I had a similar problem with high SWR on 20. Checked coax first but it was
OK. I found a 15M reflector trap with corroded screws. Figured I'd better
check them all and found most of the trap screws in a corroded condition. I
replaced them with SS screws using a non-washout conductive grease after
cleaning the contact areas. Antenna works great now.
The following came from the HyGain guy at MFJ:
A high 2 or 3:1 SWR without moving the frequency usually means that
a front or back trapped element has a problem.
A 10 meter director trap might be open.
A 15 meter reflector trap might be open.
An SWR in the 5:1 or higher range would generally indicate a 15 or
10 M DE trap being bad.
Again, these tips came from the HyGain tech at MFJ and proved accurate. The
HyGain tech also provided details for checking the TH7 traps electrically. I
found them very helpful.
Learned quickly how to easily disassemble/reassemble the traps and I'm glad
I took the time to do so. Mine was one of the original early TH7's so had up
a lot of years, the last 15 in a heavy salt air environment.
Don W7WLL
-----Original Message-----
From: Ted Boerkamp
Sent: Tuesday, June 13, 2017 6:02 PM
To: Towertalk Reflector (E-mail) (Towertalk Reflector (E-mail))
Subject: [TowerTalk] TH7 and high swr on 20m only
Hello all.....I have just noticed tonight that I have a change in normal swr
on the 20m
band of my TH7 beam. I am now getting pretty much 2:1 swr across the band.
10M and 15M are both fine.
Any suggestions as to where to look first???
Any help appreciated.
73
Ted VE3SS
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