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121. Re: [Amps] HV MOSFETs for RF (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sat, 13 May 2017 08:52:35 +0100; In terms of damaging the actual gate with overdrive, I think there's no meaningful time limit, it's all but instantaneous if it happens. For the whole device in overload, it depends on the circumstan; /archives//html/Amps/2017-05/msg00123.html (8,505 bytes)
122. Re: [Amps] Stripping Litz (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Tue, 16 May 2017 22:49:20 +0100; The Nitromors paint stripper Chris mentioned earlier *used* to be methylene chloride based, but these days in the EU it's not available to the public and Nitromors has been reformulated with somethin; /archives//html/Amps/2017-05/msg00159.html (7,761 bytes)
123. Re: [Amps] About LP100A (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Mon, 19 Jun 2017 06:57:36 +0100; The MB-1 quotes its performance compared with a Mini Circuits USB power sensor, which itself quotes an uncertainty of up to 7% in power reading. Typically it will be better than that, but 7% is the o; /archives//html/Amps/2017-06/msg00229.html (8,776 bytes)
124. Re: [Amps] ARRL 1987 3CX800 6m amplifier (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Tue, 20 Jun 2017 15:51:56 +0100; There's a single 3CX800 design in the '93 handbook I have (by W1QWJ). Is it likely to be the some one? Any particular features about it? Steve Can anyone help me obtain a copy of the the 3CX800 6m am; /archives//html/Amps/2017-06/msg00242.html (6,607 bytes)
125. Re: [Amps] Solder in pins for fabrication of A 3CX800A7 socket (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Wed, 5 Jul 2017 16:52:15 +0100; I made a homebrew socket that way many years ago. I'm fairly sure the pin size was 1.0mm. I got some sockets which were open both ends so the exact length wasn't important. I'll try to find the lefto; /archives//html/Amps/2017-07/msg00013.html (8,025 bytes)
126. Re: [Amps] Solder in pins for fabrication of A 3CX800A7 socket (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Wed, 5 Jul 2017 16:57:54 +0100; Harwin H3161-05. Intended for 2mm mounting hole so might be usable with a bit of ingenuity. Get them from Mouser or Farnell. Steve BTW, the screen ring from a dismantled 4CX250 base fits the 3CX800 g; /archives//html/Amps/2017-07/msg00014.html (9,049 bytes)
127. [Amps] 3CX800 stray C to chassis? (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Tue, 22 Aug 2017 20:48:26 +0100; Some years ago I measured some valves, including 3CX800. I don't think I have kept the results but the general result was that the C was about twice the data sheet value, and wasn't changed by the me; /archives//html/Amps/2017-08/msg00045.html (7,407 bytes)
128. Re: [Amps] Glitch resistor + fuse? (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sun, 19 Nov 2017 08:58:55 +0000; A triggering circuit such as shown on p4 of: www.qsl.net/g3uvr/4cx250/G4AJW-psu.pdf could do the job. Multiple secondary windings could feed stacked thyristors so no added PSU needed, and an extra on; /archives//html/Amps/2017-11/msg00170.html (9,080 bytes)
129. Re: [Amps] 2M W6PO Amp Cavity Zo calculations (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Wed, 22 Nov 2017 22:42:14 +0000; I think the formula you've used for impedance is for a circular coaxial line. In the amp, the metalwork forming the 'outer' is a rectangle, so much of it is spaced further away from the pipe meaning; /archives//html/Amps/2017-11/msg00184.html (8,496 bytes)
130. Re: [Amps] Low pass filters and saturated operation (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Tue, 2 Jan 2018 09:04:29 +0000; Manfred, Your amplifier reminds me of something I worked on in the 80s, trying to improve efficiency in military manpack transmitters. One approach which was promising came out of an article: F. H. R; /archives//html/Amps/2018-01/msg00011.html (9,123 bytes)
131. Re: [Amps] Looking for service manual (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Mon, 4 Jun 2018 17:20:17 +0100; That's going to be a hot and noisy way of generating power! These amps run class A. On lost-manuals.com there's some info. on the 350L and more info. on others in the range, including 3100L which is; /archives//html/Amps/2018-06/msg00008.html (8,600 bytes)
132. Re: [Amps] 8877 amp- to ground fil ct or not? (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Thu, 7 Jun 2018 14:30:42 +0100; There's no actual need for a CT on the heater transformer winding on an indirectly heated tube. If you connect the cathode to one side of the heater, you certainly don't want to ground the CT on the; /archives//html/Amps/2018-06/msg00016.html (9,035 bytes)
133. Re: [Amps] RX protection scheme, is this sound? (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Thu, 13 Sep 2018 15:43:30 +0100; I think I'd go for higher speed diodes. A professional VLF multicoupler I worked on decades ago used a string of 6 or 8 MUR120 diodes back to back. The number was needed because of extremely high sig; /archives//html/Amps/2018-09/msg00012.html (8,481 bytes)
134. Re: [Amps] Super Cathode Driven Tetrodes (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Fri, 19 Oct 2018 18:04:07 +0100; I don't know if it's exactly what you're thinking of as 'super cathode' but the guy here https://www.tapatalk.com/groups/marc/a-6-meter-400w-linear-t25.html has something along those lines which he s; /archives//html/Amps/2018-10/msg00073.html (7,545 bytes)
135. Re: [Amps] RG-213 Hi pot ? (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Sun, 12 May 2019 18:13:42 +0100; I think 213 will take that easily. It was a while ago, but I'm sure that I couldn't detect any leakage on 213 with my tester maxed out at 16kV. A local 'maker' group used it to repair a 35kV lead on; /archives//html/Amps/2019-05/msg00033.html (7,925 bytes)
136. Re: [Amps] RG-213 Hi pot ? (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Mon, 13 May 2019 15:10:33 +0100; Indeed, other brands give the same number. I wonder if they all measure exactly the same result? If you search for voltage breakdown figures for the polyethelyene dielectric you'll find numbers from; /archives//html/Amps/2019-05/msg00043.html (10,032 bytes)
137. Re: [Amps] HIGH INPUT SWR PROBLEM (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 12 Dec 2019 09:21:12 +0000; I think the GI7 is indirectly heated with a cathode, like 8877. If there's no coupling cap between the cathode and filaments, it shouldn't need a big heavy duty filament choke like you need with 3-50; /archives//html/Amps/2019-12/msg00016.html (10,683 bytes)
138. [Amps] Low efficiency on 160 m (score: 1): Author: Steve <g8gsq72@gmail.com>; Date: Mon, 16 Dec 2019 16:40:42 +0000; From what you describe I think the anode load resistance at the tube is too low. That is not necessarily linked to the Q of the matching network. There are calculators online which will help you calc; /archives//html/Amps/2019-12/msg00032.html (8,455 bytes)
139. Re: [Amps] 3CX-3000A7 at 144 (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 6 Feb 2020 22:48:39 +0000; GS35B, 8877 and the like have separate cathode - they don't need a CT for the B- return. DC switcher supplies work just fine as long as they go into constant current rather than tripping out on overl; /archives//html/Amps/2020-02/msg00062.html (10,118 bytes)
140. Re: [Amps] 3CX3000A7 on 144 MHz (score: 1): Author: Steve Thompson <g8gsq72@gmail.com>; Date: Thu, 6 Feb 2020 22:52:59 +0000; DC switch mode PSU is not good with directly heated valves such as 3CX3000, 3-500Z etc. One end of the filament ends up with different bias to the other so all the emission happens at one end. It mig; /archives//html/Amps/2020-02/msg00063.html (8,393 bytes)

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