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261. Re: [Amps] HV supply question (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Wed, 8 Apr 2009 17:40:14 +0100
The HV-minus lead (American: B-minus) is often allowed to go a little *below* chassis ground potential to permit safe metering of the anode current. In a triode amplifier, the grid current can also b
/archives//html/Amps/2009-04/msg00085.html (7,819 bytes)

262. Re: [Amps] RE K2RIW 2 Meter Amp. (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Tue, 21 Apr 2009 07:20:17 +0100
Absolutely right - the K2RIW amplifier for 432MHz was a revolution in VHF/UHF amp design and construction. Everything about it was new, different and better. But for the record, did you guys really m
/archives//html/Amps/2009-04/msg00175.html (7,912 bytes)

263. Re: [Amps] RE K2RIW 2 Meter Amp. (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Tue, 21 Apr 2009 19:39:52 +0100
There were many push-pull 4CX250B designs around for 2m at that time, but K2RIW seemed to be the first to tame the parallel connection using a wide stripline. That was a half-wave line for 432MHz in
/archives//html/Amps/2009-04/msg00187.html (10,417 bytes)

264. Re: [Amps] RE K2RIW 2 Meter Amp. (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Tue, 21 Apr 2009 22:02:42 +0100
Good grief, no! I just knew a few people, including Fred W2GN, and needed to find out some history for the DX Book. But a genuine "2 meter K2RIW" remains elusive... -- 73 from Ian GM3SEK ____________
/archives//html/Amps/2009-04/msg00193.html (8,626 bytes)

265. Re: [Amps] High SWR (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 25 Apr 2009 07:39:18 +0100
None. Improper installation can allow RF currents to flow on the outside of the feedline and/or the boom. This will change the radiation pattern, filling in nulls and possibly reducing the front/back
/archives//html/Amps/2009-04/msg00330.html (9,414 bytes)

266. Re: [Amps] High SWR (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 25 Apr 2009 10:48:20 +0100
(Pause to reload coffee pot...) Let's assume that the yagi would have a low VSWR if the coax feedline is installed correctly. If we somehow install the yagi and its feedline in a way that makes curre
/archives//html/Amps/2009-04/msg00333.html (10,616 bytes)

267. Re: [Amps] 6 meter amp (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Tue, 23 Jun 2009 16:53:04 +0100
Classic designs by W2GN (ARCOS) for 220, 2m and 6m http://www.newsvhf.com/w2gn.html -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek _______________________________________________ Amps mailing
/archives//html/Amps/2009-06/msg00099.html (6,850 bytes)

268. Re: [Amps] 3CX800 Oscillation (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Fri, 17 Jul 2009 07:17:09 +0100
How are you grounding the grid? If you are using contact fingers onto the grid ring (rather than the pins in the base) the 3CX800 should be stable up to UHF - unless there is some major external feed
/archives//html/Amps/2009-07/msg00204.html (7,344 bytes)

269. Re: [Amps] grounding grids (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Thu, 30 Jul 2009 08:15:14 +0100
It was claimed (here on AMPS a few years ago, if I recall correctly) that Heath came under heavy pressure from Eimac to use that capacitor-RFC circuit. Personally I agree with Joe that all the claime
/archives//html/Amps/2009-07/msg00397.html (10,669 bytes)

270. Re: [Amps] Cleaning Cigarette tar....? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 1 Aug 2009 07:35:13 +0100
Use a foaming cleaner that has been specifically formulated for the electronics industry, so it (probably) won't attack most common materials used in electronic equipment. (Foaming shower cleaner, on
/archives//html/Amps/2009-07/msg00466.html (9,878 bytes)

271. Re: [Amps] Asynchronous coax matching transformer (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 1 Aug 2009 07:38:38 +0100
http://www.tuc.nrao.edu/~demerson/twelfth/twelfth.htm By paralleling two lengths of 50 or 75 ohm line, it can also match to 25 or 37.5 ohms; or to even lower impedances by paralleling three lengths o
/archives//html/Amps/2009-07/msg00467.html (8,082 bytes)

272. Re: [Amps] Asynchronous coax matching transformer (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 1 Aug 2009 20:30:13 +0100
Thanks to Larry and Gerald for pointing out that the series method is much more versatile than I had imagined. Greg Ordy's program takes care of that, and also says when a match is not possible. Conn
/archives//html/Amps/2009-08/msg00009.html (9,184 bytes)

273. Re: [Amps] Manganin RF choke? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sun, 9 Aug 2009 19:50:10 +0100
Resistance in the choke would not entirely replace the surge limiting resistor in the power supply. If the amp and PSU were two physically separate units, locating the surge limiting resistance in th
/archives//html/Amps/2009-08/msg00165.html (9,654 bytes)

274. Re: [Amps] 3-500Z viable after long storage? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Mon, 10 Aug 2009 08:59:46 +0100
The following procedure came directly from a former Eimac tube designer, who was with the company when they were still manufacturing glass tubes. <quote> ** If a tube was last used years ago, or was
/archives//html/Amps/2009-08/msg00208.html (9,228 bytes)

275. Re: [Amps] Carbon film or metal oxide film resistors for low-power RF circuits? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Thu, 13 Aug 2009 07:27:30 +0100
Carbon *composition* resistors are notorious for changing value over the long term (even unopened NOS). For all practical purposes they are obsolete. Carbon film resistors are cut in a spiral the sam
/archives//html/Amps/2009-08/msg00303.html (10,374 bytes)

276. Re: [Amps] RF Choke At Amp Output ?? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Thu, 20 Aug 2009 07:27:36 +0100
A shorted quarter-wave coaxial stub would make a more robust safety 'crowbar' than a choke wound with fine wire, and it also attenuates the 2nd harmonic in the FM band. -- 73 from Ian GM3SEK http://w
/archives//html/Amps/2009-08/msg00364.html (8,428 bytes)

277. Re: [Amps] RF Choke At Amp Output ?? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 22 Aug 2009 07:26:19 +0100
Agreed - a resistor provides no protection against failure of the HVDC blocking capacitor. That's certainly the idea... but how many of us have ever confirmed that our "safety" chokes could really do
/archives//html/Amps/2009-08/msg00381.html (8,846 bytes)

278. Re: [Amps] 4CX1600U - too good to be true? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Wed, 26 Aug 2009 22:02:05 +0100
To be clear, the 4CX1600U is completely unrelated to the 4CX1600B. It is a totally different tube requiring different DC operating conditions, and intended for use in cathode-driven cavity amplifiers
/archives//html/Amps/2009-08/msg00514.html (8,930 bytes)

279. Re: [Amps] STP5NB100 - MOSFET from where? (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Tue, 15 Sep 2009 11:00:59 +0100
That's correct... just as it says on page 48 of the Tetrode Boards manual :-) -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek _______________________________________________ Amps mailing list Am
/archives//html/Amps/2009-09/msg00193.html (7,549 bytes)

280. Re: [Amps] PSU design question (score: 1)
Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>
Date: Sat, 7 Nov 2009 17:20:04 +0000
My pleasure :-) Metering circuits were outside the scope of the Radcom series, which was only about HV power supplies. My approach to metering is fully explained in the Triode Board User Manual: http
/archives//html/Amps/2009-11/msg00107.html (11,161 bytes)

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