[amsat-bb] intermod

[Jerry Pixton <jpixton@xxxxxxxxxxx>]

All,

I can still hear just fine according to UO-11 passes.

I measured these spurs by leaving the downlink constant (no doppler 
corections) and moving the transmitter frequency. Looking at ao40rcv, I set 
the mouse cursor in the middle of the pass band and the logged the 
frequency as I moved each spur under the mouse cursor.  The average 
seperation between 35 spurs was 882 hertz. The spurs went all the way from 
435.490 to 435.600. Above that no sign of spurs. So the interference is at 
the top of the S band range from 2401.450 to 2401.495. Below that the 
quarter wave stub has made them much, much less.

I don't understand the interference mechanism.  They are in-band signals 
(that is they move in same direction as real signals)
So it is not an image problem. But the seperation between spurs is 
reasonable constant (within the accuracy of my measurement technique) so 
they don't spread out as beat frequencies would.

???


Jerry, W6IHG
------------------------------------------
Dr. Jerry R. Pixton, PIXOS Designs LLC
http://www.pixos.com/designs/
jpixton@shentel.net
------------------------------------------

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