[Antennas] 80 meter delta loop

Tue, 6 Apr 2004 19:19:11 EDT

In a message dated 4/6/2004 1:19:23 PM Eastern Daylight Time, [email protected] 
writes:

> Full wave loops may be fed two ways: via a tuner and 450 or 600 ohm line 
> or
> the most common way is via a one quarter (1/4w) wave 75 ohm coax
> transformer. 
> Use the Formula of 246/f(MHz)x VF
> RG-11A is 66% VF, while RG-11 Foam is 78% VF nominal.
> 
> I used RG-59U years ago on my 80M loop, since power was limited to
> 400-500 watts at the time. Now with 1500 watts, RG-11 is a 
> M-u-s-t !
> 

I am running a full wave 40m loop (not a delta, but roughly 40' x 27') and 
have fed it both with a 1/4 wave 75 ohm section which worked out to around 35 ft 
of foam cable tv coax, and in it's current configuration fed with home-brewed 
twin lead.  The loop is horizontal and up only 20 ft but does a great job for 
what I built it for and that is for calling a net based in the SE on 7.251 
called South CARS.  I run 100 watts and I can hear as well as some of the guys 
who have room to run big or multiple antennas for 40M.  This is no DX antenna 
by any means but it is exactly what I needed for running this "local" net.

I do highly recommend feeding your loop with the 1/4 wave matching coax if 
you plan to use the antenna on one band only.  If you plan to use it on all 
bands then feed it with twin lead.  Here is the rub, and I know I will get flamed 
for this, but any convenient way of spacing 2 wires and keeping them spaced 
evenly from feed point to tuner will work on all bands.  In my case it worked 
out that I had an abundance of wire ties and 3/4" pvc pipe.  I cut 3/8" pieces 
of the pipe and after stretching my 14 gu insulated wire for a couple of days I 
wire tied the little pieces of PVC between the wires cut off what I need for 
this project and hooked it up.  Not only did it not suffer in performance for 
this but I can now run it on all bands from 60-6M. 
Good Luck, God Bless and it looks like you are getting some very good advice 
so far  so you should be able to pull this off without a hitch.
73
DE KG4FET Sandor

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