[Antennas] 80/160 trap dipole problem

Sat Jul 31 14:49:42 EDT 2010

I have a 80/160 trap dipole at 70 feet - has worked well for years, I
made a new antenna out of #12 insulated wire installed the 80 meter
traps - connected on the needed wire for 160 - hauled it up and it
worked like a champ - SWR was low 1.2:1 on both 80 and 160.... for no
reason a few days later during a contact on 80 my SWR started to
flicker between 1.2 and 5
 I thought it might be the feed line from the tower base to the apex,
I changed it out - still the same. I thought it might be a bad relay
or connector in the remote switch box - switched then around - still
the same.
I also  placed a new Balun Design 1:1 3kw isolation balun as my center
insulator. I believe all components of the antenna system are working
and everything except the trap and balun have been checked. If I run
low power(5-20 watts) the swr is 1.2:1 - as I increase the power to
anything over 50 watts or so it starts the flickering swr reading. If
I run my auto antenna tuner it will bring the swr down to 1.2:1 with
only a slight flicker of the swr reading. I never run any more then
500 watts - the traps are Undellia 80 meter traps.  One more piece of
information - one of the traps has a crack in the coil form, it has
had this crack for years.
Sorry for such a long story - my question/s are:
1 Does this sound like a balun or trap issue
2 What would cause a intermittent swr reading on 80 and a sort of
solid reading on 160 (just a hint of flickering swr)
3 What happens to a balun or a trap to cause it to fail
4 With out special equipment, what would be the trouble shooting
methods for this problem
I hate to just buy new traps if it isn't an indication based on what I
have said.
Any comments or suggestions will be appreciated.
--
Myles Byrne - W1IKO
mail.mpb at gmail.com
mpb1 at comcast.net