I don't think it's coax, I think it's simply interaction between
antennas and Les's misunderstanding of the importance of SWR as an
indicator of antenna performance.
Repeat after me --
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
SWR is NOT an indicator of antenna performance.
OTOH -- the "balun" used should be exactly what the antenna designer
recommends. The word "balun" is used to describe (at least) a dozen
different things that are VERY different from each other. The operation
of the antenna, as well as the match between antenna and feedline can be
greatly affected by which is used.
So -- study the instructions for the antenna, use exactly with the mfr
recommends, and if you want to minimize RX noise, ADD a common mode
choke on the coax side of the mfr's recommended matching device, as
described in by Cookbook. k9yc.com/RFI-Ham.pdf
73, Jim K9YC
On Tue,11/10/2015 1:38 PM, Les Kalmus wrote:
Chris,
I had a similar problem that turned out to be the coax. It leaves the
top of the tower over an arm, then hangs. The center conductor
migrated at the top of the arm.
I had to cut that section out and remounted everything but hung the
coax from the arm with a cable grip from McMaster. No problems since.
From your description, you should probably recheck the coax and make
sure there are no points where there is pressure that could cause the
center to migrate and change as the tower is raised.
Les w2LK
On 11/10/2015 12:54 PM, Chris Wynn via TowerTalk wrote:
OK, see if this changes any opinions. When I put up the A3WS at the
towers nested height of about 30 feet, 12 meters swr was flat, 30
meters was flat, and 17 meters was around 1.8:1....
Now, with the A3WS MOUNTED OVER THE th-7, 12 METERS is 1.8:1, 30
meters is 3.1:1, and 17 meters is 1.0:1........
I have the A3WS mounted about 10 to 12 feet above the TH-7. While
talking to Mark at DX Eng., he brought up the issue of spacing
between the TH-7 and the A3WS..... Originally, I thought that the 10
to 12 feet of space between the two would be enough. However, at
this point, I HAVE NO CLUE! Would it be worth moving the TH-7 above
the A3WS?????
While coming home for lunch, I worked the 5Z4 on 17 meters with the
tower nested.... Hell if I know at this point!!!
AS TO THE QUESTIONS ON HOW I MEASURED THE SWR, I have used both the
MFJ 259 and the radio's (FT-1000 field) and get the same
measurements.... And have measured the swr at the end of the coax
connected to the balun on the yagi.....
The TH-7 is working just fine......
I appreciate all of the help and advice...My XYL is livid with me as
I have been totally consumed with these problems, and as much as I
like RF, I LIKE "THAT" better and don't want to end up divorced;)
Chris
Christopher L. Wynn
Attorney-at-Law
Christopher L. Wynn, ESQ., P.C.
8473 Earl D. Lee, Suite 300
Douglasville, Ga., 30134
(770)942-8661 (Landline)
(770)577-1626 (Telecopier)
chris@chriswynnlaw.com
On Tuesday, November 10, 2015 10:40 AM, "K7LXC@aol.com"
<K7LXC@aol.com> wrote:
> Last week I had the antenna back on the ground and disassembled
every trap on it, and found nothing out of the ordinary. ? So
what was the swr when it was on the ground? Did you check it? You
need to first ascertain that your antenna looks like an antenna; i.e.
it has a dip somewhere. Put your antenna analyzer on the antenna and
work your way back from there. BTW many times an "antenna
problem" turned out to be something in the shack; e.g. coax jumper,
coax switch, etc. Cheers & GL,Steve K7LXCTOWER TECH
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