Topband: Elevated Radials
Pete Smith N4ZR
n4zr at contesting.com
Thu Mar 7 07:11:01 EST 2013
The other rule that seems to apply, based on a number of pretty serious
articles, including K3LC's NCJ series in the mid-2000s,is "they that
has, gets." By which I mean, if you have good ground conductivity, a
relatively sparse radial field can work better than a really extensive
radial field on lousy ground.
73, Pete N4ZR
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On 3/6/2013 11:54 AM, ZR wrote:
> Since the radial field for any height vertical has equal importance
> the only way to get 1/4 wave efficiency is to have zero RF loss in the
> loading coil and matching network. Cryogenics anyone?
> There is no magic wire minimalist radial or counterpoise that
> accomplishes that. All they provide is some improvement over a poor on
> ground radial attempt; I wont call it a radial system.
> ----- Original Message ----- From: "Rick Karlquist"
> <richard at karlquist.com>
> To: <topband at contesting.com>
> Sent: Tuesday, March 05, 2013 8:42 PM
> Subject: Re: Topband: Elevated Radials
>> One of the problems with discussing this topic is that
>> nearly all studies of radials deal with 1/4 wave verticals.
>> Most ham stations including mine don't have the luxury of
>> a height of 130 feet.
>> There are many cases where some "novel" grounding scheme
>> is touted as "just as good as 120 radials" and indeed it
>> may be for the 1/4 wave height case.
>> What is scarce is advice for the owner of a short vertical
>> as to what to do about grounding. What grounding scheme
>> would it take to make the proverbial 43 foot vertical play
>> as good as a 130 foot vertical? Whatever that scheme is,
>> we know that it will have very narrow bandwidth. This is
>> a good litmus test to separate short vertical installations
>> worthy of additional testing from low efficiency ones. Of course,
>> bandwidth is merely necessary, but not sufficient, to
>> prove high efficiency. The advantage of the bandwidth
>> criterion is that it is easily and unambiguously measured,
>> as opposed to field strength. The bandwidth should ideally
>> be determined by measuring the antenna drive impedance
>> directly, rather than looking at it through a matching
>> network. A matching network will to a greater or lesser
>> extent decrease the bandwidth of the antenna. Alternately,
>> the matching network can be modeled to remove its effect
>> on bandwidth.
>> I think it is less likely that you can be fooled by a bandwidth
>> measurement than you can with base impedance measurements.
>> Topband Reflector
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> Topband Reflector
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