[TowerTalk] Issue with Tri-Band Yagi SWR

[K8RI]

On 3/13/2012 12:11 AM, Bob K6UJ wrote:
> If you haven't already I would disconnect the coax from the driven element connectors and hook up connect a portable SWR unit like the MFJ with a short coax jumper.
> Run the swr profile across the bands and see whet you get.  This would rule out the coax.  You said your coax was quite old It could be the problem.

"Normally" old, bad, coax will give you a better looking SWR, not a 
higher one.  The more the loss the better it looks. Also bad coax would 
tend to affect all bands the same or similarly. Bad coax connections 
should also affect all bands.  Of course , shorts in the coax is 
something different.

He already found water in the balun. I'd be suspicious of the traps.  Do 
they have the drain holes on the bottom.  Are there drain holes. The 
traps have been removed and reinstalled/ Are you sure they are oriented 
properly?  IIRC a trap installed backwards will affect 10 the most, and 
20 the least.  If so are the correct traps on the correct elements in 
the correct order.  The traps are apparently clean.
IIRC Wilson only had a couple versions of their tribander, but the big 
and little one were fed pretty much the same and I believe they could be 
fed with a simple current/choke balun.

The only thing I can think of (because it affects 10 the most and 20 the 
least) is the orientation of the traps. OTOH I don't claim to be very 
knowledgeable about the Wilson. I used to sell them, but that was about 
35 years ago and I'm happy to remember what I had for breakfast.

Good Luck es 73

Roger (K8RI)