Drill vs. MagMount ??
 

All things being equal, is there a performance advantage (in 2meter/70cm
bands) permanently mounting an antenna via a hole in the roof vs. using a
MagMount??

How about other bands??

Thanks,
Everett

Hello,

On 2m/70cm some antennas work better when you use a mag mount (Sirio HP2070
for example) because they are tuned to be used with a mag mount: added
parasitic capacity between bottom of the mount and the car's steel. Expected
you do not drive a 'vette or an Audi...

For lower frequencies it's better to drill holes or to properly ground the
antenna to the car, as most mag mounts are not wider than a sq foot and you
would quickly be annoyed by the potential differencies between the car's
ground and the antenna ground, resulting in HF re-entry problems as your
antenna will be then antenna + coax cable and all the hassles of bad and/or
variable SWR.

73 de F8BOE Olivier ...-.-

Thanks Oliver, very clear.

73 with gratitude
Everett

"F8BOE" wrote in message
...
Hello,

On 2m/70cm some antennas work better when you use a mag mount (Sirio
HP2070 for example) because they are tuned to be used with a mag mount:
added parasitic capacity between bottom of the mount and the car's steel.
Expected you do not drive a 'vette or an Audi...

For lower frequencies it's better to drill holes or to properly ground the
antenna to the car, as most mag mounts are not wider than a sq foot and
you would quickly be annoyed by the potential differencies between the
car's ground and the antenna ground, resulting in HF re-entry problems as
your antenna will be then antenna + coax cable and all the hassles of bad
and/or variable SWR.

73 de F8BOE Olivier ...-.-

On Fri, 04 Mar 2005 23:51:18 -0800, Everett wrote:

All things being equal, is there a performance advantage (in 2meter/70cm
bands) permanently mounting an antenna via a hole in the roof vs. using a
MagMount??

How about other bands??

Thanks,
Everett

Yes a properly installed antenna will out perform a MagMount, always has
alway will.

On Sun, 13 Mar 2005 15:15:50 GMT, Korbin Dallas
wrote:

On Fri, 04 Mar 2005 23:51:18 -0800, Everett wrote:

All things being equal, is there a performance advantage (in 2meter/70cm
bands) permanently mounting an antenna via a hole in the roof vs. using a
MagMount??

How about other bands??

Thanks,
Everett

Yes a properly installed antenna will out perform a MagMount, always has
alway will.


How does the hole mount compare to the lip-mount that is well
grounded?

I don't really want to drill a hole in my roof, but I want to get off
the magnet and a lipmount on my hatch will leave the antenna at
roof-top level.


--
73 for now
Buck
N4PGW

Korbin Dallas wrote:

Yes a properly installed antenna will out perform a MagMount, always has
alway will.


By how much? Why?

Roy Lewallen, W7EL

By how much? Why?


I would assume the direct connection with the roof
metal. I tried this one time, after trashing a larson
magmount with about 84 knocks off the car...
When I converted it over to a hole mount, with the
usual NMO, there was a good bit of difference. I didn't
measure, as the mag mount was toast, but it was quite
large actually. Like maybe a change for say S9 on a
machine, to maybe 15-20 over S9. Very noticable in my
case using the larson 5/8 antenna on top of a car roof.
Was like a different antenna..
MK

That's very interesting. I can't see how the mag mount could change the
pattern shape any, so your experience indicates a severe loss in the
coupling capacitor, maybe as high as 90% or more. That's hard to
imagine, so I wonder if anyone else has had a similar experience -- or,
much better yet, actual measurements.

Roy Lewallen, W7EL

wrote:
By how much? Why?


I would assume the direct connection with the roof
metal. I tried this one time, after trashing a larson
magmount with about 84 knocks off the car...
When I converted it over to a hole mount, with the
usual NMO, there was a good bit of difference. I didn't
measure, as the mag mount was toast, but it was quite
large actually. Like maybe a change for say S9 on a
machine, to maybe 15-20 over S9. Very noticable in my
case using the larson 5/8 antenna on top of a car roof.
Was like a different antenna..
MK

I can't see how the mag mount could change the
pattern shape any, so your experience indicates a severe loss in the
coupling capacitor, maybe as high as 90% or more.....

A pretty large amount...I guess it is possible maybe my
mag mount performance was down a bit due to it being
knocked off the car so many times...Not sure why that
would effect it much though..Maybe the connections were
getting a bit corroded also...Hard to say really...
Probably would be a better test to compare against a
brand new one...The one I had was the standard rectangular
looking larson mag mount. Looks sorta like a small box with
magnets underneath..I do have to say though...When I switched
to the hole mount, the increase in performance was instantly
noticable, as I knew what all the local machines did as far
as strength before the switch.
BTW, my comparison was mainly just receive on
various repeaters...Being things are reciprical, I never
really worried about transmit tests...MK

The mag mount depends on capacitve coupling to ground while the "drill a
whole in the roof" mount is directly connected to the ground plane.

Also, when using a hole in the roof antenna there is no problem withcoaxing
being crimped in a door or window, etc. I have used the NMO (Motorola
style) in the roof mounts for 2 meters and 450 MHz since 1978 with various
vehicles. No problems. IMHO, it is the ONLY way to go.

John