I want to put my 2M 5/8-wave mag-mount on the trunk lid, which slopes
down at 20 degrees. I am concerned that most of my signal is going
into the ground or outer space.

Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?

Ken KC2JDY

Chevy454 wrote:
I want to put my 2M 5/8-wave mag-mount on the trunk lid, which slopes
down at 20 degrees. I am concerned that most of my signal is going
into the ground or outer space.

Can I bend the long whip so it stands vertically? Should I do it?

Bend away, it will be okay.

does the downward slope of the ground plane leave a problem
unaddressed?

Not really. I mean there is probably some effect on SWR, but it is the
situation that you have. So go for it.

- 73 de Mike N3LI -

Chevy454 wrote:
I want to put my 2M 5/8-wave mag-mount on the trunk lid, which slopes
down at 20 degrees. I am concerned that most of my signal is going
into the ground or outer space.

Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?

Ken KC2JDY
5/8 Wave requires a ground, but not a ground plane. I'd get a proper
clamp, but bending will probably work OK.

In message , dave
writes
Chevy454 wrote:
I want to put my 2M 5/8-wave mag-mount on the trunk lid, which slopes
down at 20 degrees. I am concerned that most of my signal is going
into the ground or outer space.
Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?
Ken KC2JDY
5/8 Wave requires a ground, but not a ground plane. I'd get a proper
clamp, but bending will probably work OK.

I'm not really sure what you mean, but a '5/8' w/l is actually resonant
as a 3/4 w/l, and does need a ground plane to work against. On a car,
this is usually the roof or the trunk lid. Bending the antenna so that
it stands vertically will probably have negligible effect on impedance
or radiation.

But why the trunk lid? Surely the roof is better? On a vehicle, every
inch above the ground helps.
--
Ian

In message , dave
writes
But why the trunk lid? Surely the roof is better? On a vehicle, every
inch above the ground helps.

The car is being used for 2M fox hunting. The Doppler antennas are on
the roof. The MFJ-1728B is on the trunk lid.

Are you saying that the 6 dB gain of this antenna is not high enough
for a 20 degree tilt to make a difference?

Ken KC2JDY

In message , Chevy454
writes
In message , dave
writes
But why the trunk lid? Surely the roof is better? On a vehicle, every
inch above the ground helps.

The car is being used for 2M fox hunting. The Doppler antennas are on
the roof. The MFJ-1728B is on the trunk lid.

Are you saying that the 6 dB gain of this antenna is not high enough
for a 20 degree tilt to make a difference?

Ken KC2JDY

Noted about the roof already being occupied.

Obviously, if the antenna is 'leaning backwards' at 20 degrees, the
radiation in the forward direction is going to point upwards more than
it would if ie was vertical and, of course, to the rear, the radiation
will point more downwards. However, even with the antenna dead vertical,
the shape of the body of the vehicle will distort the radiation pattern
considerably. I've had a quick Google, and this is one site which
provides some info:
http://www.k6mhe.com/files/mobile_vhf_ant.pdf
There will be lots of others.

This also might be of interest:
http://74.125.77.132/search?q=cache:...st.com.au/Ante
nnas/overview.html+antenna%2Bradiation%2B%225/8+wavelength%22&hl=en&ct=cl
nk&cd=25&gl=uk

As I said, you probably won't notice much difference between vertical
and 20 degrees. But the only way to find out will be to try it.
--
Ian

Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?

Although the issue may be more aesthetic than functional, I inform you that I
have a magnetic mount (built by Kathrein) that has a swivel at the whip
connection point. So, even if the mount is slanting, you can adjust the swivel
so that the whip is perfectly vertical.

73

Tony I0JX
Rome, Italy

Antonio Vernucci wrote:
Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?

Although the issue may be more aesthetic than functional, I inform you
that I have a magnetic mount (built by Kathrein) that has a swivel at
the whip connection point. So, even if the mount is slanting, you can
adjust the swivel so that the whip is perfectly vertical.

73

Tony I0JX
Rome, Italy

A 2 Meter 5/8 Wave antenna is too long for a magnet mount.

In message , dave
writes
Antonio Vernucci wrote:
Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?
Although the issue may be more aesthetic than functional, I inform
you that I have a magnetic mount (built by Kathrein) that has a
swivel at the whip connection point. So, even if the mount is
slanting, you can adjust the swivel so that the whip is perfectly vertical.
73
Tony I0JX
Rome, Italy

A 2 Meter 5/8 Wave antenna is too long for a magnet mount.

Not if the magmount is one of those which is around 7" diameter. Also,
with the one I have, the coil at the base is something like 4 turns of
1" internal diameter spring steel so, if the whip does hit something,
there's a lot of 'twang' in the system. There's almost no way that the
magnet can be dislodged.
--
Ian

Ian Jackson wrote:
In message , dave
writes
Antonio Vernucci wrote:
Can I bend the long whip so it stands vertically? Should I do it?
does the downward slope of the ground plane leave a problem
unaddressed?
Although the issue may be more aesthetic than functional, I inform
you that I have a magnetic mount (built by Kathrein) that has a
swivel at the whip connection point. So, even if the mount is
slanting, you can adjust the swivel so that the whip is perfectly
vertical.
73
Tony I0JX
Rome, Italy

A 2 Meter 5/8 Wave antenna is too long for a magnet mount.

Not if the magmount is one of those which is around 7" diameter. Also,
with the one I have, the coil at the base is something like 4 turns of
1" internal diameter spring steel so, if the whip does hit something,
there's a lot of 'twang' in the system. There's almost no way that the
magnet can be dislodged.

I stand corrected. Thanks.

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