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21. Re: [Amps] TL-922 --> 21st century (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sun, 14 Aug 2011 10:24:53 +0100; I assume that you've seen the excellent TL-922 engineering information, here: http://pa0fri.home.xs4all.nl/Lineairs/TL922/tl-922eng.htm They were thinking of "super cathode" driven design... discusse; /archives//html/Amps/2011-08/msg00056.html (8,125 bytes)
22. Re: [Amps] running two 3 phase transformer serie/parallel (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Thu, 27 Oct 2011 09:37:49 +0100; Carel, I think what you were originally suggesting might work, as long as you have access to both sides of each primary winding. If you call the phases Red (R), Yellow (Y) and Blue (B) as we used to; /archives//html/Amps/2011-10/msg00075.html (11,651 bytes)
23. Re: [Amps] Gettering 3-500 Tubes (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sat, 05 Nov 2011 19:14:21 +0000; Bob, Before you worry too much about gettering the tubes I suggest that you check them for emission and reactivating them if necessary... I found how to do this on PA0FRI's site, here: http://www.xs4; /archives//html/Amps/2011-11/msg00007.html (10,372 bytes)
24. Re: [Amps] Gettering - ETAL (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Tue, 08 Nov 2011 20:04:37 +0000; Interesting question... many external anode tubes are "self gettering" in-so-much-as the gettering substance is painted on to the cathode and the process of running the tube (heater on) is sufficient; /archives//html/Amps/2011-11/msg00035.html (7,927 bytes)
25. Re: [Amps] Gettering - ETAL (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Wed, 09 Nov 2011 17:13:33 +0000; ... and the thermal "mass" of an external anode tube is huge compared with the relatively small internal anode on something like a 572B or a 3-500Z... hence which the same amount of kinetic energy ma; /archives//html/Amps/2011-11/msg00039.html (8,189 bytes)
26. Re: [Amps] Increased ambient noise in a 2 x 8877 amplifier (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Thu, 17 Nov 2011 08:31:40 +0000; Chris, I think that I've heard about this before with 4CX250Bs on 144MHz... isn't it something to do with "shot noise" and incomplete cut-off of the tubes? ... you probably have a few tens of uA of a; /archives//html/Amps/2011-11/msg00071.html (10,030 bytes)
27. Re: [Amps] [rfamplifiers] 4CX5000/10000 Screen power supply help needed (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Mon, 02 Jan 2012 18:46:38 +0000; Hsu, You can make a good shunt screen stabiliser using an op-amp and a tetrode, this was done many times for 4CX250B, 4CX1000A etc. before the Tetrode Boards from Ian G3SEK... See here (second half o; /archives//html/Amps/2012-01/msg00022.html (10,402 bytes)
28. Re: [Amps] 3cx800a7 Grid Current Problem (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Thu, 26 Jan 2012 07:14:22 +0000; This appears to be not uncommon across several amp designs - even the venerable TL-922 shows lower output on 160m than it does on 80m/40m and no doubt if the input power is there then the output is g; /archives//html/Amps/2012-01/msg00197.html (10,363 bytes)
29. Re: [Amps] 4CX1000A (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sat, 28 Jan 2012 18:11:28 +0000; Val, With a tetrode your screen supply must be able to source and sink current wile maintaining regulation of the voltage at the screen. One way of doing this is with a series-regulator and a bleed r; /archives//html/Amps/2012-01/msg00229.html (12,000 bytes)
30. Re: [Amps] HV feed through capacitor (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Fri, 10 Feb 2012 21:18:10 +0000; Larry, At 432MHz you might be able to put a 1/4-wave stub in the HT feed, depending where you put the feedthru in the anode chassis, a 13.5cm length of RG400 (or similar) PTFE coax grounded at the fe; /archives//html/Amps/2012-02/msg00095.html (9,749 bytes)
31. Re: [Amps] More HV feed through capacitor (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sun, 12 Feb 2012 11:11:39 +0000; Hi Larry, Sounds like you have far too much RF reaching the 'cold' end of the inductor and bypass cap. This might be because the inductor is mis-placed on the anode line or because your inductor is t; /archives//html/Amps/2012-02/msg00102.html (13,295 bytes)
32. Re: [Amps] 6kW coax? (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sat, 10 Mar 2012 08:38:22 +0000; So, you're building a transmit combiner for an FM radio transmitter application? You really need a Wilkinson combiner. Al the power levels you're considering I would suggest that you make your own co; /archives//html/Amps/2012-03/msg00104.html (9,446 bytes)
33. Re: [Amps] 6kW Coax (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sun, 11 Mar 2012 09:06:55 +0000; Dave, Some thoughts: 1. your design really should be a full Wilkinson combiner, the output of each LPF should have a 100R across to the output of the other LPF so that you have circa 30dB of isolatio; /archives//html/Amps/2012-03/msg00115.html (9,576 bytes)
34. Re: [Amps] PIV requirement for identical, individual diodes (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Mon, 23 Apr 2012 16:49:43 +0100; Consider a 1000V AC transformer secondary and a simple half-wave rectifier (single diode string) and a capacitor. One one half-cycle the capacitor charges to around 1414V (when the diode forward cond; /archives//html/Amps/2012-04/msg00219.html (9,744 bytes)
35. Re: [Amps] Expert Amps 2K-FA: Any Opinions ? (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Wed, 25 Apr 2012 07:55:05 +0100; I can't speak for the Expert 2K-FA, but we used a 1F-KA in CQWW WPX this year and it performed flawlessly over 48 hours and only tripped out a couple of times when people did something silly like swi; /archives//html/Amps/2012-04/msg00233.html (8,472 bytes)
36. Re: [Amps] Coax for MHV connectors? (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sun, 24 Jun 2012 16:13:07 +0100; I have some SHV and MHV connectors that appear to be designed for RG59 and others that will take RG58. I use the latter with RG400 1/4" PTFE coax on my 8877 amps - over 10 year's service with no issu; /archives//html/Amps/2012-06/msg00399.html (12,926 bytes)
37. Re: [Amps] Coax for MHV connectors? (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Sun, 24 Jun 2012 22:59:16 +0100; Completely agree also, which is why my amps and HT packs use the following arrangements: * RG400 with MHV or SHV connectors for B+ (also provides first ground) * RG58 with TNC connectors for B- (also; /archives//html/Amps/2012-06/msg00404.html (11,030 bytes)
38. Re: [Amps] 8877 Plate Voltage (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Tue, 03 Jul 2012 12:59:29 +0100; I think that if you put a resistor in *series* with the cathode circuit (rather than an attenuator) this would provide NFB... Mike G8TIC _______________________________________________ Amps mailing l; /archives//html/Amps/2012-07/msg00014.html (8,226 bytes)
39. Re: [Amps] 8877 Plate Voltage (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Tue, 03 Jul 2012 19:19:33 +0100; Don, Agreed, I have a single 3-500Z on 6m (very good design from QST 1971) but it had a bit too much gain with 3600V on the tube, so I put 3 x 22R 3W MOF resistor in parallel (giving about 7R at 9W); /archives//html/Amps/2012-07/msg00021.html (9,283 bytes)
40. Re: [Amps] Overdrive protection (score: 1): Author: Mike Tubby <mike@tubby.org>; Date: Thu, 26 Jul 2012 22:47:32 +0100; At the risk of being somewhat controversial ... why are we using ALC these days? I have many radios but currently use an FTDX5000 on 6m and transvert to 2m. None of my tube or solid-state amplifiers; /archives//html/Amps/2012-07/msg00285.html (12,084 bytes)

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