2 Meter / 440 question.

I have an RV with a fiberglass roof and a luggage rack on top of the
roof. I'd like to use the luggage rack as an antenna mount point since
there's really no other place to attach a mobile antenna if it needs a
ground plane.

But I doubt if the rack is grounded to the vehicle frame. Should I
bother running some ground braid down to the frame or will the coaxes
shield itself provide enough ground to allow normal antenna
performance.

Thanks.

Dave

On Fri, 26 Dec 2003 06:56:06 GMT, Dave J. wrote:

2 Meter / 440 question.

I have an RV with a fiberglass roof and a luggage rack on top of the
roof. I'd like to use the luggage rack as an antenna mount point since
there's really no other place to attach a mobile antenna if it needs a
ground plane.

But I doubt if the rack is grounded to the vehicle frame. Should I
bother running some ground braid down to the frame or will the coaxes
shield itself provide enough ground to allow normal antenna
performance.

Thanks.

Dave

Hi Dave,

Depends....

Upon the size of this luggage rack. How big is it in terms of
wavelength? More than a quarter wave for 2M (probably) and it
qualifies as enough metal to do the job. You may also be able to
gamma match to the luggage rack itself and make it an Halo antenna
(provided it has a full circle of continuity); but in that regard, it
is probably too big (perhaps 6M then?).

In real estate they have the three determiners of success: location,
location, location. For us, that is not to far off, but rather:
location, size, wavelength (or Meters³, Meters², Meters¹).

73's
Richard Clark, KB7QHC

Dave I installed a radio and 5/8 gain antenna in a ambulance with a
fiberglass roof. I used aluminum tape 2 feet long in a cross
configuration. It worked great in this application as a ground plane.
They use 110 watt VHF radios.

"Dave J." wrote:

2 Meter / 440 question.

I have an RV with a fiberglass roof and a luggage rack on top of the
roof. I'd like to use the luggage rack as an antenna mount point since
there's really no other place to attach a mobile antenna if it needs a
ground plane.

But I doubt if the rack is grounded to the vehicle frame. Should I
bother running some ground braid down to the frame or will the coaxes
shield itself provide enough ground to allow normal antenna
performance.

Thanks.

Dave

The rails of my rack look like their about 2 meters long or real close
but there's bars going perpendicular to the rails too to add more
metal. There's not a lot of choices for antenna mounting on the RV but
the rack seems perfect for the truck-mirror or marine-rail type of
antenna mounts. If I don't use the rack then I need some type of
antenna that doesn't need a ground plane, right? Don't know much about
what's available that doesn't need a ground plane.

Dave


On Fri, 26 Dec 2003 16:51:34 GMT, Richard Clark
wrote:

On Fri, 26 Dec 2003 06:56:06 GMT, Dave J. wrote:

2 Meter / 440 question.

I have an RV with a fiberglass roof and a luggage rack on top of the
roof. I'd like to use the luggage rack as an antenna mount point since
there's really no other place to attach a mobile antenna if it needs a
ground plane.

But I doubt if the rack is grounded to the vehicle frame. Should I
bother running some ground braid down to the frame or will the coaxes
shield itself provide enough ground to allow normal antenna
performance.

Thanks.

Dave

Hi Dave,

Depends....

Upon the size of this luggage rack. How big is it in terms of
wavelength? More than a quarter wave for 2M (probably) and it
qualifies as enough metal to do the job. You may also be able to
gamma match to the luggage rack itself and make it an Halo antenna
(provided it has a full circle of continuity); but in that regard, it
is probably too big (perhaps 6M then?).

In real estate they have the three determiners of success: location,
location, location. For us, that is not to far off, but rather:
location, size, wavelength (or Meters³, Meters², Meters¹).

73's
Richard Clark, KB7QHC

Dave,

Why not mount the antenna in the middle of a sheet of plywood (painted if
you want), and staple 4 wire radials for 2 and 4 radials for 440 on to the
plywood. A 3 foot square piece is more than large enough if you run the 2m
radials towards the corners.

Tam/WB2TT
"Dave J." wrote in message
...
2 Meter / 440 question.

I have an RV with a fiberglass roof and a luggage rack on top of the
roof. I'd like to use the luggage rack as an antenna mount point since
there's really no other place to attach a mobile antenna if it needs a
ground plane.

But I doubt if the rack is grounded to the vehicle frame. Should I
bother running some ground braid down to the frame or will the coaxes
shield itself provide enough ground to allow normal antenna
performance.

Thanks.

Dave

On Fri, 26 Dec 2003 18:44:05 GMT, Dave J. wrote:

The rails of my rack look like their about 2 meters long or real close
but there's bars going perpendicular to the rails too to add more
metal. There's not a lot of choices for antenna mounting on the RV but
the rack seems perfect for the truck-mirror or marine-rail type of
antenna mounts. If I don't use the rack then I need some type of
antenna that doesn't need a ground plane, right? Don't know much about
what's available that doesn't need a ground plane.

Dave


Hi Dave,

You have more than enough metal to do the job. You will not find a
better situation unless you wrap the RV in aluminum foil (to add about
0.1 dB gain); but then you would run into things because of the
blocked windshield.

73's
Richard Clark, KB7QHC

Thanks to all for the ideas. They all sound good, so now I have
something to work with to get the camper set up with radios.

Merry Christmas and thanks!

Dave