Beverages depend on poor earth conductivity to work. It is this poor
conductivity that cause the velocity factor of the induced current in
the antenna to be less than the that of the incoming wave in the air.
This is the mechanism that causes the antenna to be directional. (It's
more complicated than this, for a total explaination.) For that reason
the antenna needs to be close to the ground. This also keeps the
vertical portions of the antenna from contributing to the pattern. It
really needs to be 10 ft or less. Lower is better pattern wise, at the
expense of gain. Some people even use BOG (beverage-on-ground) antennas.
It also needs a termination at the far end if you want a one direction
antenna. No termination will make it bi-directional.
With a wire of 0.7 wave on 160M or about 380 ft, 20 ft off ground, no
termination, all in a straight line, and fed singled ended with respect
to ground, you have something close to an NVIS antenna on 160M. Low
gain and max pattern is close to straight up. Front to back is maybe 5 dB.
Since you are feeding it with a coax with floating shield, the coax is
part of the antenna, and the pattern will be even more unknown and
distorted.
Beverages don't like to have bends in them. You can tolerate a little.
For a 1000 ft beverage you may be able to get away with a 50 ft jog and
have a side spur show up in the pattern, but the antenna will still be
useful. If you make this a 100 ft jog you will completely destroy the
pattern.
Jerry, K4SAV
AD5VJ Bob wrote:
>Does a beverage have to be in a straight line or can it
>have 90's in it. this wire has one 90 and a couple of
>turns less than 90
>
>It has no termination at the end and I have restructured
>it so I am now feeding it with the center conductor of
>rg-75 shield not connected just free.
>
>It then goes to the tuner and the tuner goes to a ground
>rod.
>
>Listening this morning and it seems to tune ok from
>180mtrs thru 6.
>
>The wire is approximately .7 wavelength at 1832.00 from
>end to end.
>
>It is all now pretty much at 20' above ground horizontal
>hanging from metal supports.
>
>
>
> 73 fer nw,
>Bob AD5VJ
>
>10X# 37210, FP#-1141, SMIRK#-5177
> <http://www.n5iet.com/> http://www.n5iet.com/
>Code may be taking a back seat for now,
>but the pioneering spirit that put the code
>there in the first place is out front of it all.
>
>
>
>
>
>
>
>
>
_______________________________________________
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
|