HF Beam Antenna Polarization
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| Aug 19th 2014, 02:05 | |
WA9WVXTotal Topics: 0 Total Posts: 0 |
I've been an Amateur Radio Operator for 45+ years and I have never seen anyone using their HF Multi-Band 10 thru 20 m Beam Antennas in the Vertical Position as they are always Horizontally Polarized. Of course for CW / SSB horizontal does cut down on man-made noise but when you look at a Multi-Band Omni Directional Vertical Antenna it always presents a very low radiation take off angle good for working DX stations. By my own experimenting on the 2 m band, I had a 40 element phased collinear array up at 65 feet and I could rotate the array 90 degrees from horizontal to vertical and witness a minimum of 20 dB and a maximum of 30 dB in the Tx / Rc signal strength. Years ago I had a friend who was an avid DXer who had worked a station in the Antarctic on a Thunderbird Mark V Beam on 20 m & the signal was S9 and he thought, Why don't I switch to the Hustler Vertical? So he did and the receive signal increased to 20 dB over S9 absolutely an arm chair copy and the DXer was stunned. Why are we under utilizing our HF Beam Antennas? |
| Aug 19th 2014, 15:12 | |
N0NBTotal Topics: 0 Total Posts: 0 |
This is an area that could benefit for more experimentation. I think that the horizontal position is mostly a choice of practicality. An HF yagi oriented in the vertical position would need to be some distance from the parallel mast and/or tower to avoid interaction. We accept the trade-off that comes with the ease of mounting such antennas on a tower. Last year QST published an article by Eric Nichols, KL7AJ, titled "Gimme an X, gimme an O" that offers some ideas into the reception of signals refracted from the ionosphere. Before I was licensed I would look at the drawings in the antenna book and handbook that described take-off angle and wondered why it wasn't common to be able to tilt the antenna for the desired distance. I've since learned that it is much more complicated than that! Antenna height above ground and the surrounding terrain are among the most important factors affecting take-off angle it would seem. There is still a lot of opportunity for experimentation and perhaps even some discovery. 73, Nate N0NB.us |
| Aug 20th 2014, 05:09 | |
WA9WVXTotal Topics: 0 Total Posts: 0 |
Hi Nate, I suppose you're right to some extent about mounting the antenna boom a bit differently but this can be accomplished by using a M2 elevation rotor (the smaller one) where the Multi-Band Beam's Boom can be inserted right through the M2 elevation rotor to change the Polarization 90 degees. The M2 elevation rotor will handle up 3" pipe and from my experiments on 2 m, the elements don't need to be exactly vertical, maybe 5~10 degree off so the tower and mast pipe will not interact while transmitting. I've heard that RF bounces off the atmosphere layers and the earth twisting the signal but I don't believe this is really happening as it maybe someones thoughts from years ago. Perhaps I should get in touch with Eric KL7AJ for his thoughts on my post. I wish other people would put their thoughts or 2 cents worth in on this subject. Dan WA9WVX |
| Aug 20th 2014, 05:58 | |
KL7AJTotal Topics: 0 Total Posts: 0 |
Hi Daniel: I think historically, the horizontally polarized beam became standard for purely mechanical reasons. As I mentioned in QST article that was cited (Which earned me the William Orr Technical Writing Award, by the way!), since ionospherically refracted signals are cicularly polarized anyway, you won't notice much difference in polarization...UNLESS you opt to go with a CIRCULARLY polarized yagi...which virtually no hams do! But as Nate said, this merits a lot more experimentation! 73! Eric |
| Aug 20th 2014, 13:21 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
The advantage of horizontal polarization is that you get the benefit of ground gain--it is really hard to build a vertical beam with as much gain as a horizontal polarized beam. There certainly can be elevation angle advantages to vertical beams, but to some degree this is offset by the precise aiming capability afforded by the conventional Yagi/Tower. Being able to drop a noise source into a pattern null is a distinct advantage of a conventional beam. Now that SDR receivers are becoming more common, it may make sense to connect an array of linear antennas to separate receivers and combine them with digital signal processing to optimize the polarization. Zack Lau W1VT ARRL Senior Lab Engineer |
| Aug 21st 2014, 06:20 | |
WA9WVXTotal Topics: 0 Total Posts: 0 |
Hi Eric & Zack, Thanks for your input on my question. Ironically the HF beams are already manufactured, i.e. M2, Mosley, HyGain, SteppIR, Bencher. Tennadyne & Force 12 can be mounted in the vertical plane although with many of these antenna booms, they may require additional aluminum tube inserted inside of the manufactures supplied boom material to sturdy up the boom. I'm thinking that if anything has to be done, I'll have to do this myself to prove it works or not in the real world. Now for the experimenting. Dan WA9WVX |
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