[TowerTalk] Extending Hytower

[dan hearn]

I have been down the road you describe with the Hytower. I used 4 in an
80m 4 sq array when I lived in Dallas. They were used in the
conventional configuration with the stubs removed and feeding the center
wire with the stinger insulated from the tower. 
  Since I work both SSB and CW, I became interested in improving the
efficiency and bandwidth of the towers, as you have. 
1.Strapping the stinger to the tower top raises the resonant frequency
  to about 4600 khz so it is necessary to restore 80m resonance by one 
  of the following:
  a. Increase stinger length by about 10-15 ft.
  b. Add a base loading coil.
  c. Add a center loading coil between the tower top and stinger.
2.I tried each of these and measured the Ra over a range of freq. 
  using a resistance bridge driven by a Tek 190B signal generator.
  This high level generator allows measurement of Ra in spite of BC
  broadcast pickup. Here are some data from the curves:

                         Ra    B.W.@1.5xRa    B.W. @ 2x Ra
                          
Hytower Base Loaded      37     215 khz        310khz

Hytower Center Loaded    39     340khz         460khz

Hytower Extended         40     375khz         500khz

Note: I would have thought the Ra for the extended tower would be lower.
The loading coils were Nr. 10 wire. 
The ground radial system was 20 1/4 wave radials buried 4 inches.
It has been several years since these tests were made. I cannot find
a curve for the Hytower in its original configuration, unfortunately. 
I believe it had less B.W. than these configurations.
Extending the Hytower is a fair sized project. I lived about 8 miles
from Texas Towers and was able to buy 20 ft lengths of 2"x .058 for the 
bottom of the stinger. I slipped a 12 ft piece of 1 7/8 x.058 inside 
the lower end for increased strength. In general, I built the stingers
out of a combination of available tubing pieces but it is necessary to
put inside sleeves at the lower end of each section for strength. The 
stingers on my towers move around in the wind but I have had no failures 
in the 24 ft towers or the stingers in the 5 years I have been using
them.

The center loading option looks pretty good for improving B.W.and can 
be accomplished fairly easily.

73, Dan, N5AR

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com