Avionics Upgrade - Antenna Questions

[Reid]

We are considering a panel upgrade on our M20C.  The install would include a GTN750, NGT9000+ and PMA450b.  Since the NGT9000+ requires a somewhat large NY164 antenna, for which the install manual wants 24" spacing from all other antennas I've been trying to determine if removing/relocating a few antennas is worthwhile.

I've attached a photo of our plane.  The GPS antenna is installed where the loran antenna is.  The ADF antenna has been removed, with the exception of the small mounting point on the top of the cabin.

There would appear to be nowhere where we could install the NY164 right now and maintain the recommended spacing.  My thoughts are as follows:

- Replace 'V' VOR/LOC antenna with a new 'V' VOR/LOC/GS antenna.  Does anyone have know the which antenna is now recommended for VOR/NAV/GS.  CI-158C? AV-532?  Will this be a simple swap that can be done when the old coax is being replaced with RG-400?

- Remove front GS antenna and adf antenna mounting point.

- Remove the front '7' antenna.

- Install a comm antenna on the belly. CI-122?

This would free up a lot of space for the NY164 antenna to be installed where the front '7' antenna was located.

Thoughts?

 

Edited October 11, 2018 by Reid

[Awful_Charlie]

I'd suggest you get your Avioncs tech on the case - each antenna has its own location/seperation requirements, and some antennas have approved mounting positions on each airframe type. In most cases, these are "for best performance" but in others it is a mandatory requirement. In addition, each transmitter/receiver will likely have a list of approved antennas, and using something not on that list will involve extra pain.

It will certainly help the tech if you can tell them what equipment you want to retain and what can be removed, and probably a good idea to discuss with them future plans for additional equipment

[Marauder]

We are considering a panel upgrade on our M20C.  The install would include a GTN750, NGT9000+ and PMA450b.  Since the NGT9000+ requires a somewhat large NY164 antenna, for which the install manual wants 24" spacing from all other antennas I've been trying to determine if removing/relocating a few antennas is worthwhile.
I've attached a photo of our plane.  The GPS antenna is installed where the loran antenna is.  The ADF antenna has been removed, with the exception of the small mounting point on the top of the cabin.
There would appear to be nowhere where we could install the NY164 right now and maintain the recommended spacing.  My thoughts are as follows:
- Replace 'V' VOR/LOC antenna with a new 'V' VOR/LOC/GS antenna.  Does anyone have know the which antenna is now recommended for VOR/NAV/GS.  CI-158C? AV-532?  Will this be a simple swap that can be done when the old coax is being replaced with RG-400?
- Remove front GS antenna and adf antenna mounting point.
- Remove the front '7' antenna.
- Install a comm antenna on the belly. CI-122?
This would free up a lot of space for the NY164 antenna to be installed where the front '7' antenna was located.
Thoughts?
 

As you found out there are installation requirements for these antenna. I have essentially the same set up you are installing. Here is what my “antenna farm” looks like:





They removed my back “7” antenna and replaced it a bent wire antenna underneath the plane (below the avionics bay).




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[thinwing]

The Spacing between the 2 com antennas seems excessive..I wonder if the aft one could be moved up and put the ny164 in its place

[StevenL757]

Reid, here is the arrangement on my Ovation.  Although I questioned the GPS antenna placements, my avionics shop supported the arrangement, and also had it cross-checked with Garmin's engineering folks to ensure there wouldn't be any conflicts.  Truth be told, the GPS antenna spacing on Garmin's Ovation test aircraft is actually much closer than mine, and they haven't caused any issues.

Appreciate you have a shorter fuselage to work with, but I would consider this arrangement...particularly the NY164 - if your curved fuselage close to the cockpit window allows the mounting.  My COM blades were not moved for this arrangement.

Steve

[Davarron]

I just had the 9000+ installed and the antenna was put in place of the COM 1 antenna over the front seats. The COM 1 antenna was moved to the belly as a bent whip antenna. Works fine so far.

[jetdriven]

9 hours ago, StevenL757 said:

Reid, here is the arrangement on my Ovation.  Although I questioned the GPS antenna placements, my avionics shop supported the arrangement, and also had it cross-checked with Garmin's engineering folks to ensure there wouldn't be any conflicts.  Truth be told, the GPS antenna spacing on Garmin's Ovation test aircraft is actually much closer than mine, and they haven't caused any issues.

Appreciate you have a shorter fuselage to work with, but I would consider this arrangement...particularly the NY164 - if your curved fuselage close to the cockpit window allows the mounting.  My COM blades were not moved for this arrangement.

Steve

Flush rivets would look so much cleaner on these airplanes.  

[StevenL757]

Yea, i agree.  Not sure why they only opted to flush-rivet only the front half of the airplane and not the areas aft of the speed brakes...and empennage area.  Am guessing they had their reasons at the time.

[EricJ]

17 hours ago, StevenL757 said:

Yea, i agree.  Not sure why they only opted to flush-rivet only the front half of the airplane and not the areas aft of the speed brakes...and empennage area.  Am guessing they had their reasons at the time.

The attached layer of air slows down as it moves along the surface of the airplane, so there's less benefit to flush rivets after a certain distance from the leading edge or nose.   You'll see the same thing if you take a close look at an airliner.

Edited October 13, 2018 by EricJ