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Receive Antennas (below 30MHz) - For all topics related to receive antennas used on HF, MW, LW, etc. For transmit antennas use the Amateur Radio Antennas forum.

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Old 10-13-2018, 8:47 PM
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Default Directional Beam for SWL

Living in a condo makes it very difficult to experiment with antennas but I've always been curious as to how well beam antennas used for amateur bands would perform as general SW receive antennas.
Here is a video from someone in Italy receiving RAE on 15345 kHz from Argentina with a Moxon designed for 40 meters. He starts out pointing it the exact opposite direction then aimed at the transmitter and finally comparing it to a longwire. Seems to be effective.

https://m.youtube.com/watch?feature=...;v=1UC-D1Bqckk

This is on my list of antennas to try when I get my house, along with Hertzian's Loop-On-Ground, of course...
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Old 10-13-2018, 9:39 PM
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Just a reminder - the Loop On Ground is not my doing. I came across KK5JY project, loved it, and got long-winded about it. Matt gets to the point very quickly.

https://kk5jy.net/

But yes, you've stumbled into something very important - gain is not the only factor - the directional pattern is a major part of an antenna's success or failure.
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Old 10-14-2018, 11:09 AM
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Originally Posted by hertzian View Post
Just a reminder - the Loop On Ground is not my doing. I came across KK5JY project, loved it, and got long-winded about it. Matt gets to the point very quickly.

https://kk5jy.net/

But yes, you've stumbled into something very important - gain is not the only factor - the directional pattern is a major part of an antenna's success or failure.
I just took a look at Matt Robert's antenna website, very impressive and he nails it with the S/N ratio. I used a T2FD for a number of years in a crowded suburban neighborhood outside of Philadelphia and it made a world of difference especially from 5 MHz and below. I can deal with poor propagation which will eventually change for the better but RFI kills everything all the time.
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Old 10-14-2018, 6:38 PM
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I've got a three element SteppIR Yagi that I use for ham radio.. The antenna uses computer controlled electric (stepper) motors that feed out or pull back strips of 1/2 inch wide copper tape. The visible 'elements' of the Yagi are hollow fiberglass tubes that the copper tape slides back and forth in. This allows the beam to be tuned to resonance for any frequency between 13.8 Mhz and 54 Mhz. It has a forward gain of about 6dB.

Here's a more detailed description of the operation: https://www.steppir.com/about-steppi...ntenna-design/

Since it can be made resonant at any frequency between 13.8 Mhz and 54 Mhz, it covers all the short wave bands within that frequency range. With my rotor I can point it any direction I want for best reception. It works very well on the ham and shortwave bands.
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Old 10-15-2018, 6:45 AM
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Quote:
Originally Posted by pjxii View Post
Living in a condo makes it very difficult to experiment with antennas but I've always been curious as to how well beam antennas used for amateur bands would perform as general SW receive antennas.

Have you considered a loop antenna?
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Old 10-15-2018, 7:35 PM
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Originally Posted by iMONITOR View Post
Have you considered a loop antenna?
I know loops are very directional in two directions but I was thinking more along the lines of a yagi or moxon which is more omnidirectional to zero in on a transmiter. I know terminated longwires will do it as well.

I was just considering how well a multi-element beam might do on receiving SW broadcast bands which are not the specific bands the antenna was designed for. A moxon doesn't seem too difficult to build and would have a smaller turning radius and perhaps wind load than a yagi depending on how many elements to the yagi, so one designed for the 31 meter band (my favorite band) might have decent receive range.
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Old 10-15-2018, 8:28 PM
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It would be interesting to do a plot on a 20 meter beam listening on, say 19 meters. It would probably work fairly well, but I would wager the plot would look different on 19 than it would on 20. A yagi isn't completely omnidirectional - there are sometimes side lobes to be considered. My money is that it would still favor a forward direction, but I suspect the plot would show some interesting interactions between the elements.

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