[NLRS] Favorite horizontal loop design?

[John P. Toscano]

Paul Beckmann (WAØRSE) wrote:

> I'd like to make up a stack of 3 horizontal loops for 6, 2, and .7
> meters and am wondering what tried-and-true designs the NLRS crew
> might recommend. I'm especially interested in matching section
> designed used. I'd also like any advice on spacing that will keep me
> out of trouble. I'll likely build all of them out of copper
> pipe/tubing for fixed outdoor use. Not anything for great performance,
> just to have weak signal capability from the home QTH.

This has started an interesting thread.  At home, I have an old M 
Squared SQLOOP on 6M, and a stacked pair of M Squared SQLOOPs on 2M. For 
the 2M stack, I went the "Cadillac" route with a real 2-port power 
divider and all 50 ohm coax (one half-wave section and one 3/2 wave 
section to the two antennas from the 2-port PD).  Not sure how much 
penalty I would have paid by using two odd multiples of 1/4 wavelength 
75 ohm phasing lines to a simple T, which is the other option that M 
Squared was selling at the time (the Yugo solution instead of the 
Cadillac solution).  Anyway, I realize that when you talk about stacking 
them, you mean three different single-band antennas stacked on the same 
support mast, not 2 or more antennas per band stacked for extra gain.

But, sort of on topic, I *DO* have these three antennas stacked on the 
same support mast.  The 6M loop is at the top, and the pair of 2M loops 
are below it, spaced 1/2 wavelength (about 40 inches) apart from one 
another.  I guess the optimal spacing of a pair of 6M loops would be 12 
feet apart (per M^2 web page on the 6M HOLOOP), so the capture area of 
the 6M loop at the top of the mast would extend down 6 feet, and the 
capture area of the 2M loop below it would extend up about 2 feet, so 
the interaction between them would be negligible if they were 8 feet 
apart (their capture areas just touch), and excellent if they were 6 
feet apart (the capture area of the 6M loop just reaches the actual 2M 
hardware.  Anything closer is a compromise, and the closer they get the 
worse the compromise gets.  As Jon has pointed out, a test would be in 
order to see how close they can get without an obvious performance 
penalty, but as Gerald points out, your performance testing is probably 
going to be awfully crude.

I did want to mention that the horizontal loops have been "lifesavers" 
for me in a couple of circumstances.

One, when my rotator was out of service for half a year being repaired, 
I still had SSB/CW capability on those 2 bands for which I had the 
loops. I had a lot of fun with Sporadic E and tropo openings on those 
two bands when my rotatable antennas weren't rotatable.

Another, if I want to quickly check for 6M sporadic E in *ANY* 
direction, I can just flip the coax relay to the 6M loop and listen in 
every direction at once.  In a really powerful opening, many stations 
can be worked on the loop with no pointing hassle at all.

As was also pointed out, working close-in stations is much easier with 
the loops, since they have "enough" gain with zero pointing effort, 
whereas a close-in station to your NorthWest may be hard to work with 
your high-gain beam pointed NorthEast or SouthWest. How fast does your 
rotator rotate?  :)  And, in a multi-station ragchew where the other 
folks are all in different directions from you, the omnidirectionality 
is a blessing.

Don't get me wrong, I like antennas with a lot of gain!  But there are 
times when the horizontal loop comes in handy. I never got one for 222 
or 432, and after looking at this thread, I may get motivated to build a 
couple instead of sending more money to a "real antenna" builder...

73 de W0JT