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Re: Minor issue with packet uplink on 145.990



On Sat, 26 May 2001, Miles wrote:

> One of the minor issues with QRM on the ISS packet uplink on 145.990, is
> the [terrestrial] repeater input on 146.010.
> <snip> There is not much we can do about the QRM at this time....

We could do some experimenting to validate this theory.  

Since the doppler is +/- 3 KHz, this means that at the start of passes,
the optimum uplink is 145.985 and at then end it is 145.995 for the same
performance.  But one of these is 15 KHz and the other is 25 Khz away from
the 146.010 terrestrial QRM.

If a test station operated a consistent test uplink on each of these
frquencies over time, statistics should show us a difference in the
success rates, and this difference would be related to QRM on 146.010.

But the data would also be significantly skewed by pass geometry, since an
east coast station will ALWAYS have better luck at the end of a pass due
to lack of competition over the atlantic..... nevermind...

But the degree to which the 146.010 theory is correct, tells users that
their best chances to avoid that are to work for success early in the pass
by transmitting  5 KHz low during approach.

de WB4APR, Bob


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