The problem most likely is not the raised radials per se.
That he does not have space for buried radials most likely means he also
doesn't have space for full size, dense and uniform all around raised
radials either.
Without details, but after 5 years of hearing about what people have
actually done for "raised radials", in the abstract the most probable
situation is that the redials are irregular and insufficient, limited to
what is possible on a limited property. That in turn creates a significant
input impedance to the collection of radials. This in turn makes the
feedline coax shield an easier path than the collection of radials. This
effectively makes the coax shield the counterpoise. That in turn puts the
noise from the house and the power lines into the L feedpoint.
Even if a "balun" is used, unless it was specifically manufactured *** with
160 in mind ***, or constructed from something like K9YC's cookbook, ***
for 160 meters ***, it's likely to be very poor on 160 and will let in
stuff on the coax shield any way.
An FCP and an isolation transformer has quieted down a lot of noisy
inverted L's. 1) Because the FCP counterpoise is isolated from ground and
2) it's folds make it an extremely poor RX antenna, AND 3) it's isolated
from the feedline by the isolation transformer which has NO metallic path
between the coax shield and the counterpoise.
It has been a common report that converting to an FCP and isolation
transformer cut down on noise. My best interpretation on those reports is
that the noise was coming from the house using common mode entry from the
feed coax shield.
Have him take a look at k2av.com where these issues are discussed. Also
see w4kaz.com where Kaz documents his migrating his inverted L from
"radials of convenience" to an FCP + isolation transformer.
73, Guy.
On Tue, Oct 17, 2017 at 3:57 PM, K1FZ-Bruce <k1fz@myfairpoint.net> wrote:
> Have a friend that is getting noise from raised radials connected to his
> inverted L antenna.
>
> He can not bury the radials due to space problems.
>
> Are there any recent solutions to the problem.?
>
> Thank you in advance for your input. .
>
> 73
> Bruce-k1fz
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