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Re: intermod



Jerry,

One very unusual interference source that I just found is a switching power 
supply that I have been using to power my TS-2000X.  Now interference from a 
switcher isn't all the unusual,  but it only occurred when a ham in my 
neighborhood's APRS WX station transmitted and sounded like packet.
The interference was easily audible over the 144.100 to 144.300 range
and on other radios within about 20 feet of the switching power supply.
When the AC line was disconnected from the power supply (or turned off) the 
interference totally disappears.  I assume the packet signal was mixing in
the input rectifiers of the power supply.

BTW, the power supply was a 23A Samlex as sold by Tech America/Radio Shack.

73
Mike W4LNA

On Thursday 12 July 2001 05:50 pm, you wrote:
> 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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