DTX1 Spectrum

Help and support for the BATC DTX1 ATV digital encoder and modulator system
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G8DPH
Posts: 46
Joined: Fri Mar 01, 2013 4:44 pm

DTX1 Spectrum

Post by G8DPH » Wed Nov 06, 2013 7:25 pm

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:

Image
This is the spectrum of the DTX1 set to 1275MHz


Image
DTX1 set to 437MHz
Ashley
G8DPH

g4wvu
Posts: 51
Joined: Sat Jun 22, 2013 10:42 am

Re: DTX1 Spectrum

Post by g4wvu » Thu Nov 07, 2013 1:33 pm

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

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