Topband: elevated radials

[Carl]

I would expect that after X number of elevated radials it becomes moot. 
Height and ground conductivity determine the actual number.

For my poor ground and 20' elevation it was somewhere around 24 based upon 
the antenna analyzer. Since all were run over branches and a lot of dead 
wood falls around here in the winter I went to 32 to have a few extra.

Carl
KM1H
----- Original Message ----- 
From: "Mike Waters" <mikewate at gmail.com>
To: "topband" <topband at contesting.com>
Sent: Friday, September 20, 2013 11:42 AM
Subject: Re: Topband: elevated radials


> Hello Jim,
>
> Thank you for this. I don't doubt for a second that my elevated 1/4 wave
> radial currents may be unequal. I should throw together an RF current 
> meter
> and check them sometime, and add more radials while I'm at it. After the
> ticks and chiggers here die, though. :-)
>
> I don't have any Communications Quarterly issues, but K5IU's article 
> sounds
> interesting, if anyone has a copy.
>
> 73, Mike
> www.w0btu.com
>
> **
>> Hey Mike
>>
>> Saw your post to TB reflector:
>>
>> "I suppose if you made the elevated radials long, then you could adjust
>> the current balance with series variable capacitors. You could use a 
>> simple
>> clamp-on meter like W8JI has on his site to measure the relative current,
>> perhaps.I didn't bother with that myself, I was just careful to keep the
>> radial lengths the same length and height."
>>
>> My old friend K5IU had an article "Optimum Elevated Radial Vertical
>> Antennas" in Communication Quarterly, Spring 1997, pp 9 - 27.  He showed
>> why 1/4 wave elevated radials are the worst length as it invariably 
>> results
>> in radials having unequal currents (at least on the low bands where the
>> height is small in terms of lambda).  He only concluded the pattern was
>> distorted, explicitly stating no opinion on efficiency.  Dick is pretty
>> careful - he likes actual measurements. The fix was to use non-1/4 wave
>> radials with a single lumped reactance between the shield and the 
>> junction
>> of all the radials to bring to resonance.  Using separate reactors for 
>> each
>> radial makes it too critical to adjust.
>>
>> Since some of his measurements showed next to no current in some radials,
>> I figured right off the efficiency would almost always be higher with 
>> equal
>> currents, even when using shorter radials of the same number.  I never
>> needed to use elevated radials, so it was all merely academic for me.
>>
>> I'll bet anything you have very unequal currents in your elevated radials
>> despite their being precisely the same physical length.  Dick's article
>> shows how he measured the currents with a simple HB device.  Don't know 
>> if
>> it is simpler than W8JI's or not.
>>
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