In my opinion, Jerrys question was best answered by N0AH.
He describes exactly what any vertical/inv L builder will find out eventually:
The more radials you put on - the worse the SWR gets.
This is because ideally the antenna has a feedpoint impedance of 10 - 30 Ohms.
But, when you have only a few radials, this value gets "covered up" by the
lossy earth network, so what your coax and transmitter sees is much more
near 50 Ohms which makes you think its all fine. Another reminder that good
SWR does not necessarily mean good antenna. It cant be repeated often
enough: remember, the best SWR you can get is from a dummy load.
What you need with more radials is either an UNUN or a matching network or
a tuner (ideally located at the feedpoint).
Now on to the number of radials:
I find it relieving to finally see those come out of the woods who DONT
always use 60 or 120 radials (e.g. N6RK).
For me its amazing to see the number of posts demanding such a number of
radials as "sufficient".
Amazing, because remember we are speaking about 160m radials here.
If you have a wide space available and can simply put them on the ground -
well then its a feasible task but if you have a city lot or whatever, you
will find it difficult enough to put on 4 or 8.
But - by all means, DO IT and have fun on the band! Your antenna will still
work much better than you might expect from the statements of those who
demand 60 radials.
When going on expedition or portable operation I have put up an 80m/160m
vertical/inv L (using one 80m trap) several times.
I found a practical set of radials consists of 4 radials cut for 160m (40m
long) and 8 radials cut for 80m (20m long).
Yes of course, more is better, but I said "practical". I am always trying
to bring at least 2 radial sets (8 for 160m, 16 for 80m) but I either leave
them at home for cutting down the weight or I drag them along and then dont
find the time / space to put them to work... :-)
Good luck!
mri xmas and hny 2004
73
Con DF4SA
At 21:55 17.12.2003 -0800, N6RK wrote:
>I put up a 20 meter vertical with closely
>spaced radials 4 wavelengths long spread over about
>60 degrees centered on Europe. I A/B'ed it
>with an ordinary vertical. The vertical with the
>long radials had an advantage of perhaps 3 dB
>vs the ordinary vertical toward Europe (a
>just discernable difference). In other directions,
>it had no advantage. Not what I would call
>gangbusters.
>
>Rick N6RK
>
>(A report on this and other vertical experiments
>is on my web site www.n6rk.com)
>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com]On Behalf Of Jan Erik Holm
>> Sent: Wednesday, December 17, 2003 8:37 PM
>> To: towertalk@contesting.com
>> Subject: [TowerTalk] Re: One more ground radial question
>>
>>
>> Is something like this ever confirmed by field
>> strenght measurements?
>>
>> 73 Jim SM2EKM
>> --------------------------------------------------
>>
>> Don Havlicek wrote:
>> > Yes!
>> > In my case ... 60 radials spaced 6 degrees apart .. then concentrations
>> > of ten radials at 1 degree each for Europe, Japan, South America, and
>> > VK/ZL ... works like gangbusters .. all I need now is to clean out the
>> > shack and put a new feedline out to the vertical again!
>> > Don
>> > N8DE
>> >
>> > va3pl@cuic.ca wrote:
>> >
>> >> ----- Original Message ----- From: "Don Havlicek" <n8de@thepoint.net>
>> >> To: <kb9cry@comcast.net>
>> >> Cc: <TowerTalk@contesting.com>
>> >> Sent: Wednesday, December 17, 2003 12:12 PM
>> >> Subject: Re: [TowerTalk] One more ground radial question
>> >>
>> >>
>> >>
>> >>> I believe the word "optimum" should be replaced with "sufficient".
>> >>> My experience with verticals tells me that 100 radials works much
>> >>> better than 60, especially when concentrated in certain directions.
>> >>
>> ,
>>
>>
>> _______________________________________________
>>
>> See: http://www.mscomputer.com for "Self Supporting Towers",
>> "Wireless Weather Stations", and lot's more. Call Toll Free,
>> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>>
>> _______________________________________________
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>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
>questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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