Topband: Fw: Shunt fed tower

[wb6rse1 at mac.com]

On Apr 25, 2010, at 7:10 AM, Wayne Rogers wrote:

Obviously a 40' gamma match is easier to implement
than a full height (90' in my case) shunt feed.  Is there any benefit to
going all the way to the top?
_________

I shunt feed my tower at the top of the bottom section, which is at 22 ft. The rod is 3/8 inch aluminum, 15 inches from the tower leg. I then use an omega match which obviates the need to search for the vertical sweet spot. My shunt feed works on 160 and 80 using latching relays to switch capacitors to change bands. This 22 ft feed point causes very high RF voltage across the omega capacitors which requires them to be vacuum variables. In addition to the voltage breakdown, the vacuum variables verniers make tuning very easy and precise compared to air variables. Attach point and distance from the tower leg will affect the values of the capacitors required, the RF voltage breakdown and the bandwidth vs SWR.

It works. 173 DXCC on Top Band in 10 years from a very small West Coast USA city lot.

YMWV.

GL & 73 - Steve WB6RSE