[ARC5] Second Receiver Drift Test from KE6F SWAN 600R

[millerke6f at aol.com]

Hi and thank you for your response and commentary. Very useful


As to the order of testing.  Going into this project the assumption was that the higher frequencies would be a much larger challenge for receivers that use a variable LO in the first conversion so it does bias the findings a bit by doing the low frequencies band first and allowing for a longer warm up and heat soak for the upper bands.  It's a question of time usage (mine I am afraid) but i figure it's still useful data as long as I post the testing conditions and timing and use the same criteria for all radios in the test queue.


I just finished the testing of my Collins 75S3B receiver.  Interesting observations will be posted with that post


73


Bob, Ke6F



-----Original Message-----
From: Brian <brianclarke01 at optusnet.com.au>
To: millerke6f <millerke6f at aol.com>; wrcromwell <wrcromwell at gmail.com>; arc5 <arc5 at mailman.qth.net>
Sent: Mon, Nov 30, 2015 6:06 pm
Subject: Re: [ARC5] Second  Receiver Drift Test from KE6F SWAN 600R

Hello Bob,

I applaud your efforts and your generosity in sharing your results.

Thermal engineering can be quite tricky. The thermal mass of these radios 
you're testing is not just a single number. There are all sorts of pathways 
from hot places - sources - to sinks: via radiation, conduction and 
convection. So, I would expect many differently shaped frequency vs 
temperature over time curves during the course of a day. As you have already 
noticed, the relationship with time is not linear. I suspect you are using 
time as a substitute variable for temperature.

When I was designing oscillators, I attached RTDs all over the place and 
tracked frequency vs temperature over very long time periods - like several 
days. I came to the conclusion that there is no such thing as a uniform 
change in frequency with temperature, nor a simple rise in temperature to a 
plateau. When I came to test ovenised frequency standards (and generators) - 
doesn't that tell my age? I found some of the best, in terms of long-term 
frequency stability vs ambient temperature, were in HP counters and Collins 
synthesised sets, eg, PRC-47. At one stage I had a Marconi signal generator 
(2000 series?) that I set up one morning to zero-beat against WWV; this was 
in anticipation of a sale that evening. I left the generator on till later 
in the afternoon. After an hour, there had been no drift. I came back some 6 
hours later; I listened for a zero beat. I could hear nothing. Initially, I 
thought it had drifted a long way off frequency. Then I turned the frequency 
dial a little and there was the tell-tale whoop - it had stayed on zero beat 
the whole time. I was sad to see it go. But it was a big bugger for which I 
needed to do my knee-bend exercises for a week before lifting it.

You have chosen a particular order for your tests. What happens when you 
revisit, say, the 80 m and 40 m measurements after the 10 m measurements? 
What happens if you start with the 10 m measurements?

On Tuesday, December 01, 2015 6:35 AM, you said:

<snip>

Thank you kindly for the comments though and it's fun doing this stuff and 
allows me to putter aorund with my test gear.

73  Bob, KE6F