Hi Chris,
On 07/14/2013 05:50 PM, Chris Albertson wrote:
If you are after the cheapest and smallest spectrum analyzer possible look
for a TV tuning USB dongle. Some of these tune over the range of 64-1700
MHz There is software to do FFT and plot spectrums You can set started
plotting in the UHF range for $20.
It is a bit do it yourself in that you likely need a selection of
attenuators and and so on because the dongle expects the signal level of a
cable TV or TV antenna and the bandwidth is not DC to GHz. But the cost is
right.
Here are some screen shots
http://blog.opensecurityresearch.com/2012/06/getting-started-with-gnu-radio-and-rtl.html
Been toying around with one too.
A few notes:
1) Some tuners have a "gap" in the L-band.
2) Frequency tracing to the 28,8 MHz crystal, uncompensated. Hacking up
a lock to a 10 MHz would improve things.
3) The RTL sampler provides you with just above 2 MS/s datastream as a
stable rate, which limits the bandwidth in a single sweep. I have yet
not seen a spectrum analyzer app that combines sweeps. In general I
havve not seen a "Spectrum Analyzer" style GUI for RTLs.
4) Make sure to enable the RTL in an offset LO and not in zero LO mode,
due to 1/f noise. Modern code supports it, but you need to enable it.
5) I have modifies mine to provide +5 V DC on the antenna, as it will
allow for a LNA at the antenna.
Cheers,
Magnus
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