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Re: [Amps] Tube swap

To: "Fuqua, Bill L" <wlfuqu00@uky.edu>, "Karel" <kebenstr@bmts.com>, <donroden@hiwaay.net>, <amps@contesting.com>
Subject: Re: [Amps] Tube swap
From: "Carl" <km1h@jeremy.mv.com>
Date: Tue, 28 Jan 2014 21:14:42 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
For 4-1000's and 30-40 years ago I was using a 50 Ohm Globar when I could find one, or 3 150 Ohm 2W carbons in parallel.

These days 3 of the Ohmite OY series work well or use a bulletproof 25-50W Carborundum type from fleabay. Value can be roughly 50 Ohms +/- 30% or so. If you are pushing the power over 1200-1500W then use strap or small tubing for the inductor.

I test for a parasitic with the GDO in diode mode using a best guess cold test suppressor to locate the real frequency under reduced voltage/power. Then vary the number of turns and/or spacing for no further indication on the GDO meter.

Old tubes will have their parasitic down at low VHF, often right around 6M due to long thin grid leads.

The 572B which can trace its parentage back to the 1939 811 and further back to the late 1920's 211, is around 75 MHz which requires care when using them on 6M. Poor suppressor designs will even smoke on 10M.

Later tubes such as the 4-400A 4-1000, 3-1000Z, 3-500Z, etc are in the 80-150 MHz region and ceramic-metal tubes up in the high VHF range around 150- 200 MHz.

Carl
KM1H



----- Original Message ----- From: "Fuqua, Bill L" <wlfuqu00@uky.edu> To: "Karel" <kebenstr@bmts.com>; <donroden@hiwaay.net>; <amps@contesting.com>
Sent: Tuesday, January 28, 2014 2:48 PM
Subject: Re: [Amps] Tube swap


 Many years ago I got one of his kits for my single 4-1000A amp and the
suppressor went with a bang. I went to normal suppressor. The point is
to simply introduce loss, lower the Q, of VHF parasitic resonances that
can exist in the plate circuit of the amplifier.
73
Bill wa4lav

________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Karel [kebenstr@bmts.com]
Sent: Tuesday, January 28, 2014 2:36 PM
To: donroden@hiwaay.net; amps@contesting.com
Subject: Re: [Amps] Tube swap

Sorry, I met him over internet right after his write-up for AR Handbook was
rejected and that was a long time ago. I brought up his name here once
before and got slapped for it, sorry, I should know by now. I owe cup of
coffee to all. Hopefully we will meet some day.

I still have his suppressor package for two 4-1000A 's to be installed.
Without bringing his name out again, can someone warn me about using it?

I installed his suppressor package on my friend's Henry 2K. It lasted few
years, but his plate transformer croaked recently, I wonder if the
suppressor had anything to do with that.

Karel Ebenstreit, VA3KO

----- Original Message -----
From: <donroden@hiwaay.net>
To: <amps@contesting.com>
Sent: Tuesday, January 28, 2014 10:56 AM
Subject: Re: [Amps] Tube swap


Quoting Karel <kebenstr@bmts.com>:

Hardy,
yes I made myself a Hi-pot tester as well. I forgot the specs, but I
believe I can go up to 20 kV. (It may be one of Richard Measures
designs).




Unwritten Amps Rule # 1

Never invoke the name of the witchdoctor.

You owe everyone a cup of coffee.


Don W4DNR

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