[TowerTalk] Horizontal Loop Performance??

[Jim Lux]

On 1/4/13 11:12 PM, Edward Sylvester wrote:
>
> Greetings All!
>
> I am in Saudi Arabia and had the opportunity to throw up some wire
> antennas.  I put up 30' of fiberglass mast on my 25' roof and
> installed an 80m INV VEE fed with open wire line, straight to tuner.
> Hears extremely well.  Cannot transmit until I get a license, which
> is in the works.
>
> I decided to take advantage of some tall coconut trees and installed
> a triangular-shaped horizontal loop with >700' of wire fed with open
> wire line, up 35-50', taking into account the sagging.  This goes
> straight into a 1:1 current balun at ground level.  Coax run is about
> 6'.  No issues.  Tunes perfectly.
>
> I ran some A/B comparisons with the Inv Vee and determined that they
> are very similar in performance!

Which is about what one would expect... both antennas are a decent 
fraction of a half wavelength in extent (so it's not like an amplified 6 
foot whip or something).

The receive performance is going to be dominated by the atmospheric 
noise, so whether the antenna has a different gain isn't going to make 
much difference.  Lots of people use active receive antennas on 160 to 
good effect, especially as part of a phased array so you can steer the 
null towards some noise source.

Where your two antennas may differ is on transmit: one may be better 
than the other in terms of resistive loss.  They're about the same 
height above ground (a tiny fraction of a wavelength), they're both 
horizontally polarized, they've both got a low feedline loss, etc.  I 
wouldn't expect a huge difference.  If you were comparing the big loop 
against a loaded 20m dipole, yeah, more of a difference.

What is your soil like?  Are you in Eastern Province with either 
sand/rock or with sabkha (the latter is the topband dream substrate)? 
Or rocks and such.  I doubt there's anywhere in Saudi Arabia with very 
deep topsoil (in the context of 160m wavelength and skin depth), except 
perhaps Hofuf in the middle of the Al Ahsa oasis.

If you are in a coastal area with high salt content and high water 
table, you might think about a vertical.


>
> I was hoping the Loop would blow away the Inv Vee but was
> disappointed when this did not occur.  Has this been your experience?
> I have tried to read as much as possible, but there are varying
> opinions on loop expectations.
>
> Your opinion would be greatly appreciated.  Frustrated....
>