Re: HyGain TH-7DX, tribander
I have an old TH-7DX that I am refurbishing. Everything has been cleaned up and
now I have it mounted about 12 feet up the side of a tower...for testing. I
recall having a problem on 10m and want to check out those traps before I do
anything else with the antennae, whether it be sold or used.
I have several questions relating to checking and tuning this antennae: If
anyone can offer guidance; pick-off/merge the answers or comments.
1. How do you check an antennae with traps? Yes, I know the regular way. But if
there is a problem how can you pinpoint the Pb.
Parameters, so far, at 12 feet above ground, for adjustment purposes:
I see acceptable VSWR's 15 and 20m, considering the current height above
ground, e.g. 2.5:1.
But, on 10m, I see 3:1+++ VSWR, with no appreciable null above or below 10m.
Lowest near-bye VSWR (null) was 27,440mhz with just a 3:1+ VSWR.
2. Can any of you please tell me something that can be determined from these
measurements? (re: traps)
This little jewel is 25 years old and is in immaculate condition. 14 years in
Wyoming/Montana couldn't have hurt it, except for Chinook wind damage risk,
and amazingly, 15 years in the humid/muggy/buggy, et al, South Texas
environment apparently did not hurt it. I had not used any of the special
lubricants between elements, etc, and everything came apart clean and shiny.
The stainless steel nuts and bolts, of course, were in nice condition. I did
oil them a bit before taking them loose to avoid any torque damage. I recall
that every time I moved, I had to replace too many S/S nuts and bolts damaged
from torque or galled threads.
Of course the plastic trap caps and driven element(s) insulators were trash!
Any help, tips or suggestions would be greatly appreciated !
Mike Bragassa, K5UO
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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