I added 3 x 20 dB attenuators before entering DBSRX. It works as I imagined and I didn't fry the daughtercard. I could verify that I master the si2109 demodulator.
Some images of the test setup @ http://www.poes-weather.com/~patrik/usrp/dvb-dbsrx/ Thanks to all for the help, Patrik ----- Original Message ----- From: Marcus D. Leech To: [email protected] Sent: Thursday, November 10, 2011 6:02 Subject: Re: [Discuss-gnuradio] Connecting a receiver to the DBSRX To my understanding, the DBSTX is designed for Satellite TV reception. So it should be safe to connect the output of the satellite LNB to the DBSRX without problem.In fact, I tried to connect the LNB out port of a DVB-S set top box to the DBSRX directly without problem or distortion.KZ The only difference is that the DBSRX/DBSRX2 has an extra 20dB gain stage ahead of the DBS downconverter chip. In most set-top-box situations there wouldn't be that extra 20dB of gain. So yes, the downconverter *chip* is designed to hook up directly to an LNB/LNBF, but the DBSRX family have an extra stage of low-noise gain to allow direct connection to an L-band antenna for L-band "off air" work (and for things like radio astronomy and amateur satellite work, etc, etc). Padding with an attenuator can't hurt in this case, and in *some* cases, can save the DBSRX/DBSRX2 from damage coming from things like C-band radar pulses getting downconverted by the LNB and potentially producing damaging signal levels at the DBSRX/DBSRX2. LNBs generally have very high gain (50-60dB is typical), which means that for "ordinary, expected" signal levels of roughly -120dBm or lower, the LNB converts to levels that are "comfortable" for DBS receivers/receiver chips. But on C-band, you have C-band radar to worry about sometimes, which can produce very-high-level transients. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ------------------------------------------------------------------------------ _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
