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181. [Amps] Fake transistors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 31 Dec 2013 12:38:19 +0100; It's not only from eBay and amateurs that get caught. Plessey Semiconductors stopped making the SL521 logarithmic amplifier in 1997 (having made it large quantities from 1963!) and a South African ma; /archives//html/Amps/2013-12/msg00220.html (7,506 bytes)
182. Re: [Amps] FW: negative screen current (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 31 Dec 2013 12:46:35 +0100; More than 50years ago, I was taught that it is very bad practice to rely on mounting screws to ground a PCB. You should always use a lead, or if necessary for RF, a suitable grounding strap. Especial; /archives//html/Amps/2013-12/msg00221.html (10,974 bytes)
183. Re: [Amps] negative screen current (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 31 Dec 2013 13:15:06 +0100; OK, so negative screen current is caused by secondary emission from the screen grid. According to Terman, "With surfaces treated in such a way as to enhance secondary emission, as many as ten seconda; /archives//html/Amps/2013-12/msg00222.html (9,010 bytes)
184. Re: [Amps] Russian HV Supply Capacitors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Thu, 09 Jan 2014 20:33:37 +0100; You need to know the ripple current rating. SCR commutation capacitors have the sort of ratings you need. There are a lot of physically small, high capacity (20+mFd) caps at 2.5 or 3kV around meant f; /archives//html/Amps/2014-01/msg00037.html (8,308 bytes)
185. Re: [Amps] Russian HV Supply Capacitors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Fri, 10 Jan 2014 11:16:32 +0100; I agree with Carl here. I had a string of 220mFd 500 volt electrolytics meant for photoflash work: even in a choke input filter, they didn't last very long before squirting stuff out of the vent hole; /archives//html/Amps/2014-01/msg00047.html (9,125 bytes)
186. Re: [Amps] Russian HV Supply Capacitors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Sun, 12 Jan 2014 21:41:31 +0100; It would seem that there are a number of us who are very dubious about such capacitors for this application. In view of the price, I figure that because of both that and the lack of data on ripple cu; /archives//html/Amps/2014-01/msg00052.html (8,242 bytes)
187. Re: [Amps] Russian HV Supply Capacitors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Mon, 13 Jan 2014 00:05:03 +0100; I use a 5kV ionisation tester to check things. Cost $9 (whoops - heavy money!!) but needed a rebuild - but the case and PSU would have done for a 160m AM tx if it wasn't restorable! Ideal for checkin; /archives//html/Amps/2014-01/msg00055.html (8,318 bytes)
188. Re: [Amps] Russian HV Supply Capacitors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 14 Jan 2014 11:02:28 +0100; Just over 40 years ago, I was working on the design of a 400 watt marine tx, so needed a 1kV 1 amp supply. I was using a straight transformer - bridge rectifier - electrolytic stack. Investigating th; /archives//html/Amps/2014-01/msg00059.html (16,340 bytes)
189. Re: [Amps] Permeability tuned tuning coils, with taps? (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Wed, 15 Jan 2014 11:22:05 +0100; I vaguely remember seeing a 4 channel, 2-10 MHz, 100 watt output commercial amplifier using three 'instant heat' 6146s (actually QZ06-20)which used permeability tuning on the PA coils. I think the co; /archives//html/Amps/2014-01/msg00062.html (9,324 bytes)
190. Re: [Amps] Permeability tuned tuning coils, with taps? (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Thu, 16 Jan 2014 00:23:34 +0100; Bill, The OP's licence allows 400 watts PEP at the antenna on most bands - exceptions are parts of 160 above 1850kHz, 70MHz and some higher bands. NOTE: 10 MHz allows 400 watts PEP! == Message Receiv; /archives//html/Amps/2014-01/msg00068.html (11,237 bytes)
191. Re: [Amps] high power dual directional coupler (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Thu, 16 Jan 2014 11:25:04 +0100; In the 1963 IEE Convention on HF Communication conference papers, there is a paper on 'A Wideband Directional Coupler for Power Measurements in the HF Band. Designed for 1.6 to 27.5MHz, it is a theor; /archives//html/Amps/2014-01/msg00073.html (8,311 bytes)
192. Re: [Amps] Sampling RF at input and output of an amplifier (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Thu, 16 Jan 2014 20:49:17 +0100; One of the WW2 IFF test sets for VHF IFF had a PL259/SO239 TEE that did precisely that. An M35X (X = something or other) 73 Peter G3RZP == Message Received: Jan 16 2014, 07:00 PM From: "Karin Anne Jo; /archives//html/Amps/2014-01/msg00080.html (9,673 bytes)
193. Re: [Amps] Building an Amp 101 (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Fri, 17 Jan 2014 18:01:07 +0100; Jerry, You do need some tools. An engineers square with ruler, a scriber, a centre punch and a hammer, drills - and don't get cheap ones, Sears used to and maybe still do some good German ones - a fe; /archives//html/Amps/2014-01/msg00102.html (10,684 bytes)
194. Re: [Amps] Building an Amp 101 (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Sat, 18 Jan 2014 08:44:54 +0100; Although a good sized shear is nice, you do need to watch the Chinese ones. Mine came with no guard so you could slide the metal sheet in and then your fingers. Having stood on the treadle with one f; /archives//html/Amps/2014-01/msg00122.html (8,736 bytes)
195. Re: [Amps] 811H pops fuses (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Sun, 19 Jan 2014 00:00:39 +0100; Pull all the tubes and see what happens. Take due precautions to make sure the HV is discharged - I pull the power lead out of the wall, give the HV a minute or so to discharge, then put a resistor o; /archives//html/Amps/2014-01/msg00149.html (7,821 bytes)
196. Re: [Amps] Building an Amp 101 (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Sun, 19 Jan 2014 17:07:26 +0100; After doing some simple calculations, I think you only need 6 positions on the tank switch. 160, 80, 40, 30/20, 17/15, 12/10. The Acom 1500 uses 7 positions as 160, 80, 40/30, 20, 17/15, 12/10, 6. Bu; /archives//html/Amps/2014-01/msg00158.html (8,967 bytes)
197. Re: [Amps] Newbie (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 21 Jan 2014 09:59:52 +0100; Also get some of the ARRL handbooks for the last few years - your library may be able to do that, and there's probably a local ham or two who have a selection. 73 Peter G3RZP ________________________; /archives//html/Amps/2014-01/msg00203.html (6,669 bytes)
198. Re: [Amps] 381LR Cornell Dubilier date codes? (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Tue, 21 Jan 2014 16:43:29 +0100; My guess would be 1982 week 18, but it could be week 18 2004. 73 Peter G3RZP == Message Received: Jan 21 2014, 02:21 PM From: "Alan Ibbetson" <alan@g3xaq.net> To: amps@contesting.com Cc: Subject: [Am; /archives//html/Amps/2014-01/msg00206.html (7,414 bytes)
199. Re: [Amps] anode connectors (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Wed, 22 Jan 2014 08:31:56 +0100; The places I've seen porcelain caps used were ones where tubes were exposed, and the porcelain caps were for safety reasons. How much you need to dissipate is an interesting question, since conductio; /archives//html/Amps/2014-01/msg00216.html (9,190 bytes)
200. Re: [Amps] Weird tubes in an amplifier (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Wed, 29 Jan 2014 10:53:02 +0100; Before TV, it was used a lot as the video driver in various WW2 radars. The Tung Sol data sheet issue 1 is February 1942: it was made by RCA, GE and Tung-Sol and possibly KenRad. It was also manufact; /archives//html/Amps/2014-01/msg00293.html (8,672 bytes)

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