I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Does this make sense? Or is it a wasted effort, and I should spend my
time on improving the ground in the car? What would you do?

73,
Patrick N3EO

all that tuning it off the car would prove is that it could be tuned... that
is, that it was working electrically and the adjustments were possible.
unless you were very lucky the tuning on the car would be different than any
off car rig you set up. i don't know about the saturn's construction, but
if its mostly plastic there may not be enough metal close to the antenna to
work properly. most mobile antennas are designed to be attached to a
reasonably large piece of sheet metal, having a thin braid or just frame
pieces as the ground plane would likely make the tuning much different than
it was designed for. if where it is mounted is plastic you may want to try
running several radials connected to the mounting bracket and just taped
inside the trunk lid or fender... of if you can do it stick a piece of
aluminum flashing inside attached to the bracket... the more metal the
better most likely.

"Patrick Gardella" wrote in message
om...
I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Does this make sense? Or is it a wasted effort, and I should spend my
time on improving the ground in the car? What would you do?

73,
Patrick N3EO

I used to run mobile in a SL-1 using Hamsticks and the Hustler mobile
antennas.

Where and how did you mount the antenna?

I used a lip mount on the trunk hood [which is metal] and three
different ground straps from the trunk hood to various points on the frame.

Deacon Dave, W1MCE

Patrick Gardella wrote:

I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Does this make sense? Or is it a wasted effort, and I should spend my
time on improving the ground in the car? What would you do?

73,
Patrick N3EO

On 24 Mar 2004 14:12:07 -0800, Patrick Gardella wrote:
I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

Those Saturn's are plastic panelled aren't they? There is 80% of your
answer right there! If I were you I would try to run a thick braid
directly to the car FRAME from your antenna ground point, as there is
probably little real metal in that trunk. The frame would connect all
large pieces of metal in your car to your antenna ground.

I would also do the same at the rig end, directly to the engine block
and firewall panel.


So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Tuning the antenna away from the car would only prove that the antenna
is tuneable, in the very unlikely chance there is something wrong with
it. That I doubt very much.

Patrick, I'm afraid that with that car, despite doing the above, that
you might never get as good a ground or signal as someone with a metal
panelled car. But then I have heard some good signals from mobile
antennas mounted to fiberglass recreational vehicles, so you never know!

Good luck with your efforts.

Larry Gagnon VE7EA

********************************
to reply via email remove "fake"

Patrick,
Sorry, tuning the antenna 'off of' the car won't work
(miracles
do happen, but don't count on it). The most likely problem is
as
you thought, a not so good 'ground', but maybe not. Does
anything
you do change the tuning of the antenna at all? Maybe not get
it
to where you want it (freq.), but does change it's resonant
freq?
If not, then there's something else 'going on' besides the
inadequate
grounding/counterpoise. Make sure you have a good connection
through
the mount, no shorts/opens except as they should be, etc. And
you
probably should do something about the grounding/counterpoise,
maybe
clip a wire to the base of the mount as a counterpoise to see
what
difference it makes (just lay it on the surface of the car for
now).
The length of the counterpoise isn't that critical, but too long
is
'better' than too short. Changing the location of the mount is
also
something you might try.
Good luck...
'Doc

"'Doc" wrote in message ...


Patrick,
Sorry, tuning the antenna 'off of' the car won't work
(miracles do happen, but don't count on it). The most likely problem is
as you thought, a not so good 'ground', but maybe not. Does
anything you do change the tuning of the antenna at all? Maybe not get
it to where you want it (freq.), but does change it's resonant
freq? If not, then there's something else 'going on' besides the
inadequate
grounding/counterpoise. Make sure you have a good connection
through the mount, no shorts/opens except as they should be, etc. And
you probably should do something about the grounding/counterpoise,
maybe clip a wire to the base of the mount as a counterpoise to see
what difference it makes (just lay it on the surface of the car for
now). The length of the counterpoise isn't that critical, but too long
is 'better' than too short. Changing the location of the mount is
also something you might try.
Good luck...
'Doc

Perhaps I should enter the text BEFORE hitting the send button, eh?

Doc has a good idea here with an "external" ground/counterpoise ae a
test.

However, I would ask: How are you determining when it is tuned? What
are you using to determine if it is tuned?

I don't think this talk about connecting braid to the FRAME is good.
The antennas are usually designed to have a ground-plane right at the base
of the antenna and a length of braid can be easily more than a quarter wave
at 2M and 440 and the frame is far from the antenna base. With plastic
paneled cars it is common to put some sort of foil or plate inside the body
to provide the ground plane.

--
Steve N, K,9;d, c. i My email has no u's.

"Steve Nosko" wrote in message
...

"'Doc" wrote in message ...


Patrick,
Sorry, tuning the antenna 'off of' the car won't work
(miracles do happen, but don't count on it). The most likely problem is
as you thought, a not so good 'ground', but maybe not. Does
anything you do change the tuning of the antenna at all? Maybe not get
it to where you want it (freq.), but does change it's resonant
freq? If not, then there's something else 'going on' besides the
inadequate
grounding/counterpoise. Make sure you have a good connection
through the mount, no shorts/opens except as they should be, etc. And
you probably should do something about the grounding/counterpoise,
maybe clip a wire to the base of the mount as a counterpoise to see
what difference it makes (just lay it on the surface of the car for
now). The length of the counterpoise isn't that critical, but too long
is 'better' than too short. Changing the location of the mount is
also something you might try.
Good luck...
'Doc

Thanks, Dave. The mount is on the trunk lip. I've got the
grounding strap running
from the mount set screws to the frame of the car.

So you basically ensured that the trunk lid had good contact with the
rest of the car?

73,
Patrick N3EO


Dave Shrader wrote in message news:K1p8c.1594$w54.9895@attbi_s01...
I used to run mobile in a SL-1 using Hamsticks and the Hustler mobile
antennas.

Where and how did you mount the antenna?

I used a lip mount on the trunk hood [which is metal] and three
different ground straps from the trunk hood to various points on the frame.

Deacon Dave, W1MCE

Patrick Gardella wrote:

I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Does this make sense? Or is it a wasted effort, and I should spend my
time on improving the ground in the car? What would you do?

73,
Patrick N3EO

Thanks, Doc.

I don't have an antenna analyzer, so I can't check the resonant
freq that way. I was relying on an SWR meter (my shack one).
Nothing at all changes when I adjust the antenna. SWR doesn't
move. I may try to borrow an analyzer from someone to check
that out.

The mount and cable are fine. Just got a new 2m/70cm dual
band antenna to use until I can get the UHV-4 working.
It has a nice SWR of around 1.3 on 2m.

On the UHV-4 antenna, I can't get below an SWR on 2m of
around 5 or 6, even though it's supposed to be ground
independant (1/2 wavelength). I can't adjust the 2m/70cm
at all anyway. It's fixed.

So as you said, there may be something else wrong with the
antenna itself. I may just ship it back to Comet to see what they
can find out. That high an SWR is just wrong on 2m.

But I may try the counterpoise initially, just to find out.

73,
Patrick N3EO

'Doc wrote in message ...
Patrick,
Sorry, tuning the antenna 'off of' the car won't work
(miracles do happen, but don't count on it). The most
likely problem is as you thought, a not so good 'ground',
but maybe not. Does anything you do change the
tuning of the antenna at all? Maybe not get it
to where you want it (freq.), but does change it's resonant
freq?
If not, then there's something else 'going on' besides the
inadequate grounding/counterpoise. Make sure you have
a good connection through the mount, no shorts/opens
except as they should be, etc. And you probably should
do something about the grounding/counterpoise, maybe
clip a wire to the base of the mount as a counterpoise to see
what difference it makes (just lay it on the surface of the
car for now).
The length of the counterpoise isn't that critical, but too long
is 'better' than too short. Changing the location of the
mount is also something you might try.
Good luck...
'Doc

Patrick Gardella wrote:

Thanks, Dave. The mount is on the trunk lip. I've got the
grounding strap running
from the mount set screws to the frame of the car.

I ran three different ground strap, 1.5 inches wide, from the trunk
lip/lid to the car frame. First, I burnished the finish off the lip
right under the antenna mount. I added a strap from that point to the
nearest point of metal connected to the frame at the wheel well.

Next I loosened the two trunks lip supports, hinges, and burnished the
finish off under them. A strap was connected from one mount to the metal
that houses the Saturn's speakers [rear deck]. The second strap was
fastened to a burnished surface under the latch for the trunk mount.

All burnished surface/strap locations were weather sealed with "Coax
Seal" from HRO.

Note: the radio, IC706 MKIIg, was bolted to the rear deck between the
speakers and the remote head was installed at the drivers seat. The bolt
locations were burnished to bare metal.



So you basically ensured that the trunk lid had good contact with the
rest of the car?

73,
Patrick N3EO


Dave Shrader wrote in message news:K1p8c.1594$w54.9895@attbi_s01...

I used to run mobile in a SL-1 using Hamsticks and the Hustler mobile
antennas.

Where and how did you mount the antenna?

I used a lip mount on the trunk hood [which is metal] and three
different ground straps from the trunk hood to various points on the frame.

Deacon Dave, W1MCE

Patrick Gardella wrote:


I'm stumped on a problem I've been having with a Comet UHV-4 quad band
antenna (10m/6m/2m/70cm). It's mounted to a Comet CP-5M mobile mount
on my Saturn SL1. The problem I have is that I cannot get it to
tune. I figure that it's an insufficient RF ground. I've tried
running braid from a good ground location in the trunk to the mount
(good metal to metal contact on the "car" end of the braid). Still
nothing.

So I was wondering if there would be a way to tune the antenna off the
car. I was thinking of creating a ground plane with several 1/4
wavelength wires on each of the bands, and then adjusting the antenna
to bring it into tune. That way I would know if the ground braid I
put into the car is working well enough.

Does this make sense? Or is it a wasted effort, and I should spend my
time on improving the ground in the car? What would you do?

73,
Patrick N3EO