Time for me to mount too
I'm planning on drilling holes in the other woman next weekend.
Transponder (Stub) - Belly, left side, not sure how far back. Trying to keep at least 3 feel from the transponder so it won't interrogate itself.
Marker Beakon (Blade) - Belly, near midline past bulkhead by elevator bellcrank.
Nav/GS (Whisker V) - Top of vertical stab and already mounted.
Comm 1/2 (Bent Whip) - Belly, each side and aft of the welded gear attachments but forward of the steps.
GPS - Top of Fuselage, aft of slider track.
ELT - Tail, Under fiberglass fairing.
I'm planning to run RG400 from Steinair for all runs (except Nav/GS) which came prewired.
I've been told to expect 1 or 2 knots airspeed loss.
I read several posts regarding line loss. From what I've read, RG-400 has a line loss of about 4db per 100 feet (it's really 4.4 @ 144 MHz according to 1 manufacturer). Considering your run is likely to be about 10 feet, your loss is going to be less than 1db. Keep in mind that a 3db loss is a 50% reduction in power so such a small line loss is very acceptable for your comm radio(s). Although I didn't get out my ARRL Antenna Handbook, I suspect the later is close enough for governement work. Ladder line is better than most coax but no way should it be used in a plane.
What many do not understand that radio transmitting power is not a straight line relationship. Doubling power in a radio does not double range. Improvements in range are influenced much more by radiation patterns of directional antennas. An example might be a yagi or phased aray and use an active element, reflector, and director(s). Such type of antenna is preferred by a ground based radio when that antenna can be oriented in the desired direction. Directional antennas also "hear" with the same efficiency they transmit. Good in the desired direction and poor to the sides. Airports don't use directional antennas because they need to talk 360 dgrees just like airplanes.
For you - terrain is your enemy, followed by atmospheric conditions and interference. Your setup can influence radio performance, but for the most part, I would estimate it's not as great as many think since most use commercial antennas, todays antenna wire, and short antenna runs (unlike that of a home based ham shack). Altitude will affect communications most.
For your Comm antennas:
#1 - Dipoles should be avoided because of polarization and they are directional. Unidirectional antennas are preferred and you'll find those on most all aircraft for comms.
#2 - Avoid wingtip - shielding by aluminum ribs occurs.
#3 - Keep your line losses down by using high quality coax, minimum number of connectors, and runs a short as possible.
#4 - Remember communication is 2 way. You can only talk as far as you can hear (Ham expression for all the power in the world will do you no good if your can't hear the response).
#5- If you really want to tweak it, have the SWR checked on your radio to be sure the antenna is tuned. Your radios should be looking at a 50ohm match.
#6 - Be sure you can get to the back of the antenna for service.
Probably the best advice, is to quit worrying about the radio performance of your comm radio(s). With today's solid state radios, commercial antennas, good wire and connectors, I'm sure you'll have a winning combo. You should really worry about mounting it so it won't break off, be used as a handhold, step or land on it.
btw - don't ever grab hold the antenna when testing out your transmitter. I'm not sure that 10 watts would cause a microwave burn, but you never know and I sure wouldn't want to find out.
One last thing - make sure you have good grounds. Without those, it's all junk.
73's OM,
AD4AC
Larry