Help with "safe" and "clean" band

Hi there,

I’m brand new at this GNU Radio thing, so please forgive me if my
question
has a “well-known” answer. I’d like to try out some performance tests on
a
few modulation schemes, so I need a clean band for these tests.
Obviously
the 2.4GHz ISM band is full of interference, and I assume that this goes
for all the other ISM bands, right?

If this is the case, is there a well-known relatively quiet band where I
can run these tests without interfering with anything important, without
being interfered with, and without getting in trouble with FCC?

I imagine that if I’d have all the daughter boards I could do a
long-term
(1-2 days) scan and find a quiet band and play in there (the tests are
likely short and low powered). The problem is that I only have the
2.4GHz
daughter-boards and I’d like to buy only the “right” daughter-boards (as
opposed to all of them to find an empty band).

Thanks for the help,
Mihai

On Thu, Jun 12, 2008 at 12:24 PM, Mihail L. Sichitiu [email protected]
wrote:

can run these tests without interfering with anything important, without

Welcome to GNURadio. I’m not sure which bands will be noisy for you, a
lot depends on your location and what’s around you. The best thing to
do is use a spectrum analyzer, if you have access to one, and see
what’s out there. If you don’t have one, you can fake it by using
usrp_fft.py and scanning around in frequency, looking for interferers,
etc. How “clean” is “clean”? If your signal is strong enough, your SNR
should be plenty high to run your tests. If you truly need a very
quiet environment, you may need access to special facilities, such as
an anechoic chamber.

HTH
-Steven

Mihail L. Sichitiu wrote:

being interfered with, and without getting in trouble with FCC?
The easiest thing to do would be not doing your tests wireless.
Connect TX twith coax to an attenuator and connect that to the RX side
with coax.
That is about as clean as you can get, and you won’t interfere with
anyone on any band.

Make sure you use enough attenuation. The RFX2400 TX side has much more
power at its output then the RX side can handle.
You will blow up your daughterboards if you don’t have at least 30 dB
attenuation.

The best attenuators I found for high frequencies are the SMA inline
types
You can mount them directly at the TX output and connect a SMA-SMA coax
to the RX side of a second RFX2400.

Things are much more relaxed with basicRX and basicTX.
basicRX can be connected directly to basicTX without any chance of
damage.

I do a lot of my testing with basicRX and basicTX.
The output of basicTX is also very low which is an advantage in this
case.

Greetings,
Martin

Yes, a cable would be nice and easy, but I’m also planning for a “demo”,
and the cable would spoil the effect :-). Additionally, I’m looking for
multiplexing (multiple parallel transmissions) and there the cable
doesn’t
help.

Thanks,
Mihai

On Thu, 12 Jun 2008, Martin D. wrote:

can run these tests without interfering with anything important, without


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Whatever you are, be a good one.
Abraham Lincoln

Would running your tests with all your equipment inside of a Faraday
cage be possible?

In my dreams my lab is all a Faraday cage :-). Now back to reality :frowning:
M.

Thanks for the help,


Whatever you are, be a good one.
Abraham Lincoln

Would running your tests with all your equipment inside of a Faraday
cage be possible?

On Thu, Jun 12, 2008 at 12:24 PM, Mihail L. Sichitiu [email protected]
wrote:

can run these tests without interfering with anything important, without


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