Frank has the good fortune of having decent ground conductivity, not all of
us have that luxury.
Carl
KM1H
----- Original Message -----
From: "Tim Duffy K3LR" <k3lr@k3lr.com>
Cc: <towertalk@contesting.com>; "Barry Kirkwood" <barry.kirkwood@gmail.com>
Sent: Monday, July 23, 2007 1:21 PM
Subject: Re: [TowerTalk] 160m Inverted L
> Anyone who is concerned with the difference in antenna efficiency with
> respect
> to elevated radials VS. ground mounted radials (assuming you have a
> choice)
> should re-read Frank, W3LPL's excellent post last year here on TowerTalk.
> It concerned his 160 meter 4 square array and the real world operational
> difference he noticed when he converted from elevated radials to ground
> mounted
> ones.
>
> I know he is not sorry that he made the change.
>
> 73!
> Tim K3LR
>
> jeremy-ca wrote:
>
>> My take on the subject from many years of 80/160M operation at different
>> locations is as follows:
>>
>> Superb to very good ground such as a salt water marsh, a fresh water
>> swamp
>> with plenty of dead vegatation (gooey muck). Anything works, 4 to 16 1/4
>> wave radials is fine, more cant hurt but dont go overboard. 4' ground
>> rods
>> at the ends and at the base.
>>
>> Good to average ground as in a midwest farm field. 32 to 64 on ground
>> radials, 128 is overkill.
>>
>> Poor to average ground. 64-128 on ground radials, maybe a ground screen
>> within 30-50' of the base. Consider 30-40 elevated radials if possible.
>>
>> Very poor ground, most of New England, etc. Dont waste your time with on
>> ground radials unless there is no other choice. 30-60 elevated radials
>> and
>> even a ground screen if feasible; this is becoming a popular choice among
>> AM
>> broadcasters either installing a new system or having found their 50 year
>> old buried radials have become one with Mother Nature.
>> The FCC has actually asked some stations to reduce power since their
>> proof
>> of performance field strength with elevated radials is actually higher
>> than
>> their as new buried system.
>>
>> Im a big fan of elevated radials since I live on top of a ridge; granite
>> has
>> poor conductivity! At a prior location with damp but sandy soil a ground
>> screen made a huge difference when placed over 60 on ground radials.
>>
>> At the cottage in Maine 100 yards from the ocean I use only a 50' long
>> ground screen covered with 1/2' loam and reseeded. Thats almost the size
>> of
>> the available open ground. The antenna is 50' of mast with a 4 wire top
>> hat
>> and a coil at the base to complete the required resonance. With a
>> shielded
>> loop for RX that setup has worked a few new ones when Ive had to be there
>> for family reasons.
>>
>> The fencing sold at garden centers works well. Get the type with a 2 x 4"
>> mesh that is welded, then galvanized and then plastic coated. Peel off
>> enough plastic to solder to and seal the joint with automotive undercoat,
>> roofing tar, etc. I found my mesh (5 50' x 4' rolls) in a local weekly
>> Want
>> Advertiser, it was one year old and like new and 1/3 of new cost.
>>
>> Remember that the better the ground the lower the angle for maximum gain
>> up
>> to almost the free space model. This may become self defeating since some
>> DX
>> comes in at angles above 40* or so. I worked 3Y0A some years ago (1989 or
>> 90) on 160 with an inverted Vee at 60' apex. It took all of one call in a
>> monster pileup.The operator later told me at Dayton I was way above the
>> din.
>>
>> Carl
>> KM1H
>>
>> ----- Original Message -----
>> From: "Barry Kirkwood" <barry.kirkwood@gmail.com>
>> To: <towertalk@contesting.com>
>> Sent: Monday, July 23, 2007 10:20 AM
>> Subject: [TowerTalk] 160m Inverted L
>>
>> > FWIW:
>> > Talking the 160m problem:
>> > The subject of counterpoises, ground planes etc is a subject in itself.
>> > My 02c worth:
>> > There are two main questions:(a) How to configure the
>> > antenna/earth/radial
>> > etc system so as to get current flowing in the thing.
>> > (b) What the effect of the environment (salt water, seaside, mountain
>> > top
>> > etc) and whatever arrangements conspire to get most of the radiation at
>> > a
>> > reasonably low angle.
>> > My limited experience: Made an inverted L out of my 50ft tower and
>> > tribander
>> > plus a 20ft topmast of alumin tube. One thick insulated wire run up
>> > tower
>> > and off the top of the top mast (up 70ft) and tied off to tree. Gave
>> > 150ft
>> > wire in all (about 80ft in the L loading wire, sloping down to about
>> > 50ft
>> > high at end.
>> > Fed with gamma match wire connecting at 40ft level, held off 3ft by
>> > spreader.
>> >
>> > Tried loading against a collection of maybe 16 random length radials,
>> > most
>> > only 50-60ft. Had little joy until I made two radials like a 160 m low
>> > dipole, snaked around my boundary fence and one leg along top of fence
>> > of
>> > kind neighbour. Grid dipped to 1830. Connected to the braid of coax at
>> > feedpoint.
>> > Series variable C feed to gamma wire.
>> > Effect was obvious and immediate. Thing tuned up, could bring swr to
>> > 1:1
>> > by
>> > adjusting C and fiddling gamma match spacing from tower.
>> > Should mention my ground quality very poor.
>> > Did not connect the random radials.
>> >
>> > This set up could work Eu from ZL whenever they could be heard.
>> >
>> > My take on this: Get some part of the system that you know is resonant
>> > in
>> > band, maybe even one 1/4 radial would do. Then there is a good chance
>> > that
>> > the rest of the system will tune up against it.
>> >
>> > Of course if you can come up with a great radial system ,the above
>> > would
>> > not apply.
>> >
>> > Quarter wave inverted Ls may not be the greatest, but given a
>> > reasonable
>> > earth system give a good bang for the buck. Get the impression that
>> > most
>> > users are reasonably pleased with them.
>> >
>> > --
>> > Barry Kirkwood PhD ZL1DD
>> > barrykirkwood@gmail.com
>> > _______________________________________________
>> >
>> >
>> >
>> > _______________________________________________
>> > TowerTalk mailing list
>> > TowerTalk@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/towertalk
>> >
>>
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