Ed wrote in
. 192.196:

....
Apparently well enough to cause a problem. Its now 9 days
later from the above comment, and I see today that the original poster
followed my suggestion to install a balun which has solved his problem.

Ed, that defines how you define the problem.

If the problem was different measurements, that was caused by disturbing
the thing that was measured.

The different measurements hints another possible problem, common mode
feedline current. The baluns have changed the effect of those, and
probably differently at different frequencies.

But fundamentally, it is wiser to preserve the common mode current path
(even if you reckon the baluns help to reduce it) when making the
measurments.

The whole exercise demonstrates that the measurements from shack were
valid, it was disconnecting the feedline and making measurements at the
feedpoint that was invalid. (BTW, the measurements in the shack should be
done with the shield path connected as normal.)

A good example of the limited thinking in the proposition that you can
only make valid measurements at the feedpoint.

Owen

Hi, Thanks for all your input. Hustler recommended using 5-6 foot of coax in
there manual. This I did follow and the antenna tuned very nice. When I
connected the 75 ft buried coax it threw me because the resonance frequency
on each band went higher. I do not have a balun at the base of the antenna.
I thought that after connecting the buried coax the frequency would go down
because of the capacitance of the longer coax. After rethinking this I can
see that adding a balun may help. Thanks for your help and will let you know
how things turn out.
Vern M0WQR

"Jim Higgins" wrote in message
...
On Fri, 25 Jul 2008 18:44:46 +0100, "826" wrote:

Hi. Have a new Hustler 6 band vertical. Installed the radials and
also buried 75 foot of RG213 coax between shack and antenna.
I used a 6 foot peace of coax connected to adjust the antenna
with a MFJ-259. Every band was tuned to the middle and SWR
was lower than 1.7:1 at the edges. After the adjustments, I
reconnected the buried coax to the antenna and on all bands
everything had shift up by any where from 200 to 400 khz.
Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?
Thanks Vern M0WQR

I have a 5BTV with buried radials. Works and tunes like crap without
the radials. Tune the antenna with the 259 connected to it with the
shortest piece of coax you can work with, like 1 foot. If you're a
purist - which I advise - lie down so you're as much out of the
antenna field as possible when taking readings. Or back way off and
read with binoculars. (Just don't let your body affect the antenna
tuning.) When that's done, coil the main coax or use a common mode
choke where the coax connects to the antenna to prevent the coax
shield from acting like a radial. Forget that nonsense of adjusting
SWR by adjusting coax length unless you're prepared to use a different
length for every band.

The MFJ 259 reads SWR with respect to it's own 50-ohm nominal
impedance so if you can adjust to a very low SWR (and you can with a
5BTV or 6BTV), it should read the same at the radio end of a longer
50-ohm coax.

On Sun, 27 Jul 2008 21:49:05 +0100, "826" wrote:

Hi, Thanks for all your input. Hustler recommended using 5-6 foot of coax in
there manual. This I did follow and the antenna tuned very nice.

I more than just suspect the length recommendation has a lot to do
with the effect of your body closer to the antenna and nothing to do
with the varying length of the coax as a matching network.

When I
connected the 75 ft buried coax it threw me because the resonance frequency
on each band went higher. I do not have a balun at the base of the antenna.
I thought that after connecting the buried coax the frequency would go down
because of the capacitance of the longer coax. After rethinking this I can
see that adding a balun may help. Thanks for your help and will let you know
how things turn out.
Vern M0WQR

You're welcome. Yes, I would be interested in hearing how it turns
out for you. Works well for me.

BTW, my coax lays on top of the ground. Shouldn't matter with the
choke at the feed point.

73, Jim KB3PU


"Jim Higgins" wrote in message
.. .
On Fri, 25 Jul 2008 18:44:46 +0100, "826" wrote:

Hi. Have a new Hustler 6 band vertical. Installed the radials and
also buried 75 foot of RG213 coax between shack and antenna.
I used a 6 foot peace of coax connected to adjust the antenna
with a MFJ-259. Every band was tuned to the middle and SWR
was lower than 1.7:1 at the edges. After the adjustments, I
reconnected the buried coax to the antenna and on all bands
everything had shift up by any where from 200 to 400 khz.
Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?
Thanks Vern M0WQR

I have a 5BTV with buried radials. Works and tunes like crap without
the radials. Tune the antenna with the 259 connected to it with the
shortest piece of coax you can work with, like 1 foot. If you're a
purist - which I advise - lie down so you're as much out of the
antenna field as possible when taking readings. Or back way off and
read with binoculars. (Just don't let your body affect the antenna
tuning.) When that's done, coil the main coax or use a common mode
choke where the coax connects to the antenna to prevent the coax
shield from acting like a radial. Forget that nonsense of adjusting
SWR by adjusting coax length unless you're prepared to use a different
length for every band.

The MFJ 259 reads SWR with respect to it's own 50-ohm nominal
impedance so if you can adjust to a very low SWR (and you can with a
5BTV or 6BTV), it should read the same at the radio end of a longer
50-ohm coax.

"826" wrote in
:

Hi. Have a new Hustler 6 band vertical. Installed the radials and also
buried 75 foot of RG213 coax between shack and antenna. I used a 6
foot peace of coax connected to adjust the antenna with a MFJ-259.
Every band was tuned to the middle and SWR was lower than 1.7:1 at the
edges. After the adjustments, I reconnected the buried coax to the
antenna and on all bands everything had shift up by any where from 200
to 400 khz. Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?

Vern,

An oft asked question, and there are usually emphatic answers readily
proffered.

You might find my article at http://www.vk1od.net/VSWR/displacement.htm
relevant to understanding what goes on 'within' the transmission line,
and the 'Traps for players' heading offers reasons why behaviour that is
inconsistent with transmission line behaviour may be observed.

In your case, one of the things you appear to have done is the change the
thing that was measured. You adjusted the antenna with the shield of the
main feedline disconnected. This is discussed under the heading
'Disturbing the thing being measured'.

Owen

Owen Duffy wrote:
"826" wrote in
:

Hi. Have a new Hustler 6 band vertical. Installed the radials and also
buried 75 foot of RG213 coax between shack and antenna. I used a 6
foot peace of coax connected to adjust the antenna with a MFJ-259.
Every band was tuned to the middle and SWR was lower than 1.7:1 at the
edges. After the adjustments, I reconnected the buried coax to the
antenna and on all bands everything had shift up by any where from 200
to 400 khz. Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?

Vern,

An oft asked question, and there are usually emphatic answers readily
proffered.

You might find my article at http://www.vk1od.net/VSWR/displacement.htm
relevant to understanding what goes on 'within' the transmission line,
and the 'Traps for players' heading offers reasons why behaviour that is
inconsistent with transmission line behaviour may be observed.

In your case, one of the things you appear to have done is the change the
thing that was measured. You adjusted the antenna with the shield of the
main feedline disconnected. This is discussed under the heading
'Disturbing the thing being measured'.

Owen

But, if the choke/balun/unun suggested is implemented, shouldn't one
expect the transmission lines influence to measurements be expected to
drop to near zero effect/affect?--i.e., re-routing/lengthening/etc. that
xmission line (coax), opposed to measurements taken?

Or, in effect, your measurement(s) with a 1 ft. length of xmission line
will remain very stable if that length were lengthened to one-hundred
feet?; Given that the choke/balun is of proper construction to offer
HIGH impedance to the freq(s) in question on the outer braid/shield?

I certain have grown to expect this ... have I just been lucky?

Regards,
JS

"Owen Duffy" wrote in message
...
"826" wrote in
:

Hi. Have a new Hustler 6 band vertical. Installed the radials and also
buried 75 foot of RG213 coax between shack and antenna. I used a 6
foot peace of coax connected to adjust the antenna with a MFJ-259.
Every band was tuned to the middle and SWR was lower than 1.7:1 at the
edges. After the adjustments, I reconnected the buried coax to the
antenna and on all bands everything had shift up by any where from 200
to 400 khz. Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?

Vern,

An oft asked question, and there are usually emphatic answers readily
proffered.

You might find my article at http://www.vk1od.net/VSWR/displacement.htm
relevant to understanding what goes on 'within' the transmission line,
and the 'Traps for players' heading offers reasons why behaviour that is
inconsistent with transmission line behaviour may be observed.

In your case, one of the things you appear to have done is the change the
thing that was measured. You adjusted the antenna with the shield of the
main feedline disconnected. This is discussed under the heading
'Disturbing the thing being measured'.

Owen

Hi,
Sorry I didn't rely sooner. The weather hasn't been too good hear. This
morning I disconnected the coax from the shack and measured the antenna with
the six foot length of coax. It looked OK. I then connected just the shield
of the long coax going to the shack and still measuring with the short coax
it shifted just like measured before in the shack. I have then made up a
choke balun and installed it at the base of the antenna and it improved
everything by about 60%. I will now make another one for the shack end. I
think everything is under control now. Thanks to all for heading me in the
right direction.
Vern M0WQR

"826" wrote in
:

Hi,
Sorry I didn't rely sooner. The weather hasn't been too good hear.
This
morning I disconnected the coax from the shack and measured the
antenna with the six foot length of coax. It looked OK. I then
connected just the shield of the long coax going to the shack and
still measuring with the short coax it shifted just like measured
before in the shack. I have then made up a choke balun and installed
it at the base of the antenna and it improved everything by about 60%.
I will now make another one for the shack end. I think everything is
under control now. Thanks to all for heading me in the right
direction. Vern M0WQR

Vern, whilst the choke made a difference, the fact that there remains a
difference in the feedpoint impedance with the shield connected and
disconnected, even when using the choke, indicates that there is some
effects observable from common mode feed line current in your scenario.

If you want a measurement of the antenna as it would be used, measure it
as it would be used... make sure the shield current path is as it would
be used.

Owen

"Owen Duffy" wrote in message
...
"826" wrote in
:

Hi,
Sorry I didn't rely sooner. The weather hasn't been too good hear.
This
morning I disconnected the coax from the shack and measured the
antenna with the six foot length of coax. It looked OK. I then
connected just the shield of the long coax going to the shack and
still measuring with the short coax it shifted just like measured
before in the shack. I have then made up a choke balun and installed
it at the base of the antenna and it improved everything by about 60%.
I will now make another one for the shack end. I think everything is
under control now. Thanks to all for heading me in the right
direction. Vern M0WQR

Vern, whilst the choke made a difference, the fact that there remains a
difference in the feedpoint impedance with the shield connected and
disconnected, even when using the choke, indicates that there is some
effects observable from common mode feed line current in your scenario.

If you want a measurement of the antenna as it would be used, measure it
as it would be used... make sure the shield current path is as it would
be used.

Owen
Hi all,
The antenna is now working very well on all bands. After installing both
choke baluns at the antenna base and in the shack, the resonant points
measured from the shack end were the same as with the short coax at the
antenna without the longer coax shield connected. Everything is OK now. All
it needed was the two baluns.
Regards
Vern M0WQR

826 wrote:

...
Owen
Hi all,
The antenna is now working very well on all bands. After installing both
choke baluns at the antenna base and in the shack, the resonant points
measured from the shack end were the same as with the short coax at the
antenna without the longer coax shield connected. Everything is OK now. All
it needed was the two baluns.
Regards
Vern M0WQR



Your path sounds very similar to mine. At first, unless the plans/specs
called for a balun/choke, I ignored the need. Now I use one, or more,
no matter what ... I picked up that knowledge here. At first, the loss
of the balun/choke made me hesitant--I no longer worry about those
trivial matters. :-)

Regards,
JS