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121. Re: [Amps] Bleeder Resistor Inquiry (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sun, 24 Apr 2005 15:28:26 +0100; I guess it is not sufficiently heatsinked, but you seem to have very little safety margin on what is an important component. I would tend to allow a much greater safety margin than you are. That 225W; /archives//html/Amps/2005-04/msg00475.html (9,286 bytes)
122. Re: [Amps] Resistors (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Mon, 25 Apr 2005 20:30:08 +0100; Just be aware the mean time before failure (MTBF) of small fans is orders of magnitude smaller than most components, and considerably shorter than decent fans. Most PC power supplies have fans with s; /archives//html/Amps/2005-04/msg00533.html (8,672 bytes)
123. Re: [Amps] Resistors (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Mon, 25 Apr 2005 22:42:44 +0100; Ball bearning fans are generally noiser than sleve bearings - at least that was what I found when I looked at replacing the fan on the DC-DC converter some time back on my Sun. That was a real pain,; /archives//html/Amps/2005-04/msg00537.html (9,404 bytes)
124. Re: [Amps] No more HP/Agilent manuals on BAMA (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Mon, 25 Apr 2005 22:35:37 +0100; It is not that. A few days back I contacted Agilent via a web link on their test and measurement page, to ask for permission to put manuals of unsupported equipment and application notes on the web.; /archives//html/Amps/2005-04/msg00543.html (10,061 bytes)
125. Re: [Amps] No more HP/Agilent manuals on BAMA (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Tue, 26 Apr 2005 22:55:12 +0100; I think it might well backfire on them. I asked Agilent for permission and will be given it for obsolete products. I just needed to sign something and are waiting confirmation of permission. This is; /archives//html/Amps/2005-04/msg00561.html (9,325 bytes)
126. Re: [Amps] ATS website (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Wed, 27 Apr 2005 00:13:54 +0100; I did not look over it much, but did not like the bit at the bottom about the user of "Copperplate Gothic Lite" font. Is that really necessary - not everyone uses Windoze you know. Last time I looked; /archives//html/Amps/2005-04/msg00564.html (9,626 bytes)
127. Re: [Amps] eBay (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Wed, 04 May 2005 19:31:01 +0100; In theory no. But of course there are employees in eBay who do. There are rules about them not bidding within the last day or so (check the site), but how can you tell. You are far better off putting; /archives//html/Amps/2005-05/msg00064.html (8,689 bytes)
128. [Amps] Receiving lower spec items than ordred. (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Fri, 06 May 2005 01:11:30 +0100; I have on two occasions been troubled when buying surplus electronic items that in both cases have been mis-advertised. Do others get this problem, and how do you resolve it? The first was here on th; /archives//html/Amps/2005-05/msg00092.html (9,826 bytes)
129. [Amps] Vector voltmeter on eBay - complex impedance. (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 14 May 2005 03:17:23 +0100; Some time back there was a discussion on here about measuring complex (R + jX) impedance. I mentioned a vector voltmeter is a way I have done it in the past. There is one on eBay at the minute http:/; /archives//html/Amps/2005-05/msg00166.html (9,097 bytes)
130. Re: [Amps] Vector Voltmeter (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 14 May 2005 22:11:40 +0100; Although your method assumes the couplers are perfect, which is not so. They will not have infinite directivity. A lot of the sophistication of modern vector network analysers is in the removing thes; /archives//html/Amps/2005-05/msg00174.html (8,995 bytes)
131. Re: [Amps] [AMPS] How to start? (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sun, 15 May 2005 01:28:47 +0100; A complete data sheet on the tube is on my web site - see http://www.g8wrb.org/data/Eimac/4CX250B.pdf At UHF, it needs to be lower than 6V. At 432MHz it should be 5.5V. 375V is a bit high on the scre; /archives//html/Amps/2005-05/msg00177.html (8,883 bytes)
132. Re: [Amps] Amp using 4-400 tubes (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sun, 15 May 2005 01:32:07 +0100; Take a look at http://www.g8wrb.org/tetrodes.shtml where you will find links to Eimac and RCA data sheets on the 4-400A, IF that is the tube you have. I don't know the 4-400, but one might exist. --; /archives//html/Amps/2005-05/msg00178.html (7,227 bytes)
133. Re: [Amps] Dummy Load (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Wed, 25 May 2005 23:17:05 +0100; If you do build an attenuator, I would suggest using the minimum attenuaton you can get away with using the lower quality resistors, and making the last 6~10 dB or so from a decent quality attenuator; /archives//html/Amps/2005-05/msg00296.html (8,443 bytes)
134. Re: [Amps] questions on my tranformer test (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Tue, 14 Jun 2005 07:53:17 +0100; Hi, Can you not infer the average temperature rise by measures the DC resistance cold and then after some time the DC resistance when hot? The temperature coefficient of copper will give you the mean; /archives//html/Amps/2005-06/msg00094.html (9,373 bytes)
135. Re: [Amps] HV Switch Mode Power Supplies (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Wed, 22 Jun 2005 09:59:11 +0100; There was a design for one several years ago in QEX (the ARRL's technical journal). There are also some corrections to it. I can't recall the power rating, but it was about 2 kW - too small for what; /archives//html/Amps/2005-06/msg00173.html (9,183 bytes)
136. Re: [Amps] HV Switch Mode Power Supplies (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Fri, 24 Jun 2005 00:39:13 +0100; But look at the regulation (or lack of). http://wattsunlimited.com/_wsn/page3.html -- David Kirkby, G8WRB Please check out http://www.g8wrb.org/ of if you live in Essex http://www.southminster-branch; /archives//html/Amps/2005-06/msg00214.html (9,038 bytes)
137. [Amps] Cheap network analyser on eBay (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 25 Jun 2005 00:44:47 +0100; There is on eBay at the minute what appears to be a very cheap HP network analyser, which I guess would double as a cheap power meter too. The "buy it now" is under $75. Cheaper than the amateurish i; /archives//html/Amps/2005-06/msg00219.html (8,244 bytes)
138. Re: [Amps] HV Switch Mode Power Supplies (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 25 Jun 2005 01:16:56 +0100; I would have thought that cause serious non-linearity problems on SSB. Having gone to a switch mode design, I would have thought they used some feedback to keep the voltage constant. But it seems not; /archives//html/Amps/2005-06/msg00221.html (10,986 bytes)
139. Re: [Amps] HV Switch Mode Power Supplies (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 25 Jun 2005 16:41:32 +0100; Did he make measurements of IMD? I'm surprised the amp did not weigh more than that, but anyway, that is not the main issue. The graph of regulation (which does not state if this is typical, or guara; /archives//html/Amps/2005-06/msg00230.html (15,079 bytes)
140. Re: [Amps] Cheap network analyser on eBay (score: 1): Author: David Kirkby <david.kirkby@onetel.net>; Date: Sat, 25 Jun 2005 17:23:21 +0100; It's clearly going to be some work to do a full S-parameter characterisation, but for simple things like analysing antennas, I think all you would need is a couple of directional couplers and of cour; /archives//html/Amps/2005-06/msg00232.html (14,654 bytes)

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