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CJ-6A comm antenna

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k7wx(at)earthlink.net
Guest

Posted: Tue Sep 08, 2009 7:49 pm Post subject: CJ-6A comm antenna

Guys,



Looking to buy several of the standard comm antennas the normally come  

with the CJ-6A. I know that many of you routinely take them off. Here  

is an opportunity to give yours a good home.



If possible, looking for the entire assembly:



    Antenna.

    Bakelite (I think that's what it is) insulating / mounting plate.

    Intact female coax connector on underside.

    Nut plate.



If you have one or more of the Chinese coaxial cable connectors, that  

would be a plus. The Chinese ones have a much coarser thread on the  

screw sleeve than the American PL-259.



Refurbished, and with a suitable copper counterpoise, these antennas  

actually work very nicely with a very low SWR in the middle of the  

aviation band. Am doing a project for myself and several other CJ  

owners.



Thanks,



Warren Hill

Mesa, AZ

cjpilot710(at)aol.com
Guest

Posted: Tue Sep 08, 2009 9:24 pm Post subject: CJ-6A comm antenna

In a message dated 9/8/2009 11:50:46 P.M. Eastern Daylight Time,  k7wx(at)earthlink.net writes:

  

 I have every thing but the antenna.  I have it also however its broken  and if you can find someone to repair that, you'll be all set.

  

 386-467-3313-h     386-559-1942 c

  

 Jim "Pappy" Goolsby

  

  	  Quote: 	
		  -->    Yak-List message posted by: Warren Hill    <k7wx(at)earthlink.net>



Guys,



Looking to buy several of the    standard comm antennas the normally come  

with the CJ-6A. I know that    many of you routinely take them off. Here  

is an opportunity to give    yours a good home.



If possible, looking for the entire    assembly:



    Antenna.

    Bakelite (I think    that's what it is) insulating / mounting plate.

    Intact female    coax connector on underside.

    Nut plate.



If you have    one or more of the Chinese coaxial cable connectors, that  

would be a    plus. The Chinese ones have a much coarser thread on the  

screw    sleeve than the American PL-259.



Refurbished, and with a suitable    copper counterpoise, these antennas  

actually work very nicely with a    very low SWR in the middle of the  

aviation band. Am doing a project    for myself and several other CJ  

owners.



Thanks,



Warren    Hill

Mesa, AZ

	


 

  [quote][b]

Noplugs

Joined: 27 Aug 2009
Posts: 35
Location: Houston, TX

Posted: Wed Sep 09, 2009 4:04 am Post subject: Re: CJ-6A comm antenna

I have everything you need. I am restoring my CJ and getting rid of all the original comm equipment and radio nav gear. All the coax is un-cut, the Antenna is in good shape and the insulator is good to.

 

Thanks 

Mike

cjpilot710(at)aol.com
Guest

Posted: Wed Sep 09, 2009 4:31 am Post subject: CJ-6A comm antenna

In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,  qas44n(at)yahoo.com writes:

  

 I wish I had known that a week ago.  I just bought and  installed a new one.  

  

 Anyway my local radio shop, told me that the Chinese antenna was a "little  to long" for the frequency band and may have been the reason some guys were  complaining of not hearing me to well over my Terra radios.

  

 Jim

  

  	  Quote: 	
		  -->    Yak-List message posted by: "Noplugs" <qas44n(at)yahoo.com>



I have    everything you need. I am restoring my CJ and getting rid of all the original    comm equipment and radio nav gear. All the coax is un-cut, the Antenna is in    good shape and the insulator is good to.



Thanks    

Mike





Read this topic online    here:



http://forums.matronics.com/viewtopic.php?p=262237#262237===============================================

_-=   e  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


 

  

 

  [quote][b]

k7wx(at)earthlink.net
Guest

Posted: Wed Sep 09, 2009 6:43 am Post subject: CJ-6A comm antenna

Jim,



I'm sure that your radio guys mean well, but they're not be seeing the  

whole picture.



The efficiency of a vertical radiator at VHF frequencies not only  

depends on its length (which determines the resonant frequency), but  

also the efficient transfer of power through the coax (RG-58 pretty  

lossy at 120 MHz), the transfer of power from the coax to the antenna  

(a non-refurbished Chinese PL-259 is low quality and an American one  

doesn't mate well to the Chinese SO-239), the counterpoise (kinda like  

a ground), it's angle (which influences the input impedance) and the  

counterpoise conductivity (anodized aluminum is a poor choice).



With high quality coax (not the stuff that's normally available), a  

copper counterpoise and the Chinese SO-239 / PL-259 connectors  

refurbished, the resonant frequency for my CJ comm antenna is 124.82  

MHz, around the center of the aviation band. The frequency range for  

an acceptable SWR (standing wave ratio, which determines how much  

transmitted power gets reflected back to the radio) is much broader  

than any aviation wire antenna I've seen. This is because the width of  

the radiating element also influences its bandwidth.



My take... getting this to work properly is simply way too much work  

for a standard repair station with guys who are mostly trained to  

"assemble and test." I've been working with antennas for more than 40  

years. Set up correctly, the CJ comm antenna works great.



All the best,



Warren Hill

Mesa, Arizona



On Sep 9, 2009, at 5:27 AM, cjpilot710(at)aol.com wrote:



 	  Quote: 	
		   In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time, qas44n(at)yahoo.com 

  writes:



 I wish I had known that a week ago.  I just bought and installed a  

 new one.  



 Anyway my local radio shop, told me that the Chinese antenna was a  

 "little to long" for the frequency band and may have been the reason  

 some guys were complaining of not hearing me to well over my Terra  

 radios.



 Jim



 



 I have everything you need. I am restoring my CJ and getting rid of  

 all the original comm equipment and radio nav gear. All the coax is  

 un-cut, the Antenna is in good shape and the insulator is good to.



 Thanks

 Mike





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php? 

 p 62237#262237===============================================

 ================================================              -  

 MATRONICS WEB FORUMS  

 ================================================            - List  

 Contribution Web Site sp;                          

 ===================================================

k7wx(at)earthlink.net
Guest

Posted: Wed Sep 09, 2009 6:43 am Post subject: CJ-6A comm antenna

Mike,



Wonderful. Can I have your phone number off line?



Warren Hill

Mesa, Arizona

On Sep 9, 2009, at 5:04 AM, Noplugs wrote:



 	  Quote: 	
		   



 I have everything you need. I am restoring my CJ and getting rid of  

 all the original comm equipment and radio nav gear. All the coax is  

 un-cut, the Antenna is in good shape and the insulator is good to.



 Thanks

 Mike





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 62237#262237

talew(at)bellsouth.net
Guest

Posted: Wed Sep 09, 2009 8:19 am Post subject: CJ-6A comm antenna

I use the original commie antenna on my cj aqnd it works great.

Terry Lewis



---

cjpilot710(at)aol.com
Guest

Posted: Wed Sep 09, 2009 8:45 am Post subject: CJ-6A comm antenna

In a message dated 9/9/2009 10:44:24 A.M. Eastern Daylight Time,  k7wx(at)earthlink.net writes:

  

 Warren,

  

 Boy I am glad someone understands this magic stuff about antenna's.   For some 50 plus years, my total knowledge was "press the button and  talk".  Honest.  I was so happy when we got 'single side band' our HF  radios, so that I didn't have to listen to hour on hour of static, listening to  every transmission.  I had not idea what "single side band" was (nor  do I need to now!!!!) but it was great magic. 

  

 Nice thing about this list, even an old dog can appreciate the smart  guys who understand the details of what appears to be a simple device.

  

 Thanks.

 Jim "Pappy" Goolsby

  

  

  	  Quote: 	
		  -->    Yak-List message posted by: Warren Hill    <k7wx(at)earthlink.net>



Jim,



I'm sure that your radio guys    mean well, but they're not be seeing the  

whole picture.



The    efficiency of a vertical radiator at VHF frequencies not only     

depends on its length (which determines the resonant frequency), but     

also the efficient transfer of power through the coax (RG-58 pretty     

lossy at 120 MHz), the transfer of power from the coax to the    antenna  

(a non-refurbished Chinese PL-259 is low quality and an    American one  

doesn't mate well to the Chinese SO-239), the    counterpoise (kinda like  

a ground), it's angle (which influences the    input impedance) and the  

counterpoise conductivity (anodized    aluminum is a poor choice).



With high quality coax (not the stuff    that's normally available), a  

copper counterpoise and the Chinese    SO-239 / PL-259 connectors  

refurbished, the resonant frequency for    my CJ comm antenna is 124.82  

MHz, around the center of the aviation    band. The frequency range for  

an acceptable SWR (standing wave    ratio, which determines how much  

transmitted power gets reflected    back to the radio) is much broader  

than any aviation wire antenna    I've seen. This is because the width of  

the radiating element also    influences its bandwidth.



My take... getting this to work properly is    simply way too much work  

for a standard repair station with guys who    are mostly trained to  

"assemble and test." I've been working with    antennas for more than 40  

years. Set up correctly, the CJ comm    antenna works great.



All the best,



Warren Hill

Mesa,    Arizona



On Sep 9, 2009, at 5:27 AM, cjpilot710(at)aol.com    wrote:



 	  Quote: 	
		   In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight    Time, qas44n(at)yahoo.com 

  writes:



 I wish I had    known that a week ago.  I just bought and installed a  

 new    one.  



 Anyway my local radio shop, told me that the    Chinese antenna was a  

 "little to long" for the frequency band    and may have been the reason  

 some guys were complaining of not    hearing me to well over my Terra  

 radios.



    Jim



 --> Yak-List message posted by: "Noplugs"    <qas44n(at)yahoo.com>



 I have everything you need. I am    restoring my CJ and getting rid of  

 all the original comm    equipment and radio nav gear. All the coax is  

 un-cut, the    Antenna is in good shape and the insulator is good to.



    Thanks

 Mike





 Read this topic    online here:



 http://forums.matronics.com/viewtopic.php?    

    p=262237#262237===============================================

    ================================================                 -  

 MATRONICS WEB FORUMS  

    ================================================               - List  

 Contribution Web Site sp;                                

    ===================================================



<========================e  ties  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================


	


	


 

  

 

  [quote][b]

mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 09, 2009 9:04 am Post subject: CJ-6A comm antenna

Warren, concur on most of your comments.  Obviously a fellow ham radio

operator.  Just some additional thoughts.    



The best replacement coax for RG-58 (with cost considerations) would

likely be RG-142B/U ... Double shielded, silver coated, solid center

conductor Teflon dielectric.  Higher velocity factor than most others,

(less loss) but somewhat less flexible.  Failing that, RG-223.  Same

stuff,  but with a polypropylene dielectric instead of Teflon.  Standard

.66 Vp.  RG-142 is good up to over 1 GHz for short runs.  



I do not know CJ's at all, and possibly a better counterpoise is

necessary, however I respectfully disagree that anodized aluminum is a

poor choice.  Anodized aluminum is used as a counterpoise on every

commercial and most civilian aircraft in the world.  Anodized aluminum

is used to construct a wide variety of HF and UHF antennas (WA3JPY

Warren     Concur that copper is a better choice, and silver would be

even better than copper, but in the real world, I honestly offer that

the difference in antenna performance between aluminum and copper is

extremely small. 



The main problem when using anodized aluminum as the counterpoise to the

1/4 wavelength vertical is that you might not get a good electrical bond

TO the actual aluminum because of the alodine used to cause the

artificial corrosion method that is part of the anodizing process.  This

is why current military aircraft designs have gone to using AVDECK seals

between the base of the antenna and the aircraft skin.  



Point being is that if you take care to make sure that the shield of the

coax is properly bonded to the aluminum skin of the aircraft AT THE

ANTENNA (however you manage to do it), a copper counterpoint should not

be necessary.  This could be as simple as using some light sanding to

bare metal at the proper bonding point.  Once a good grounding bond is

achieved, the radiation performance between a copper counterpoise and an

aluminum counterpoise is very minor. 



Just my 2 cents.  



Mark Bitterlich

   



--

Noplugs

Joined: 27 Aug 2009
Posts: 35
Location: Houston, TX

Posted: Wed Sep 09, 2009 9:28 am Post subject: Re: CJ-6A comm antenna

Warren

Call me anytime after 4pm Central time

(832) 252-9298

k7wx(at)earthlink.net
Guest

Posted: Wed Sep 09, 2009 11:10 am Post subject: CJ-6A comm antenna

Mark,



Nice to hear the thoughts of a pilot and fellow radio amateur. Got my  

ticket in 1964. While in graduate school I also ran an antenna  

business where I designed and made VHF and UHF antennas... K7WX .



As you know, at VHF frequencies small things matter in terms of  

losses. A poorly done BNC connector at both ends of some bargain  

basement coax with an oxidized connection between the airframe and the  

outer conductor and the losses are significant. I agree that a good  

connection between anodized aluminum would work, but these are old  

airframes this can be difficult to maintain long-term. A copper  

counterpoise could easily be considered more than is needed, but it's  

100% dependable and requires no additional work after instillation.



Agreed. RG-142B/U is an elegant choice. I also like LMR-195 at these  

frequencies. The dual outer shield is aluminum foil tape and a 90%  

braid with a micro-cell foam dielectric. It's a little more flexible  

and perhaps 1/3 the cost. Properly terminated, the losses for a 20 to  

30 foot run at VHF frequencies for a 5 watt radio are very low.



Real world... Most of the work that we're doing involves distances  

that are only a few miles apart, with typical signal strengths that  

overcome many of the sins of a lossy antenna instillation. But for  

trying to copy ATIS from way out, or tune that VOR from a significant  

distance, I'll take the set-up with the lowest loss. Just my  

preference after years of playing with all of this and trying to  

maintain the original look of the CJ-6A.



Great stuff. Thanks for the thoughtful comments.



Warren Hill

On Sep 9, 2009, at 9:53 AM, Bitterlich, Mark G CIV Det Cherry Point,  

MALS-14 64E wrote:



[quote] 

 Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>



 Warren, concur on most of your comments.  Obviously a fellow ham radio

 operator.  Just some additional thoughts.



 The best replacement coax for RG-58 (with cost considerations) would

 likely be RG-142B/U ... Double shielded, silver coated, solid center

 conductor Teflon dielectric.  Higher velocity factor than most others,

 (less loss) but somewhat less flexible.  Failing that, RG-223.  Same

 stuff,  but with a polypropylene dielectric instead of Teflon.   

 Standard

 .66 Vp.  RG-142 is good up to over 1 GHz for short runs.



 I do not know CJ's at all, and possibly a better counterpoise is

 necessary, however I respectfully disagree that anodized aluminum is a

 poor choice.  Anodized aluminum is used as a counterpoise on every

 commercial and most civilian aircraft in the world.  Anodized aluminum

 is used to construct a wide variety of HF and UHF antennas (WA3JPY

 Warren     Concur that copper is a better choice, and silver  

 would be

 even better than copper, but in the real world, I honestly offer that

 the difference in antenna performance between aluminum and copper is

 extremely small.



 The main problem when using anodized aluminum as the counterpoise to  

 the

 1/4 wavelength vertical is that you might not get a good electrical  

 bond

 TO the actual aluminum because of the alodine used to cause the

 artificial corrosion method that is part of the anodizing process.   

 This

 is why current military aircraft designs have gone to using AVDECK  

 seals

 between the base of the antenna and the aircraft skin.



 Point being is that if you take care to make sure that the shield of  

 the

 coax is properly bonded to the aluminum skin of the aircraft AT THE

 ANTENNA (however you manage to do it), a copper counterpoint should  

 not

 be necessary.  This could be as simple as using some light sanding to

 bare metal at the proper bonding point.  Once a good grounding bond is

 achieved, the radiation performance between a copper counterpoise  

 and an

 aluminum counterpoise is very minor.



 Just my 2 cents.



 Mark Bitterlich

 --

mark.bitterlich(at)navy.m
Guest

Posted: Wed Sep 09, 2009 1:12 pm Post subject: CJ-6A comm antenna

Hi Warren, 



Got my ticket in 1967, have worked with microwave and EW emitter antenna

designs myself for about the last 30 years or so, and have actually

participated in some antenna designs, but not at your level !!  



Concur on all of your reply comments.  Your observations concerning good

bonding between antennas and aluminum grounds is especially apt.  This

is why we have gone to AVDECK seals and special dielectric grease on

most military models.  



Nothing wrong with anyone who wants to go to the effort of installing

copper ground planes in their aircraft.  I did not mean to imply there

was.  It comes down to a personal decision really.   I am a proponent of

making sure there is a good bond to an existing aluminum ground.  It is

clearly arguable which method is best.  Both will work, and your method

has definite merit!  I guess it all depends on your point of  view and

your personal experience.  



Nothing wrong with LMR-195 either.  Since most of our aircraft are

Experimental, the use of it is perfectly legit.  However, coming from my

background, I tend to try and use hardware that is approved for use in

certificated aircraft, which is why I mentioned RG-142.  It is the

preferred type, and in some cases (particularly with GPS systems) the

manufacturer will not honor your warranty if you use a substitute.  On

our Yak and CJ model aircraft, we don't usually run coax lines

physically close to any high heat sources, but never-the-less, it needs

to be pointed out that any type of foam dielectric coax cable, while

increasing the velocity factor and also reducing the loss, also tends to

melt.  Very easily.  RG-142 simply will not do that.  Another factor is

crush rating, or damage by stepping on it, etc., etc.  You can pretty

much stand on RG-142 with very little (if any) damage,  that can not be

said about foam dielectric coax types.  



I mention all this not to argue, because when it comes down to how well

each type of transmission line will actually operate... As in, how well

the radio will transmit and receive, there is no question that LMR-195

will work as well or even better than other types INCLUDING RG-142!  It

is cheap, it will work exceptionally well (if.. As you mentioned.. The

connectors are put on right) and will last a long time, as long as it is

not exposed to high heat, and it is protected from physical damage.

(FAA Avionics Repair Station guys will raise their eyebrows when they

see it in your airplane, but since it is Experimental, they can't say

much about it, and it will work well!!)



Take care, 



Mark



       



--

mlbjr(at)earthlink.net
Guest

Posted: Wed Sep 09, 2009 2:40 pm Post subject: CJ-6A comm antenna

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