Topband: Temporary antenna suggestion for 160

[donovanf at starpower.net]

Mike, 


I think the performance of a 4-square array may relate to the reason 
why switching to 30,000 feet of radials made a dramatic improvement. 
The currents in the elevated radial currents might be badly mismatched 
by proximity to currents in nearby radials. I never tried to measure 
them. 


73 
Frank 
W3LPL 

----- Original Message -----

From: "Mike Waters" <mikewate at gmail.com> 
To: "Frank Donovan" <donovanf at starpower.net> 
Cc: "topband" <topband at contesting.com> 
Sent: Saturday, December 21, 2019 5:10:31 PM 
Subject: Re: Topband: Temporary antenna suggestion for 160 


Hi Frank! 


Thank you for sharing this experience. This is interesting, because (as you are probably aware of) no less a guru than N6LF published results showing that with a single antenna, four λ/4 elevated radials were nearly identical in performance to 120 on the ground. This is true only if RF was prevented from either flowing into the lossy earth or back along the feedline shield (thus detuning the elevated radials, since the shield would try and act as a radial and couple to the lossy earth). 


Was anything connected to ground at the feedpoints? And what type of coax feedline choke unun did you use at the feedpoints? Perhaps there are factors in an array vs. a single vertical that would explain your results, but I can't think of any. 


73, Mike 
W0BTU 



On Mon, Dec 16, 2019, 3:04 PM < donovanf at starpower.net > wrote: 




Hi Mike, 


Years ago my 4-square transmitting array used "gull-wing" elevated 
radials sloping 45 degrees from the feedpoint at ground level to about 
ten feet high. 


When I replaced the radials with sixty 120-foot radials laid on the ground 
I had to shorten the verticals by about five feet to maintain resonance, 
suggesting that the current at the bottom five feet -- or so -- of the verticals 
was attenuated by the sloping radials in close proximity to the verticals. 


As an aside, the performance of the array improved dramatically... 


73 
Frank 
W3LPL 




From: "Mike Waters" < mikewate at gmail.com > 
To: "thoyer" < thoyer1 at verizon.net > 
Cc: "topband" < topband at contesting.com > 
Sent: Monday, December 16, 2019 8:52:41 PM 
Subject: Re: Topband: Temporary antenna suggestion for 160 

CORRECTION 

It was just pointed out to me that I neglected to mention that the 
feedpoint on my 160m inverted-L was much lower than 10 feet high! 

The tuner sits on the earth, and the two wires go straight up from that to 
the insulator block holding the antenna and the radials, which is less than 
4 feet high. 
>From that point, the two radials angle upwards at roughly 45° (?) to nearby 
trees, and level out at 10' high to the North and to the South all the way 
to the ends. (The South radial zigzags back and forth since the distance 
from the base to the neighbor's fence in that direction is less than 1/4 
wavelength.) 

I had photos of it online, but w0btu.com crashed. Looking for a place to 
upload it to. 

I hope this makes sense. Sorry for the lack of details below. 

73, Mike 
W0BTU 


On Sun, Dec 15, 2019, 8:22 PM Mike Waters < mikewate at gmail.com > wrote: 

> Do the inverted-L, but use at least two 10' high 1/4 wave radials. 
> 
> Do NOT use an RF ground rod, or any radials on or near the earth. Just 
> connect the coax shield to the junction of the radials and any remote 
> tuner. At that point a good choke balun is necessary. 
> 
> Leaving out the choke or grounding the shield will result in very poor 
> performance. 
> 
> 73, Mike 
> W0BTU 
> 
> 
> On Sun, Dec 15, 2019, 7:04 PM thoyer via Topband < topband at contesting.com > 
> wrote: 
> 
>> With only 9 more to go for DXCC on 160 and all of the recent posts about 
>> how good the band has been recently "best in years....) I find myself with 
>> no 
>> antenna for the low bands and cringing after each post on how good the 
>> band has been. 
>> ... 
>> Options - I have a 45' tower with TH6DXX, 6m and 2m yagis. I could easily 
>> string a makeshift inverted L with about 45' vertical and around 100' 
>> horizontal. This I could string up in a few hours. the Horizontal portion 
>> would be pointed south. Not the best of configurations but that's what I 
>> have to work with. ... 
>> 
>> Tom 
>> W3TA