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1-10 of 117 messages
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43ft multiband vertical
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by ES1TU on November 17, 2008
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Hello,
I finally got my 43ft vertical up last night (and made my first 4 qso-s).
my setup:
* buried 3000ft of radial wire
* Icom 756p3 (with built in ATU and 100W of power)
* 60ft of LMR400 coax from my shack to the vertical
* 4:1 balun at the antenna base
Before first test on 40m band I measured SWR with tranceiver. SWR was 3.0. Another measurement with MFJ259 antenna analyzer gave me SWR 3.0 as well.
But okay..756p3-s internal antenna tuner should handle this.
Real test on the air was kind of disappointing (my expectations were much higher based on the eham reviews of that vertical).
During the nighttime on 40m band my most distant QSO was 1500 miles (from ES1 to TA3AX). I usually got signal reports from 5-3 to 5-6 while other vertical antenna users (also using 100watts) gave each other solid 59-s.
On 80m nobody even heard me (while other stations gave 59+ to each other).
What am I doing wrong? Is SWR 3.0 normal (measured with 60ft of coax and a balun)?
Maybe I should skip this multiband idea for now and make my vertical resonant at 40m. Can I skip balun in this case?
Any ideas will be VERY MUCH appreciated!!
73,
ES1TU
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RE: 43ft multiband vertical
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by VR2AX on November 17, 2008
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Increase power.
1KW = +10 db.
10 KW = +20 db
Add a tuner at the amp/shack end.
Be patient.
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RE: 43ft multiband vertical
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by N1OU on November 17, 2008
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Don't give up yet, long verticals are great DX antennas but are touchy.
You said 3000 feet of radials -- that's lots of wire but how is it laid out? Radiating from the antenna base (hence the term "radial") is best with at least some being at least 1/4 wave length at your lowest desired frequency. You can bend them if you have to, but the more "radial" the better and the more of them the better.
How are the radials attached to the antenna mount? Several manufacturers make plates that provide multiple attachment points, affix firmly to the DC ground, and make laying out the radials easier.
DC grounding? You need some. The non-radiating part of the antenna and the radials should be well grounded.
Check: Is something grounding the radiating element of the antenna (either RF or DC ground)???
3:1 SWR might be a "best case". These antennas aren't resonant for the most part and will present very high SWR on many of the amateur bands. I doubt the tuner in your Pro III can cope across much spectrum. You'll need a broader range tuner. A shack "indoor" tuner will match the feedline, but it won't stop the feedline from radiating (and I'm guessing you've got this condition). A remote tuner like SGC or ICOM AH-4 will tune the antenna to the feedline at its base and will avoid all the potential problems on the feedline.
Finally, what is in the general area of the antenna? If you have metal or stucco buildings close-by, they might be affecting your pattern. Generally, verticals should be in the clear.
There's my two cents worth -- keep trying.
73
Gordon, N1OU
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RE: 43ft multiband vertical
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by K2KW on November 17, 2008
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Sounds like you have loss someplace - I would suspect either the radial system or 4:1 balun.
I would first use your MFJ antenna analyzer and check the impedance of the vertical at it's resonant freqency (maybe around 5.5 MHz) WITHOUT the 4:1 balun. The impedance at resonance without the 4:1 balun should be about 25-35 ohms. If the impedance is higher (even if it's 40 ohms), you still have losses due to your radial system. (Though it sounds like you have a reasonable amount of wire in the ground).
If the above test is OK, then try tuning the vertical without the balun and see how it performs.
I personally try to avoid tuners on antennas that are not near self resonance on the band you are using them on. Antennas that are not self resonant tend to hear and transmit less effectively than resonant antennas. Though sometimes you have no choice.
Kenny K2KW
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RE: 43ft multiband vertical
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by K0OD on November 17, 2008
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"Real test on the air was kind of disappointing (my expectations were much higher based on the eham reviews of that vertical). "
---
I own one and...
You've just discovered what I've said previously here, 43 footers ***aren't very good antennas***. And no, ***verticals aren't GREAT DX antennas*** on 40 and up. They are just a bit better on the long haul than close-in.
It didn't take long for the usual comment of "add more radials" to appear. Once you have 16 or so radials, adding more won't turn a sows ear into a silk purse.
Still your Zerofive should work well on 40 with your setup.
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RE: 43ft multiband vertical
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by K0OD on November 17, 2008
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"Is SWR 3.0 normal (measured with 60ft of coax and a balun)?"
--
The Zerofive has a very high SWR on most bands because it is only resonant on 60 meters (which is of no interest in Estonia, I believe). The 4:1 balun improves the SWR somewhat (except on 60), but a tuner in the shack is still needed to match it properly to the radio.
EZNEC shows that your SWR on 40 should be around 4:1 which is about what you're getting. Without the balun, you'd have about 10:1 .
I wouldn't shorten it into a 40 meter vertical although you could telescope the radiator down to 33' for a test. The stock 43' Zerofive should work nicely on 40, plus 30 meters and for DX on 20.
On other bands, don't expect much. I should also add that one evening on one band isn't much of a test. Certainly try it in the CQWW CW coming up. That will give you the best idea of its performance.
43 footers have SOME merit, but they're not as good as eHam reviews suggest.
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RE: 43ft multiband vertical
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by AD4U on November 17, 2008
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What is the basis of the Love Affair some HAMs have with 43 foot verticals? Is 43 feet the magic length for verticals, or did the laws of physics change, or did advertising hype finally overcome all reason?
Dick AD4U
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RE: 43ft multiband vertical
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by N3OX on November 17, 2008
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"
Maybe I should skip this multiband idea for now and make my vertical resonant at 40m. Can I skip balun in this case? "
Just keep using the antenna for a while. If you're using a 4:1 balun and decent coax, it seems like your 40m losses will be minimal, and 3:1 SWR isn't so far off from what you might see. I calculate 3.4:1 for a 43 foot tall 2 inch diameter radiator seen through an ideal 4:1 impedance transformer and 60 feet of RG-213 coax. (Using EZNEC and VK1OD's transmission line calculator). Loss in the feedline is just a fraction of a dB over matched loss in this case.
I think if anything you're going to work too hard just to find that the glowing eHam reviews are written by people who were really badly exaggerating how well an antenna works. It's not that they're wrong, per se, but rather that with no frame of reference other than memories of what must have been awful antennas, they act like their new 0.5dBi antenna is a world beating flamethrower.
Even if you feed it 100% efficiently (which on 40m you're probably not so far from doing, honestly), it's still just a single vertical a little tiny bit taller than a quarterwave. You'll work plenty of DX with it if you stick to it, but it's no 4 element yagi on a 90 foot tower like some reviewers make it out to be. It can't be.
I ran a 40 foot wire vertical on a fiberglass pole with matching networks at the base for a while:
http://www.n3ox.net/projects/lowbandvert
I had realistic expectations of it, and as such, found it to be a pretty good DX antenna on 30, 40 and 80m. Of course, it was properly matched, but on 40m with your antenna I doubt it's much of a problem.
If you feel like trying something a bit different, you could look at the 40m matching network on that page and see if feeding the antenna with it instead of the balun makes any noticeable difference in performance. It could be there if the balun is very, very lossy which is not something I took into account in my comments initially.
The networks won't be exactly right but they should get you close enough if you use a variable capacitor and/or spread and compress coils or add and subtract a turn to get a good match. But I don't think it will help too much, I just think eHam reviewers of popular items are a bit crazy with their reviews.
I can say from experience that a 40 foot vertical with efficient power feed is a pretty OK DX antenna, but I wouldn't go around trying to give it an 11 out of 5 review because it changed my life. It's just a solid radiator as long as you keep losses out. So just use it, maybe make the minor efficiency improvements you could with matching networks (80m is actually the most important, in my opinion) and eventually some good pacific DXpedition contacts will grace your log ;-)
73
Dan
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