[TowerTalk] More shunt fed 80/160 vertical info

[Gary Slagel]

Hi TowerTalkians,
 
I had someone ask about my shuntfed 80/160 vertical and after replying and explaining the whole thing to him I thought someone else might be interested so am forwarding this.  I"m definitely not recommending anyone build a vertical this way.... just thought someone might find it interesting how easy it is to get on the air.
 
Thanks Dan,
 
Problem solved... I blew the antenna :)  Going to hang an inv L in the next couple days.  
 
I've got  a 51' tower with a tribander on top plus a 40/80/160 trap dipole hanging off an wooden stick about 1' away from the top of the tower.  I know having 80/160 verts underneath the dipole isn't ideal but wanted to experiment with it.  Experimenting, I attached a wire to the tower at about 12' up along with about a 120' elevated radial.  Checked it with an mfj antenna analyzer and it was resonant very near to 1.8mhz!  Obviously the 51' tower with tribander couln't have that much electrical length but I assume that its interacting with the dipole (even though the dipole is completely isolated from the tower) to give it the extra length.  So, I adjusted the radial length to get the thing resonant exactly where I wanted it.  Then I attached a coax at that point and fed the coax to an ameriton remote coax switch.  
 
For 80M I ran a wire up the tower, about 18" away, and attached it at the top of the tower.  Since the whole tower /tribander is resonant at 1.8mhz I knew I'd have to really shorten it to get it to load up on 80M.   I built a trombone capacitor using 2 sizes copper tubing, mounted the capacitor at about 12'  and fed it against a 63' elevated radial.  Between adjusting the capacitor and the radial length I got a nice match with this vertical at 3.525.  Attached coax and ran it to the coax switch.  Also ran the tribander into the coax switch and I select the antenna from the shack.  This, of course is the antenna that couldn't handle the 800W (I'm not worried about the 160M vert handling high power cuz my amp doesn't do 160M). 
 
Now I'm going to replace the 80M with an inv L.
 
None of this is ideal of course.... especially the 1 elevated radio per band situation... but fun to play with.  The antennas seem about on a par with the dipole.   On 160 I'd say the vert beats the dipole, on 80M the dipole beats the vert.  But on both, there are times when the vert is better and times when the dipole is better.  More radials, I'm sure, would make a significant difference and I'll do that soon.  I'm going to add a couple for the 80M vert before the weekend contest and I think, for dx, I'll see the 80M vert significantly better the the dipole.  
 
Good luck with your experiments.... 73,
Gary
 
Gary Slagel
Hot Springs, SD
N0SXX
http://marina.fortunecity.com/sanpedro/351


 
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