Topband: Inverted L or 1/4 wave sloper?

Augie Hansen augie.hansen at comcast.net
Mon Nov 26 10:11:31 EST 2007


Ryszard Tymkiewicz wrote:
> ...
> Jim I agree with Don K5AQ.. My tower is slightly higher ..18 meters and the yagi is just above it.
> I was using 1/4 wave sloper for almost 15 years and I'v thought its the best  solution (#280 wkd using that sloper),
> but 3 years ago I tuned the tower and I used gamma match..the difference between 1/4 wave sloper and 
> matched tower was 1 to 3 S...favouring the tower. Its easy to make and to try it....

Hi Rys,

My tower is  58 feet tall and supports an LPDA at 60 feet (plus some 6m 
antennas at 70 feet, but they don't influence the top-loading 
significantly).

Regarding your shunt-fed tower:
- What kind of radial system do you have for the tower?
- What wire or tubing size do you use for the gamma "rod""
- What is the rod-to-tower spacing and how high up is the tap point?
- Do you use a single series capacitor or an Omega match (two caps) at 
the input?

I ask because I am currently using a 1/4-wave sloper and would like to 
try the shunt-fed arrangement again. I had used a shunt-fed tower at a 
previous QTH with good success, but haven't done it here due to a very 
limited area for a radial field on a city lot.

Cheers,
Gus Hansen
KB0YH






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