|That "hula-hoop" looking thing is a magnetic loop antenna that covers from 100 kHz to 30 MHz. It is much less sensitive to noise than a traditional wire antenna, as it works with the magnetic component of the EM radio signal.|
It doesn't like to be near metal, that reduces the magnetic fields it is designed to intercept; that's why it's up in the air like that, away from the trailer frame. It's also not a good idea to mount it anywhere near your computers... as I can tell you from experience.
After a few abortive attempts to place it near the house, I mounted it on that trailer so I could move it around and find the location that resulted in the lowest noise and strongest signal. That accomplished, I marked the spot, and then I wired my Suzuki Samurai to connect to it. I have shortwave and other radios in that vehicle. So now I can just pull the trailer out into the country where there is no noise at all, and enjoy extremely high quality reception. The 2x4 needs to be painted to render it weather resistant, I'll do that come the first warm spring day. In the meantime, it works fine as is.
The original mount was simple: I put the loop and its amplifier on a 2x4 close enough together to create a "drip loop" with the stock cable, cut a 2x4 sized hole in the back of the trailer, made a "foot" inside the trailer that can receive the end of the 2x4 to prevent it from moving around. The assembled result withstands high winds (which, coincidentally, we had the day I built this) and can still be unmounted and remounted without any tools for trailering tasks that don't involve radio.
After some time, I added a rotor, and really enjoy the convenience on the low bands, where low angle reception makes the loop orientation critical. It's great for noise and interfering station rejection, too.
The antenna itself was purchased in a fit of desperation; I have serious noise problems around my home, and listening to shortwave and ham stations presents a problem. This antenna is advertised as being comparable to most wire antennas in terms of sensitivity, and superior to them in terms of absolute noise level and sensitivity to electrical noise. It sounded more like voodoo and marketing speak to me than reality, but as I said, I was desperate. Also, I confess to having bought into the idea that the more wire involved in an antenna, the better it would work.
Well, surprise, surprise, the loop works precisely as advertised — in fact, it FAR outperforms my wire antennas. For instance, on 20 meters, on 14.200 MHz, my carefully tuned 20m inverted vee wire antenna was picking up a signal at S9 over an S7 noise level. The loop also picked up the signal at S9... but the underlying noise level was S3 !!!!!!!! Of course, with that superior S/N ratio, the signal sounded marvelous on the loop, and terrible on the inverted vee.
And the inverted vee, of course, only really works well on 20 meters (14 MHz), because it is a classically tuned system. The loop... it works well everywhere. Every shortwave band is crammed full of excellent signals, the AM broadcast band is packed with strong stations, all the ham bands are received extremely well, long wave beacons and utility stations at random points on the spectrum thunder in... it's really pretty spectacular. Coupled with SdrDx and my SDR (software defined radio), which are also good from well below 100 kHz to 30 MHz, this loop is the cat's meow.
I've rigged my Yaesu FT-2000 up now so that it transmits on my wire antennas (you can't transmit on this loop), but receives using the loop, and man, is that a sweet setup. I can hear incoming stations really well, and the inverted vee does a good job transmitting, so they make an excellent pair. So far, I have yet to hear a station on the inverted vee that I couldn't also hear on the loop. I'm constantly switching back and forth because it's entertaining as heck to see the loop clobber the vee over and over. 😊
Overall, I rate the discovery of this loop as one of the most fun and productive events of my ham radio experience — we're talking about well over 30 years of avid fooling with radios and antennas. Before I had used it, I thought it was overpriced — and probably qualified as snake oil to boot. Now, after having actually used it, I think it represents the best value for the money of any radio antenna I have ever owned.
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