2m lna4all IMD with moxon antenna


#1

Here is a video of a local problem I, and appearently many others, have trying to use an lna4all for mast preamp - the main receiver is tuned to 144.8MHz, and another is monitoring a local pager transmitter on 152.48MHz. Everytime the pager transmitter goes off, we can hear 96.1FM station in wfm very clearly on 144.8MHz!

Was playing around with a coax stub notch filter - 1/4 wave at 152.5MHz + velocity factor with open end should look like a short at that frequency - with not much luck. Looks like a major undertaking - appreciate anyone elses input in the battle, googling all I can.


#2

sounds like you need a FM broadcast filter like the one here


#3

Just got one put in line, exact same model, seems to have knocked the intermod out for sure! Just picked up a brief cw beacon from a triton-1 pass.


#4

Can see as in here https://network.satnogs.org/observations/663672/ the severe intermod is much reduced with the FM trap, but the 152MHz pager is still raising the noise floor by about 5db. Researching pager filters, like in Par Electronics http://www.parelectronics.com/amateur.php but they are pricey.