BATC Forum

We are told to use a filter on the output because of unwanted signals
I've made some measurements on the output. My analyzer only goes up to 3GHz but here are the results:


This is the spectrum of the DTX1 set to 1275MHz



DTX1 set to 437MHz

They don't need a filter any more than any other kit IMO. - certainly at the 70cm & 23cm frequencies.
The closer in spectrum is really very clean as long as as the output level is being used generally at more than about 50% (so the wanted RF signal is well above general digital noise etc.) I measured non Harmonic related spurii at better than -60dB on 437 with the output at 100% on the unit I have here. Harmonics of the wanted are obviously not a concern as the amps/PA will have their own LPF/BPF (or should )
Antennair are just being safe / cautious I suggest. (- sensibly)

Mark

G4WVU