[Elecraft] K2 problem or is it the antenna?

[Darwin, Keith]

Good Q's Ron.

The antenna is a 28' tall home-brew vertical using telescoping sections
of alum. tubing.  I put Penetrox at all the joints to avoid issues.  No
traps or anything, just a big piece of alum sticking up in the air.  It
is U-bolted to a pressure treated 4x4 buried in the ground.   I have 15
radials buried a couple of inches down.  Each radial is 20 feet long
IIRC.  It's been up since about Nov.

Yes, indeed, narrow bandwidth on a shorter-than-quarter-wave vertical
can be a good sign that efficiency is up.  My antenna is fairly close to
1/4 wave and with only 15 radials, having bandwidth of about 250 KHz at
7 MHz is not unreasonable.  With the bandwidth suddenly dropping to 90
KHz, that sounds like the vertical just got shorter.  I wonder if the
top broke off? :-)

The feedline is bolted to the base of the radiator and the braid is
bolted to the radial plate.  The feedline itself is 6 months old.  I
coated the antenna end of the feedline with coax seal to prevent water
from working its way back up into the coax.  I even mounted the coax a
foot or so up the 4x4 post and brought the connection end down to the
antenna so the water would drip down and off the end rather than back
into the coax.

So I doubt it is an issue with the coax itself.

I'll find it eventually.  Maybe a bad PL259 on the RG213 coax.  Maybe an
issue inside the tuner.  One thing is sure, I won't need a solder sucker
to fix the problem :-)

73!

- Keith -

-----Original Message-----
From: Ron D'Eau Claire [mailto:rondec at easystreet.com] 
Sent: Wednesday, April 19, 2006 4:36 PM
To: Darwin, Keith; 'elecraft'
Subject: RE: [Elecraft] K2 problem or is it the antenna?

Keith wrote:
Also, the bandwidth of the tuned system has become much narrower.  I
used to get 2:1 bandwidth across most of the 40 meter band.  Two nights
ago, I struggled to get 2:1 over 90 KHz.

----------------

Narrow bandwidth is a sure sign of a reasonably efficient, but
physically small antenna compared to the wavelength. That would cause me
to look at something intermittent in the antenna itself that is
disconnecting part of the radiator. You said it was a ground mounted
vertical. Does it have any traps or other bits beyond a vertical
radiator? I'd sure look for a connection that is opening up, as you
mentioned. Possibly even an intermittent feedline connection to the
antenna. 

Ron AC7AC