Reconditioning Antenna

[Huckster79]

the bird is brand new to me… Just got my first 1.7 of transition training in it- loved it… 

 

But as I make plans to rejuvenate the paint- this antenna caught my eye in terms of looking a lil ratty… But typically you can’t paint antennas correct? Is there any other options besides replacement or live with it? Or could these style of antenna be painted?  

Edited April 26, 2023 by Huckster79

[Janat83]

I believe YES you can paint your antenna as long as the paint doesn't have any metal in it.

[N201MKTurbo]

I have sanded one of those. The fiberglass under the paint is super hard. You can sand the crap out of it. That antenna has been painted in the past, that's why it looks so bad. I would remove it first, it will be so much easier to sand and paint. It is kind of a PITA to get to the screws. Mine was all rusty and corroded, so removing it and reinstalling it will probably do it some good, just remember the screws need to ground the antenna well.

[N201MKTurbo]

I don't see a gasket on that antenna. If you don't have one, re-install it with tank sealer.

 

[Fly Boomer]

42 minutes ago, N201MKTurbo said:

I don't see a gasket on that antenna. If you don't have one, re-install it with tank sealer.

 

CS-3330 work okay for that?

[N201MKTurbo]

26 minutes ago, Fly Boomer said:

CS-3330 work okay for that?

Yes

[EricJ]

If there's any evidence of corrosion having gotten to the conducting element of the antenna, find somebody with a Network Analyzer to sweep it and make sure the antenna itself is in good shape before spending a lot of time refinishing it.    Sometimes those goes wonky and need replacement after being in service so long, but except for corrosion they don't really wear out.    If it's working pretty well it should be fine, but might be worth checking if it looks like it might be an issue.

 

[Hank]

If you replace it, get one of these. 

[SLOWR426]

Which antenna is this? Comm? Nav?  VOR?  IFR?

[MB65E]

These are comm antennas. The 7 antennas are NLA. The CI-196 antenna is kinda neat. The connector is off center which allows the antenna to be placed on centerline. No gaskets required, just clean corrosion and seal it nicely. Bare metal on the base when sealed is ok. 
Ok to sand and repaint. Most store bought rattle cans will fade to an off white and full over time. Beats what you have. 
-Matt

[SLOWR426]

@N201MKTurbo and @MB65E, on my 67 F, the 7 antenna seems to have a traditional gasket, black, that looks worn.  I saw some green corrosion on the interior, so I think it's leaking, and I'd like to remove, clean, and re-install.  Are you guys saying that I should fully re-secure the antenna, then apply a fillet of polysulfide sealant around the outside of the joint?  The CI-196 lists a gasket B19604, but no mention of gasket material, shape.

Thanks much.

Edited March 10 by SLOWR426

[N201MKTurbo]

4 hours ago, SLOWR426 said:

@N201MKTurbo and @MB65E, on my 67 F, the 7 antenna seems to have a traditional gasket, black, that looks worn.  I saw some green corrosion on the interior, so I think it's leaking, and I'd like to remove, clean, and re-install.  Are you guys saying that I should fully re-secure the antenna, then apply a fillet of polysulfide sealant around the outside of the joint?  The CI-196 lists a gasket B19604, but no mention of gasket material, shape.

Thanks much.

There needs to be a water tight seal around the antenna. I think the polysulfide works better than the original gasket. You want a generous coat on both the airplane and the antenna. Then screw down the antenna and let the sealant extrude out around the base. Carefully wipe the excess off to make a nice fillet. Let it cure and then clean it up with your fingernails or plastic scrapers and finally MEK or denatured alcohol.

[cliffy]

I worked for COMANT back when they started up at KSMO

We included GROUNDING base gaskets with each antenna. 

Grounding the base is vital to the efficiency of the antenna

The screw holes on the top of the antenna "may" be able to be 

used as a ground path on some models IF the bottom of the are cleaned to bare metal

so the screw heads make contact to transfer the ground path to the nuts inside the fuselage.

Make sure the washers and nuts are clean and the metal inside is also clean.

[N201MKTurbo]

8 minutes ago, cliffy said:

I worked for COMANT back when they started up at KSMO

We included GROUNDING base gaskets with each antenna. 

Grounding the base is vital to the efficiency of the antenna

The screw holes on the top of the antenna "may" be able to be 

used as a ground path on some models IF the bottom of the are cleaned to bare metal

so the screw heads make contact to transfer the ground path to the nuts inside the fuselage.

Make sure the washers and nuts are clean and the metal inside is also clean.

The grounding gasket doesn’t do much when the antenna is mounted on a painted surface. My antenna didn’t work very well. The antenna mounting screws were rusty, the steel tube structure was rusty where the screws attached. I cleaned it all up and painted it with the last zinc chromate I had. I assembled the antenna with new SS screws and put star washers under the heads. The antenna works much better now.

[SLOWR426]

On 3/10/2024 at 9:40 AM, cliffy said:

I worked for COMANT back when they started up at KSMO

We included GROUNDING base gaskets with each antenna.

Wow, thank you, @cliffy!  What kind of conductive gasket?  Rubber with carbon? Metallic cloth with rubber around the outside?  Perhaps I can find some sheets and make my own!

Here's what I could use, if resistance is low enough: https://www.mcmaster.com/products/conductive-gaskets/electrically-conductive-high-temperature-silicone-rubber-sheets/

Edited March 13 by SLOWR426

[N201MKTurbo]

6 hours ago, SLOWR426 said:

Wow, thank you, @cliffy!  What kind of conductive gasket?  Rubber with carbon? Metallic cloth with rubber around the outside?  Perhaps I can find some sheets and make my own!

Here's what I could use, if resistance is low enough: https://www.mcmaster.com/products/conductive-gaskets/electrically-conductive-high-temperature-silicone-rubber-sheets/

https://www.americanaviationparts.com/gasket-for-ci-196-revision-k.html
 

[cliffy]

It was black with a metallic matrix

The  base mount area on the fuselage had to be cleaned to bare metal for conduction

A spot about 60-&)% of the base size was sufficient back then. 

The same theory applies to the plain bent wire whip antenna that mount in one small hole (frankly for small GA airplanes they do a good job)

You would drill the hole and the center of the coax cable was hooked to the vertical whip and the shielding of the coax was attached to the base where it connects to the fuselage skin (called a Ground Plane) You big white antenna has the same requirement for a "ground  plane" connection.   

You always need a good clean connection to the ground plane on any communications antenna (not VOR antennas). 

[EricJ]

FWIW, the antenna ground plane connection can be made on the unpainted side of the sheet metal, opposite the antenna.    This is usually done through the mounting hardware and the connector to the shielded side of the cable.   This allows the paint on the exterior side of the sheet metal to be maintained and reduce the likelihood of corrosion on the exposed side of the sheetmetal or where leaks might retain moisture under the antenna base.   Usually the gasket and any sealant is primarily to prevent moisture intruding under the base where it can contribute to corrosion.