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Total 14 documents matching your query.

1. [Amps] Alpha 87a 10 m Mod. (score: 1)
Author: "GEORGE WALLNER" <aa7jv@atlanticbb.net>
Date: Tue, 15 Feb 2011 08:28:47 -0500
G'Day, I have an Alpha 87a which I had for 18 years. We are out in the Bahamas for the ARRL DX contest and I've just discovered that the 10 m band has not been enabled in the amp. (I guess I am a low
/archives//html/Amps/2011-02/msg00114.html (7,151 bytes)

2. Re: [Amps] door knob capacitors (score: 1)
Author: "GEORGE WALLNER" <aa7jv@atlanticbb.net>
Date: Mon, 28 Feb 2011 18:32:00 -0500
Rob, It depends on the capacitor. The ones intended for high RF currents are marked to show the maximum reactive current they can handle. Some time ago I had the same experience as you, with a cap li
/archives//html/Amps/2011-03/msg00002.html (7,607 bytes)

3. Re: [Amps] New Alpha 8410 photos + Video (score: 1)
Author: "GEORGE WALLNER" <aa7jv@atlanticbb.net>
Date: Wed, 09 Mar 2011 12:27:42 -0500
Paul, A cooling fan is very useful in a high power antenna tuner, where heating generally occurs on one component (usually the inductor). The fan moves the air around preventing the development of h
/archives//html/Amps/2011-03/msg00079.html (9,823 bytes)

4. Re: [Amps] copper vs steel /SS /brass conductors in a HF tank circuit (score: 1)
Author: "GEORGE WALLNER" <aa7jv@atlanticbb.net>
Date: Thu, 24 Mar 2011 09:47:26 -0400
Although for practical purposes on HF this is mostly true, there is a difference. Copper oxide is an insulator while silver oxide is a conductor. As the copper oxidizes, the skin current encounters i
/archives//html/Amps/2011-03/msg00182.html (9,373 bytes)

5. Re: [Amps] QRO-PARTS.com very rude behavior (score: 1)
Author: "GEORGE WALLNER" <aa7jv@atlanticbb.net>
Date: Sun, 10 Apr 2011 22:33:14 -0400
I have bought some relays and capacitors from this guy and he was all proper and reliable then. It was some time ago, and he may have gone nuts in the meantime, but when I dealt with him he was OK. G
/archives//html/Amps/2011-04/msg00324.html (7,669 bytes)

6. Re: [Amps] Dummy load varying R (score: 1)
Author: "GeorgeWallner" <aa7jv@atlanticbb.net>
Date: Wed, 08 Jun 2011 13:03:37 -0400
Al, You should measure the dummy load with an impedance analyzer. It may be that the load resistors have some inductance, resulting in the impendance being frequency dependent. High quality dummy loa
/archives//html/Amps/2011-06/msg00105.html (7,602 bytes)

7. Re: [Amps] Cheap auxiliary amp cooling (score: 1)
Author: "GeorgeWallner" <aa7jv@atlanticbb.net>
Date: Fri, 30 Mar 2012 09:12:54 -0400
On Fri, 30 Mar 2012 00:29:21 -0700 <a 250mm (10"!) 12V PC case fan has a Jim, That sounds like a good fan and it will likely prolong the life of you amp. Do not automatically assume, however, that "b
/archives//html/Amps/2012-03/msg00354.html (7,970 bytes)

8. Re: [Amps] Tubes vs. Solid State (was) Expert Amps 2K-FA: Any Opinions ? (score: 1)
Author: "GeorgeWallner" <aa7jv@atlanticbb.net>
Date: Sun, 29 Apr 2012 20:44:10 -0400
I have been using two bridged SG-500 amps for years without trouble. Output is 1000 W on 160, 1100 W from 80 to 15 meters, and 890 W on 12 and 10. (I have modified the T/R control to eliminate the ti
/archives//html/Amps/2012-04/msg00267.html (10,209 bytes)

9. Re: [Amps] Alpha 87A (score: 1)
Author: "GeorgeWallner" <aa7jv@atlanticbb.net>
Date: Mon, 09 Jul 2012 22:59:24 -0400
I have a 1993 vintage Alpha 87A. The only problems I had were with the T/R switching PIN diodes (DPX-X103), which I had to replace three times so far. The amp is getting about 50 hours of use per yea
/archives//html/Amps/2012-07/msg00149.html (8,438 bytes)

10. Re: [Amps] 3 phase power supply? (score: 1)
Author: "GeorgeWallner" <aa7jv@atlanticbb.net>
Date: Sun, 02 Apr 2017 22:49:48 -0400
I used a rotary single-to-3-phase converter for 12 years. (It is not really a 3 phase converter, as the original phase is re-used - and only to phases are added) to power a 2 x GU84B (4X1500B) amplif
/archives//html/Amps/2017-04/msg00009.html (10,160 bytes)

11. Re: [Amps] SS Amps are expensive...why? (score: 1)
Author: GEORGE WALLNER <aa7jv@atlanticbb.net>
Date: Mon, 21 Jan 2019 10:30:34 -0500
I have built my amp from one of the Russian water-cooled kits (eb104.ru). The kit cost about $2100. I had to add a power supply and a few controls, which cost around $400. It was easy and quick. Work
/archives//html/Amps/2019-01/msg00097.html (8,894 bytes)

12. Re: [Amps] 3CX3000A7 on 144 MHz (score: 1)
Author: GEORGE WALLNER <aa7jv@atlanticbb.net>
Date: Sun, 09 Feb 2020 16:54:36 -0500
Conrad, I don't think you should give up on the switching power supply yet. I have recently built a 1.5 kW solid state PA for DXpeditions and because of the weight issues, I had to use a switch mode
/archives//html/Amps/2020-02/msg00090.html (13,309 bytes)

13. Re: [Amps] LDMOS HF amps (score: 1)
Author: GEORGE WALLNER <aa7jv@atlanticbb.net>
Date: Mon, 10 Aug 2020 14:35:28 -0400
Don, I doubt that you will reliably get 1500 W out of a single BLF189 device. I have built three amps with single 188 pallets. With 49 V VDD they had outputs of 860 to 1140 W from 160 to 10 meters. (
/archives//html/Amps/2020-08/msg00040.html (10,494 bytes)

14. Re: [Amps] KPA1500 Efficiency vs. RF-Kit B26 (score: 1)
Author: GEORGE WALLNER <aa7jv@atlanticbb.net>
Date: Fri, 16 Jul 2021 09:45:01 -0400
I have built 8 amplifiers with water cooling. I can testify that it is much more effective than air cooling, and with less noise. There is a much simpler way to do it than shown in the video (althoug
/archives//html/Amps/2021-07/msg00068.html (10,715 bytes)

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