>
>
>On Sat, 12 Sep 98 18:44:33 -0800 Rich Measures <measures@vc.net> writes:
>>
>>>
>>>
>>>On Fri, 11 Sep 98 13:23:18 -0800 Rich Measures <measures@vc.net>
>>writes:
>>>>>
>>>>> > If you are interested, I can mail you a copy
>>>>> of a schematic with needed changes.
>>>>>
>>>>>I tried them...they dont work.
>>>>
>>>>You tried the RCA Transmitting Tube Manual recommended cathode
>>>>feedback resistors and they don't work?
>>>
>>>
>>>That is correct....they do not work in the NCL2000's I tried and the
>>amp
>>>goes wild on 10/15M. The problem can be traced to the marginal screen
>>>bypassing that is used, only 500pf per pin coupled with the 2W
>>cathode
>>>resistor lead lengths.
>>
>>Are you saying that was with resistors supplied by us?
>
>
>Who is "us" ?
Me and my biz partner/helper, who recently graduated from nursing college
and now has a real, fulltime job in Santa Barbara.
>I used 2W Allen Bradley carbon composition. This was 10-12
>years ago remember.
>
We were selling kits in 1988.
>:.......
>>A mistake. So is using a too-inductive resistor.
>
>Allen Bradley MIL-Spec are not inductive at HF.
>
Every conductor and every superconductor in the universe is inductive.
Four inch silver strap is inductive at LF, MF, HF, VHF, on and on. My
guess is around 100nH per foot. #10 wire is inductive - and not that
much more inductive than 4" silver strap thanks to the logarithmic
relationship between width, length and L. .
> > So is using too much lead length.
>
>You have to use some lead length, I had them as short as possible.
>I suspect that even with proper screen bypassing using the resistor in
>the cathode method would lead to instability at VHF.
Svetlana recommends cathode feedback R . RCA recommends cathode feedback
R. Eimac recommends cathode feedback R.
>.......
>>.So is not using at least one resistor per filament pin.
>
>
>Why filament pins?
strike that. Cathode pins.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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