constant voltage source, not a constant current source. The capacitor must be there to provide a low reactance at the lowest audio frequency. Thus the audio currents have little effect on the input impedance of the filter and the transformer sees only the average current. The reverse situation, that of a large capacitor and no choke, is another extreme. The inductance of the power transformer becomes important as does the resistance of the rectifiers. As these become smaller, the peak current drawn by the supply becomes very high. The current from the transformer occurs in very short, narrow pulses. This not only creates problems with the transformer, it also creates noise and transients in the power line. The capacitor has to be there, but it can be far, far smaller with the choke input filter. If the standard practices do not convince Bill, and the above arguments do not either, perhaps the following detailed example will... For this analysis, let us assume a full-wave center tapped transformer with a voltage rating of 707-0-707 RMS volts on the secondary. This gives a peak voltage of 1000 volts. Let us further assume a full load of 1 amp and an idling current of 0.1 amp. Since a choke with a value above the critical inductance is used, the output voltage will be 0.9*1000 = 900 volts. The critical inductance is: Lcrit = (900/0.1)/1000 = 9 Henry Let us assume that the lowest audio frequency to be transmitted is 300 Hz. If the output capacitor impedance is no more than 10% of the total impedance at this frequency, we consider the response acceptable. This sets the value of the output capacitor to: XCout = 0.1 * 900 = 90 ohms Cout = 1/(6.28 * 300 * 90) = 5.9 microfarad Knowing the choke inductance and the output capacitance, we can calculate the ripple factor of the filter. r = Er/Edc where Edc is DC output voltage and Er is the RMS ripple voltage. For single phase full wave systems: r = (8.3E5/(Lcrit * Cout)) * (60/fs)^2 = 0.015 Since the output voltage is 0.9 * 1000 = 900 volts, the RMS ripple voltage is 13.5 volts. Now let us compare what values would be needed for a capacitor only filter. We can calculate the required capacitance to match the same ripple factor above. r = Sqrt(2)/(2*Pi*f*Cout*Rload) This calculates to a value of capacitance slightly over 250 microfarads. At this point, we have to assume something about the series resistance of the rectifier. Since Bill promotes silicon diodes, a reasonable resistance might be 1 ohm. The ratio of series resistance to load resistance is a parameter on the Schade graphs [Referenced in a previous post.]. In this case the parameter is 1/1000 = 0.001. The product of the load resistance and the output capacitance is the other parameter. >From the graph that gives the ratio of direct current output voltage to the crest of the alternating voltage as a function of the filter constants, the DC output voltage is: Vout = 0.983 * 1000 = 983 volts. So the voltage is a little higher - but this is expected. Now we need to calculate the diode currents. From the other Schade graphs we can get: RMS current/DC current (per diode) = 4 Peak current/DC current (per diode) = 20 Since the maximum current of one diode is 1 amp/2, the RMS current for each diode is 2 amps. The peak current of the same diode is 10 amps. A diode rated for at least two amps DC should be used since the heat the diode must dissipate is based on its RMS current. The diode must also be able to withstand 10 amps of peak current EVERY charging cycle. Compare this to the 0.5 amp RMS and peak current the diodes will be subjected to in the choke input filter. Furthermore, the transformer current reflected back into the power lines with the capacitor input filter is as high as 120 amps peak compared to less than 6 amps with the choke input filter. This 20 to 1 difference can cause some big voltage drops in your house wiring! Ever wonder why the lights blink at an audio rate? :-) At least Bill concedes that capacitor input filters need some sort of soft-start circuitry. When adequate bleeder current is drawn from a choke input supply, this is rarely necessary. There is one other consideration when using capacitor-only filtering: The initial current surge on turn-on needs to be taken into account so no components are over stressed. A delay or "step- start" circuit is often used, and in my own station, I have added one to two different commercial amplifiers I have. I chose the component values to allow about three seconds for the capacitors to charge before the full line voltage is applied to the transformer. I've never had a power supply failure with either one, and I credit that partly to the delay circuit. To use Michael Silva's comment: It sounds like there's more going on in a PS filter than most of us realize. It'd be interesting to scope different points on a filter to see what's happening. I agree fully. But to play it safe, use a relatively low voltage supply to probe around in. Remember, it is not only your life we are talking about - it is also the life of the venerable old Tektronix too! :-) Probing around the power supply in a transformer operated receiver is a very educational experience. Finally I would like to add that the analysis here was NOT a theoretical one. It uses all sorts of engineering approximations (like neglecting the choke resistance, the transformer inductance, the rectifier voltage drops, etc.). These are the things that should be taught in school, at least AFTER the rigorous analysis has been performed enough that you realize why the approximations are reasonable. [And by the way, I am not aware of any BSEE programs that use Horowitz and Hill's "Art of Electronics". This book is excellent, however, as a guide for those that do not want to get deeply into electronics theory. It was written for physicists but every amateur who wants to go one step beyond the ARRL handbook but wishes to avoid differential equations should buy one. It is much like Terman's "Radio Handbook"s - not a true engineering text but an excellent reference for an engineer or a beginner alike. Unfortunately, it deals almost exclusively with solid- state devices.] Finally to correct a mistake in my previous posting, an 8877 is a 3CX1500A7. 73, Barry WA4VZQ ornitz@eastman.com {Use this address or the "Reply-To:" address that is probably stripped off when passing through the reflector.} ------------------------------ Date: Mon, 13 Nov 95 20:13:56 MST >From: af852@rgfn.epcc.Edu (William R Colbert) To: glowbugs@theporch.com Subject: 6AG7 circuits Message-ID: <9511140313.AA21433@rgfn.epcc.Edu> Conard and others - found one of the references to the 6AG7 linear- was by Norm W6GEG, rather than W6BLZ. Anyway, used 4 6AG7's in parallel (works with 6L6's also) cathode fed, grounded grid, 750 v on the plates for 150 watts p.e.p. I seem to remember the original article was entitled "The little firecracker amplifier", but haven't found the original article. The one reference, with schematic, i did find was in the "New Sideband Handbook" edited by Don Stoner, W6TNS, published by CQ, 1958/1959. A couple of other articles that may be of interest are: June 1966 CQ - 6AG7/6L6 in a 40 mtr rig, and QST March 64 - 6AG7/6146 in a 2 band 40 watt rig. Good Luck and 73 Ray, W5XE, El Paso ------------------------------ Date: Mon, 13 Nov 1995 23:10:48 -0800 >From: mjsilva@ix.netcom.com (michael silva) To: glowbugs@theporch.com Subject: Re: regens - a couple comments Message-ID: <199511140710.XAA12722@ix12.ix.netcom.com> Tony, K4KYO, wrote: > >You reminded me that Antique Electronic Supply has a reprint of the 1937 >Hammarlund Short Wave Manual that has a number of (excuse me) really >neat-o project receivers including a one tube (type 30) receiver, "A Boy >Scout's Receiver" built by Scout Robert Crockett of Pelham, New York (NOT >"NY"... New York!). It's a great time warp book! > In a very similar vein is the "1934 Official Shortwave Radio Manual", by Lindsay and also at AES. 260 large pages of receivers, both homebrew and commercial, and a few transmitters thrown in as well. I picked it out of the AES catalog because it had the most pages, and it's been great fun to keep by the bed (wisecracks cheerfully ignored). 73, Mike, KK6GM ------------------------------ Date: Tue, 14 Nov 1995 00:42:05 -0800 >From: Bill Turner To: ornitz@eastman.com Cc: Glowbugs Mailing List Subject: Re: More on choke versus capacitor input filters Message-ID: <199511140842.AAA11767@mail.eskimo.com> The bandwidth on this subject is getting pretty large, but a few more comments would seem to be in order: (I've made some snips here and there, but I'll try not to distort anything Barry said) At 09:17 PM 11/13/95 -0500, Barry L. Ornitz wrote: >This argument is simply that a Single Sideband Suppressed Carrier >amplifier is no different that an AM or CW transmitter as far as power >supply requirements go. The current draw from the power supply will >vary at an audio rate exactly as if the power supply were powering a >class AB1, AB2, or B (or even a switching class D) stage. In all of >these cases, what is needed is a relatively constant supply voltage. A >properly designed choke input filter can and does meet this requirement. Of course it can and does. That wasn't the original question. >Is Bill saying that all of the older classic amateur rigs, AM and CW, >had power supplies that supplied constant current rather than constant >voltage? They virtually all used choke input filters. What about >broadcast transmitters? How can you argue with standard practice? Something has gotten turned around here. I'm arguing that chokeless power supplies ARE standard practice, at least in the amateur field. Check any recent ARRL handbook -- the supplies are all chokeless, just what I'm advocating. (Emphasis on "recent"...) >Bill appears to be confused about the energy storage in a choke. A >capacitor stores electric charge but an inductance stores a magnetic >field. Not confused at all -- I know that. >Bill seems to be confused by the properties of an inductor when used as >a relay. From his post: > > Barry is correct of course about cost, size and weight, but I stand > by my original comment about the rapidly varying current draw and > the "inductive kick" phenomenon. Inductive kick is familiar to > anyone who has powered a relay coil from DC. When the power is > removed from the coil, the stored energy in the field attempts to > maintain the existing current flow (which it can't) and the result > is a sudden voltage spike across the coil. Nearly all designers > place a reversed-polarity diode across the coil to absorb the > spike. > >When the power is removed from the coil of a relay, its magnetic field >collapses generating a voltage across the coil in an attempt to maintain >the coil current. In fact, the inductance does a damn good job of this >- to the point of generating enough voltage across switch contacts for >them to arc, or for the collector of a transistor to "punch through" to >the emitter. Placing the reversed polarity diode across the coil does >provide a current path but there is NO spike generated when the diode is >there. The presence of this diode actually slows down the response of >the relay since the coil current continues to decay after the switch is >opened. [In the real world, the diode has a finite turn-on time so there >may be a minuscule spike. Diode capacitance and the distributed >capacitance of the coil usually prevent this.] A resistive or >resistive-capacitive snubbing network may be used instead of the diode. >This will turn the relay off faster since the resistance provides an >additional way for the energy in the magnetic field to be dissipated as >heat. With a perfect diode (no forward resistance), all of the stored >energy in the relay's inductance will be dissipated by the coil >resistance. Again, not confused at all. Your understanding and mine are the same. What exactly made you think I was confused? >However a power supply is quite different electrically from a switch >turning off a relay coil. As the input voltage to the choke drops, due >to the collapsing magnetic field of the choke, the transformer and the >rectifier still supply current to the choke. If the inductance is >greater than the critical inductance, this current will continue to flow >over the entire half cycle. As the next half cycle begins, the other >rectifier in the full-wave center-tap circuit begins supplying current >to the choke which replenishes its magnetic field. At no point in the >entire cycle is the current to inductance totally switched off. No argument here. What the choke is doing in this case is simply supplying energy to the capacitor and/or the load to help maintain a constant voltage source over the 1/2 cycle until the transformer/rectifiers can replenish them again. My original point was that the capacitor is perfectly capable of doing this by itself -- while the choke can and does assist, it isn't absolutely necessary. And they are expensive. >Bill postulates the following scenario: > > In a power supply, the same effect will happen if a choke is > supplying a constant current and the load is suddenly removed (or > varied, as with SSB). The difference in a power supply is that the > voltage spike is absorbed by the output filter capacitor instead of > a diode. > >Since the voltage on the capacitor cannot change instantaneously either, >you have a LC circuit. The damping will depend on the value of the >output resistance. Exactly. And since the resistance (with SSB) is varying all over the place, so is the damping. Not a desirable situation, in my opinion. If I may make a rough analogy: A capacitor has no "agenda" of it's own. It simply delivers energy depending on what the load wants. An inductor, on the other hand has it's own ideas about how much current should be flowing. Try to change it and the inductor will resist mightily. Not what we want. > > My point is that if the capacitor has to be there anyway, why > bother with the choke? As an illustration, imagine a power supply > with a very large inductance choke and little or no output > capacitance. For SSB, it simply wouldn't work. The reverse > situation -- big capacitor and little or no choke would work fine. > The reason for that is that a power supply for an SSB transmitter > should be a constant voltage source, not a constant current source. > >The capacitor must be there to provide a low reactance at the lowest >audio frequency. Thus the audio currents have little effect on the >input impedance of the filter and the transformer sees only the average >current. The reverse situation, that of a large capacitor and no choke, >is another extreme. The inductance of the power transformer becomes >important as does the resistance of the rectifiers. As these become >smaller, the peak current drawn by the supply becomes very high. The >current from the transformer occurs in very short, narrow pulses. This >not only creates problems with the transformer, it also creates noise >and transients in the power line. The capacitor has to be there, but it >can be far, far smaller with the choke input filter. The comments about current pulses, noise and transients are all true of course, but at amateur power levels, pretty much irrelevant. There are thousands of amplifiers in use every day without trashing the power grid. It's a non-issue unless perhaps you're powering the VOA. To sum up my point of view: nobody is saying choke input filters won't work or can't be made to work. But -- the marketplace is a very efficient determiner of what works for a given expenditure of dollars, and the consensus is that chokes are not needed. For a widely varying load, you need a constant voltage source, which capacitors provide. A choke is a constant current source and will function to supply energy to the capacitor and load, but the fundamental current-sourcing action of a choke is the opposite of what is needed. A capacitor can do the job all by itself; a choke cannot. My advice is to spend your hard-earned money elsewhere. 73, Bill W7LZP wrt@eskimo.com ------------------------------ Date: Tue, 14 Nov 1995 13:10:23 +0100 (MET) >From: Duncan Cadd To: glowbugs@theporch.com Cc: dcadd@luc.ac.be Subject: 6AG7s and more... Message-ID: <9511141210.AA17302@alpha.luc.ac.be> Greetings, Buggites, from a dull but dry Diepenbeek in N.E. Belgium! > Wow, and I do mean WOW! And these are 9 watt tubes! Did anybody ever > run a Novice gallon using 6AU6s? :) I don't recall the exact tube type off the top of my head, but one of the double digit number series, maybe 45 . . . our forebears seemed to have a penchant for squeezing the last erg out of the available technology, I read in the manual manufacturer's rated absolute maximum plate volts 250, then read in a 30s vintage transmitter article, 'recommended plate volts 400-450'!! I also recall my Father telling me of the British LS6A triode running with its plates a nice cherry red as the 'normal' state of affairs . . . also 1930s. Must've been the decade, inter-war joie de vive or whatever. 73, Duncan ON9CHU / G0UTY G-QRP 8117 ------------------------------ Date: Tue, 14 Nov 1995 10:36:19 -0500 (EST) >From: "Tony Stalls (K4KYO)" To: William R Colbert Subject: Re: 6AG7s and more... Message-ID: On Mon, 13 Nov 1995, William R Colbert wrote: > There was also early articles using the 6ag7 in a linear amp. > I think W6BLZ (now W6XM), Ed Marriner, writing for CQ had > one up and running in the early 50's with an output of a couple > hundred watts. In the area of not-the-usual-use trivia like using 6AG7's as amplifiers, years ago (like the mid-1950's), somebody brought their "pushed way beyond the limit" 6L6 amplifier to a Nashville Amateur Radio Club meeting that was used with the chassis sitting on a bucket of water so the tubes would be submerged. Memories both fade and embellish so I can't say for sure, but I think I recall the water boiling. Funny! 73, Tony K4KYO ------------------------------ Date: Tue, 14 Nov 1995 09:31:36 -0700 >From: dmedley@indirect.com (David Medley) To: glowbugs@theporch.com Subject: FS Tubes Message-ID: <199511141631.JAA07590@ns1.indirect.com> Last week I posted two boxes of tubes, one 2v battery types and one auto radio types. I got very little response. Does anyone out there want these things? If I put a too high price then make an offer. No reasonable offer refused. Regards Dave ------------------------------ Date: Wed, 15 Nov 95 03:27:13 AES >From: kellymed@tmxbris.mhs.oz.au (Murray Kelly) To: glowbugs@theporch.com Subject: Power supplies L-C ? Message-ID: <631@tmxbris.mhs.oz.au> This group is devoted to using tubes where the spec. sheets leave off. Right? Enough of this mathematik! Volts can only go up. A. Re the choke v. capacitor storage power supply. It seems to me that both arguments are right. I am only a young feller (59) and got my ticket in '77. Real recent! When I was reading for the exams there was quite a bit about valves (tubes). None of your multiple choice rubbish then, mind you - 7 questions, four choices each and 2 hrs to get it down. At that time common knowledge had it that the problem with high tension supplies was there wasn't enough farads available. I have a drawer full of 8, 16, and EVEN 32 uF (!) cans. Nowadays there are 200-300uF at 450WV because of better technology. But, power supply design now says that a rule of thumb is - 4000uF per amp. should be available. This plainly impossible at 2500v. It would be enough to kill an elephant. Or a string of them. (Would their tails act like fuses?) Therefore both solutions are correct. Use as much capacitance as you can lay your hands on, (this is high current stuff - volts and no current is for wimps, right?) and put a little choking into it too as an extra storage device. Nothing to give you a hernia, tho. The other thing I recall is that thermal emission devices (valves) had this little problem passing any decent sort of current. A semi-conductor diode (hands up who isn't using them?) doesn't drop much voltage and keeps relatively cool. The power supply was limited by the tube's capacity to supply current at high volts. (power). AS a consequence (surely) the best compromise today would be as I said, lots of C and some L. Semiconductor diodes have a huge single cycle surge rating usually and the argument that they are unable to handle that is not borne out in practice. Charging up the caps at switch-on is probaly limited by the ability to supply of the transformer - think of it a kind of choke, perhaps? None of the argument (sri - 'discussion') so far has helped the original query. How to drop the output volts of a transformer? What is the feeling of the group to a bucking (easy - that's a 'b') voltage applied to the primary of the supply? One can trim the input voltage with a lower voltage transformer in series with the primary if it has sufficient current carrying capacity (ie the same as the primary). I must say it always seemed so wasteful to oppose an output with a counter-input, but the result is legitimate. B. Another question raised was the usefulness of a pot to control the feedback in a regen rig. I notice the MFJ solidstate (gasp) regen receiver uses pots to regulate the feedback and allegedly does it most successfully. Should work anywhere. C. I have this little pile of 6BM8 s and have long wanted to use them for a QRP osc/trx. Anyone see why they won't fly? Ideally I would like to try a ceramic resonator as the frequency determining device - in the triode, but that's just an extra. D. Finally (whew!) has anyone had experience with air-cored toroids? I have made some big ones (2.5in) but would like to get some glass or plain ceramic formers to experiment with. I have been trying multiple windings in the opposite direction, but same sense, to get some really hi 'Q' coils and would like to try it out on smaller stuff. I have never seen any source of such a thing mentioned. Thanks, Murray Kelly. vk4aok. ------------------------------ Date: Tue, 14 Nov 1995 15:45:58 -0600 (CST) >From: Bob Roehrig To: Murray Kelly Cc: Multiple recipients of list Subject: Re: Power supplies L-C ? Message-ID: On Tue, 14 Nov 1995, Murray Kelly wrote: > > None of the argument (sri - 'discussion') so far has helped the > original query. How to drop the output volts of a transformer? > What is the feeling of the group to a bucking (easy - that's a 'b') > voltage applied to the primary of the supply? One can trim the input > voltage with a lower voltage transformer in series with the primary > if it has sufficient current carrying capacity (ie the same as the > primary). I must say it always seemed so wasteful to oppose an output > with a counter-input, but the result is legitimate. > Murray brings up a good point. I mentioned earlier in another post that I had obtained a WW2 vintage Japanese clone of an HRO. Its power supply was, of course, intended to run from 100 VAC. The first thing that came to mind was a bucking transformer arrangement. I used a 24V job to oppose the primary of the main transformer - worked like a charm. Nice thing about this method is little heat generated as there would be using resistive dropping. Also the output is constant regardless of the load. 73 de BOB, K9EUI ------------------------------ End of GLOWBUGS Digest 18 ************************* --simple boundary Content-Type: text/plain; charset=US-ASCII; name="GLO-POR0.019" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="GLO-POR0.019" GLOWBUGS Digest 19 Topics covered in this issue include: 1) 3A5 Regen RX....Lives! by k7yha@ix.netcom.com (Richard H. Arland ) 2) Re: Power supplies L-C ? by Bill Turner 3) This is getting serious... by mjsilva@ix.netcom.com (michael silva) 4) Re: This is getting serious... by johnmb 5) Fleming valve by Duncan Cadd 6) "WET" 6L6 by BOB.LIESENFELD@hamlink.mn.org (BOB LIESENFELD) 7) RE: "WET" 6L6 by "ALLIN1.US054298" ---------------------------------------------------------------------- Date: Tue, 14 Nov 1995 16:34:17 -0800 >From: k7yha@ix.netcom.com (Richard H. Arland ) To: k7yha@ix.netcom.com Subject: 3A5 Regen RX....Lives! Message-ID: <199511150034.QAA04355@ix6.ix.netcom.com> HI Gang: Been having troubles posting to this list and boatanchors. So here it goes...again. Last night I completed the 3A5 RX in the Sept issue of CQ mag (1995). It works, although not well. Very little volume, tuning is extremely critical at the high (7.0 MHz) end of the dial. Coverage is from 3.4 to 7.4 MHz. Using a 65 ft end fed wire I can get the big-time SW broadcasters, but no ham QSOs. I'm thinking about removing about 10 turns from the main coil which sould drop 7 MHz down to the low end of the capacitor tuning range (yielding better bandspead) and also allow me to receive 30 meters. (I never did like 80 mtrs.) Any thoughts? 73 rich ------------------------------ Date: Tue, 14 Nov 1995 20:57:11 -0800 >From: Bill Turner To: kellymed@tmxbris.mhs.oz.au, Subject: Re: Power supplies L-C ? Message-ID: <199511150457.UAA27085@mail.eskimo.com> At 11:31 AM 11/14/95 -0600, Murray Kelly wrote: -snip- >At that time common knowledge had it that the problem with high >tension supplies was there wasn't enough farads available. I have a >drawer full of 8, 16, and EVEN 32 uF (!) cans. Nowadays there are >200-300uF at 450WV because of better technology. But, power supply >design now says that a rule of thumb is - 4000uF per amp. should >be available. This plainly impossible at 2500v. It would be enough to >kill an elephant. -snip- -------------------------------------------------------------------- May I offer a suggestion? Instead of "rule of thumb", there is an easy way to calculate how much capacitance is needed for a given power supply application. I came across this years ago in a consumer electronics magazine of all places, and I've never seen it anywhere else. It's based on the definition of a farad, slightly rewritten: When supplied with a constant current of one ampere for one second, a one farad capacitor will charge up to a voltage of one volt. The same thing is true for discharging too, and here is how you use it. If you have a power supply using a full wave rectifier feeding directly into a capacitor (no choke), the filter capacitor is fully recharged 120 times per second, or looking at another way, every 8.333 milliseconds. If, for example, it were a one farad capacitor supplying a current of one ampere, the voltage would only drop for 8.333 milliseconds before it was recharged again. How far would it drop? Lets make an assumption that the current is constant at one ampere. In one full second it would drop one full volt from where it started at, but in 8.333 milliseconds, it will only drop 8.333 millivolts. Since it is recharged as soon as it has dropped to that point, you would see a ripple of -- you guessed it -- 8.333 millivolts. Hardly any of us use one farad capacitors or exactly one ampere loads, of course, so in order to scale this for other variables, just use this formula: C = (1000*I)/(F*V) where C = required capacitance in microfarads I = load current in milliamps F = ripple frequency in Hz V = the desired ripple voltage For example, if you're building a legal-limit amplifier with a plate supply of 3000 volts, a full wave rectifier (120 Hz) and a current drain of 800 ma, and you want no more than 50 volts of ripple, you will need: (1000*800)/120*50 = 133.3 microfarads. If more ripple is acceptable, lets say 120 volts.... the required capacitance is now 55.5 microfarads. Use a half wave rectifier instead (60 Hz) and the capacitance required is doubled, and so on. There are two small caveats with this. One, electrolytic capacitors are notorious for being way off their marked capacity, so take that into account, and two, the formula assumes that the capacitor is instantaneously recharged and that the current drain is perfectly constant. In the real world neither one will be true, but you will be pleasantly surprised how close you will come to the correct value required. And of course with a little rearranging of the formula, you can determine the amount of ripple you'll get from given values of capacitance, load and frequency. 73, Bill W7LZP wrt@eskimo.com ------------------------------ Date: Tue, 14 Nov 1995 23:42:48 -0800 >From: mjsilva@ix.netcom.com (michael silva) To: glowbugs@theporch.com Subject: This is getting serious... Message-ID: <199511150742.XAA09093@ix3.ix.netcom.com> I dropped by a surplus place after driving out to visit my sister, picked up five dollars worth of miscellany, and then I ran across...a variable DC supply, adjustable voltage ranges of 250/500/1000v, adjustable current ranges of 250/500/1000mA. It's BIG! Made by Hipotronics (anybody ever heard of 'em?). While I stood there scratching my head the owner started dropping the price, and at some point I said "uncle!" and handed him a credit card! I really don't need this monster (but I'm glad I've got it!). He said he had it running 3 months ago, and it's got a 90 day warranty, but tomorrow I'm going to open it up, poke and sniff around, and only then *slowly* power it up (it's got a built-in variac). Finally I can make my own cherry-red plates! Like I said, this is getting serious. 73, Mike, KK6GM ------------------------------ Date: Wed, 15 Nov 1995 06:55:32 -0500 (EST) >From: johnmb To: michael silva Cc: Multiple recipients of list Subject: Re: This is getting serious... Message-ID: Hipotronics is/was a manufacturer of HiPot testing equipment. Im not sure if they are still in the biz. Welcome to the addiction! :-) /john ------------------------------ Date: Wed, 15 Nov 1995 13:15:58 +0100 (MET) >From: Duncan Cadd To: boatanchors@theporch.com Cc: dcadd@luc.ac.be, glowbugs@theporch.com Subject: Fleming valve Message-ID: <9511151215.AA20062@alpha.luc.ac.be> Greetings, from a changeable Diepenbeek in N.E. Belgium! The Science Museum in London has a large Web page with a small (but nice) illustration of one of Fleming's original experimental tubes dating from 1889. The original is on display in one of the galleries (Nick England take note!) http://www.nmsi.ac.uk/galleries/objects/flemmv2.htm will get you the pretty picture. 73, Duncan ON9CHU / G0UTY G-QRP 8117 ------------------------------ Date: Wed, 15 Nov 1995 08:27:05 -0100 >From: BOB.LIESENFELD@hamlink.mn.org (BOB LIESENFELD) To: glowbugs@theporch.com Subject: "WET" 6L6 Message-ID: <816433225.AA04238@hamlink.mn.org> Hi gang, I had to laugh when I saw the post about the 6L6 TX set upon a bucket 'o water with the tubes down in the drink. I too have seen this with a single bulb and a glass of water. While the water did not boil, it was *hot*. You had to stir it up once in a while to do much good. 72 Bob WB0POQ Technology is OUT of control.... ---NoSnail v1.17 ******************************************************************* HAM>link< RBBS - Serving the Amateur Radio Community Since 1983 - 612/HAM-0000 v.34 Ham Radio Spoken Here!! - 612/HAM-1010 v.32b Reply to sender @ hamlink.mn.org ******************************************************************** ------------------------------ Date: Wed, 15 Nov 1995 12:33:54 EST >From: "ALLIN1.US054298" To: glowbugs@theporch.com Subject: RE: "WET" 6L6 Message-ID: <199511151736.LAA09594@uro.theporch.com> Won't the grid leak out?? ------------------------------ End of GLOWBUGS Digest 19 *************************  --simple boundary Content-Type: application/octet-stream; name="GLO-POR0.020" Content-Transfer-Encoding: base64 ICAgICAgIEdMT1dCVUdTIERpZ2VzdCAyMA0KDQpUb3BpY3MgY292ZXJlZCBpbiB0aGlzIGlzc3Vl IGluY2x1ZGU6DQoNCiAgMSkgUmU6IDNBNSBSZWdlbiBSWC4uLi5MaXZlcyENCiBieSBVb2ZTc3R1 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