First I want to point out that I am standing on the shoulders of giants, so without their work I would need a lot more time...... The giant in this case a French man: Jean-François Fourcadier, F4DAY
On his website, one I think started many amateur DTV projects, he provides a simple test file and description of his setup:
Anyways, armed with that test file what could I do?
This 'Anything Transmitter' board only does ONE frequency, basically is designed for GPS replay (attack), so how to cleverly use this for digital TV?
AHA! Being not a total newby (bee) as I wrote much of the soft in use all over the world (boast boast), especially xdipo satellite dish positioned, I was well aware all the time of the IF output of the LNB satellite converters:
Basicially, if I disconnect the LNB from my satellite receiver, and feed the Anything Transmitter into that cable (on the receiver end of course ;-) ), we get: Local oscillator (lower than Rx in a LNB) 9,750,000,000 Hz Anything Transmitter output: 1,575,420,000 Hz ---------------- + The sat receiver should thus be set for 11,325,420,000 Hz
The trick: As the LNB is removed, there IS no local oscillator, and the sat receiver now expects 1,575,420,000 Hz on its tuner input. It will set 13 V on the cable (low band oscillator select in LNB). I select vertical polarization, this will remove the 22 kHz control tone on that cable. Bit of AC coupling (small cap at 1.5 GHz) to get rid of the 13V DC... is all that is needed.
On the F4DAY website he specifies the required parameters for the test file: symbolrate 1024000, FEC 1/2, .. etc etc.. So I already programmed my xdipo satellite receiver controller:
So what is still to be done? Make a cable, add a capacitor, AND write a new version of my 'send_iq' program that does the serialization, where F4DAY uses a CPLD, I will use software running on the Raspberry... It seems to me as he only uses 1 bit signals for I and Q (QAM 4) that I can just dump 0 or 255 in the IQ channels of the Anything Transmitter. Will have to turn down the CD4046 sample speed generator to 2048 kHz (from 4096 kHz) to get that 1.024 Msamples / second required.
Sometime this year all the above could be done... I mean ye never knoow, with all them earthquakes EARTHQUAKES??? well, and then some.
Anyways, I will have a go, it is still early in the morning of 2013 so..
It is interesting how much I may / will have to modify this plan, just to test that I decided to post it. LOL :-)