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41. Re: [Amps] WTB Supplemental Question: E.F. Johnson socket #124-311-100fo (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Tue, 03 Apr 2012 22:36:23 +0100; I have a vague memory that the 3CX800 grid and 4CX250 screen are the same diameter - or close enough that a screen connector from a '250 socket will fit, for a low cost option. Steve ________________; /archives//html/Amps/2012-04/msg00044.html (8,332 bytes)
42. Re: [Amps] LDMOS Solid State Amplifiers (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Mon, 07 May 2012 08:29:00 +0100; I think the underlying point is that IMDs add together as voltages not powers so you have to work back to the levels in Volts, not power, in order to can see the relative contributions and the total; /archives//html/Amps/2012-05/msg00228.html (7,675 bytes)
43. Re: [Amps] Blower recommendations 8877 amp. (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 09 Aug 2012 08:28:54 +0100; I'll second that. DC driven also means easy speed control if you want it. Steve _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailm; /archives//html/Amps/2012-08/msg00144.html (7,908 bytes)
44. Re: [Amps] current threads about silver solder and resoldering (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Tue, 28 Aug 2012 15:00:57 +0100; For hi-rel and space applications double soldering is done where there's gold in the mix. Above a certain concentration gold and solder can go brittle with time and/or heat - I've seen it in old soli; /archives//html/Amps/2012-08/msg00500.html (8,720 bytes)
45. Re: [Amps] SS Amp questions (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Mon, 10 Sep 2012 09:41:05 +0100; Manfred has said most of what I was going to say. I'd add a couple more comments. RF power fets don't have quite the uniformity of characteristics that switching fets have. In particular, threshold v; /archives//html/Amps/2012-09/msg00145.html (8,413 bytes)
46. Re: [Amps] This Month's QST Article (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Wed, 26 Sep 2012 08:19:17 +0100; I haven't seen QST but have built some 1kW amps using the current crop of LDMOS transistors - several for 144MHz, 50odd for 200MHz pulsed applications. 27dB gain - yes, that's what you get. I haven't; /archives//html/Amps/2012-09/msg00296.html (7,736 bytes)
47. Re: [Amps] This Month's QST Article (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Wed, 26 Sep 2012 14:45:35 +0100; Yes, I should have added that. I agree, 750-800W pep max for reasonable linear operation. Steve I would add that the IMD is not great and would ask people to use it at 800w max , but I'm sure I won't; /archives//html/Amps/2012-09/msg00300.html (7,799 bytes)
48. Re: [Amps] AL-1500 filter caps (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 18 Oct 2012 08:20:45 +0100; Have they changed the resistors to ones properly rated for the job? It's certainly an efficient spares service, but a shame they designed something with a fundamental flaw built in. Steve A friend's; /archives//html/Amps/2012-10/msg00101.html (7,886 bytes)
49. Re: [Amps] Microwave Oven Power Transformer (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Fri, 16 Nov 2012 09:39:21 +0000; Various thoughts, in no particular order. Typically, the secondary gives 2.2-2.5kV across the caps with FWB. I've played with a handful of them. Hipot testing the secondary with the wire to the frame; /archives//html/Amps/2012-11/msg00104.html (8,296 bytes)
50. Re: [Amps] Microwave Oven Power Transformer (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sun, 25 Nov 2012 21:29:07 +0000; Doubling up does solve the flux problem, but means a lot of resistance - MOTs usually start with high Rs for their rating. More transformers in parallel can compensate so size is then the downside. N; /archives//html/Amps/2012-11/msg00166.html (9,111 bytes)
51. Re: [Amps] Microwave Oven Power Transformer (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Tue, 04 Dec 2012 08:21:25 +0000; I can't pretend my comment came from such detailed understanding or analysis - I just wound the primary volts down until the (no load) primary current dropped noticeably and the core didn't fry witho; /archives//html/Amps/2012-12/msg00013.html (8,329 bytes)
52. Re: [Amps] Eimac AS-47 2m 8877 amp? (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Fri, 18 Jan 2013 19:18:59 +0000; Steve Hello, Has anyone here ever built such an amp? I'd like to see pictures of its internals, if possible. I am not sure how C5 connects to ground, seems like the brass tube would fit and move dire; /archives//html/Amps/2013-01/msg00107.html (8,201 bytes)
53. Re: [Amps] LDMOS PAs and high power low pass filters/diplexers (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Wed, 06 Feb 2013 12:03:39 +0000; You can't have too much heatsink, only too little - same as with airflow for big valves. Even a large heatsink is useless if the thermal contact between it and the spreader is no good. Concentrate on; /archives//html/Amps/2013-02/msg00055.html (8,355 bytes)
54. Re: [Amps] SHV connectors... (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sat, 16 Feb 2013 08:39:50 +0000; I think the 1900V rating applies under circumstances which are very different from using the cable with SHV connectors. The breakdown voltage for polyethylene is something around 20kV/mm. I have test; /archives//html/Amps/2013-02/msg00130.html (8,042 bytes)
55. Re: [Amps] Heatsinks for SSPAs (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Mon, 04 Mar 2013 21:18:23 +0000; Many years ago I visited the Philips (as it was then) factory in Nijmegen. Their production test fixtures for parts like BLF278 and BLF378 had cutouts under the transistor flange so that cooling wate; /archives//html/Amps/2013-03/msg00059.html (8,579 bytes)
56. [Amps] Expert 1k amp (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 07 Mar 2013 08:50:10 +0000; Yesterday I did some minor repairs to a friend's amp - resoldering joints on the current sensing resistor. Looking at the circuits later I noticed that the main supply voltage is regulated by having; /archives//html/Amps/2013-03/msg00073.html (6,873 bytes)
57. Re: [Amps] Expert 1k amp (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Thu, 07 Mar 2013 10:21:43 +0000; The diagrams I looked at came from here: ok1hra.nagano.cz/Expert_Schematic_diagramsII.pdf I can't see any mains filtering, and no power factor correction. The repairs on my friend's amp required no m; /archives//html/Amps/2013-03/msg00075.html (8,191 bytes)
58. Re: [Amps] Power factor correction on tube amps (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 07 Mar 2013 22:05:43 +0000; I found these fairly simple guidance notes from the power supply manufacturer's association: www.epsma.org/pdf/PFC%20Guide_November%202010.pdf which say that most equipment over 75W has to meet specs; /archives//html/Amps/2013-03/msg00082.html (7,603 bytes)
59. Re: [Amps] Expert 1k amp (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 07 Mar 2013 22:17:28 +0000; Thanks for the info. Paul, very interesting. The supply voltage drops from 40odd to 30odd volts with power reduction so I'm guessing the current drops 20% or so, with dissipation roughly halving. Ste; /archives//html/Amps/2013-03/msg00083.html (8,784 bytes)
60. [Amps] rms Volts, Amps and Watts (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sat, 09 Mar 2013 22:12:57 +0000; Power meters measure RMS current and RMS voltage. But Watts RMS only equal V rms x I rms when the power factor is 1. For lower power factors you pay for Vrms x I rms which is greater than Wrms. Sorr; /archives//html/Amps/2013-03/msg00118.html (8,407 bytes)

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