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PilotjohnS

Well Known Member
Just curious what antennas i need for an IFR gps equiped RV9. For planning purposes i will be using a garmin g3x system without ADF.

So far i have 2 nav/com antennas, one in each wingtip and glide slope in the gear fairing.

What else do i need and where inside the plan can i put it?
 
Need some clarification here. There are nav antennas and com ones, but since they require different polarizations there are not 'nav/com' antennas.
A wingtip nav antenna ('Archer' is one brand name) works okay for Localizer and VOR signals, although not as good as a pair of tail mounted cat whiskers. They are sensitive to installation details. The com versions of wingtip antennas only work fair to poor; it's hard to get enough of the vertical polarization that's required, inside the wingtip.
For glide slope you can always use your VOR antenna with a splitter. Some nav radios (like the SL-30) have an internal splitter, and no way of inputting an external GS antenna.
So you need to decide on specific radios before finalizing antennas. But for best results they should be external, with the possible exception of the wingtip nav.
 
Aren't you forgetting GPS antennas? Transponder and ADS-B antennas? ELT antenna? Do you want to have a marker beacon receiver? Do you want to receive XM weather/radio?

No advantage in having two NAV antennas - you can feed a single antenna to multiple receivers. You still need two COM antennas since those are used to transmit.

Also with a G3X alone you can't be IFR certified, you need an IFR navigation receiver (such as the GTN750), which likely also adds at least one more GPS antenna.

I made a post when I decided my antennas, hope this helps:
http://www.airplane.build/2015/11/research-antennas.html
(I have already changed it slightly since I posted - for instance, now I can use the GTX345R which does both ADS-B and transponder with the same antenna).
 
Thanks for the post

Rodridgo,
Thank you for your post. This is what I was looking for..
I had a passing thought I could stuff all the antennas out of the breeze, but guess that was just a dream.
 
Comant - Comdat 200

I recently purchased a Comant - Comdat 200 antennae that says it will suffice for both GPS and VHF com.

I am building an RV 7 and plan on putting this behind the baggage compartment on top where the doubler already exists from VANS.

My question is do any of you have this antennae and was it good for you?

I know many like to use bent whip underneath but i fear loosing it on rough grass strips where i will fly.

I am using RG 58 coax and wonder what you have used and why RG 400 would be any different?

Dave C.
 
dave4754 said:
I know many like to use bent whip underneath but i fear loosing it on rough grass strips where i will fly.

I am using RG 58 coax and wonder what you have used and why RG 400 would be any different?

Dave C.
Click to expand...

Dave,

Lots of tail draggers have the bent whip antenna on the bottom of the fuse but it would be under the pilot seat area where ground clearance is sufficient.

RG400 is far superior to 58. The former has dual shielding while the latter is single.
 
Not sure if you need to Nav antenna specially that GPS will be the primary method for navigation. In addition to your list, I have a marker beacon antenna but hardly ever use it. I am also using my Nav antenna for my glide slop by the way of a slitter.
 
dave4754 said:
I better get some RG 400
Click to expand...

It's not that much more money, in the total cost. RG58 will work okay for the com, but at GPS frequencies, not so well. If you have a certified (TSO) gps I doubt the TSO even allows you to use RG58 (coax is much more critical at a GHz).
 
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