XCOM 760 Installation And User Manual page 15

aluminum sheet inside the structure, I have also seen the use of self adhesive foil
but I have found this usually breaks down due to movement of the aerial base and
it eventually becomes useless.
There are also several ground plane independent aerials available and some we
have trialed with good results but it is my belief a solid aluminum ground plane is
the best. To prevent corrosion and water entering your aircraft always use a sealant
like silicone or RTV approved for the structure of your aircraft around the aerials
base.
The final choice now comes down to the aerial construction, most VHF aerials used
on sport aircraft are ¼ wave whip type aerials made from either metal or fiberglass,
the better aerials sometimes costing 5 times more than the cheaper ones with only
a fractional increase in performance. Basically I believe the more you spend the
better the aerial and the better range you could expect from the transmission.
Most aerials sold today are already 'tuned' for the VHF range with frequency 127.00
being about the norm. After installation of your radio and aerial it is recommended
a SWR test be performed at 127.00 MHz and the aerial tuned to try and get the
SWR reading as low as possible, ideally you should try for a reading around 1.5:1
but up to 3:1 is still considered acceptable. Try to keep the aerial cable as short as
possible and don't wrap it up with other cables like those from the strobes or
battery as interference will be expected and never coil excess cable, always cut the
aerial cable to the correct length.
Release 1.2 © XCOM Avionics 2004 www.xcom760.com Page 15