[TowerTalk] 80 meter vertical question

[David Gilbert]

That statement is completely true as far as it goes, but I think it is 
possible to get a 1.1 SWR with a vertical portion that is electrically 
longer than 1/4 wavelength and radials that are somewhat shorter.  The 
combination can still be resonant but the feedpoint is essentially 
"off-center" to raise the impedance.  I've modeled that in EZNEC and 
verified it in practice with roof-mounted "ground plane" antennas I had 
at my previous QTH.

I'm not saying that's what John has ... just making a general comment 
for clarification.

73,
Dave   AB7E



On 3/20/2014 10:54 PM, Jim Brown wrote:
> On 3/20/2014 4:40 PM, john nistico wrote:
>> I have put up a 80 wire vertical in some trees seeing I do not have a 
>> tower. I cut it 62ft6in so it should be on 3.750 however it seems 
>> long and the swr is 1:1 at 3550 or so. I have 10 radials and my 
>> longer version worked just fine. Any feedbck would be helpful.
>
> Hi John,
>
> If you have 1:1 SWR with a resonant quarter wave vertical, you have a 
> poor radial system. The resistance at resonance of a quarter wave is 
> about 35 ohms with an ideal radial system. That means you have 15 ohms 
> of loss in the radials. 1:1 SWR is NOT a design objective for a 
> quarter wave vertical! Instead, I would work on improving the radial 
> system. Either a LOT more on-ground radials, or raise the radials as 
> high as you can.
>
> 73, Jim K9YC
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