Looking for Inexpensive Antenna for AFEDRI SDR-Net Receiver

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K5KNT

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Hello all,

I am relative new to Monitoring and have only used a Grundig G3 with telescoping antenna in the past. I just received an AFEDRI SDR-net receiver and would like to build an antenna for it. I am somewhat limited in what I can put up, so I've been considering a longwire or random wire antenna (I'm not sure of the correct terminology :) ).

The radio has a SMA connector and the antenna will be fed through a window. What I'm looking for is the easiest and least expensive way to get an antenna outdoors. I've read different things about needing or not needing a "unun" or "balun" and the more I read the more confused I get. My amateur radio experience has been VHF/UHF mobile only, so this is all really new to me. My main objective is to keep it simple.

thanks,
 

SCPD

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Start by building a simple dipole antenna. You didn't say how much space you have to work with so just start with whatever size fits your yard, etc.

Since you're receiving the wire length won't matter that much. Again, you may be limited to what you can put up anyway. You'll need to use a RF adapter to mate the SMA to BNC or PL259. These can be found on EBay and/or at Radio Shack.

 

ka3jjz

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Yup that's certainly one possibility. Keep in mind that a dipole works the best on the freq to which it's cut, then odd wavelengths - for example a 40m dipole will also work well on 15. This is much less critical just for listening, although you might notice some peaks/valleys where the antenna seems not to work quite so well.

Random wires and inverted Ls are where many folks start, but they're susceptible to picking up noise from the home, nearby buildings, ect. A better solution would be to use a 9:1 transformer (sometimes called a 'magnetic longwire balun') to help isolate the noise off the feed. The very popular PAR antenna uses a similar technology.

You didn't say much about your home, but the best place - even for this dipole - to put antennas is as far away from the home and power lines as possible. NEVER put an antenna where it could fall across a phone or power line!

We've got several ideas for antennas - homebrew and commercial - in our wiki, the article with all the links is here...

HF Antennas - The RadioReference Wiki

HTH...Mike
 

K5KNT

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....

You didn't say much about your home, but the best place - even for this dipole - to put antennas is as far away from the home and power lines as possible. NEVER put an antenna where it could fall across a phone or power line!

We've got several ideas for antennas - homebrew and commercial - in our wiki, the article with all the links is here...

HF Antennas - The RadioReference Wiki

HTH...Mike
Below is a overhead photo of my home, courtesy of Google Maps. I've rotated the image so North is up. The black line at the top is the power line. The blue dot is the air conditioner and the red dot is the location of the window to the room my computer and radio are located. The green trees in the lower right are the neighbor's. The front of the house faces South. The white "V" shape is tree limbs I erased as they are no longer there. The structure in the upper right is an un-insulated storage shed. There are two Mesquite trees in the backyard. One located in the upper left corner and the other by the shed at the top point of the "V". the back yard is surrounded by a 8' wooden privacy fence. Sorry, but I don't have dimensions.

This was also posted on the HFUnderground forums before I found this site.
 

shortwaver

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Lil Rhody
Hello all,

I am relative new to Monitoring and have only used a Grundig G3 with telescoping antenna in the past. I just received an AFEDRI SDR-net receiver and would like to build an antenna for it. I am somewhat limited in what I can put up, so I've been considering a longwire or random wire antenna (I'm not sure of the correct terminology :) ).

The radio has a SMA connector and the antenna will be fed through a window. What I'm looking for is the easiest and least expensive way to get an antenna outdoors. I've read different things about needing or not needing a "unun" or "balun" and the more I read the more confused I get. My amateur radio experience has been VHF/UHF mobile only, so this is all really new to me. My main objective is to keep it simple.

thanks,
I use a Par End Fedz swl antenna with good results. Its cost may seem a bit high at $70 from UniversalRadio, though what you get in performance and simplicity is really amazing.
Google it for reviews. Eham.net is a good place to check for reviews.
 
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ka3jjz

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You could make a fairly effective hidden antenna by taking wire and wrapping it around the perimeter of the roof of your home, then tie it back to a 9:1 transformer, then feed that with coax down to the SDR.

Even crude skyloops like this one are terrific performers - and if you feed it right, your neighbors won't even notice

Just a note here that many of the world's top DXers usually have more than 1 type of antenna available to try to hear a signal. What doesn't make it on one sometimes will on another - it's all a matter of how the signal happens to arrive at your destination. So having both the PAR and a loop is an enviable combination

Mike
 

Markb

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Planet Earth
I just bought an Afedri about 6 months ago and LOVE it! Great SDR for the price. As was mentioned previously, try to get the wire element high and away from the house. I am using a different long wire/balun combo and it made a huge difference vs in the eaves. The power line to your service drop might complicate placement, but either way, you might need to try different placement locations and see which one works best for you.

73,
Mark


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