Topband: AM broadcast tower and 160m dxpedition

[Carl]

Make them shorter and they will often do well over tidal marshes but not 
over open water.

For a 240' tower Id suggest gamma feeding it up at the 1/4 wave point and 
use 4 elevated radials. It the AM BCB radials are installed they will make 
an excellent ground screen but do not connect them to the 160M feedline.

Carl
KM1H


----- Original Message ----- 
From: "Charlie Cunningham" <charlie-cunningham at nc.rr.com>
To: <Gary at ka1j.com>; <Topband at contesting.com>
Sent: Tuesday, March 25, 2014 5:24 PM
Subject: Re: Topband: AM broadcast tower and 160m dxpedition


> That's not so surprising Gary !!  te Way the Beverages and similar 
> slow-wave
> antennas work is that they depend on the lossy GND  underneath for their
> operation, so a salt marsh would not be a very beneficial GND structure
> under a Beverage!
>
> 73,
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Gary
> Smith
> Sent: Tuesday, February 25, 2014 5:09 PM
> To: Topband at contesting.com
> Subject: Re: Topband: AM broadcast tower and 160m dxpedition
>
> My Inv-L is on a salt marsh on Long Island Sound in Connecticut & I
> ran two bidirectional 860' beverages over the salt marsh. I had
> terrible results with the beverages, very noisy and hardly any
> improvement over the Inv-L, much of the time the Inv-L was more
> effective on Rx. With that, my experience of beverages & salt marshes
> says to avoid this route.
>
> I ended up with a HI-Z Triangular array for Rx and it works very well
> at the same location.
>
> Gary
> KA1J
>
>> No, I don't believe 240' is too high - especially if the tower has a base
>> insulator!  It would be so close to 1/2 wave on 160, that it could be fed
>> very well as a 1/2 wave radiator on 160, either via a parallel tuned tank
> or
>> a 1/4 wave of perhaps 450 oh ladder line. A 1/2 wave radiator wis an
>> excellent transmit antenna, and, because of the high feed-point impedance
>> can be driven against a very modest ground arrangement
>>
>> Like you, though, I believe they would do well to put up some terminated
>> loops, or perhaps a Beverage (or 3?) for receive antennas! A 240' 
>> vertical
>> would, I think,  be a VERY noisy receive antenna. If they put up a KAZ
>> terminated loop that only requires one overhead support, they could steer
> it
>> around with ropes and weights on the ground. The KAZ is like ON4UN's
> FO0AAA
>> 160 receive loop.
>>
>> 73,
>> Charlie, K4OTV
>>
>> -----Original Message-----
>> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of 
>> Richard
>> Karlquist
>> Sent: Tuesday, February 25, 2014 3:38 PM
>> To: topband at contesting.com
>> Subject: Re: Topband: AM broadcast tower and 160m dxpedition
>>
>> Congratulations on your adventure.
>>
>> In the past, I have seen some of these AM tower efforts
>> ruined by lousy receive conditions.  I suggest you
>> get an advance team out to the site to check
>> out the noise level etc. and maybe put up some
>> temporary beverages, loops, whatever and LISTEN
>> on them.  Use WWV and WWVH on 2.5 MHz as a beacon.
>>
>> Others can comment on whether 240 feet is too high.
>>
>> Rick N6RK
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>
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