Mystery antenna problem
 

After the bout of windy weather we had a week or so ago, my mini antenna
farm was wrecked. My HF6V sustained a broken mast, which was easily
repairable.

My OCF dipole on the other hand, stopped working properly.

Originally cut for the standard 80-40-20-10 config, the best SWR near
80 meters has risen to around 4.37 MHz, 40 meters is around the correct
frequency, but has SWR has risen a bit to around 2.5. 20 meters is over
3, and 10 is better than 7.

18 MhZ also has a 1.2:1 SWR.

SWR measured with a MFJ259 meter.


The specs of the antenna are (roughly, as I'm doing this from memory)

48 feet short side, 130 long side

4:1 Balun

Height around 50 feet.

Coax coiled balun near house entrance Coax split just above balun for
lightning arrester installation.


Since I bought a new 4:1 balun at Dayton last year to replace one that I
fixed a while back, I decided to replace it. Same result.

I took the choke balun and lightning arrester out of the picture to
isolate them, and measured from there. No difference.

Coax connectors look good.

So what I am left with is the coax and the antenna wire itself.

Unless someone has played an *awesome* practical joke on me, the
antenna dimensions haven't changed.

So can coax go bad in a way that will raise the lowest SWR in the way I
describe? Of course I could just replace it, but I'd like to know why.



- 73 de Mike KB3EIA -

Mystery antenna problem
 

Michael Coslo wrote:
After the bout of windy weather we had a week or so ago, my mini antenna
farm was wrecked. My HF6V sustained a broken mast, which was easily
repairable.

My OCF dipole on the other hand, stopped working properly.

Originally cut for the standard 80-40-20-10 config, the best SWR
near 80 meters has risen to around 4.37 MHz, 40 meters is around the
correct frequency, but has SWR has risen a bit to around 2.5. 20 meters
is over 3, and 10 is better than 7.

18 MhZ also has a 1.2:1 SWR.

SWR measured with a MFJ259 meter.


The specs of the antenna are (roughly, as I'm doing this from memory)

48 feet short side, 130 long side

4:1 Balun

Height around 50 feet.

Coax coiled balun near house entrance Coax split just above balun for
lightning arrester installation.


Since I bought a new 4:1 balun at Dayton last year to replace one that I
fixed a while back, I decided to replace it. Same result.

I took the choke balun and lightning arrester out of the picture to
isolate them, and measured from there. No difference.

Coax connectors look good.

So what I am left with is the coax and the antenna wire itself.

Unless someone has played an *awesome* practical joke on me, the
antenna dimensions haven't changed.

So can coax go bad in a way that will raise the lowest SWR in the
way I describe? Of course I could just replace it, but I'd like to know
why.



- 73 de Mike KB3EIA -




Hi Mike,

You do not mention what type of Coax /fittings your using But I've had
the foam insulated type change in high winds here in the past. Also was
there any driving rain with the wind.. check for moisture penetration at
the connectors. if moisture has gotten into the coax braid it may
produce the results you speak of also.
good luck
73 Dave Kc1di
let us know what you find :)

Mystery antenna problem
 

i'd guess you won't really know w/out a detailed physical inspection
unless somthing happens drastic when it rains vs a long dry spell

sure the coax could have gone bad but you have a nice meter seems you
could actually test it ,

any chance animals chewed any of the coax did anything touch the
raditors such as a branch or such perhaps near a endpoint tie off?

prb i am not much help but good luck

In article ,
KC1DI wrote:

Michael Coslo wrote:
After the bout of windy weather we had a week or so ago, my mini antenna
farm was wrecked. My HF6V sustained a broken mast, which was easily
repairable.

My OCF dipole on the other hand, stopped working properly.

Originally cut for the standard 80-40-20-10 config, the best SWR
near 80 meters has risen to around 4.37 MHz, 40 meters is around the
correct frequency, but has SWR has risen a bit to around 2.5. 20 meters
is over 3, and 10 is better than 7.

18 MhZ also has a 1.2:1 SWR.

SWR measured with a MFJ259 meter.


The specs of the antenna are (roughly, as I'm doing this from memory)

48 feet short side, 130 long side

4:1 Balun

Height around 50 feet.

Coax coiled balun near house entrance Coax split just above balun for
lightning arrester installation.


Since I bought a new 4:1 balun at Dayton last year to replace one that I
fixed a while back, I decided to replace it. Same result.

I took the choke balun and lightning arrester out of the picture to
isolate them, and measured from there. No difference.

Coax connectors look good.

So what I am left with is the coax and the antenna wire itself.

Unless someone has played an *awesome* practical joke on me, the
antenna dimensions haven't changed.

So can coax go bad in a way that will raise the lowest SWR in the
way I describe? Of course I could just replace it, but I'd like to know
why.



- 73 de Mike KB3EIA -




Hi Mike,

You do not mention what type of Coax /fittings your using But I've had
the foam insulated type change in high winds here in the past. Also was
there any driving rain with the wind.. check for moisture penetration at
the connectors. if moisture has gotten into the coax braid it may
produce the results you speak of also.
good luck
73 Dave Kc1di
let us know what you find :)

Mystery antenna problem
 

Water in the balun or feedline?

Michael Coslo wrote:

After the bout of windy weather we had a week or so ago, my mini antenna
farm was wrecked. My HF6V sustained a broken mast, which was easily
repairable.

My OCF dipole on the other hand, stopped working properly.

Originally cut for the standard 80-40-20-10 config, the best SWR
near 80 meters has risen to around 4.37 MHz, 40 meters is around the
correct frequency, but has SWR has risen a bit to around 2.5. 20 meters
is over 3, and 10 is better than 7.

18 MhZ also has a 1.2:1 SWR.

SWR measured with a MFJ259 meter.


The specs of the antenna are (roughly, as I'm doing this from memory)

48 feet short side, 130 long side

4:1 Balun

Height around 50 feet.

Coax coiled balun near house entrance Coax split just above balun for
lightning arrester installation.


Since I bought a new 4:1 balun at Dayton last year to replace one that I
fixed a while back, I decided to replace it. Same result.

I took the choke balun and lightning arrester out of the picture to
isolate them, and measured from there. No difference.

Coax connectors look good.

So what I am left with is the coax and the antenna wire itself.

Unless someone has played an *awesome* practical joke on me, the
antenna dimensions haven't changed.

So can coax go bad in a way that will raise the lowest SWR in the
way I describe? Of course I could just replace it, but I'd like to know
why.



- 73 de Mike KB3EIA -

Mystery antenna problem
 

ml wrote in :

i'd guess you won't really know w/out a detailed physical inspection
unless somthing happens drastic when it rains vs a long dry spell

sure the coax could have gone bad but you have a nice meter seems
you could actually test it ,

any chance animals chewed any of the coax did anything touch the
raditors such as a branch or such perhaps near a endpoint tie off?

prb i am not much help but good luck




Thanks to everyone for the input.


As it turns out, the problem ended up being something else
entirely. I replaced the coax the other evening, and indeed it changed
the VSWR. But it still wasn't correct! Ith just moved it on the other
side of where I wanted it - what was once minimum SWR at too high a
frequency was now at too low a frequency (on 80-75 meters. Then the 40
meter was spot-on, and 20 meters was still off.

Seriously confused, I thought for a few seconds. Why on earth would
this weird stuff be happening? Then it hit me. THe OCF is not terribly
critical as far as lengths go, but it depends on the height from ground
to determine SWR and where that SWR is best. My antenna and support
structure was hit pretty hard by the storm we had a couple weeks ago, and
probably stretched a bit, and wasnt at the same height as before.
(drooped) I suspect that the 40 meter shift, and the 20 meter SWR problem
was caused by the drooping ends which didn't get beat up in the storm.

I took it down today, and put up a general purpose dipole running
through ladder line and a tuner. Working FB now.

- 73 de Mike KB3EIA -