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[TowerTalk] Checking / Testing traps??

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Subject: [TowerTalk] Checking / Testing traps??
From: "Mike Bragassa" <>
Date: Tue, 31 Aug 2004 19:04:49 -0500
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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)

side note:
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
Conroe, Texas


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