On 09/23/2013 10:59 AM, Juha Vierinen wrote:
I was playing around with the rtl_sdr dongles and came up with a
trivial hack to build a receiver with multiple coherent channels. I do
this basically by unsoldering the quartz clock on the slave units and
cable the clock from the master rtl dongle to the slave units (I've
attached some pictures).
You still have to do sample alignment in software, but this is
relatively easy. There are a lot of cool applications, such as a dual
frequency beacon satellite receiver, interferometry, or passive radar
that you can now do with $16.
juha
So, what were your test conditions?
I'm feeding a +3.3dBm signal from a high-precision communications test
set at 28.8Mhz to two of those dongles.
Then I'm feeding in a 45Mhz sine wave into the two devices RF input
through a splitter and variable attenuator.
The result is horrible relative-phase-noise between the two channels.
They dance all over the place on the scope display.
In comparision, a B100 with TVRX2, under the same conditions, works
flawlessly, with no appreciable relative phase jitter between the
two channels.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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