Happy New Year

I am trying mobile operations for the first time...FT8900 Quad band XCVR
and Diamond CR8900 quad band antenna (10, 6, 2M and 440Mhz). I am
mounting the antenna on the hatchback of an Element.

I am wondering how significant is the proximity of the AM antenna (a
stubby affair presumably housing some sort of coil?) to the new ham
antenna. I can mount the antenna on the driver's side of the hatchback
or the passenger side. The passenger side is within a foot or two of
the AM stub antenna.

I would think in either case the AM antenna is in the Near Field.
Will the antenna pattern be significantly more affected on the passenger
side?

Thanks in advance for all helpful replies

John
AB8O

On Sun, 31 Dec 2006 12:47:29 -0500, jawod wrote:

I would think in either case the AM antenna is in the Near Field.
Will the antenna pattern be significantly more affected on the passenger
side?

Happy New Year John,

Then it is best to resign yourself to the inevitable. Yes both will
be in the other's near field.

It isn't going to matter all that much unless the AM antenna becomes
resonant on one of those bands you use. Even then, it will only
matter in terms of match as the parasitic element is going to pull the
source. Unless it means punching holes in sheet metal, you can try
all possible sites and check SWR.

As for patterns, again the parasitic element (the AM antenna) will
have to support substantial currents (through coupling and matching -
and hence a significant SWR hit) to disturb the pattern. More likely
is that the sheet metal of the car and the site location of the
transmitting antenna is going to be of a far greater determiner of
pattern shape.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

On Sun, 31 Dec 2006 12:47:29 -0500, jawod wrote:

I would think in either case the AM antenna is in the Near Field.
Will the antenna pattern be significantly more affected on the passenger
side?

Happy New Year John,

Then it is best to resign yourself to the inevitable. Yes both will
be in the other's near field.

It isn't going to matter all that much unless the AM antenna becomes
resonant on one of those bands you use. Even then, it will only
matter in terms of match as the parasitic element is going to pull the
source. Unless it means punching holes in sheet metal, you can try
all possible sites and check SWR.

As for patterns, again the parasitic element (the AM antenna) will
have to support substantial currents (through coupling and matching -
and hence a significant SWR hit) to disturb the pattern. More likely
is that the sheet metal of the car and the site location of the
transmitting antenna is going to be of a far greater determiner of
pattern shape.

73's
Richard Clark, KB7QHC


Another mounting option may be to use the location for the roof rack. Look
for the rectangular plastic parts above the driver's door. They pop out and
under some you will find the mount for the roof rack. This would get you
3-4 feet from the AM/FM antenna.

The stubby antenna is probably active so it may not appreciate high signal
levels.

craigm

jawod wrote:
Happy New Year

I am trying mobile operations for the first time...FT8900 Quad band XCVR
and Diamond CR8900 quad band antenna (10, 6, 2M and 440Mhz). I am
mounting the antenna on the hatchback of an Element.

I am wondering how significant is the proximity of the AM antenna (a
stubby affair presumably housing some sort of coil?) to the new ham
antenna. I can mount the antenna on the driver's side of the hatchback
or the passenger side. The passenger side is within a foot or two of
the AM stub antenna.

I would think in either case the AM antenna is in the Near Field.
Will the antenna pattern be significantly more affected on the passenger
side?

Thanks in advance for all helpful replies

John
AB8O
Thanks for your thoughts!
Looks like the bigger challenge is programming the FT8900!

John
AB8O