Posted: 12/1/2013 1:29:15 PM EDT
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Any of you that chase DX know how important it is to be able to hear weak signals above the noise, especially on the lower bands. W8JI, ON4UN, and others have a great deal of info on low noise receiving antennas so I won't go into all of that.
I have a low 160 Inverted-L and a low 80 + 40 Inverted-V fan dipole. 40 is pretty good but I get a lot of noise on 80 and way too much noise on the 160 antenna. My yard is 142' x 132' and I don't have much for tall trees, so I'm limited on what I can do for better antennas on the low bands. I tried a Beverage antenna around 150' long on my back privacy fence last winter. It was low noise but also low signal, and it pointed straight East so its use was limited. Okay on 40 but too short to perform well on 80 and 160. I unhooked it after trying it for that winter and never used it again. I've researched them all and figured my only other option might be a K9AY loop. Well then I came across the Hi-Z vertical antenna arrays, and the 3 element model spaced 40' on each side would fit in my yard pretty well. It should also have great performance for its size and be as good as an array of 4 K9AY loops. Sick of the noise I bought one and put it together in 15 degree weather before and during the recent CQ WW CW DX contest. I could have crammed a 3 or 4 element at 50' a side in my yard but it would have been too close to other objects, so I went with the 40'. Here's a couple links if you want to read more about the antennas. http://www.k7tjr.com/3element.htm http://www.hizantennas.com/ Here's my impressions after using it for about a week including the last half of the CQ contest. The Hi-Z is connected to the 2nd receiver on my Flex 5000 so there's no A-B switching here, it's real time side by side comparison. 160 meters - Much more quiet than my 160-L. The noise floor is around 10 dB lower on the Hi-Z, and the SNR is almost always better too. Rotating the controller shows it has a nice null on the back and gain in the front. Nulls out local point noise sources and undesired stations with ease. My best experience was trying to work Z81X on 160 earlier this week. I could not hear them at all on the 160-L but I heard them 100% on the Hi-Z for over an hour straight until they finally got too weak. I was transmitting on the 160-L but never got through the pile-up... I noticed similar performance listening to and working other stations on 160. The Hi-Z is just the better receiving antenna. 80 meters - Similar to what I saw with 160, but not quite as pronounced since I could receive fairly well on the old 80 antenna. The Hi-Z system has a preamp, and on 80 and higher bands the noise floor and all signals are around 5 dB higher than with other antennas due to the gain of the amp. I've been experimenting with an attenuator, etc, but I'm not worried because the SNR is better on the Hi-Z. PI4DX was heard 100% on the Hi-Z but not at all on the other 80 antenna. Worked him too! Directivity seems good and most of the time it's a better receive antenna. Hear some powerline noise or other pesky noise source, just put it in the null and it's gone! 40 meters - Similar to 80. Still decent directivity but depending on noise, conditions, and the station it may or may not be better than the 40 antenna. Still better more often than not. The higher I go in frequency the less I see the directivity and advantage to the Hi-Z, but I'm also comparing it to a rotatable dipile and Yagi on those bands. There was a Caribbean station that I could hear on 30 with the Hi-Z but not at all on the dipole. Another strange one was a Utah station that I could hear on 15 with the Hi-Z but not at all on the Yagi! I see no directivity on 10 with the Hi-Z, but it's still a great receiving antenna there. Overall the Hi-Z is a great receiving antenna for below AM broadcast to 30 MHz just as advertised. I don't have other receiving arrays to compare it to but I'd say it's also a great low band DX receiving antenna too. It's not magical but it can let me copy stations that I don't even know are there with some of my other antennas, null out noise that's covering stations, and I'm looking forward to using it all winter and beyond! Don't forget I installed this the snow when it was 15 degrees out. The 1" PVC pipe insulator was too flexible for me to trust so I added 1" fiberglass inside it for strength. 
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I have a friend that is a big low band DXer......he just installed one of the Pixel Technologies magnetic receive loops. He has is ground mounted in a 5 gallon bucket of concrete on a short piece of pipe with a rotator.
He claims its the best RX antenna he has ever installed. I suppose the loop has peaks and nulls helping him work that rare low band DX. Linky I haven't heard it in action, but at $499.00 it had better be good. 
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+1... Very nice KCC. Now I have antenna envy, big time.   Quoted:
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That is one hell of an antenna farm you've got there, even without the new receive array! +1... Very nice KCC. Now I have antenna envy, big time. You're not the only one with envy, BigDaddy! Wish we had a comparison to a 43' so I'd know how much I'm missing. |
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Thanks guys. I'm still envious of the Hams with the huge receiving arrays that blow this one away, and of course I still want a tower and a better Yagi, etc too, but this will have to do.
I wondered if this received some signals that I couldn't hear on my other antennas because of the difference in polarization. I don't have any other verticals installed right now so I can't check that idea. I have thought of installing a 43' vertical though, maybe next year.
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Quoted:
Thanks guys. I'm still envious of the Hams with the huge receiving arrays that blow this one away, and of course I still want a tower and a better Yagi, etc too, but this will have to do. I wondered if this received some signals that I couldn't hear on my other antennas because of the difference in polarization. I don't have any other verticals installed right now so I can't check that idea. I have thought of installing a 43' vertical though, maybe next year. In addition to polarization, you might also consider take-off angle (elevation angle) as a potential source of performance differences. |