G. Fred McCutchen
August 7th 04, 11:47 AM
"Bill French" > wrote in message
...
> I have been having some transmission problems in my rag wing airplane -
> not getting the transmission distance I should be getting.
>
> On the way to the radio shop for a SWR check I could send and recieve at
> 2000' AGL for a distance of 40 miles behind me. Report of 5 square.
>
> Returning over the same course I was at the same altitude but could only
> get a 4 x4 at 30 miles.
>
> SWR check showed between 2.5 and 2.9 - acceptable but just barely.
>
> Changed antenna and had the same reading.
>
> My ground plane is an aluminum plate about 12" by 8" and the antenna is
> mounted at the extreme forward end - that is toward the cockpit.
>
> This probably accounts for the differences in for and aft transmissions.
>
> I've read that the ground plane or reinforcement plate that the antenna
> is mounted should be grounded.
>
> Is it sufficient to have it grounded through the coax shield and then
> have the shield grounded to the airframe at the radio or should the
> plate be grounded at the antenna?
>
> Would I be better off trying to increase the size of this plate with
> aluminum foil or something similar?
>
> Any help greatly appreciated.
>
> Bill French
The grounding should ideally be at both ends of the coax.
Make sure that it is a good solid ground to give the best results.
When grounded to the airframe, the airframe also becomes part of the ground
plane , so your signal will radiate best to the rear. if possible, try
moving the antenna toward the center of the fuselage.
>
...
> I have been having some transmission problems in my rag wing airplane -
> not getting the transmission distance I should be getting.
>
> On the way to the radio shop for a SWR check I could send and recieve at
> 2000' AGL for a distance of 40 miles behind me. Report of 5 square.
>
> Returning over the same course I was at the same altitude but could only
> get a 4 x4 at 30 miles.
>
> SWR check showed between 2.5 and 2.9 - acceptable but just barely.
>
> Changed antenna and had the same reading.
>
> My ground plane is an aluminum plate about 12" by 8" and the antenna is
> mounted at the extreme forward end - that is toward the cockpit.
>
> This probably accounts for the differences in for and aft transmissions.
>
> I've read that the ground plane or reinforcement plate that the antenna
> is mounted should be grounded.
>
> Is it sufficient to have it grounded through the coax shield and then
> have the shield grounded to the airframe at the radio or should the
> plate be grounded at the antenna?
>
> Would I be better off trying to increase the size of this plate with
> aluminum foil or something similar?
>
> Any help greatly appreciated.
>
> Bill French
The grounding should ideally be at both ends of the coax.
Make sure that it is a good solid ground to give the best results.
When grounded to the airframe, the airframe also becomes part of the ground
plane , so your signal will radiate best to the rear. if possible, try
moving the antenna toward the center of the fuselage.
>