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Antenna mounting-doubler

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larkrv10(at)gmail.com
Guest

Posted: Thu Apr 19, 2012 7:16 pm Post subject: Antenna mounting-doubler

Hi Bob,

 

I'm aware that a doubler plate/skin connection for mounting a nav or com antenna requires a nice shiny surface.  But, will alodining the surfaces make any difference with antenna performance?

  

Thx,  Rick

Vans #40956

Southampton, Ont

  [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Apr 19, 2012 8:28 pm Post subject: Antenna mounting-doubler

At 10:13 PM 4/19/2012, you wrote:

 	  Quote: 	
		  Hi Bob,



I'm aware that a doubler plate/skin connection for mounting a nav or 

com antenna requires a nice shiny surface.  But, will alodining the 

surfaces make any difference with antenna performance?


	


   I presume you're talking about a commercial comm

   wisker that mounts with 3 or 4 screws and has

   a BNC connector centrally located in the hole

   pattern.



   See:



http://tinyurl.com/6rwodso



   Practical electrical connection is made with

   the airframe only at the areas where there are

   large clamp up forces around the screws. These

   forces go to essentially zero at more than 1/4"

   away from the mounting hardware. The goal is to

   things clean if not bright around each

   of the mounting screws on all mating surfaces.

   The end product will be the best we know how

   to do . . . short of welding the antenna base

   to the skin. The goal is 'gas tightness' within

   the cleaned areas . . . so screw the nuts down

   good and tight. Metal lock-nuts would be good.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Apr 20, 2012 6:51 pm Post subject: Antenna mounting-doubler

At 08:33 PM 4/20/2012, you wrote:

 	  Quote: 	
		  Yup, Bob you presume correctly, and yes I'm well aware of keeping 

the antenna base tight to the create a gas tight mount.  I was 

simply wondering about having the surfaces alodined as opposed to 

possibly taking the alclad surfaces off when creating a "shiny" 

surface.  Can't imagine that the alodined process would alter the 

antenna ground plane properties of the surfaces.




	


   It's relative. Bonding processes at places like

   Beech call for cleaning, buffing, perhaps some

   passivation, then clamp 'er up tight. If it's

   a critical bond, some inspector gets out a

   micro-ohmmeter to see that it 'meets specs'.



   Now, if some guy wipes it off with a rag

   soaked in solvent, bolts the antenna down

   without fanfare or process, would the pilot

   know the difference?



   Not trying to be obtuse. But in a manufacturing

   (particularly a 'certified') operation, one

   is driven to establish standards that usually

   drive toward the best we know how to do. Once

   those standards are in place, they tend to

   be invoked whether anyone knows if it matters

   or not.



   I can only advise that any departure from

   process results in a degradation of end result.

   Just how bad is anybody's guess without doing

   a tests. I have no foundation for quantifying

   that difference but I agree that is small.

   So if you'd rather 'not go for shiny', it's

   your experiment. In able to tell any difference.

   Bob . . .

   Bob . . .

aerobubba(at)earthlink.ne
Guest

Posted: Sat Apr 21, 2012 3:41 am Post subject: Antenna mounting-doubler

Let's try this from a different angle:  How conductive is an Alodined surface?



Glen Matejcek

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Apr 21, 2012 4:44 am Post subject: Antenna mounting-doubler

At 06:37 AM 4/21/2012, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Glen Matejcek <aerobubba(at)earthlink.net>



 Let's try this from a different angle:  How conductive is an Alodined surface?

 	
  Good question. There are descriptions of the process at:



  http://tinyurl.com/7odr8ay



  http://tinyurl.com/7sn63nx



  Others have wondered about the conductivity of the process . . .



  http://tinyurl.com/83qsqhe



  http://tinyurl.com/74f759b



    here's an excerpt from a book where the relative   conductivity of surface coatings are being examined   for use on antenna reflectors . . . though I'm not   sure if there's a direct correlation between   effectiveness as a reflector and conductor of DC 



  http://tinyurl.com/83pnyn7



   This page speaks to the use of chromate coatings thusly:



  http://tinyurl.com/7n3rx7n



 

 Based on the product series, Buckeye uses the following undercoats 

 to protect your investment:

   



 Alodine:  Yellow and Clear. Primary functions are for paint adherence, rust inhibiting, and conductivity. 

 Anodize:   Clear and Blue. Primary functions are for cosmetic appearance, hardness, and rust inhibiting.

 Zinc Chromate:   Yellow, Clear, and Black. Primary functions are for conductivity and rust inhibiting 



  Don't have time to delve into it deeply right now but I'll invite interested individuals to Google "chromate" and  "conductivity" for some sense of magnitude of conductivity effects on bare metals.

  I used to know some folks in the Process Lab at HBC. If they're still there, I might be able to get a 'numbers' dump on the topic.    

   



 

 

   Bob . . .    [quote][b]

aerobubba(at)earthlink.ne
Guest

Posted: Sun Apr 22, 2012 5:06 am Post subject: Antenna mounting-doubler

Hi Bob-



I suspect that what you've posted already more than answers the original question, although the comment about passing DC makes me wonder a bit about passing RF.  



Your comments about reflectors also has me wondering about a few gee-whizz things about the radar reflectors you can still see at some airports...

As ever, thanks!



Glen Matejcek

dougshep

Joined: 22 Jul 2010
Posts: 7
Location: Santa Barbara, CA

Posted: Mon Apr 23, 2012 2:22 pm Post subject: Antenna mounting-doubler

I had the same question last year when I was using  Alodine coated ALCAD for a bus bar.  I talked with the manufacturing tech. staff and got the following reply...I also included another comment.  I noticed when using it, not to let your part submerge too long in the Alodine bath, else excess Alodine can coat your aluminum surface:



AL 1201



From: Kristina.Tkacz(at)us.henkel.com 

To:dougshep(at)netzero.com 

Sent: Fri, Jun 10, 2011 11:14 AM



Doug, 



Per our discussion yesterday about the Alodine 1201, we unfortunately do not have any documentation or data regarding the resistivity capabilities. This product is approved on the QPL-81706 (see: http://www.chemical-supermarket.com/files/Henkel%20Alodine%20Conversion%20Coatings/Mil-DTL-81706B.pdf) for Class 1A. However, we do believe that because of its similarities in chemistries to the Alodine 1200S it should pass the electrical resistance testing. Again, we do not have any data to confirm this. As for the thickness of the coating, an average application would be around 100 nm. Please let me know if you have any further questions.



Kind Regards / mit freundlichen Gr��en, 

Kristina Tkacz 



Kristina Tkacz

Technical Service Representative Surface Treatment Application Specialist 

Aerospace, Global 

Henkel Corporation 

( Office: +248.577.2115 � Mobile: +248.376.9294 

* Email:Kristina.Tkacz(at)henkel.com		www.henkel.com



-	-	-	-	-	-	-	-	-	-	-	-	-	-

(another question/answer from someone else)

Electrical properties of Alodine 1200 (from;  http://www.finishing.com/364/48.shtml )

I would like to know the electrical properties of ALODINE 1200. We are using it as protection on our metallic housing of Door Control Unit. Is it necessary to protect the ground stud from ALODINE 1200 ? 

Emmanuel SEREZAT	transport - FRANCE

Alodine 1200 is one of chromate chemical conversion coating that meets requirements of MIL-C-5541 (you can find a lot of other processes). Mil-C-5541 [link is to spec at TechStreet] Class 3 requires maximum 5000 µOhm per sq. inch electrical resistance. Actually, electrical resistance for properly performed Class 3 is usually 1000-2000 µOhm per sq. inch. MIL-C-5541 Class 1A does not require electrical conductivity. Most chemical conversion coatings from QPL (including Alodine 1200) can be performed as both Class 1A and Class 3. Therefore you should check which class is processed on your parts.



-	-	-	-	-	-	-	-	-	-	-	-	-	-



Alodine 1200, 1201, & 1200S:	(from: http://www.chemical-supermarket.com/home.php?cat=109)

Alodine 1200 is Henkel’s product family for hexavalent chromium conversion.  Contained in this family are two primary products; Alodine 1201 and Alodine 1200S.  Alodine 1201 is a ready-to-use liquid product which, when brushed-on or diluted and immersion-applied, produces a gold-colored Chromate Conversion Coating which contains hexavalent chromium.  Consistent with Class 1A of the mil spec, it is formulated to provide maximum corrosion prevention when left unpainted as well as to improve adhesion of paint finish systems on aluminum and aluminum alloys.  Alodine 1200S is the powdered composition dissolved by professional industrial facilities into their immersion baths.



 Doug Shepard, RV-9A construction

_________________
Doug Shepard, RV-9A

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 23, 2012 9:10 pm Post subject: Antenna mounting-doubler

At 09:16 PM 4/23/2012, you wrote:

 	  Quote: 	
		  Guys, I believe I started this thread about a week ago.



Today I came upon a "General Antenna Installation Guidlines", 

written by Cobham which I think is the parent company to Comant.  In 

those instructions they state that electrical bonding is best 

accomplished by "direct metal to metal" contact of the antenna base 

to the aircraft skin.  Also paint is to be removed and to protect 

the aluminum against corrosion, the surface can be alodined. They 

then also mention using the mounting screws to provide a good ground 

as an alternate method with a couple of other stipulations.  As well 

to test the bonding, a reading of .003 ohms between the base and the 

ground should be achieved.



So since I'm mostly using Comant on my -10, I guess I will continue 

alodining.  I will check to see what kind of readings I get with my VOM.


	


   Your VOM is incapable of resolving resitance

   measurements this low. A 4-wire, low ohms adapter

   is called for. See:



http://tinyurl.com/4l3tuj6



   If you're not inclined to roll your own,

   this is another option . . .



http://www.aeroelectric.com/Catalog/AEC/9008/



   Bob . . .

pwmac(at)sisna.com
Guest

Posted: Tue Apr 24, 2012 5:00 am Post subject: Antenna mounting-doubler

Is your AEC9008 still available for sale? Price?

Paul

===

At 11:08 PM 4/23/2012, you wrote:

 	  Quote: 	
		  

<nuckolls.bob(at)aeroelectric.com>



At 09:16 PM 4/23/2012, you wrote:

>Guys, I believe I started this thread about a week ago.

>

>Today I came upon a "General Antenna Installation Guidlines", 

>written by Cobham which I think is the parent company to 

>Comant.  In those instructions they state that electrical bonding 

>is best accomplished by "direct metal to metal" contact of the 

>antenna base to the aircraft skin.  Also paint is to be removed and 

>to protect the aluminum against corrosion, the surface can be 

>alodined. They then also mention using the mounting screws to 

>provide a good ground as an alternate method with a couple of other 

>stipulations.  As well to test the bonding, a reading of .003 ohms 

>between the base and the ground should be achieved.

>

>So since I'm mostly using Comant on my -10, I guess I will continue 

>alodining.  I will check to see what kind of readings I get with my VOM.



   Your VOM is incapable of resolving resitance

   measurements this low. A 4-wire, low ohms adapter

   is called for. See:



http://tinyurl.com/4l3tuj6



   If you're not inclined to roll your own,

   this is another option . . .



http://www.aeroelectric.com/Catalog/AEC/9008/



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Apr 24, 2012 6:11 am Post subject: Antenna mounting-doubler

At 06:16 AM 4/24/2012, you wrote:

 	  Quote: 	
		  



Is your AEC9008 still available for sale? Price?


	


  It's in the catalog



http://tinyurl.com/36e7ddd



   Bob . . .

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