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Mounting a VOR Antenna

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art(at)zemon.name
Guest

Posted: Thu Mar 02, 2017 12:54 pm Post subject: Mounting a VOR Antenna

Folks,

UPS brought my VOR antenna yesterday, a RAMI AV-532. I have a couple of questions about mounting it. The installation instructions are "terse," to say the least.

Am I right in assuming that neither one of the two studs should come in contact with the metal fuselage?

How do I seal the antenna to the fuselage so that it is weather proof? Squirt some RTV under it before bolting it on and then run a bead of RTV around the outside edge? Just a bead around the outside? Something entirely different?

Thanks,

    -- Art Z.

-- 

https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

cluros(at)gmail.com
Guest

Posted: Thu Mar 02, 2017 1:21 pm Post subject: Mounting a VOR Antenna

For sealing I used Alex Plus 



http://www.dap.com/dap-products-ph/alex-plus-acrylic-latex-caulk-plus-silicone/

On Thu, Mar 2, 2017 at 12:49 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:

 	  Quote: 	
		  Folks,

UPS brought my VOR antenna yesterday, a RAMI AV-532. I have a couple of questions about mounting it. The installation instructions are "terse," to say the least.

Am I right in assuming that neither one of the two studs should come in contact with the metal fuselage?

How do I seal the antenna to the fuselage so that it is weather proof? Squirt some RTV under it before bolting it on and then run a bead of RTV around the outside edge? Just a bead around the outside? Something entirely different?

Thanks,

    -- Art Z.

-- 

https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

cluros(at)gmail.com
Guest

Posted: Thu Mar 02, 2017 1:21 pm Post subject: Mounting a VOR Antenna

Whoops, didn't read the whole question . Bead around the outside edge after installation.

On Thu, Mar 2, 2017 at 1:18 PM, Sebastien <cluros(at)gmail.com (cluros(at)gmail.com)> wrote:

 	  Quote: 	
		  For sealing I used Alex Plus 



http://www.dap.com/dap-products-ph/alex-plus-acrylic-latex-caulk-plus-silicone/

On Thu, Mar 2, 2017 at 12:49 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:

 	  Quote: 	
		  Folks,

UPS brought my VOR antenna yesterday, a RAMI AV-532. I have a couple of questions about mounting it. The installation instructions are "terse," to say the least.

Am I right in assuming that neither one of the two studs should come in contact with the metal fuselage?

How do I seal the antenna to the fuselage so that it is weather proof? Squirt some RTV under it before bolting it on and then run a bead of RTV around the outside edge? Just a bead around the outside? Something entirely different?

Thanks,

    -- Art Z.

-- 

https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

ceengland7(at)gmail.com
Guest

Posted: Thu Mar 02, 2017 1:26 pm Post subject: Mounting a VOR Antenna

On Thu, Mar 2, 2017 at 2:49 PM, Art Zemon <art(at)zemon.name (art(at)zemon.name)> wrote:

 	  Quote: 	
		  Folks,

UPS brought my VOR antenna yesterday, a RAMI AV-532. I have a couple of questions about mounting it. The installation instructions are "terse," to say the least.

Am I right in assuming that neither one of the two studs should come in contact with the metal fuselage?

How do I seal the antenna to the fuselage so that it is weather proof? Squirt some RTV under it before bolting it on and then run a bead of RTV around the outside edge? Just a bead around the outside? Something entirely different?

Thanks,

    -- Art Z.



	
According to the 2nd image on that site, there are 2 mounting holes; those shouldn't have any issue with their screws contacting the a/c structure. You can use RTV to seal it to the fuselage, but be sure you get 'sensor safe' RTV for that use. Typical RTV releases acetic acid, which is corrosive.

https://en.wikipedia.org/wiki/RTV_silicone



 I couldn't find the installation docs on the site, but it's logical that the pair of inner terminals would connect to the balun, and neither of those should contact the a/c structure. Note that since it's already a 50 ohm antenna, all the balun does is convert the transmission line from balanced, which is what the 'cat whisker' VOR antenna is, to 'unbalanced', which would be your coax that runs to the receiver. I think Joe pointed out that you can just hook the coax center lead to one terminal & the shield to the other, & go fly. It'll probably work perfectly, until some day you take it to a real antenna range and hook a multi-kilobuck RF analyzer to it. Then it won't work right, because that multi-kilobuck tester said it doesn't.

Charlie

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Mar 02, 2017 1:52 pm Post subject: Mounting a VOR Antenna

 	  Quote: 	
		   I think Joe pointed out that you can just hook the coax center lead to one terminal & the shield to the other, & go fly. It'll probably work perfectly . . . 	




   Cessna flirted with baluns on their vertical fin cat-whiskers

   but the experiment didn't last long. I think for the duration of

   my tenure there (~5 years) they simply connected the coax shield

   and center to the two whiskers.  



  	  Quote: 	
		  . . .  until some day you take it to a real antenna range and hook a multi-kilobuck RF analyzer to it. Then it won't work right, because that multi-kilobuck tester said it doesn't . . . 	




   The balun shown at  http://tinyurl.com/yytxwd3 is easy to make

   and would keep the $kilo$ tester happy.



 

 

   Bob . . .

bobsv35b(at)aol.com
Guest

Posted: Thu Mar 02, 2017 2:13 pm Post subject: Mounting a VOR Antenna

Good Afternoon Art, 

 

   I have not been following this discussion, but it appears to me that you have an antenna that was designed to be mounted in a vertical fn or on the belly of an airplane very near the aft point of the fuselage. Some years ago, those wre used at the rear of Bonanzas just barely ahead of the aft bulkhead. 

  

 

  In any case, if it is not mounted quite far away from a flat portion of the fuselage, it wll have lousy reception. 

  

 

  On the other side of that question, at the range (distance) from the station we tend to be using such an antennna, a wet noodle would probably work OK.  Enroute most of us use a GPS to figure out where we are. If we are shooting a VOR approach or an approach using a localizer, we are so close to the transmitting antenna , it would be hard NOT to get an adequate signal.  

  

 

  What am I missing?

  

 

  Happy Skies,

  

 

  Old Bob

 

 

  --

art(at)zemon.name
Guest

Posted: Thu Mar 02, 2017 3:59 pm Post subject: Mounting a VOR Antenna

Thanks, everybody. I'm glad that I didn't spend a lot of money on a cable with an internal balun. I will apply a bead of "sensor safe" RTV to the VOR antenna after mounting it and expect to fly high 'n' dry.

Cheers,

    -- Art Z.

-- 

https://CheerfulCurmudgeon.com/"If I am not for myself, who is for me? And if I am only for myself, what am I? And if not now, when?" Hillel

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Thu Mar 02, 2017 4:25 pm Post subject: Mounting a VOR Antenna

Old Bob,

You are probably correct for "most" VOR/Loc approaches, but some, rather 

than being within 10-12 mi of the transmitter, go more than 20 nm from 

the VOR and would probably do a lot of hunting with the needle at that 

range. While we do use GPS a lot, a lot of aircraft do not have a 

certified GPS in the panel, so the VOR is the "legal" nav method, and 

some airways still have 100 or slightly more nm from VOR at the 

changeover point. A good antenna with good install will receive that 

100nm no sweat at say 10,000 ft.



On 3/2/2017 3:09 PM, bobsv35b(at)aol.com wrote:

[quote] Good Afternoon Art,



  I have not been following this discussion, but it appears to me that

 you have an antenna that was designed to be mounted in a vertical fn or

 on the belly of an airplane very near the aft point of the fuselage.

 Some years ago, those wre used at the rear of Bonanzas just barely ahead

 of the aft bulkhead.



 In any case, if it is not mounted quite far away from a flat portion of

 the fuselage, it wll have lousy reception.



 On the other side of that question, at the range (distance) from the

 station we tend to be using such an antennna, a wet noodle would

 probably work OK.  Enroute most of us use a GPS to figure out where we

 are. If we are shooting a VOR approach or an approach using a localizer,

 we are so close to the transmitting antenna , it would be hard NOT to

 get an adequate signal.



 What am I missing?



 Happy Skies,



 Old Bob

 --

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

bobsv35b(at)aol.com
Guest

Posted: Thu Mar 02, 2017 4:48 pm Post subject: Mounting a VOR Antenna

Good Evening Kelly,  

 

  My point, not well made, is that the type of antenna he is using will not have a good reception pattern mounted close to the ground plane of the airframe. However. it will work adequately close to the VOR or Localizer transmitter.  I still like the blades on the tail, but they are expensive. 

  

 

  The antenna in question will work quite well mounted on the fixed vertical tail feather of a Tri Pacer!! <G>

  

 

  Happy Skies,

  

 

  Old Bob

  

 

 

  --

bobsv35b(at)aol.com
Guest

Posted: Thu Mar 02, 2017 5:05 pm Post subject: Mounting a VOR Antenna

Good Evening Kelly 

 

  If I may make another comment, I think you will find that most low altitude VOR airways have the VORs less tham one hundred miles apart. 

  

 

  Back in the nineties, I had to do some testing to get some blade antennas approved. The FEDs only asked that I check the reception pattern 50 mles from the station at ten thousand feet or less.

  

 

  Happy Skies,

  

 

  Old Bob

 

 

  --

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