Wayne wrote:
Installing my avionics and its time for antennas, I installed a comm antenna in the vert/stab years ago and everything is closed back there.
I am installing a S/L30 Nav/Com which has an internal diplexer and the manuel says not to install an external diplexer, however I am thinking
they are talking about using an external diplexer for one antenna for Nav/Com. I am also installing a GNS530W and in the rear of the unit there
is a place for a Nav and GS antenna. My plan is to install a Bob Archer VOR antenna in the ceiling of the baggage area and that would give me
one Nav ant and one Comm ant. I would use a splitter coming from the Nav ant and connect to the Nav port on the S/30 and to the Nav port
and the GS port on the 530W GPS which has two different ports for GS and Nav. I would use a T/R switch for the com on the S/L30 and the
com on the 530W GPS. I emailed Bob about this installation and he said he believed it would be ok but didn't know if the GS connection fr the
splitter to the 530W would completely rob the signal from the S/L 30. Please give me your recomendations as I know there are many 2 place
Lancairs flying with no antenna problems.
Wayne,
Diplexers work, but for the cost of another antenna (probably less than the diplexer?) you can build true redundancy in your radio system, and I’d recommend that. I have a Bob Archer antenna installed in the tail of my IV-P and a “bent whip” antenna on the belly with a 32” aluminum ground plane inside the fuselage behind it. I have an SL-30 for Comm/Nav 1 and an SL-40 for Comm 2. After some testing, I hooked the belly antenna to #1 (the SL-30), and can routinely talk out to the line of sight of the other radio. Not so with my Bob Archer hooked to the SL-40…it’s good out to 40-50 miles or so, and with more static on receive. I often move ATC to the #2 when I need to talk to flight service because of the significantly better range and reception on the #1 system with the whip antenna. The bent whip like I have would easily work on a 2-seat Lancair.
My 2 cents…
Bob Pastusek