[TowerTalk] What do do on 80 when height restricted?

[Bob K6UJ]

Jim,

You said :   "Also, it really helps to raise the antenna and use 
elevated radials. While it's BEST for those radials to be resonant, I'd 
put in as many shorter ones as I could before giving up."
To me anyway this begs the question would it be an advantage to use four 
elevated radials (too short) and
put a loading coil in each one so they are resonant ?

Bob
K6UJ


On 10/25/16 1:26 PM, Jim Brown wrote:
> On Tue,10/25/2016 12:35 PM, Tom_N2SR via TowerTalk wrote:
>> Go back and read K9YC's articles about many short radials close to 
>> the feedpoint.  Isn't the idea to reduce/eliminate losses?
>
> Exactly right. With on-ground radials, more copper is better, longer 
> is better.  I covered this in great detail in the piece about 160M.
>
>>     When I added added the HF2V, I had about 4 radials and the BW on 
>> 80 was about 150 kc.  I kept adding radials, and the bandwidth kept 
>> dropping - which is good, since that means that that ground losses 
>> are being reduced.
>> The bandwidth finally dropped to about 50 kHz.  For an 1/8 wave 
>> antenna, that is pretty good.
>
> Yes. AND loss in coax is quite small on 160 and 80M, so it's very 
> practical to use a tuner in the shack once you've got it close to 
> resonance in the middle of the range where you want to work. This is a 
> great application for big coax (RG8 or RG213 size), not for power 
> handling, but to reduce loss with mismatch.
>
> "Also, it really helps to raise the antenna and use elevated radials. 
> While it's BEST for those radials to be resonant, I'd put in as many 
> shorter ones as I could before giving up." NEVER let the perfect be 
> the enemy of the "good enough." And best, by far, is one of those 
> vertical dipoles that doesn't need radials.
>
> Yes, top-loading is ALWAYS a good thing if it doesn't reduce the 
> overall height of the vertical section. If, for example, you're using 
> conductive guy wires as top loading, the vertical part of the guy wire 
> will shorten the effective height of the radiator, reducing its 
> efficiency.  Let's say that you've got a 40 ft tall radiator, are 
> guying it with wires that form a 45 degree angle with the ground, and 
> the conductive section of the guy is 14 ft long. Doing the trig, the 
> wire drops 10 ft, so the effective height of the radiator is 40 ft - 
> 10 ft  = 30 ft. This means that SOME top loading is a good thing, but 
> don't overdo it, or try to tie off the guys as far from the antenna as 
> possible.
>
> 73, Jim K9YC
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