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Total 19 documents matching your query.

1. [Amps] New Guy, Old 813 amp (score: 1): Author: "Bowen, Scott M. (JSC-CC)[LM]" <scott.m.bowen@nasa.gov>; Date: Thu, 26 Apr 2007 07:40:23 -0500; Hello all, I just joined this group and recently purchased a homebrewed amplifier running a pair of 813's in parallel. It looks like it is set up for 2 bands, 80/75 and 40 meters at the moment. I am; /archives//html/Amps/2007-04/msg00314.html (6,894 bytes)
2. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: Gudguyham@aol.com; Date: Thu, 26 Apr 2007 09:06:07 EDT; Scott, welcome aboard. To my knowledge there were very few commercial amplifiers built with 813 tubes. The ones that were built I do not believe had any tuned input circuits. The 813 is an older tube; /archives//html/Amps/2007-04/msg00315.html (7,418 bytes)
3. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "k7fm" <k7fm@teleport.com>; Date: Thu, 26 Apr 2007 06:33:11 -0700; Hello Scott: Congratulations on the 813 amp. I had one many years ago and worked about 150 countries on 75 meters. The tubes are instant on - and that is worth a couple of db when you hear a rare sta; /archives//html/Amps/2007-04/msg00317.html (8,944 bytes)
4. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: Doug <dcoffman@iquest.net>; Date: Thu, 26 Apr 2007 13:14:19 -0400; I cannot remember the company that makes it, but there is a small autotuner designed to be retrofitted into a 6M-HF amplifier that sells for $100.00 that would fit the bill. Regards, Doug - N9XTF Quo; /archives//html/Amps/2007-04/msg00320.html (10,159 bytes)
5. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: Doug <dcoffman@iquest.net>; Date: Thu, 26 Apr 2007 13:19:53 -0400; Here is the link, it is a product from LDG. http://www.ldgelectronics.com/products.php?cID=7&pID=2&v=1 73, Doug N9XTF Quoting k7fm <k7fm@teleport.com>: _______________________________________________; /archives//html/Amps/2007-04/msg00321.html (9,977 bytes)
6. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Apr 2007 14:20:59 -0400; The problem with autotuners are:: 1.) The impedance of a tube is dynamic. It changes with drive level and even the output tuning. As such autotuners tend to "hunt" and never settle correctly. 2.) Th; /archives//html/Amps/2007-04/msg00322.html (8,212 bytes)
7. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: Roger D Johnson <n1rj@adelphia.net>; Date: Thu, 26 Apr 2007 14:29:32 -0400; I have a bit of heartburn with this scheme. The LDG tuner is an L network. The Q of an L network is not independently selectable. It depends on the ratio of impedances to be matched. For example, to; /archives//html/Amps/2007-04/msg00323.html (8,948 bytes)
8. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: N7SC <n7sc@charter.net>; Date: Thu, 26 Apr 2007 14:16:42 -0700; Would it be possible to find a parts amp and get the tuned input out of it? I would like to set the amp up for 75, 40 and 10 meters mainly. Hi Scott... Here's another link to add to your list of opti; /archives//html/Amps/2007-04/msg00326.html (7,884 bytes)
9. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Thu, 26 Apr 2007 18:25:15 -0400; The biggest problem is mechanical, like mounting a switch in the amp. It's pretty easy to handle the rest. I think you are asking for more problems by using a transplant because none of the componen; /archives//html/Amps/2007-04/msg00327.html (8,260 bytes)
10. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Bowen, Scott M. (JSC-CC)[LM]" <scott.m.bowen@nasa.gov>; Date: Thu, 26 Apr 2007 19:29:45 -0500; I guess that is a big option, at the moment. I think I need to learn how to build tank circuits, as I am trying to figure out how to add 10 meters to it, but the 813 GG circuits I have seen are not h; /archives//html/Amps/2007-04/msg00330.html (8,759 bytes)
11. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Pat Barthelow" <aa6eg@hotmail.com>; Date: Thu, 26 Apr 2007 18:11:04 -0700; I think there might be difficulties getting to 10 meters for the output netowrk.. for a pair of 813's due to large plate capacitances. 73, DX, de Pat AA6EG aa6eg@hotmail.com; Skype: Sparky599 Moon or; /archives//html/Amps/2007-04/msg00331.html (9,928 bytes)
12. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "k7rdx" <k7rdx@charter.net>; Date: Thu, 26 Apr 2007 21:05:49 -0700; The LDG amp module is easy to install and use in a HB amp. The purists will all agree against using an L network for cathode matching and I tend to agree to some extent. I bought an LDG amp module fo; /archives//html/Amps/2007-04/msg00334.html (11,736 bytes)
13. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 27 Apr 2007 09:03:09 -0400; This is an important point. Tubes with very low cathode impedances and operated with higher conduction angles have significantly more stability in input impedance as the drive level and output loadi; /archives//html/Amps/2007-04/msg00337.html (10,349 bytes)
14. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Robert Bonner" <rbonner@qro.com>; Date: Fri, 27 Apr 2007 08:19:11 -0500; Interesting Jim. That's cool that the tuner worked for you. When I banged together my single band PLASMATRON the pair of 8877's for 80 meters a few months ago, I hadn't built an input network for it; /archives//html/Amps/2007-04/msg00338.html (13,865 bytes)
15. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Robert Bonner" <rbonner@qro.com>; Date: Fri, 27 Apr 2007 08:22:37 -0500; OK so now my question is answered I suppose. Higher cathode impedance more swinging - lower more stable. This is an important point. Tubes with very low cathode impedances and operated with higher co; /archives//html/Amps/2007-04/msg00339.html (11,092 bytes)
16. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "k7rdx" <k7rdx@charter.net>; Date: Fri, 27 Apr 2007 08:18:06 -0700; Bob,did you use a toroidal balancing transformer before the coupling caps and cathodes?(Like Alpha 77sx) A pair of 8877`s must look close to 25 ohms at the input.The LDG module will cycle if more tha; /archives//html/Amps/2007-04/msg00340.html (15,710 bytes)
17. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "Tom W8JI" <w8ji@w8ji.com>; Date: Fri, 27 Apr 2007 13:05:54 -0400; You also very often cannot pass the dc through the filament choke winding that carries filament current. It can cause hum even without a center tap connection simply because of the I*R drop of the c; /archives//html/Amps/2007-04/msg00341.html (9,687 bytes)
18. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: "k7rdx" <k7rdx@charter.net>; Date: Fri, 27 Apr 2007 12:16:17 -0700; I have done this both ways,thru a seperate choke and thru the cathode side of the filament choke...Same results both ways...73,Jim.. -- Original Message -- From: "Tom W8JI" <w8ji@w8ji.com> To: "k7rdx; /archives//html/Amps/2007-04/msg00345.html (10,436 bytes)
19. Re: [Amps] New Guy, Old 813 amp (score: 1): Author: rgroh@swbell.net; Date: Fri, 27 Apr 2007 22:14:42 -0700 (PDT); Possibly because the unterminated input meant that feedback (i.e. output reflected back to the input port via the tube capacitance) was having a much greater effect than with a lower impedance tuned; /archives//html/Amps/2007-04/msg00353.html (13,250 bytes)

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