For what it's worth :
I designed and built a multiband tower vertical for 40, 60, 80 and 160. Last
night I worked VK9CZ Cocos Keeling, 11,000 miles on 40 CW.
It is 1/2 wavelength on 40,
1/4 wave on 60, 80 and 160
I use a matching network at the base for 40 and another for 160.
It has a 60 meter trap.
Total height is 59 ft. The trap inductance adds length for 80.
It is an insulated base tower.
I have a good 50 ohm match at the base due to the matching networks.
These networks are remotely switched from the shack.
But I will say that my HyGain AV-640 works like a charm. It does not have
traps. It has loading coils with capacity hats above each coil. And a few
stubs on the side for some other bands. The advantage of the 640 is that it
is a 3/8 wave vertical which gives a lower angle of radiation than a 1/4
wave vertical.
3/8 wave and 1/2 wave give pretty good low angle radiation. Then more than
1/2 wave you start to get some other lobes, as I have been told.
Best Regards
Dan Schaaf
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K3ZXL www.k3zxl.com
60 Meters www.60metersonline.net
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-----Original Message-----
From: n8de@thepoint.net
Sent: Saturday, April 06, 2013 7:07 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Vertical comparison question
Those who have heard my 80/40/WARC signals may be aware that I am
using an insulated tower vertical (photo on qrz.com).
This antenna on 40m is a 1/2-wave vertical. Estimates of feedpoint
impedance are in the 2000 ohm range, but I feed it with 50-ohm coax.
There is also a 40m 1/4-wave vertical available for use on that band.
Both verticals have 60 1/4-wavelength radials spaced equally about
them. (on the ground).
Comparisons are interesting, depending on DX distance.
From here in Michigan to the Caribbean, the 40m vertical seems a bit
better (one s-unit in most cases), but for JA and YB, the difference
is quite astounding! While the 40m vertical 'hears' those areas quite
well, there is a 5 S-unit difference in favor of the 80m vertical! My
concept of this difference is 'take-off angle'.
I have NO IDEA why it works so well with that 40:1 feedpoint SWR, but
I will never complain.
73
Don
N8DE
On 4/5/2013 6:56 PM, John G. wrote:
How do the "radialless" verticals, like the R5, R7000, MA5V, Gap ones,
compare in performance to the standard 1/4 wave verticals that are roof
mounted with radials? Does one tend to outperform the other? I am
looking how each performs for DXing and longer haul communications.
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