[KYHAM] Advice About HF

[Steve N4LQ]

Hi Mike and ya'll:
Here's a copy of another post to another group about my loop.
My loop is cut for 80m at 3550. It is horizontal and 50' above ground at all
points. It is supported at 3 points, thus a triangle. Made from 14ga
insulated electrical wire.
At the corner feedpoint I have a 4:1 current balun. Either the Radio Works
or W2DU version is fine since there are no really high voltages involved.
I feed it with about 75' of RG-8. SWR on the low end of 80m is 1:1. The 40m,
20, 15 and 10m SWR is also 1:1.
30m is 5:1, 17m and 12m are 2:1. The internal tuner easily handles those low
swrs on the WARC bands.
Modeling programs show that a triangle shaped horizontal loop has more lobes
than the typical square loop thus this tends to make a better omni
directional antenna on all the harmonics. Square loops have a rather strong
lobe opposite the feedpoint which tends to dominate.
At 50', the radiation angle on 80m max is 90 degrees making it great for
200-600 miles at night however I have worked some dx. On 40m, the max angle
drops down to about 45 degrees making it a good all around antenna for both
local and dx work in any direction.
On 14mhz and higher it becomes a great omni directional dx antenna with very
low angles.
The same plan can be scaled to 160m although you can expect the swr to be
higher on 160 due to the relatively low height. I have tried several 160m
versions using various feed methods including open wire feed and performance
is slightly poorer than a simple inverted vee on the top band. It's simply
too low unless you can get it up to about 90' which would be a tall order.
The 160m version when used on 80m does rather well for dx since the max
angle resembles the 80m loop being used on 40m.

Remember. The low swr happens on ALL harmonics. 3.5mhz X 2 + 7 mhz etc.
If you are a 75m phone guy and cut it for 3.9mhz then 3.9mhz X 2 = 7.8mhz , 
15.6mhz etc. Woops! Wrong band!
This means that your antenna should be cut for the lowest frequency on the 
fundamental that when multiplied makes the harmonic come out somewhere in 
the next band up. Hmmm. That's hard to put into words but I think you'll 
understand.
The formula for a full-wave length loop is 1005/Fmhz.
Mine came out around 275' or so, a little over 90' for each of the 3 sides.
The feed point should be stationary but the other 2 corners should be 
floating. When the trees sway, the loop needs to be able to slide around. 
I've tried various insulators and pvc parts. After searching for 20 years, I 
discovered these wonderful pulleys.
http://www.pennplastics.com/pulley.htm
I got mine a Lowes in the clothesline area. They are hard to find! They are 
fully insulated and hold up great in sunlight for many years. Your loop will 
love this. Get your rope over the tree and hoist up the pulleys. Let the 
loop slide through it. No insulators are necessary!
Recommended reading:
http://www.arrl.org/tis/info/Loop-H.html
ARRL members only can log in and view these.
If you can't get the loop up 50' then you may have some swr to deal with on 
80m. No big deal. It won't be very high and the internal tuners easily 
provide a match.
You can also scale the loop for 40m and use it up through 10m.
Various method of feed have been tried over the years here. This is the only 
one that doesn't require a tuner. The original article in 1985 QST called 
for coax feed with no balun. That works but requires some tuning and can 
result in some RFI on some bands. Stick with the balun. Be sure it's a 
"current balun"  and 4:1 ratio.
Have fun!
Steve Ellington
N4LQ at iglou.com
----- Original Message ----- 
From: "Mike Pugh" <mikepugh at mikepugh.net>
To: "n4lq" <n4lq at iglou.com>
Sent: Monday, June 06, 2005 4:11 PM
Subject: Re: [KYHAM] Advice About HF


>
>
> n4lq wrote:
>
>> I use an 80 meter horizontal loop fed on the corner with a 4:1 balun. My 
>> swr is 1:1 on all but the warc bands. WARC bands require the use of the 
>> rigs internal tuner, an easy match. This loop is a triangle and is fairly 
>> omnidirectional on all bands, having many lobes. Total cost, about $50 
>> for balun, wire and pulleys.
>
> Hey Steve, got any plans, or dimensions for this monster? Thanks! Mike 
> KA4MKG
>
>