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381. Re: [Amps] Triode amp. Problem - Low output (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 20 Jan 2008 00:14:44 +0000; Having thought for a few minutes I sat down to type and found Jeff had taken the words out of my mouth. Steve _______________________________________________ Amps mailing list Amps@contesting.com htt; /archives//html/Amps/2008-01/msg00119.html (6,512 bytes)
382. Re: [Amps] EB104 600W HF amplifier questions (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 05 Feb 2008 08:44:38 +0000; The Ameritron circuit has some differences - there are low value gate loading resistors not in EB104, and the feedback resistance is lower. This is going to lower the impedance on the transistor sid; /archives//html/Amps/2008-02/msg00024.html (7,908 bytes)
383. Re: [Amps] Step start (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 05 Feb 2008 21:53:09 +0000; As other replies show, people do it both ways - as have I. One thought relates to the (very rare) situation where there's a fault in the transformer or ht system that results in heavy current draw a; /archives//html/Amps/2008-02/msg00027.html (8,424 bytes)
384. Re: [Amps] Step start (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 07 Feb 2008 22:12:09 +0000; If turn on speed isn't a major issue, I like the idea that the maximum surge at turn on doesn't exceed the maximum peak current during normal operation. That means higher value resistors and longer; /archives//html/Amps/2008-02/msg00042.html (8,232 bytes)
385. Re: [Amps] SWR / forward / reverse power with PIC (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Wed, 20 Feb 2008 17:51:54 +0000; The problem is that you don't know the phase. 2:1 VSWR can be 25 ohms or 100 ohms resistive, or an infinite combination of R+/-jX. When the SWR is high, you can't assume that the forward power the r; /archives//html/Amps/2008-02/msg00136.html (8,827 bytes)
386. Re: [Amps] filament tube life, turn on's and time on target (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sat, 01 Mar 2008 07:43:25 +0000; My main fear would be for the on/off switch. The repeat inrush current could see it off - I'd suggest leaving it on and adding an external boxed switch which could be generously rated and would be e; /archives//html/Amps/2008-03/msg00016.html (6,883 bytes)
387. Re: [Amps] Yaesu Quadra (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 11 Mar 2008 22:22:32 +0000; I think the Quadra uses MRF150s. I've used them in industrial applications where they've survived serious abuse with minimal protection. To be fair to them, they're slower fuses than some finals out; /archives//html/Amps/2008-03/msg00110.html (6,989 bytes)
388. Re: [Amps] UK Transformer manufacturer?? (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 14 Mar 2008 07:37:35 +0000; Harrison and Greenwood in Halifax is one to try. I know they have done HV stuff at multi kW powers, I used them for 440V stuff and was very happy with the prices. Some years ago I used Carnhill in O; /archives//html/Amps/2008-03/msg00117.html (6,795 bytes)
389. Re: [Amps] thyristor controlled soft start? (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 23 Mar 2008 16:56:17 +0000; A comment, in case it's not self evident - a zero crossing switch won't give you a soft start function. It turns on at (almost) zero voltas and stays on until the current falls to zero. To use a tri; /archives//html/Amps/2008-03/msg00223.html (7,510 bytes)
390. Re: [Amps] mounting (UHF) RF powermodules (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 24 Mar 2008 08:23:23 +0000; The substrate in these is alumina, so it's important to follow Hank's comments. Expanding on those, any heatsink you buy will not be flat enough without machining, ideally with a large diameter 'fly; /archives//html/Amps/2008-03/msg00232.html (7,671 bytes)
391. Re: [Amps] mounting (UHF) RF powermodules (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 25 Mar 2008 08:08:18 +0000; The choice probably varies with the machinery available. Up to 6" wide I get things skimmed on a single pass and they give me a low roughness finish. With end cutters or slot drills the finish is us; /archives//html/Amps/2008-03/msg00247.html (8,420 bytes)
392. Re: [Amps] ALS-600 Blowing Out Finals (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 31 Mar 2008 07:51:50 +0100; You might not need to worry about going inside the amplifier. With anything other than the smallest antenna and deafest of rigs, 2, 3 or even 6dB in the rx path is unlikely to make any difference to; /archives//html/Amps/2008-03/msg00379.html (7,487 bytes)
393. Re: [Amps] Dual power supplies in EB104 4X MRF150 design (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 08 Apr 2008 08:05:54 +0100; If the supplies operate with constant current limiting then you can parallel them through diodes - a big bridge rectifier will give you what you need for very little. Add .05 or .1 ohm in series wit; /archives//html/Amps/2008-04/msg00111.html (8,052 bytes)
394. Re: [Amps] Bias Scheme (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 14 Apr 2008 08:01:17 +0100; Is this the sort of thing you're thinking of: http://www.somis.org/D-a-07B.jpg Steve _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com; /archives//html/Amps/2008-04/msg00188.html (7,091 bytes)
395. Re: [Amps] current in primary of microwave oven transformer (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Sun, 27 Apr 2008 07:51:46 +0100; I've been searching (without succss) for a post I remember where someone talked about the ratings on these transformers and how the primary current dropped if you reduced the line voltage a bit. I th; /archives//html/Amps/2008-04/msg00305.html (8,422 bytes)
396. Re: [Amps] Silver Strap (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 11 Jul 2008 08:04:43 +0100; Many years ago there was an article in RF Design magazine that looked at this - the analysis was that if the tarnished surface is higher resistivity than the underlying metal, than the current tends; /archives//html/Amps/2008-07/msg00103.html (8,508 bytes)
397. Re: [Amps] Help with ARRL handbook design 4CX1000A 2m PA (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Wed, 23 Jul 2008 07:22:55 +0100; On the face of it, the anode load impedance is too low. Screen current can be an indicator of loading - what's that running at, and how does it vary as you wind up the drive power? Steve ____________; /archives//html/Amps/2008-07/msg00204.html (8,293 bytes)
398. Re: [Amps] 3-500Z glitch resistor (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 08 Sep 2008 09:13:57 +0100; I like the look of Vishay RCH series or similar (Tyco do an equivalent). The 50W version is rated at 5.5W without heatsink and is specified to handle 2500Vrms (that's 3500V peak) short term overload; /archives//html/Amps/2008-09/msg00042.html (7,081 bytes)
399. Re: [Amps] 3-500Z glitch resistor (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Mon, 08 Sep 2008 15:06:48 +0100; Agreed. One clarification for anyone looking up the Vishay part I mentioned - while they have the same footprint and similar shape to the metal cased resistors, they are totally different inside. The; /archives//html/Amps/2008-09/msg00044.html (7,515 bytes)
400. Re: [Amps] 3-500Z glitch resistor (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Tue, 09 Sep 2008 22:14:22 +0100; A few times I've built in an inch or so of suitably sized bare wire just open between two terminals as a HV fuse. I've yet to have one blow, but shouldn't be any arcing problems if it does happen. St; /archives//html/Amps/2008-09/msg00094.html (8,527 bytes)

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