What antennas do I have on top of my C?

[Brian E.]

MS friends - looking for your wisdom in identifying some antennas on the top of my plane.  I know this first picture is for my LORAN-C antenna.  I removed the interior components earlier this year and will remove the antenna if I don't need the hull penetration.

 

I have 2 KX-155s installed (one with GS).  I have intended to pop open the avionics cowling this weekend but the exceptionally cold weather got the best of me.  With that in mind, I'm curious what these two other antennas are.

 

The blade like antenna is labeled as a Narco.  There's no brand name on the other which is mid fuselage.  I appreciate your thoughts on this as I am considering installing a GNX375 and removing VOR, localizer, marker beacon antennas (on the bottom), etc...

 

[Marauder]

MS friends - looking for your wisdom in identifying some antennas on the top of my plane.  I know this first picture is for my LORAN-C antenna.  I removed the interior components earlier this year and will remove the antenna if I don't need the hull penetration.

 
I have 2 KX-155s installed (one with GS).  I have intended to pop open the avionics cowling this weekend but the exceptionally cold weather got the best of me.  With that in mind, I'm curious what these two other antennas are.

 
The blade like antenna is labeled as a Narco.  There's no brand name on the other which is mid fuselage.  I appreciate your thoughts on this as I am considering installing a GNX375 and removing VOR, localizer, marker beacon antennas (on the bottom), etc...
 

The whip type look like a Comant 109. Not sure on the Narco one.


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[Brian E.]

The Comant 109 is a VHF antenna.  Would it serve both VHF comms or would I expect there to be an antenna for each VHF radio?

[EricJ]

31 minutes ago, Brian E. said:

The Comant 109 is a VHF antenna.  Would it serve both VHF comms or would I expect there to be an antenna for each VHF radio?

Each comm radio has a separate antenna, and the second two antennas you show are the two VHF comm radio antennas.

The VOR/localizer/GS antenna is usually the whiskers at the top of the tail.  You probably don't want to remove that.    If you still have a marker antenna it will probably be on the belly, maybe a "skid" type or a flat antenna.

 

[Brian E.]

Just now, EricJ said:

Each comm radio has a separate antenna, and the second two antennas you show are the two VHF comm radio antennas.

Curious why my two VHF antennas are different.  Is one model better than the other?  BTW, as you can imagine they all use RG-58 cable.  The reason I ask about the difference is that I get somewhat difference performance from my two radios.  I know I need to inspect or replace cabling , antenna connections and the antenna ground planes...

[EricJ]

Just now, Brian E. said:

Curious why my two VHF antennas are different.  Is one model better than the other?  BTW, as you can imagine they all use RG-58 cable.  The reason I ask about the difference is that I get somewhat difference performance from my two radios.  I know I need to inspect or replace cabling , antenna connections and the antenna ground planes...

One or both of the antennas has probably been replaced at one time or other with whatever was thought to be the best choice at the time.   Performance differences between radios can be due to the antennas, corrosion in the connections, old cabling in bad condition (kinks, crimps, crushes, splits, etc.), or just differences in the radios themselves, or even the audio panel.   So it's hard to pin down without doing some sleuthing.   Cables and connectors sometimes reveal problems just by visual inspection, so that's not a bad place to start.    If the two radios are the same kind, you can try swapping their positions and see if the trouble follows the radio or the slot.

[Brian E.]

1 minute ago, EricJ said:

   If the two radios are the same kind, you can try swapping their positions and see if the trouble follows the radio or the slot.

Good words.  I haven't got that far and may not.  As noted in my first post, I'm contemplating getting out of the KX155 business while I can.  But wanted to better understand the current configuration I have on top of the plane for antennas since no two were alike.

Thanks for the thoughts,

[carusoam]

+1 on Eric’s path...

Also review the logs... some of the detail of what got installed with what and when... may be clearly written...

Best regards,

-a-

[Brian E.]

6 hours ago, carusoam said:

Also review the logs... ..

-a- Nothing of consequence in the logs.  They are woefully lacking avionics info.  Radio info yes, nothing on antennas...

[Yetti]

Dirty Antennas.   That's what kind you have.   Generally VHF.   There is a version of the Comant that has VHF and GPS in the same form factor.

[vorlon1]

2 hours ago, Yetti said:

There is a version of the Comant that has VHF and GPS in the same form factor.

How many knots is that worth?

I have a birthday coming up...

[Hank]

28 minutes ago, vorlon1 said:

How many knots is that worth?

Not many, GPS pucks are pretty small and maybe an inch tall. It will save drilling another hole in the roof . . . . .

[Brian E.]

3 hours ago, Yetti said:

Dirty Antennas.  

Actually they are not  that dirty.  The paint is plum worn off...

[RobertGary1]

The Garmin GPS puck perfectly covers the hole for that Loran mount.

 

-Robert

[Hank]

37 minutes ago, Brian E. said:

Actually they are not  that dirty.  The paint is plum worn off...

Don't paint GPS antennas!

[EricJ]

Just now, Hank said:

Don't paint GPS antennas!

Don't paint any antenna unless it sez you can.

 

[Brian E.]

2 minutes ago, Hank said:

Don't paint GPS antennas!

I can only dream of GPS at this point!

[Skates97]

37 minutes ago, RobertGary1 said:

The Garmin GPS puck perfectly covers the hole for that Loran mount.

 

-Robert

Yes, that is exactly what I did when I removed the Loran antenna and put in the GA35 for my ADS-B Out.

[Yetti]

my loran was in the bottom.   I asked the IA about doing a patch.   He said why don't you just put the bolt back in the hole.   He is a wise IA....

 

[Brian E.]

1 hour ago, RobertGary1 said:

The Garmin GPS puck perfectly covers the hole for that Loran mount.

 

-Robert

My Loran is far back by the dorsal fin.  Would that be considered a unobstructed view of the sky suitable for GPS installation?

[Yetti]

18 hours ago, Brian E. said:

My Loran is far back by the dorsal fin.  Would that be considered a unobstructed view of the sky suitable for GPS installation?

Yes but a pain to get to.   One recommendation (from Dynon) is to have the GPS Antenna 3 feet away from a VHS antenna.  It's not a huge deal in our planes, but there is a way to set offset from the Centerline of the plane for use of ground based ADSB.  The other cool thing about the Dynon antenna is that is does the processing in the antenna so you don't run coax to the antenna.  Just 4 wires.   8volts/Ground    GPS TX/ GPS Rec.

Mine are going in over the baggage area.

 

[Brian E.]

Good to know---very interested in the HDX.

[Hector]

In a somewhat unrelated question, is there data to show the aerodynamic drag of the various types of VHF antennas. I believe the circular cross-section antenna the OP has shown pictures of are probably the worst. The blade antennas is better. The 7 antenna even better?? Is the drag improvement worth replacing a dirty whip antenna that is working just fine?


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[Brian E.]

10 hours ago, Hector said:

 is there data to show the aerodynamic drag of the various types of VHF antennas.

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Part of my larger end game is cleaning up unused antennas while improving radio performance.  I've been looking at combining antennas, eliminating unnecessary ones while trying to be aerodynamic efficient.  I didn't see any quantifiable data in the Comant antenna catalog other than "low drag" design.  I also found this drag formula which was too much for me at this time in the morning :  D=1/2CDρV2A (this was poorly cut and pasted--don't go engineering anything with it!)

As a bridge between absolute quantifiable science and subjective assessments. I found a soaring website that has the following data on transponder antennas.

Rod style transponder antenna has 0.41 lb @ 250 mph.

They then have a note that purports, "Note: The blade style antennas below are more expensive, but they have about 1/5 the drag of this rod and ball antenna."

Blade style transponder or DME antenna has 0.09 lbs @ 250 mph.

So what the practical impact at the speeds a C model (with the guppy mouth, flap gaps, etc) operates?  Probably negligible...but like -a- I'm not a CFI, aero engineer or anything else relevant to this discussion...

 

 

[Jerry 5TJ]

This manufacturer’s site has drag figures for a number of common GA antennas. 

RAMI Antennas

Your com antennas have 2-3 pounds drag each at 250 mph.  

Antenna drag (approximately) increases at the square of the speed increase.  So at Mooney C speeds the antenna drag will be perhaps 1/3 of the 250 mph figures.