Topband: Shunt feeding a tower with side mounted yagi

[Pete Smith]

At 02:36 PM 5/28/02 -0400, Tom Cathey wrote:
>Interesting info on the lower mounted Yagi on a 160M shunt fed tower!
>
>I am in the same situation with a 110' shunt fed Rohn 45 tower with a full
>sized 40M rotary dipole at 35' and a large 14el  13-32mhz  60'  boom log
>periodic at 65'. Lots of mid loading!  These antennas are at optimum heights
>for their jobs. This shunt fed tower also has a parasitic reflector and
>director for 160M.


I have a 104' shunt fed Rohn 25 tower that combines the complication of a 
mid-mounted tribander with feedlines for a K3LR/W9LT lazy vee dipole array 
coupling to the tower at about 45 feet up.  A series of models (with a lot 
of help from K6SE) proved not to be very close to the real world in this 
strange setup.  Even at the 55' level, the measured R at the bottom of the 
shunt feed was only about 6 ohms!  I undoubtedly had some interference from 
a nearby 1550 kHz BC station affecting this measurement, but the bottom 
line was that I had to go to an omega match to bring the feedpoint to 50 
+/-j0 at 1830.  I was finally able to do that, and the resulting antenna 
has proved to be at least an adequate transmitting performer on 160 with 
200 watts, though about as disastrous on receive as you might 
expect!  Receiving antennas are on the list for this summer.

73, Pete N4ZR

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