Topband: 2 element vertical for 80m with 1/8wavelength spacing

[Kees Nijdam]

Hello Filipe,

Yes, I have such a system.
Cost me several days to optimize it.
My comments.
The 2x157 and 39 degrees phasing lines are based on very good earth systems 
(2-3 Ohm). When your radial network is 5 Ohms, it is a different story. That 
is because the driving impedances are very low (in my case 19,27+j21,14 Ohms 
and 13,86-j15,73 Ohms) and the influence of the earth system on these 
impedances is big (a 1/4 lambda system is not that critical)
If you do not know the impedances of your verticals, the only way to go 
forward is to measure the self impedances and the coupled impedances. After 
that you can follow the calc
ulations in ON4UN's book and software.

My system is optimized for 3510 kHz and with a signal source at 400 meters I 
found a front to back ratio of 24 dB for this frequency.
On 3500/3520 kHz is was  20 dB, on 3540 kHz only 10 dB and higher in 
frequency  the antenna becomes more and more omni directional.
However, the swr was OK over the whole band, also on 3800 kHz.
So it can be used on 3800 kHz but without directivity.

You need a very good radial system and to decide for CW or SSB . My advice: 
better and less critical is to increase the distance between the verticals 
with a few meters.

Is it worth the effort? Yes I think so. I have one vertical permanent and 
during the winter I install the other. The few dB extra gain is good but I 
was also very happy with the system as RX antenna. I have it oriented 
north-south and it is nice to hear KH6AT over the south pole and not over 
the north pole..

Kees, PE5T
--------------------------------------------------
From: "Filipe Lopes" <ct1ilt at gmail.com>
Sent: Tuesday, April 19, 2016 4:53 PM
To: "topband" <topband at contesting.com>
Subject: Topband:  2 element vertical for 80m with 1/8wavelength spacing

> Hi guys,
>
> Has anyone tried spacing 2 verticals on 80m 1/8 wavelength, instead of 1/4
> wavelength?
>
> I am starting some new project and I will use the 2x157º and 1x39º phasing
> lines but my question is regarding it's performance in both CW and SSB
> portions of the band.
>
> I wonder, if I tune both verticals to 3.650 MHz, if the degradation of F/B
> and Gain in the higher and lower parts of the band will be significant?
>
> If Yes, which is the best way to tune both in CW and SSB?
>
> Thanks in advance for help.
>
> 73's Filipe Lopes
> CT1ILT - CR6K
> F4VPX - TM3M
> _________________
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