Forum: GNU Radio SBX TX/RX RX leakage

Hi, guys, I am doing full duplex on SBX. Is there any leakage from TX
to RX? Is that much?

Best,
Gang

On 07 Feb 2013 11:31, gang li wrote:

> Hi, guys, I am doing full
duplex on SBX. Is there any leakage from TX
> to RX? Is that much?
>
>
Best,
> Gang
>
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>
Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
>
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There's roughly
40dB isolation TX/RX on these cards.

When the signal received on RF2 port has a very weak strength, the
energy leaked from TX to RX will dominate in the total received
energy. I have observed this in my experiments. Are there any ways to
measure the leaked signal so i can compensate it? I am thinking a way
of by connecting the RF1 and RF2 ports with a long cable and 60db
attenuators. And then i record the received signal. I assume it is the
leaked signal from TX. Are there any better ways? Thanks for your
reply.

Best,
Gang

On 02/08/2013 04:10 PM, gang li wrote:
> Gang
Are you TX/RX on the same frequency, or different frequencies?

The usual way to deal with this on different-frequency setups is to use
a duplexor, or a deep notch filter on the RX port, and probably boost 
your
   antenna signal a bit with an external amplifier.

But if this is *same-frequency* duplex, the on-board leakage is really
minor compared to the coupling between your antennae.



--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org

Yes. I am doing full duplex on the same frequency, transmitting from
TX/RX and receiving on RX2 at the same time. When I put the antennas
far way from each other, the received signal amplitude is very low.
And when I change the distance between them, i found the received
signal amplitude is kind of stable. So i think maybe the leakage takes
the major. Am I right?

Just put 50 Ohm dummy loads onto the connectors and check for a signal, 
then
you see if it is leakage or not :)

Ralph.

> TX/RX and receiving on RX2 at the same time. When I put the antennas
> >> energy leaked from TX to RX will dominate in the total received
> > Are you TX/RX on the same frequency, or different frequencies?
> >
> > The usual way to deal with this on different-frequency setups is to use
a
> > duplexor, or a deep notch filter on the RX port, and probably boost your
> >   antenna signal a bit with an external amplifier.
> >
> > But if this is *same-frequency* duplex, the on-board leakage is really
minor

Thanks for your reply. I dont have a dummy load in hand. Are there
any other ways to check that?

On Sat, Feb 9, 2013 at 2:35 AM, Ralph A. Schmid, dk5ras