TopBand: 160m shunt feeds

[km1h @ juno.com]

Although it obviously radiates Bill, I question the efficiency of a #12
wire 4' away from a large tower cross section. 
Do you have anything to show that this is a correct  d1/d2 ratio and
spacing?  It just does not seem proper IMO and I would think that it
could be improved. 

An accurate way to grid dip a tower was explained in my 12/86 CQ article.
Simply drop a #12 or so wire from the very top of the tower and couple
loosely to the gdo at the base via a one turn loop and the antenna
appears as a folded unipole.  This required a minimum of 4 radials at the
tower  to function properly for me. .
Most GDO's do not cover below 2MHz. I used a Millen 90651-A tube gdo with
the 46702 coil which covers 925 to 2000kHz.   The Measurements Corp Model
59 with the 59LF head and coils is another choice.  I am not aware of any
SS GDO that includes that low a  frequency coverage. 

The 100' tower at the old QTH with the 10/15/20 monobanders reasonated at
1425 KHz.   A 140' tower with a 4el 40 and 4el 10/15 above that
reasonated at 1290KHz.  Altho both  matched and worked well individually,
 all attempts to phase them were not successful. Spacing was a tight 70'.
 

When I moved here I followed Bill's Colorado example and just hung a 1/4
wave wire from the top guy of a 160' tower and used elevated radials. It
worked so well I added a second wire and phased them. The tops are only
about 50' apart and the bases are 135' .  Directivity with a simple ON4UN
78 degree coax phasing line is over 15dB and often 25dB, depending on
arrival angle.  Since I am on a hill with solid rock just below the grass
I am amazed it works so well....all the textbooks say do not use a
vertical on a hill at 160M and BC frequencies. 
I also have an inverted V at 160' which is superior out to 1500-2000
miles but the vertical blows it away on long haul including greyline
either East or West. 

All of the responses here have been very informative; keep them coming.

73....Carl   KM1H

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