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
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