[Amps] Tube swap

[Carl]

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 at uky.edu>
To: "Karel" <kebenstr at bmts.com>; <donroden at hiwaay.net>; 
<amps at 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 at contesting.com] on behalf of Karel 
> [kebenstr at bmts.com]
> Sent: Tuesday, January 28, 2014 2:36 PM
> To: donroden at hiwaay.net; amps at 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 at hiwaay.net>
> To: <amps at contesting.com>
> Sent: Tuesday, January 28, 2014 10:56 AM
> Subject: Re: [Amps] Tube swap
>
>
>> Quoting Karel <kebenstr at 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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>> Amps at contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
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