[ARC5] Re-reading Gordon White article...

[john rose]

My speculation, "cold" is specified because the capacitance(s) of the tube element(s) change(s) as the tube(s) heat. 

----------------------------------------
> From: kgordon2006 at frontier.com
> To: jfor at quikus.com; arc5 at mailman.qth.net
> Date: Thu, 6 Jun 2013 20:32:50 +0000
> Subject: Re: [ARC5] Re-reading Gordon White article...
>
> On 6 Jun 2013 at 12:43, J. Forster wrote:
>
>> ???
>>
>> I just looked at the print and L-2 is in the plate circuit of the 12SK7 RF
>> Amplifier, and sees the received frequency.
>>
>> -John
>
> Yes. Exactly. Weird, but obviously done for some very good reason.
>
> I would really like to know what that reason (or reasons) might have been.
>
> One other factor here that brought this to my attention was that I was "finding" the peak in the
> RF input circuit of a 1.5 - 3.0 MHz receiver the other day (when I suspected that a previous
> hacker had modified the coils), with all the tubes removed, and found that the peak in the
> tuning of the RF stage is at least 100 KHz LOWER than the dial reading, yet with everything
> in place and operating, the RF peaks in the correct place.
>
> I had connected my signal generator to the antenna connector, and had connected my
> 'scope to the grid pin connection on the RF amplifier tube socket, then adjusted the signal
> generator frequency for a peak in the signal on the grid. The peak is actually quite sharp too.
>
> Ken W7EKB
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