DX RX - Random Length Wire or Loop?

[ultravista]

I have been using a long/random length wire for DX RX with SDR and would like to improve the receive.

My backyard perimeter will allow me to build a 40x24 rectangle about 10 feet off the ground. I could cross corners with the wire to connect the corners and create an electrically longer loop.

Would there be a benefit of creating a loop vs. a long wire of equal length and would connecting the corners to each other (think rectangle with an X) make a difference?

Adding the cross-points to the wire would give me another ~60 feet of wire from point to point.

 

[ka3jjz]

Never cross antenna wire upon itself - the results might cause voltages induced in the wire to cancel each other out, or act in other unpredictable ways. The loop may work better, with a little matching or a 9:1 balun at the feedpoint..

PLEASE go back and buy some antenna books as has been recommended in other threads. You will learn a great deal more (and be able to answer your own questions) than asking here, where our answers are limited by the board's software.

Mike

 

[WA8ZTZ]

PLEASE go back and buy some antenna books as has been recommended in other threads.

Good advice. You will soon see that there is more to the antenna thing than can answered here in a quick reply. Even after reading about antennas, you may find that it is as much art as science. Many hams are never satisfied and are constantly tinkering with their antennas.

Anyway, with a random wire antenna, you will need to impedance match (unun/balun) it to the receiver for best results. Also, some kind of tuner or preselector is usually necessary. You mentioned in your other thread that you are interested in MW and below. That SDR that you are using is very widebanded and will probably perform better on the AM broadcast band with some type of tuning and filtering up front. My guess is that you are experiencing front end overload on the frequencies you mention. The received signals look weak and buried in noise. This is not necessarily the fault of your antenna but rather the receiver being perhaps too sensitive. You need to understand how to limit the gain on that SDR, how to use the AGC and the LNA.

For an experiment, try a regular superhet non-SDR receiver with your antenna and see what you hear by comparison.