[Boatanchors] antenna question

Sun Aug 24 18:53:33 EDT 2014

Ray --

If a trap failed open, it would affect both 15 and 20 meter performance; if a trap failed shorted, it would cause the behavior you are seeing. Seems to me, anyhow.

73,

Carl W6UO

-----Original Message-----
From: RAY FRIESS <rayfrijr at msn.com>
To: boatanchors <boatanchors at mailman.qth.net>
Sent: Sun, Aug 24, 2014 3:33 pm
Subject: [Boatanchors] antenna question

I'm a bit puzzled about something even after about 40  years as a ham.  Would be 
interested in comments or
thoughts from the group.

I have a triband beam for 10, 15 and 20.  It's one of the old Hy-Gain Explorer 
beams.  It has two traps in the reflector
and two in the driven elevent and four traps in the director.    It worked 
perfectly on all three bands for a long long time,
and now on 15 it is unusable, but remains perfect on 20 and 10.

As I understand the operation of the driven element, everything (element wise) 
between the boom and the trap is for 10 and 15 meters.  Everything from the 
outside of the trap to the end of the element is for 20 meters.

My problem is this...  I have a fantastic SWR on 20 and 10 ...  practically a 
1.2 to 1 on each band across the entire band.
I am able to work just about anything I can hear with 100 watts barefoot, and 
seldom have to turn on the 30L-1 except
in big pileups.   However, on 15, the beam is unusable.  It pegs the SWR meter 
at infinity and in my TS 50, the protection
circuit drops the power output from 100 watts to barely visible.

My question is this ...   what could be causing the high SWR on 15 meters, while 
not affecting 20 and 10 at all?
If everything from the outer edge of the trap to the end of the element is for 
20 and the trap is for 15/10 discrimination,
shouldn't 20 SWR also be through the roof if the trap was bad on 15?  The RF for 
20 has to go through the trap and
if it has gone bad on 15, wouldn't it also mess up 20?

what should I be looking for or at?

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