Vertical antenna problems
 

We are setting up an active Amateur Radio station at Colorado's
"Wings Over the Rockies Air and Space Museum" here in Denver. We
are currently installing a Hustler 6-BTV Vertical on the very
large metal roof of the hangar which is about 40 to 50 high, but
are having difficulty with proper tuning.

We initially assembled the antenna with the following dimensions
(in inches) according to the manual:

A = 1, B = 1-5/8, C = 1-1/16, D = 1-1/2, and E = 1-1/2

The mast and metal roof are well grounded and show continuity
between all panels. The mounting bracket had to be placed 24"
above the roof and, although the mast/bracket/roof are grounded
and bonded, we have placed a grounding cable from the mounting
bracket to the roof.

We have also made the 6" RF choke coil, however, SWR measurements
are not significantly different with or without the coil OR with
or without the ground cable.

Initial measurements with an MFJ Antenna Analyzer show that the
lowest SWR measurement is significanly below each of the band
segments.

For instance, our measurements on the 10-meter band we

SWR dipped to 1.5:1 at 25.9 mHz with the 72" tube fully shortened.
SWR dipped to 1.6:1 at 25.8 mHz with the 72" tube extended 1",
SWR dipped to 1.6:1 at 25.7 mHz with the 72" tube extended 2",
SWR dipped to 1.5:1 at 25.6 mHz with the 72" tube extended 3", and
SWR dipped to 1.5:1 at 25.4 mHz with the 72" tube extended 4".

According to those measurements we would have to cut over 30" from
the 72" tube to get to a tuned frequency of 29 mHz.

That does not seem right, so I would appreciate any comments or
suggestions to help make this antenna work.

73,

KB6CC

Vertical antenna problems
 

Vertical antenna problems
 

An alternative way to view your antenna is a large metal ground plane with
the vertical mounted on it and fed 24" up from the base. In that case,
resonances would be lower than expected, explained by the vertical being
24" longer than design.


Gee, it makes obvious sense, now that you say it. Guess I don't have
to be
afraid of cutting the tubes now.

Thanks

Vertical antenna problems
 

Vertical antenna problems
 

On Nov 7, 9:49 pm, Owen Duffy wrote:
wrote roups.com:



An alternative way to view your antenna is a large metal ground plane
with the vertical mounted on it and fed 24" up from the base. In that
case, resonances would be lower than expected, explained by the
vertical being 24" longer than design.

Gee, it makes obvious sense, now that you say it. Guess I don't have
to be
afraid of cutting the tubes now.

It is not obvious that you need to cut more than the lowest tube.

Remember, measure twice, cut once...

Owen

The coupling to the steel roof pulls the traps out of resonance...
Call Hustler ... They have an updated tuning schedule for the 6BTV...
I don't have mine here at the office or I would offer it to you...
I found the 6BTV to be impossible to get tuned properly - even when
ground mounted per their instructions...
The answer - after I called them - was in tuning the traps along with
the length of the sliding sections... Their updated tune schedule
explains how to do it...

If after tuning the traps you have problems still, then I would
suggest an insulated mount with insulated-wire radials laid on the
roof... Put tape on the ends of the radials so they don't arc...
denny / k8do

Vertical antenna problems
 

On Nov 8, 5:34 am, Denny wrote:
On Nov 7, 9:49 pm, Owen Duffy wrote:



wrote roups.com:

An alternative way to view your antenna is a large metal ground plane
with the vertical mounted on it and fed 24" up from the base. In that
case, resonances would be lower than expected, explained by the
vertical being 24" longer than design.

Gee, it makes obvious sense, now that you say it. Guess I don't have
to be
afraid of cutting the tubes now.

It is not obvious that you need to cut more than the lowest tube.

Remember, measure twice, cut once...

Owen

The coupling to the steel roof pulls the traps out of resonance...
Call Hustler ... They have an updated tuning schedule for the 6BTV...
I don't have mine here at the office or I would offer it to you...
I found the 6BTV to be impossible to get tuned properly - even when
ground mounted per their instructions...
The answer - after I called them - was in tuning the traps along with
the length of the sliding sections... Their updated tune schedule
explains how to do it...

If after tuning the traps you have problems still, then I would
suggest an insulated mount with insulated-wire radials laid on the
roof... Put tape on the ends of the radials so they don't arc...
denny / k8do

I wish they would post this type of information on their web site, or
include it in their manual. I have not yet been able to get in touch
with a Hustler/New-Tronic technical person after several calls and
e-mails. Will try again this morning.

tnx de KB6CC