[Premium-Rx] Dangerously off-topic, diversity again

[Bob Milne]

Hi Scott,

By pre-mix oscillator are you referring to the VFO? That is likely to
be the major cause of frequency differences between the two receivers.
I fact, I'm surprised you got results as good as 20 Hz. One possible
approach is to use the oscillators from one receiver to control the
other. For example, you could buffer the the BFO in receiver A, break
the connection to the BFO injection point in receiver B, and connect
receiver A's BFO in place of it, etc.

Regards....
....Bob

On Mon, 01 Sep 2003 09:20:14 -0400 (EDT), you wrote:

>Wading into this diversity topic again, but on the theory that the general 
>nature of the question may be universally applicable to those slaving better 
>stuff here goes.
>
>On a pair of R4b's, slaving the pre-mix oscillator without slaving the IF 
>crystal oscillator or the 50 khz bfo has resulted in long term stability between 
>the receivers of between near zero and about 20 hertz, which is fine for AM 
>but sometimes a little 
>much for SSB/cw.  I'm calculating this by counting audio beats, as I don't 
>have a decent freq counter to acomplish this, or I'd answer my own questions 
>that follow....
>
>What I'm wondering is whether anyone familiar with this stuff has a good 
>guess as to which (or both) 
>of these oscillators is the major source of the drift, as I'd like to take a 
>step wise approach to slaving them with as little alteration of the radios as 
>
>possible.  I am aware the C line has a 50 khz output jack, which makes me 
>suspect Drake knew the BFO drifted, and thatDrake color coded IF crystals 
>according to their temperature coefficient, which makes me suspect that they knew 
>that oscillator drifted as well (I have a "C" and a "R", another possible 
>cause)
>
>If anyone has any ideas on this, or the best way to slave those oscillators, 
>I'd really appreciate hearing your thoughts.
>
>Thanks, Scott
>
>
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