Re: [amsat-bb] Re: More Microwave Modulation Musings

[Bob Bruninga <bruninga@xxxxxxxx>]

On Tue, 3 Dec 2002 G0MRF@aol.com wrote:

> Hi Bob.
> Take a listen to your oven first.
> It's not just 50 or 60 Hz wide.   It's tens of megahertz wide with QRM peaks
> every 50 or 60Hz.

Yep, and so with a DSP processor, looking for such a raster of signals at
say something like every 67 Hz (if one could transmit with that) then
would have 55 copies of such a signal in a 3.3 KHz voice bandwidth
receiver.  And a very crude guess would tell me that that equates to
something like 17 dB processing gain...

But I think the real way to calculate processing gain is to compare the
DSP resolution bandwidth with the 3 KHz (donno what that is).  Now then if
you had a wider band receiver and could feed say 12 KHz audio into the DSP
you could pick up another 6 dB processing gain...

THe idea here is to get the oven away from 60 Hz so that it can be
distinguished from all the other 60 Hz noise... and be detectible..

Microwave ovens should peak about 44 MHz above the downlink from AO-40?

Bob


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