[NLRS] 2m Pager? noise

[Doug Reed]

I believe that most of the digital EME is near 144.110MHz? APRS is at
144.390MHz, just 300KHz away. That is why PAR can't build a filter for
you. That is also why a notch filter built with flexible cable is not
going to work. A 4" diameter VHF cavity will not provide a narrow
enough passband. You might get lucky with a 12" diameter cavity as a
pass cavity for the EME frequencies. But if you want a really narrow
bandpass you also get high insertion loss.... A 4" diameter cavity as
a suck-out notch filter might work, but it may still be hard to get
more than about 20-30dB attenuation of the APRS signal. At least that
is my experience. But that might be all you need.

You said the receiver in your 746Pro handles the APRS signal but the
rtl-sdr dongles don't. That is simply an indication of the over all
signal handling capability. The dongle isn't designed to tolerate high
signals. It was designed for satellite TV signals so overload wasn't
an issue. You are lucky the EME RX is far enough from the FM broadcast
band that you don't get those signals in the dongle too.

73, Doug Reed, N0NAS.





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