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[TowerTalk] DMS Antenna

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Subject: [TowerTalk] DMS Antenna
From: (Charles W. Shaw)
Date: Tue, 09 Dec 1997 13:21:16 +0000
Hello again,

        Last February I posted a note saying:

"I am about to try a Double Magnetic Slot antenna on 80 meters as described
by Lew, K4VX, in Vol. 4 of the ARRL Antenna Compendium.  Who else has tried
this?  Suggestions, advice, results, comments?  Thanks."

        About 6 members of this list were interested.  I  have finally built 
it, and  offer this very preliminary report:

        The antenna is completely described by Lew Gordon, K4VX, on pages 18-21 
of the reference above.  The model I selected is illustrated in his Fig. 7--a 
single-wire DMS 227 feet long by 22.4 feet tall.  I am feeding it direct with 
50 ohm coax at one of the top-outside corners.  Its placement is far from 
ideal.  The top wire is about 60 feet high on one end, and the other end is 
only about 32 feet high.  By making it into a  parallelogram, I have kept the 
three vertical parts practically vertical.
        With this installation the antenna shows resonance a about 50 KHz below 
the bottom of the band.  SWR at 3.005 is about 1.7:1.  I have not had a chance 
to "prune" it, but I have put the tuner in line and made a few contacts.  I am 
quite encouraged.  I hope to do some more work and on-the-air testing this 
week.  (Pending El Nino WX.)
        The contacts were DX except for trying it with a group of my 75 meter 
friends nearby (100-350 miles).  These nearby stations report that my signal is 
very much down--and tell me to put the dipole at 60 feet back up and quit 
fooling around.  (They are not DXers and don't like to strain their ears.)  The 
7 DX contacts (first 7 DX heard) using a KW output so far are:
       12-5-97   HP      12-8-97   LY      12-9-97   UA0
       12-5-97   JD1     12-8-97   HA      12-9-97   RA0
                         12-8-97   FG
All 7 were worked on the first call, except the HA took 2 calls.
        If you want to skip over your neighbors and hit the DX, this antenna 
may prove useful.  Likewise, local reception is weaker than with the dipole.  I 
would be glad to give details of my construction if anybody is really 
interested and needs ideas.  The biggest problems are:  1. What holds it up.  
2. How do you manage 530 feet of wire until it is hanging in the air!

73, Charles

Charles W. Shaw, N5UL
Hobbs, NM (near the SE corner)

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