Posted for "Wretlind Family"
<stockmos@algonet.se>:
Hi Lancair fellows! Thank you for all good advices and pics about my
interiorinstallation in my
Lancair IV - the one and only flying in Sweden.
We know now excactly what to do around the windows. The Lancair forum is
really
invaluable specially for us living in this corner of the world.
Now to next and I hope final problem before certifikation. First
flight with
my 6 year projekt Lancair IV with reg SE-XXX was May 11, 2007. The panel was
wired by Lancair radioshop in Redmond back
in august 1999 by Jon Hadlich.
Two radios were installed. One KX155 and one Garmin 430. At the beginning
radios worked
pretty well but not more. It was possible to transmit and make
oneself understand to the towers but not more. After some time
the
transmitting quality went down and that after doing absolutely nothing with
the installation. By end of summer 2007 it was so
bad nobody could anymore
hear any details. It was just a lot of noise when transmitting. The same
with both radios. The funny thing
was that my transmitting was OK when
aircraft was on ground even with engine running full speed. But as soon as
airborne the
transmitting quality went down. All the time I could receive
radiotraffic pretty good.
From the very beginning we placed the
antennas according to the information
in the builders manual. It means in the fin in the rear part of the
aircraft. By any reason it
didn't work well in this position. One reason was
problably depending on the bad SWR (stand wave radio) and maybe the length
of the
coaxcable was not perfect. The type of cable used is RG58.
Because of the bad function we mounted two antennas on the belly
instead. We
used whip antennas of a type normally used. In this position we got both a
very good SWR but also an acceptible
reception and transmitting quality as
long we were on grond. We could speak to a station tens of miles away and
still get a reading
of five.
Those antennas were mounted with a distance of about 2 feet from eachother.
Afterwards we heard it is too close and that
they can spoil eachother when
transmitting on radio and the other one stands on same frequency. In my
case the Garmin 430
was detected to have a destroyed receiving unity and I
had to send it far awy to UK for repair. Anybody experienced
something
simular?
Everything changes when airborn. Normally the reception is OK but the
transmitting is normally
unreadable. Often the radiostations read me 2 and
sometimes they cannot read my transmitting at all. All the time there is a
big
noise in the background. We have tried every possible action to find out
what is disturbing the transmitting. The number one radioshop in
Sweden has
investigated with no result. Now we are running out of ideas. The antenna
groundplane is placed outside under the belly.
It is a copper sheet of the
right size. The foil is also grounded to aircraft earth but also via the
coaxcable connected to the
radio. From the beginning we mounted an alu
groundplane on cabinfloor with no good result and therefore we changed to
the outside
copper variety just to check. The problem is why the radio works
on ground but not in the air.
We have also changed
headset and used the handmike but transmitting problem
is still there. On ground when running engine at full speed does not
affect
the transmitting quality.
Many people around us have a lot of ideas how to solv this radioproblem.
One
reason is said to be static electricity that is building up during flight
causing a bad transmitting quality. To check this out
we have mounted a
whipantenna inside the plane at the copilots place. The antenna is pointing
out to the front window. Unefortunable
the transmitting problem is still
there and maybe there is no static electricity causing our problem.
Enclosed is a photo
of the peculiar front seat antenna which gives a looking
of a spyplane.
Help please - I want to talk to
people
Christer Wretlind
Box 29
179 03
Stenhamra
Sweden
Tel +46-856044100
Fax +46-856044103
Cell
+46-703777212
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