[ARC5] BC-453 drift test

[Bob kb8tq]

Hi

It takes a tube radio hours to stabilize into the “drift” region. You are still looking at
warmup many hours after turn on….. A “couple of Hz” is doing fine for a 453. 1 Hz
at 500 KHz is 2 ppm. Anything under 20 ppm / C is inside the temperature spec 
on the caps and coils. Your shack likely varies at least 2C over an hour. 

Bob

> On Jan 10, 2018, at 6:45 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net> wrote:
> 
> I recapped this radio and tested the LO drift afterwards.
> Coupling the plate via 7pf cap and a x10 scope probe to a frequency counter, the results were as follows:
> The LO dropped in frequency at a rate of about 1 HZ / second upon power up.
> The drop rate slowed until it more or less stabilized an hour later 700 Hz lower than the start up
> measurement.
> Once at the bottom of the descent, it would sit and go up and down a couple of Hz in a very slow undulation.
> 
> I guess this a normal warmup scenario? What say you?
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