Saturday 20 December 2014

Initial 146.5 MHz DVB-S exciter tests

333KS/s 10 MHz BW
333KS/s 2 MHz BW
333KS/s 1 MHz BW

I thought I would share with you some initial tests of DATV-Express operating
at 146.5 Mhz. This is the exciter only, I will post some results of it combined
with a G.H Engineering brick based PA in a few days. These were taken with a
Rigol spectrum analyser. There was no additional filtering on the output.

The new FPGA code uses a x64 interpolater, it will only operate between about
100K and 400KS/s but this should be fine for the 2m DATV tests.

I was able to lock to the signal with an MER of around 28 using Tutioune with a
TT-Budget S2-1600 card. Work progresses on developing a matching
Software Receiver.  


  1. Great work. I have built an LDMOS PA using one of the new Freescale devices and more than capable of 400W so maybe good for 100W of DATV. That will go a long way.

    I think you might need to get the bandwidth down just a little more - 80dB at +-500kHz to avoid interference to the adjacent bands.

  2. That is easy I just need to re-quote the figures relative to an equivalent unmodulated carrier :) I am not sure how feasible -80dB is. A Handheld operating next to the exciter can't detect anything. I could use a sharper roll off to the filter (0.2 instead of 0.35) or reduce the symbol rate (which is programmable). I only chose 333K as that is what others seem to be using.