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Removable comm antenna

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holger-d(at)shadowbrush.c
Guest

Posted: Tue Dec 11, 2012 6:45 pm Post subject: Removable comm antenna

Hi all,



Knowing next to nothing about antenna installations, can I run this one 

by you for a sanity check? I'd like to be able to quickly disconnect the 

comm antenna on a regular base so I can throw a full body cover of my 

motor glider.



The antenna sits on the top of the fuselage and currently is a simple 

1/4 wave SS bent back whip antenna. Now I want to mount the fat part of 

a Workman QDS1 inside the fuselage so it's flush with the outer skin. 

Then drill a hole in the small part of the QDS1 and install the whisker 

analog to Bob's article. Next is screwing an isolated BNC panel mount 

into the QDS1 and make an electric connection between the middle 

connector of the BNC and the QDS1. The QDS1 is isolated against the 

fuselage. Would it need to be shielded as well? I could put it into an 

aluminum box. Alternatively to the BNC, I could also go with a 3/8" to 

SO-239 adapter.



What do you say, would that work?



Here are links to the parts:



Workman QDS1: 

http://www.amazon.com/QUICK-DISCONNECT-Stainless-Antenna-thread/dp/B004X70UCO/ref=pd_sxp_redirect



Isolated BNC panel mount: 

http://www.allelectronics.com/make-a-store/item/BNC-148/BNC-JACK-ISOLATED-PANEL-MOUNT-CONNECTOR/1.html 

Bob's article: 

http://aeroelectric.com/articles/Antennas/DIY_Comm_Ant/DIY_Comm.html



Thanks much!



Holger

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 12, 2012 8:02 am Post subject: Removable comm antenna

At 08:44 PM 12/11/2012, you wrote:

 	  Quote: 	
		  

<holger-d(at)shadowbrush.com>



Hi all,



Knowing next to nothing about antenna installations, can I run this 

one by you for a sanity check? I'd like to be able to quickly 

disconnect the comm antenna on a regular base so I can throw a full 

body cover of my motor glider.


	


   Is this a metal airplane?

   Bob . . .

holger-d(at)shadowbrush.c
Guest

Posted: Wed Dec 12, 2012 9:08 am Post subject: Removable comm antenna

On 12/12/12 8:01 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		     Is this a metal airplane?




	


Yes, Bob, it's an all metal plane.



Thanks,



Holger

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 12, 2012 9:52 am Post subject: Removable comm antenna

 	  Quote: 	
		  The antenna sits on the top of the fuselage and currently is a 

simple 1/4 wave SS bent back whip antenna. Now I want to mount the 

fat part of a Workman QDS1 inside the fuselage so it's flush with 

the outer skin. Then drill a hole in the small part of the QDS1 and 

install the whisker analog to Bob's article. Next is screwing an 

isolated BNC panel mount into the QDS1 and make an electric 

connection between the middle connector of the BNC and the QDS1. The 

QDS1 is isolated against the fuselage. Would it need to be shielded 

as well? I could put it into an aluminum box. Alternatively to the 

BNC, I could also go with a 3/8" to SO-239 adapter.


	


   Consider this alternative. Since this is a slow speed

   airplane with relatively low duty cycle, perhaps something

   simpler and less robust would be attractive.



   Mount 7/16 x 1/2" stainless bolt on a phenolic/fiberglas

   skin doubler over a clearance hole for bolt head. Drill

   and tap both threaded end and head of bolt for 10-32 screw.

   Tread antenna-length piece of 3/16" steel rod about 1/2"

   of 10-32 thread. Mount bolt on doubler head facing up.

   Thread antenna into bolt and secure with lock-nut. Attach

   feed line directly to nut-side of bolt with 10-32 screw

   and PIDG terminal. Use PIDG terminal to ground the shield

   to one of the doubler attach screws.



   Low parts count. Low number of mated joints in the RF

   current paths.



   Antenna can be easily dismounted and stowed.

   Bob . . .

dlj04(at)josephson.com
Guest

Posted: Wed Dec 12, 2012 10:26 am Post subject: Removable comm antenna

On 12/12/12 2:57 AM, AeroElectric-List Digest Server wrote:

 	  Quote: 	
		   by you for a sanity check? I'd like to be able to quickly disconnect the

 comm antenna on a regular base so I can throw a full body cover of my

 motor glider.

You certainly don't need all that extra hardware. Get or make an antenna 
	


that terminates in a BNC male connector, and mount a BNC female 

connector on top of the fuselage. You can get panel mount connectors 

that install directly on RG-58 cable. Assuming your glider is 

fiberglass, add 3 or 4 quarter-wave radial elements from the shell of 

the BNC and extending outward along the inside surface of the fuselage. 

You can then make a dummy plug, maybe dome shaped, that goes on the BNC 

when you want to cover the aircraft to protect the connector and let the 

cover slide over it freely.

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 12, 2012 12:14 pm Post subject: Removable comm antenna

 	  Quote: 	
		  You certainly don't need all that extra hardware. Get or make an 

antenna that terminates in a BNC male connector, and mount a BNC 

female connector on top of the fuselage. You can get panel mount 

connectors that install directly on RG-58 cable. Assuming your 

glider is fiberglass, add 3 or 4 quarter-wave radial elements from 

the shell of the BNC and extending outward along the inside surface 

of the fuselage. You can then make a dummy plug, maybe dome shaped, 

that goes on the BNC when you want to cover the aircraft to protect 

the connector and let the cover slide over it freely.


	


    Another good idea. I seem to recall somebody

    here on the list used a 'rubber duck' antenna

    for a hand-held as his choice of removable

    external antennas.



    I have crimp-on, bulkhead mount BNC connectors

    in stock if you want to go that route and need

    one.

   Bob . . .

holger-d(at)shadowbrush.c
Guest

Posted: Wed Dec 12, 2012 1:35 pm Post subject: Removable comm antenna

On 12/12/12 12:14 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

    Another good idea. I seem to recall somebody

    here on the list used a 'rubber duck' antenna

    for a hand-held as his choice of removable

    external antennas.


	


Thank you, Bob and DL for your suggestions.



Bob, your solution isn't fully clear to me. Is the 3/16" rod silver 

soldered into the 10-32 screw? To disconnect, one would unscrew the 

10-32 screw? If the antenna is bent back, that may be a little tricky, no?



I've seen BNC connectors used as antenna bases on ultralights but wasn't 

sure about the speed limits. Mine has a 100kts cruise. The BNC 

connectors that looked beefy enough also looked pretty draggy. Same for 

antennas that have a BNC mount. Bob, you think your crimp-on BNC 

connector would support a whip antenna, vs. a rubber duck one? In this 

case I'd like to order it from you. I guess I could machine a stainless 

steel support sleeve to beef up the antenna side BNC.



Thanks!



Holger

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 12, 2012 4:52 pm Post subject: Removable comm antenna

 	  Quote: 	
		  

Bob, your solution isn't fully clear to me. Is the 3/16" rod silver 

soldered into the 10-32 screw? To disconnect, one would unscrew the 

10-32 screw? If the antenna is bent back, that may be a little tricky, no?


	


  No, I'd leave the nut loose for a couple of reasons.

  First, it would let you orient a bend and tighten the nut

  later (this could be a finger nut made from a piece

  of flat sheet with a drilled and tapped hole in the

  middle but with enough O.D. to let you hand tighten.

  Yeah, it would have a slight 'lengthening' effect

  on the antenna which would be shortened accordingly

  using SWR meter



  (2) heating the rod to silver solder temps in

  the thread area places the heat treat of the

  material in doubt right at the threads (manufactured

  stress riser).



 	  Quote: 	
		  I've seen BNC connectors used as antenna bases on ultralights but 

wasn't sure about the speed limits. Mine has a 100kts cruise. The 

BNC connectors that looked beefy enough also looked pretty draggy. 

Same for antennas that have a BNC mount. Bob, you think your 

crimp-on BNC connector would support a whip antenna, vs. a rubber 

duck one? In this case I'd like to order it from you. I guess I 

could machine a stainless steel support sleeve to beef up the antenna side BNC.


	


   The worst that happens is you break it and need to

   replace. If you want a laid back antenna, consider

   making the element out of piano wire and leave it

   un-bent. A smaller wire will produce less drag,

   less stress on connector, and would lay back all

   by itself in the breeze.



   If you'd like to order a connector, go to the website

   catalog, fill out top form data, go to bottom and put

   BNC Bulkhead Connector in the comments box. I'll

   send you a PayPal invoice.



   Over what distances do you expect this antenna/comm

   configuration to work? I used to fly my J-3 with a

   hand-held fitted with a head-set using a coax taped

   half way up the strut and grounded to a sheet copper

   'wrapper' and a 1/4 wave trailing wire dangling from

   the center conductor.



   Worked over the distances (airport traffic area)

   and approach to the home field (7-10 miles out).

   A trailing wire would be less drag yet.



   Bob . . .

holger-d(at)shadowbrush.c
Guest

Posted: Sat Dec 15, 2012 10:06 pm Post subject: Removable comm antenna

On 12/12/12 4:51 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		    No, I'd leave the nut loose for a couple of reasons.

  First, it would let you orient a bend and tighten the nut

  later (this could be a finger nut made from a piece

  of flat sheet with a drilled and tapped hole in the

  middle but with enough O.D. to let you hand tighten.

  Yeah, it would have a slight 'lengthening' effect

  on the antenna which would be shortened accordingly

  using SWR meter


	


Bob, many thanks for explaining it in detail. With your suggestions in 

mind, I picked up some parts I had laying around and put this together: 

https://www.dropbox.com/sh/rylqm9cect5ndut/XyaFh-jLE2



I'll have to find someone with an SWR meter and cut it to the proper 

length. Then we'll see if it actually does what it's supposed to do. But 

it's solid, and removed in seconds.



Thanks,



Holger

dlj04(at)josephson.com
Guest

Posted: Sun Dec 16, 2012 8:05 am Post subject: Removable comm antenna

 	  Quote: 	
		   Bob, many thanks for explaining it in detail. With your suggestions in

 mind, I picked up some parts I had laying around and put this together:

 https://www.dropbox.com/sh/rylqm9cect5ndut/XyaFh-jLE2



 I'll have to find someone with an SWR meter and cut it to the proper

 length. Then we'll see if it actually does what it's supposed to do. But

 it's solid, and removed in seconds.

Holger, that looks fine. If everyone were as able to deal with a small 
	


machining project like that as you are, there wouldn't be so many 

lashed-up antennas out there. An SWR check will be useful but don't be 

too worried about it. You should expect better than 2:1 over a range of 

a few MHz. Trim the length so the center of this range is the center of 

the range of frequencies you normally use.

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Dec 16, 2012 9:03 am Post subject: Removable comm antenna

 	  Quote: 	
		  

 Bob, many thanks for explaining it in detail. With your suggestions in mind, I picked up some parts I had laying around and put this together:  https://www.dropbox.com/sh/rylqm9cect5ndut/XyaFh-jLE2



 I'll have to find someone with an SWR meter and cut it to the proper length. Then we'll see if it actually does what it's supposed to do. But it's solid, and removed in seconds. 	


   Nice work!  I'd like to add your photos to the archives on

   aeroelectric.com.



   Help me out a bit . . . 



 [img]cid:.0[/img]



   It appears that your coax center conductor

   is attached to the 4-bolt flange (pop rivet?)]

   which in turn is insulated from the mounting

   bolts with a combination of insulating bushings

   and washers. Where does the coax shield find

   connection to the groundplane/skin?



   It's not clear how the antenna element is retained

   on the aircraft/



   As D.L. suggested, SWR isn't a terribly critical concern.

   If you cut it for an overall length from skin to tip

   of 22", you're going to be close enough for government

   work.



   It would be interesting to see a plot of your measured

   SWR over the range of interest at say 1 Mhz steps. If

   you've got better things to do on your airplane, don't

   let this academic exploration get too high on the list

   of priorities.



 



 

   Bob . . .

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holger-d(at)shadowbrush.c
Guest

Posted: Sun Dec 16, 2012 10:24 am Post subject: Removable comm antenna

On 12/16/12 9:02 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		     It appears that your coax center conductor

   is attached to the 4-bolt flange (pop rivet?)]

   which in turn is insulated from the mounting

   bolts with a combination of insulating bushings

   and washers. Where does the coax shield find

   connection to the groundplane/skin?



   It's not clear how the antenna element is retained

   on the aircraft/


	


D.L., Bob, thanks again! I'll go with 22 inches until I find someone 

with a SWR meter. If this person and I can get the data for the plot, I 

will send it to you, Bob.



That's correct, the coax center is attached to that rectangular flange 

with a PIDG terminal. There is a threaded hole in the flange for it. The 

flange is welded to a SS tube that receives the antenna rod. As you 

said, the flange and tube is insulated against ground. I measured for 

conductivity. There is a spring in the tube, just to make sure there's 

good contact.



The coax shield is connected to ground a few inches away. I left that 

unchanged from the previous whisker antenna installation.



That riveted skin doubler is the result of my damaging the original 

antenna on the ground. Not going to happen anymore. But the main thing 

is, I can now sew a full cover to keep it dry outside, and won't have to 

put it on a trailer when a bit of wet weather is moving in. Means more 

flying for me! )



Thanks,



Holger

BobsV35B(at)aol.com
Guest

Posted: Sun Dec 16, 2012 10:39 am Post subject: Removable comm antenna

Good Afternoon Holger,

  

 Great workmanship! What I really love is that V-Tail. <G> What kind  of a machine is it?

  

 Happy Skies,

  

 Old Bob

 Downers Grove, Illinois

 V-Tail Aficionado 

  

  In a message dated 12/16/2012 12:25:01 P.M. Central Standard Time,  holger-d(at)shadowbrush.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: Holger Selover-Stephan    <holger-d(at)shadowbrush.com>



On 12/16/12 9:02 AM, Robert L.    Nuckolls, III wrote:

 	  Quote: 	
		     It appears that your coax center    conductor

   is attached to the 4-bolt flange (pop    rivet?)]

   which in turn is insulated from the    mounting

   bolts with a combination of insulating    bushings

   and washers. Where does the coax shield    find

   connection to the    groundplane/skin?



   It's not clear how the antenna    element is retained

   on the aircraft/


	


D.L., Bob,    thanks again! I'll go with 22 inches until I find someone 

with a SWR    meter. If this person and I can get the data for the plot, I 

will send it    to you, Bob.



That's correct, the coax center is attached to that    rectangular flange 

with a PIDG terminal. There is a threaded hole in the    flange for it. The 

flange is welded to a SS tube that receives the antenna    rod. As you 

said, the flange and tube is insulated against ground. I    measured for 

conductivity. There is a spring in the tube, just to make    sure there's 

good contact.



The coax shield is connected to ground a    few inches away. I left that 

unchanged from the previous whisker antenna    installation.



That riveted skin doubler is the result of my damaging    the original 

antenna on the ground. Not going to happen anymore. But the    main thing 

is, I can now sew a full cover to keep it dry outside, and    won't have to 

put it on a trailer when a bit of wet weather is moving in.    Means more 

flying for me!  )



Thanks,



Holger

holger-d(at)shadowbrush.c
Guest

Posted: Mon Dec 17, 2012 1:01 am Post subject: Removable comm antenna

Thanks, Old Bob, and that's a little,       humble Monnett Moni. Sometimes the shadow of this V-tail makes it       look like a fighter jet! Its day job, though, is providing its       owner with cheap (2gal/hr), but very enjoyable flying:       http://www.youtube.com/watch?v=M_FvBS6MncA . The V-tail works       splendidly, the pilot is trying his best. 

       

       Holger

       

       

       On 12/16/12 10:38 AM, BobsV35B(at)aol.com (BobsV35B(at)aol.com) wrote:

     

     [quote]                              Good Afternoon Holger,

          

         Great workmanship! What I really love is that V-Tail.           <G> What kind of a machine is it?

          

         Happy Skies,

          

         Old Bob

         Downers Grove, Illinois

         V-Tail Aficionado 

          

         

       [b]

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