2008/10/31 Martin Dudok van Heel
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Hi Vincenzo.
How are things going with your exams.
I hope well.
Thanks for your help so far.
I finally got your DVB-T dump streams working.
I first tried using an undersampled basicTX but never got it to work.
(use a niquist mirror in the VHF range on channel 11 or 12 (219.5 Mhz or 226.5 Mhz))
I now use a RFX900 and that works with a pinnacle PCTV-Solo 72e usb DVB-T receiver card plugged into my PC.
I use 858.0 Mhz (channel 69)
I used a 10 dB attenuator on the antenna output to limit output power.
I also modified the RFX900 to enable transmitting outside of the ISM band. (disable saw-filter. add 220 pF capacitor)
Apparantly the pinnacle 72e can receive 7 Mhz channels on the UHF channels.
My standalone settopbox DVB-T receiver can't handle it.
I noticed you don't use the full possible range in your 16 bit streams.
(only goes from -80 to +80 while you could use -8192 to 8192)
Is this on purpose?
I can multiply samples by 64 and get a cleaner signal. (But also more output power)
I do have a request, I hope it is not too much work.
Could you make a stream with 10 Msamples/sec samplerate and 8 Mhz wide channel.
This way I can use standard standalone DVB-T receivers and don't have the 7Mhz bandwith on UHF problem.
For the 10 Msps stream I would have to use my USRP2 to output it.
It has a 100 Mhz DAC (in stead of 64 Msps in the USRP1)
It has a gbit ethernet connection for the samples, so I can go up to 25 Msps.
It can only do fixed interpolation rates so I have to choose from the table below.
(8 Msamples/sec is not supported on the USRP2)
USRP2
dac_rate interp ethernet_sample_rate
100 4 25
100 5 20
100 6 16.67
100 7 14.29
100 8 12.5
100 9 11.11
100 10 10 <----I think 10 Msamples/sec should be optimal
100 11 9.09
100 12 8.33
100 13 7.69
100 14 7.14
I think 10 Msamples/sec would be a good candidate.
Have you also tried using 8 Msamples/sec on the USRP1?
I know there would be no room left for IF channel filtering, but it could in theory still work.
If this works I would also very much appreciate a 8Mhz bandwidth stream with 8 MSPS samplerate so I can demonstrate with a standard USRP1.
Thanks for your help so far.
I appreciate it very much.
And good luck with your exams.
Have a nice weekend.
Greetings,
Martin