Thank you fo rthe response John.. and the group
I was also wondering how close the trees were that you cut.
I have a location on my property where I could run a flat top antenna
of perhaps 70 to 80 feet high with a top hat made of parallel wires at least
200 feet long.
I have a tower on my property that is 130' high and could attache to that
with the proper insulator
if I did not mind the tophat sloping from 130' to around 80 feet.
Trees would be about 75 feet away in any direction ...
Your thought?
----- Original Message -----
From: "John Sexton" <[email protected]>
To: "Paul Cianciolo" <[email protected]>
Sent: Monday, June 04, 2001 12:59 PM
Subject: Re: LF: Re: "Ground" losses
Hi Paul,
Yes they are. they behave like leaky capacitors. This has been discussed
several times on the reflector.
The problem is exacerbated by the high voltages that short antennas suffer
from, and at these frequencies most antennas are short.
This is one of the reasons, why a top loading coil is a good idea, because
it reduces the voltages in the lower part of the vertical which is close to
the ground, plus it moves high current up the vertical where it does most
good.
My situation is particularly bad, because the back garden is on the side
of a hill, and at the top there is a beech wood with trees over a 100 foot
high. So inevitably the antenna is always near the ground or these leafy
capacitors.
As to increasing the radiated power, it does have some effect, but the
losses are tens of ohms compared with the milli-ohms of radiation
resistance, so until I get it down to less than 30 say, it won't make much
difference. Nevertheless every little helps and it is useful to know how
much of an effect such changes can make. I am still learning.
73, John, G4CNN
-----Original Message-----
From: "Paul Cianciolo"<[email protected]>
To: [email protected]
Date: Mon Jun 04 14:18:43 PDT 2001
Subject: LF: Re: "Ground" losses
>Hello John,>
>Paul Cianciolo calling here from the States.
>
>Reading your post below it would lead one to believe that trees are
somehow
>in series with the antenna?
>Or atleast the ground return path? Could you describe your antenna and
the
>trees configuration?
>
>Also does this decrease in resistance cause an increase in the rediated
>field?
>
>Thank you John
>
>PaulC
>
>----- Original Message -----
>From: "John Sexton" <[email protected]>
>To: <[email protected]>
>Sent: Monday, June 04, 2001 11:05 AM
>Subject: LF: "Ground" losses
>
>
>> Hi Guys,
>> By risking life and limb at the top of a precarious ladder, cutting off
as
>much of the surrounding greenery as possible, I have further reduced my
>apparent "Ground" resistance by a further 8 ohms. Now down to 85 ohms.
>> It seems that an extra metre separation of far end (highest voltage)
from
>trees can make that much difference.
>> So I just have to cut back another 10 metres of the surrounding forest
to
>reduce it to zero, then alle achtung, hi!
>> John, G4CNN
>>
>>
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