[TenTec] 30 meter loop antenna

[Bob McGraw - K4TAX]

Interesting approach Carl.  And also, you have coax ready cut for 18 pieces 
of 12" jumpers!  Just add connectors.

73
Bob, K4TAX


----- Original Message ----- 
From: "Carl Moreschi" <n4py at arrl.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, February 02, 2008 8:27 PM
Subject: [TenTec] 30 meter loop antenna


>I thought I would share with this group how I matched a 30 meter loop I 
>made
> to use with my Omni VII and Orion.
>
> I made a full wave delta loop for 10.1 mhz.  I used 14 gauge wire and
> erected the delta as an equilateral triangle with a flat side on top and 
> the
> point of the triangle directly at the bottom.  The triangle is 33 feet on 
> a
> side for 10.1 mhz.  I have the top side (33 feet) at 50 feet above the
> ground and stretched between 2 trees.  At the bottom point, which is 22 
> feet
> above ground,  I connected some very low loss 75 ohm cable I had.  I made 
> a
> tight coil of 18 feet of this cable ( 6 inch diameter) at the feed point 
> to
> act as a current balun to stop radiation from the feedline.  Now full wave
> loops are 100 ohm antennas at this feedpoint.  The normal way to match 
> them
> is to run a quarter wave of 75 coax and then switch to 50 ohm cable.  The
> quarter wave of coax will convert a 100 ohm impenace to 50 ohms.  But I 
> had
> a huge amount of this low loss 75 ohm cable so I decided I could run the
> entire length I needed (150 feet) in all 75 ohm cable.  As long as the 
> total
> length of cable is an odd multiple of quarter waves, it will still match 
> 50
> ohms.  So I used 150 feet to get to my antenna switch box and then I added
> an additional half wavelength of cable (40 feet).  I then used an MFJ
> antenna analyzer and began shortening the cable length 1 foot at a time
> until I found the 50 ohm point.  I ended up cutting back 18 feet of cable 
> to
> get to this point.  So now I have my 30 meter loop with a 1.0 SWR and no
> splice points at all along the entire cable.  I am finding this loop is
> performing very well.  I have been comparing it with my 130 foot inverted 
> L.
> My inverted L favors north-south and my new loop favors east-west, so the 
> 2
> antennas give me excellent all around coverage.
>
> Carl Moreschi N4PY
> 121 Little Bell Drive
> Bell Mountain
> Hays, NC 28635
>
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