Having a strong high angle lobe can be a benefit when seperate receiving
antennas are used. It keeps locals further away and is a favorite trick of
contesters on all bands. With yagis just feed a small portion to a low
antenna pointing backwards from the direction being worked.
Ive repeatedly mentioned on here that there are many times where a high
angle works best for 160M DX and throwing it away may not be a good idea. It
might also be geographically dependent.
OTOH modeling has shown that the 1/4 wave Inverted L I had installed for
600M at 160' vertical and 300' sloping to 60' could be improved by 1dB going
to a 2 wire tophat.
It hasnt been detemined if the missing high angle will be detrimental.
Carl
KM1H
----- Original Message -----
From: "Jim Brown" <jim@audiosystemsgroup.com>
To: <topband@contesting.com>
Sent: Tuesday, September 06, 2011 12:47 PM
Subject: Re: Topband: Newbie Antenna Question (long)
> On 9/5/2011 8:03 PM, Jim Bennett wrote:
>> The ARRL Antenna Book, and ON4UN's Low Band DX'ing book, I accept the
>> fact that a vertical antenna is the best bet (for transmitting, anyway)
>> 160 meters, AND that the Inverted L is basically a vertical antenna. If
>> that is the case, does this mean that it radiates just like any other
>> vertical, primarily omnidirectional? If it is omnidirectional, does it
>> matter in which direction the horizontal portion of an Inverted L is
>> aimed?
>
> The vertical wire is omni and radiates at a low angle, the horizontal
> wire serves to resonate it and radiates at a high angle (for local
> contacts). A Tee top to the vertical (rather than the L) provides the
> same top-loading to resonate the wire, but the radiation from the top
> section cancels itself out so that only the bottom section is working.
> Thus, a Tee is a better low-angle antenna.
>
> The K6MM vertical is a compromise for when you can't string something
> into a tree. The wire in the tree is likely to work a lot better. With
> either, do the best you can with radials and have fun.
>
> It's worth trying to make that vertical as tall as practical, given your
> limitations. Taller means a higher radiation resistance, which means
> less loss in your radial system.
>
> 73, Jim K9YC
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1392 / Virus Database: 1520/3881 - Release Date: 09/06/11
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
|