[NLRS] 2m Pager? noise

[Dr. Gerald N. Johnson]

144.390 is the US national frequency for APRS. APRS uses 1200 baud AFSK 
on FM much like packet radio, except APRS rarely connects, just sends 
beacons through digipeaters, and other APRS stations allowing 
digipeating. There are a few APRS stations not far from your location. 
One to the west but east of I-494. The standard antenna polarization for 
APRS is vertical so your horizontal EME antenna may not respond well or 
be predictable. If you have adjustable polarization the signals should 
show directivity with polarization vertical, but there probably are a 
few dozen independent APRS stations in the western Minneapolis suburbs, 
and each will be sending short bursts of data, simply waiting for the 
previous one to finish.

A repeater quality cavity might act as a notch without messing up EME 
frequencies too much, and in theory it should be possible to use a 9th 
overton quartz crystal to make a narrow notch filter to attenuate the 
APRS. Otherwise it may take work on your station to make it tolerate the 
strong signals. I see from QRZ.com that its not a transverter, so the 
places to add attenuation for strong signal handling aren't handy. I 
went through a situation decades ago where one strong station was every 
where in the band until I worked on reducing the 2m converter gain after 
the RF stage and also in my IF receiver a 75S-3B. Those won't work 
easily with your rig. I wrote an article on the topic that was published 
in the EME newsletter a few years ago. I have it on line at:
http://geraldj.networkiowa.com/papers/EME/Intermod2.pdf
Intermod from other band activity is not a new EME problem.

73, Jerry, K0CQ


On 10/28/2017 7:31 AM, Kirk P wrote:
>
>
> Good morning,
>
> I recently installed a 4x7 array for EME and a SDR RX for all bands.
>
>
> I have some very loud noise that sounds like a pager system at 144.390.
>
>
> I have tried all measures I can think of to determine if it is my network or something from within my home. I have disabled network, unplugged wifi and router, inserted a 2m bandpass filter etc. No luck.
>
>
> If I move antennas there is no change in signal ...
>
>
> Stumped here looking for ideas. Can anyone else hear this locally or has anyone experienced this at all?
>
>
> My main concern here is that it does at time seem to desense WSJTX ability to hear and decode which of course isn't good if I want to succeed at EME.
>
>
> Kirk N0KK
>
>
> Thank you
>
>
>
>
>
> Sent from Outlook<http://aka.ms/weboutlook>
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