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Re: [Discuss-gnuradio] USRP need antenna?

From: Suvda Myagmar
Subject: Re: [Discuss-gnuradio] USRP need antenna?
Date: Wed, 20 Apr 2005 15:39:12 -0500
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Eric Blossom wrote:

As far as I know nobody has said anything about not needing an
antenna. You need something. Try a 3 foot long piece of wire.
For the broadcast AM band, longer is better.

A cheap "FM dipole" works great for the FM broadcast band.  By "FM
dipole" I mean those really cheap T-shaped wire antennas that came with
your stereo.  They're typically available at the local drugstore for
about $3.  Don't bother trying RadioShack, they don't carry them, only
the $20 amplified antennas that you don't need.

I tried 2 different antennas. First, tried with FM/UHF tv antenna that has 2 extendable wires and one loop. Had to cut off the input connector of the antenna and just stick the bare coaxial wires in one of the RX A/RX B jacks on the USRP receiver board. I could tune and hear only one FM station among several; and even that one with a lot of noise.

Next, tried FM dipole that looks like T shaped tape, the one you hang on wall. This one had 2 parallel inputs, each flat U shaped, I guess they're supposed to be secured between nut and bolt. I cut them off, stuck bare wires in the receiver jacks. Nothing, can't tune to a single AM/FM station.

These antennas I assume don't have any gain control. I read on Ettus website the following:

Can I do interesting things with just a USRP and BasicTX/BasicRX, but no RF frontend? Do I need a separate RF front end to capture, say, CW or phone transmissions in the amateur bands? Or can the BasicRX fill that role?

For reception you would need to add gain and filtering in front of the BasicRX daughterboard. This can be done pretty easily with MiniCircuits parts, or you can use the 10.7 MHz IF output of common scanners and receivers. The BasicRX board will handle signals up to around 100MHz directly. For higher frequencies you'll need to downconvert.

It seems like I need an antenna with gain and filtering... Where do I get those? I'm totally illiterate in harware, electronics areas.

Many thanks


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