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121. Re: [Amps] plexiglas isolation in coils (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Thu, 27 Jul 2006 09:08:00 +0100; The microwave oven test is good for sorting materials into ranking order. Based on the temperature rise that you observe (with similar samples, heated together in the same average field strength) you; /archives//html/Amps/2006-07/msg01213.html (8,891 bytes)
122. Re: [Amps] Arc distance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Fri, 28 Jul 2006 20:29:37 +0100; There are two long-term sources of gas in tubes. One is a leak to atmosphere, and the other is "outgassing" of structural materials. Leaks can be large or small, but they are always a one-way trip, w; /archives//html/Amps/2006-07/msg01254.html (12,549 bytes)
123. Re: [Amps] Arc distance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 29 Jul 2006 14:11:44 +0100; Just to clear up a few details, then... The bake-out can only be done *after* having pumped the tube down to quite a good vacuum. If it was done at atmospheric pressure, all the metals would oxidize!; /archives//html/Amps/2006-07/msg01283.html (13,339 bytes)
124. Re: [Amps] Arc distance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 29 Jul 2006 17:28:12 +0100; What is your reference for the behavior of various getter materials as a function of temperature, Will? "Full of hydrogen gas" would be an exaggeration, but I see the point you're making. -- 73 from; /archives//html/Amps/2006-07/msg01306.html (10,576 bytes)
125. Re: [Amps] Arc distance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 29 Jul 2006 22:26:38 +0100; Sorry, I don't have that book of Terman's, only the other one. However, the chapter on Getters in Kohl's 'Handbook of Materials and Techniques for Vacuum Devices' confirms the same general picture, a; /archives//html/Amps/2006-07/msg01325.html (11,824 bytes)
126. Re: [Amps] Pre-heating of tubes (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 29 Jul 2006 23:12:01 +0100; It depends how careful you want to be. The full routine recommended by the Eimac tube designer was: a. Bring the filament up to rated voltage slowly, to limit the shock of turning it on. b. Then aft; /archives//html/Amps/2006-07/msg01328.html (12,416 bytes)
127. [Amps] Mouser or Digi-Key BOM for Tetrode Boards? (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sun, 30 Jul 2006 08:30:24 +0100; Does anyone in the USA have a bill of materials for ordering parts from Mouser and/or Digi-Key for my Tetrode Boards, please? -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ____________________; /archives//html/Amps/2006-07/msg01355.html (6,608 bytes)
128. Re: [Amps] Limits of a Power transformer (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Wed, 2 Aug 2006 10:50:41 +0100; Don't forget the effect of primary resistance. It may seem low (often so low that it's difficult to measure accurately) but the value has to be multiplied by (turns ratio)-squared, and then added to; /archives//html/Amps/2006-08/msg00038.html (8,966 bytes)
129. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 5 Aug 2006 08:06:39 +0100; In straight-through VHF/UHF amplifiers that have the grid ring grounded through a finger-stock collet, the 8877 is stable up to at least 432MHz. With a tuned circuit at both input and output, those a; /archives//html/Amps/2006-08/msg00172.html (9,615 bytes)
130. Re: [Amps] GS-35B on 6 meters (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 5 Aug 2006 08:27:35 +0100; People do that... but just because you can remove the anode cooler of a GS35/31 or GI-7, that doesn't make it a good idea. Remember that up to 1500W of heat has to flow through the interface between; /archives//html/Amps/2006-08/msg00173.html (8,734 bytes)
131. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sat, 5 Aug 2006 11:19:14 +0100; Has anybody published a detailed analysis of how a GDO works? Bill gave a good description yesterday, but I mean something that goes deeper and includes some verifiable math. 'Coefficient of mutual i; /archives//html/Amps/2006-08/msg00178.html (10,678 bytes)
132. Re: [Amps] Options (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sun, 6 Aug 2006 10:13:58 +0100; The 8930 is a 'special' version of the 4CX250R with an over-sized 350W anode cooler. Steve is right - your HV transformers are not well suited to the tubes, so think about them separately. Other majo; /archives//html/Amps/2006-08/msg00203.html (9,790 bytes)
133. Re: [Amps] GS-35B on 6 meters (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Sun, 6 Aug 2006 17:40:58 +0100; Apologies, Bill. I see what you mean now. The potential problem is only when a strap or a plate line is sandwiched *between* the tube and the cooler -- 73 from Ian GM3SEK ___________________________; /archives//html/Amps/2006-08/msg00212.html (8,688 bytes)
134. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Mon, 7 Aug 2006 10:09:32 +0100; Surely the important thing is whether there is a CIRCUIT, in the strict literal sense of that word - a closed loop around which current can circ-u-late. Without a closed loop, no current can flow fro; /archives//html/Amps/2006-08/msg00244.html (10,414 bytes)
135. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Mon, 7 Aug 2006 13:43:51 +0100; I'm saying you can't even have an L-C resonance without a circuit - literally a closed, hard-wired loop. For example, if you simply connect an L and a C in series, with opposite ends floating, you do; /archives//html/Amps/2006-08/msg00248.html (9,208 bytes)
136. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Mon, 7 Aug 2006 16:53:58 +0100; Sorry, wondrousness is not a valid SI unit. I thought the intention of a measurement was to quantify something. Probably not - but the instrument never tells you what that dip MEANS, and with a dipme; /archives//html/Amps/2006-08/msg00260.html (9,521 bytes)
137. Re: [Amps] grid resonance (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Mon, 7 Aug 2006 18:27:07 +0100; In between - not long enough to be a significant fraction of a wavelength, but end-loaded by capacitance to other parts of the tube. As I said in the previous posting: "The grid in a "grounded grid"; /archives//html/Amps/2006-08/msg00265.html (11,168 bytes)
138. Re: [Amps] GS-35B on 6 meters (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Tue, 8 Aug 2006 06:19:28 +0100; Sorry, my mistake - Tony's perfectly right. It's only the GS31 and GI7 that would allow a lug or a stripline to be sandwiched between the anode and its cooler. -- 73 from Ian GM3SEK http://www.ifwtec; /archives//html/Amps/2006-08/msg00276.html (8,474 bytes)
139. Re: [Amps] Spam from Members of this List ... (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Wed, 9 Aug 2006 08:22:29 +0100; Agreed. A large chunk of this problem is the creeping habit of sending an individual 'courtesy' copy of a reply that is also being posted to the list. Many kinds of e-mail software do this by default; /archives//html/Amps/2006-08/msg00327.html (10,179 bytes)
140. Re: [Amps] Tuned Input - IMD and efficiency (score: 1): Author: Ian White GM3SEK <gm3sek@ifwtech.co.uk>; Date: Thu, 10 Aug 2006 19:51:01 +0100; Possibly this is because the pioneering work on the linearity of tube amplifiers was done in the 1950s and even earlier. Spectrum analysers were in their infancy, and IMD measurements were slow and d; /archives//html/Amps/2006-08/msg00386.html (11,591 bytes)

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