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Frequency problem update

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danb

Joined: 29 Sep 2010
Posts: 7

Posted: Mon Feb 09, 2015 5:27 pm Post subject: Frequency problem update

A little over a week ago I mentioned I recently purchased a Bose headset that would not allow me to make a call to tower. I could talk to ground, yet , when I switched over to tower I got nothing but a loud high-pitched squeal. I wanted to give an up-date as I have the problem resolved. All it took was going to Radio Shack and purchased a couple ferrite beads. I snapped one on the coax behind my radio, started my engine and hit the PTT. It was almost gone but still a chirp here and there. I shut down and snapped the second one on the coax just in front of the antenna. Works perfect now. Hope this can help others with similar problems.

Dan B



 [quote][b]

Kellym

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

Posted: Mon Feb 09, 2015 6:40 pm Post subject: Frequency problem update

Sounds like your antenna coax has compromised shielding, that allows     RF leakage. Most likely the ferrite beads mask the problem. A new     coax would likely give same result.

     

     On 2/9/2015 6:25 PM,       danielj.billingsley(at)yahoo.com (danielj.billingsley(at)yahoo.com) wrote:

     

     [quote]                A little           over a week ago I mentioned I recently purchased a Bose           headset that would not allow me to make a call to tower. I           could talk to ground, yet , when I switched over to tower I           got nothing but a loud high-pitched squeal. I wanted to give           an up-date as I have the problem resolved. All it took was           going to Radio Shack and purchased a couple ferrite beads. I           snapped one on the coax behind my radio, started my engine and           hit the PTT. It was almost gone but still a chirp here and           there. I shut down and snapped the second one on the coax just           in front of the antenna. Works perfect now. Hope this can help           others with similar problems.

         Dan B

       

        	  Quote: 	
		  

	
     [b]

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

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 11, 2015 7:31 am Post subject: Frequency problem update

On 2/9/2015 6:25 PM, danielj.billingsley(at)yahoo.com wrote:

A little over a week ago I mentioned I recently purchased a Bose 

headset that would not allow me to make a call to tower. I could talk 

to ground, yet , when I switched over to tower I got nothing but a 

loud high-pitched squeal. I wanted to give an up-date as I have the 

problem resolved. All it took was going to Radio Shack and purchased 

a couple ferrite beads. I snapped one on the coax behind my radio, 

started my engine and hit the PTT. It was almost gone but still a 

chirp here and there. I shut down and snapped the second one on the 

coax just in front of the antenna. Works perfect now. Hope this can 

help others with similar problems.

Dan B

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



At 20:39 2015-02-09, Kelly wrote:

Sounds like your antenna coax has compromised shielding, that allows 

RF leakage. Most likely the ferrite beads mask the problem. A new 

coax would likely give same result.



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



I agree. The OUTSIDE of a properly installed coax is radio frequency

neutral . . . i.e. nothing of what exists inside the coax will

exist outside the coax.  The fact that adding anything outside

has an influence on observed behaviors suggests that your coax

is behaving more like a piece of wire than a properly functioning

transmission line.



Metal or composite airplane? If composite, what kind of

ground plane under your antenna?  Where is antenna located

on airplane? Check your coax connectors at both ends . . .



   Bob . . .

danb

Joined: 29 Sep 2010
Posts: 7

Posted: Wed Feb 11, 2015 10:29 am Post subject: Frequency problem update

Bob, This is a tube and fabric plane (Kitfox). My connection to the radio was straight forward, however, the antenna (which is in the vertical stab.) is a simple SS pole with just a thread and nut end. I crimped a washer like connector on the primary wire and tightened it with a nut. The outside strand was twisted and crimped on the same type of connector and I bolted that to the frame. I always felt as if this were Disneyland-type engineering. Are there any other options or ideas?

Thanks,

Dan B



        From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Wednesday, February 11, 2015 8:29 AM

 Subject: Re: Frequency problem update

  

 

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>



On 2/9/2015 6:25 PM, danielj.billingsley(at)yahoo.com (danielj.billingsley(at)yahoo.com) wrote:

A little over a week ago I mentioned I recently purchased a Bose 

headset that would not allow me to make a call to tower. I could talk 

to ground, yet , when I switched over to tower I got nothing but a 

loud high-pitched squeal. I wanted to give an up-date as I have the 

problem resolved. All it took was going to Radio Shack and purchased 

a couple ferrite beads. I snapped one on the coax behind my radio, 

started my engine and hit the PTT. It was almost gone but still a 

chirp here and there. I shut down and snapped the second one on the 

coax just in front of the antenna. Works perfect now. Hope this can 

help others with similar problems.

Dan B

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



At 20:39 2015-02-09, Kelly wrote:

Sounds like your antenna coax has compromised shielding, that allows 

RF leakage. Most likely the ferrite beads mask the problem. A new 

coax would likely give same result.



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



I agree. The OUTSIDE of a properly installed coax is radio frequency

neutral . . . i.e. nothing of what exists inside the coax will

exist outside the coax.  The fact that adding anything outside

has an influence on observed behaviors suggests that your coax

is behaving more like a piece of wire than a properly functioning

transmission line.



Metal or composite airplane? If composite, what kind of

ground plane under your antenna?  Where is antenna located

on airplane? Check your coax conna href="http://www.matronics.com/Navigator?AeroElectric-List" target="_tp://forums.matronics.com/" target="_blank">http://forums.matronics.com</                     -Mats.com/contribution" target="_blank">http://www.matronics.com/contribution==============

 

 

  

 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 11, 2015 3:15 pm Post subject: Frequency problem update

At 12:27 2015-02-11, you wrote:

  	  Quote: 	
		  Bob, This is a tube and fabric plane (Kitfox). My connection to the radio was straight forward, however, the antenna (which is in the vertical stab.) is a simple SS pole with just a thread and nut end. I crimped a washer like connector on the primary wire and tightened it with a nut. The outside strand was twisted and crimped on the same type of connector and I bolted that to the frame. I always felt as if this were Disneyland-type engineering. Are there any other options or ideas?

 Thanks,

 Dan B

 	


   Does this installation have a service history? Are there

   exemplar installations flying? The first Kitfox structure

   image that popped up in a search looks like this . . .



 [img]cid:.0[/img] 



 



 If this is applicable to your airplane, where is the antenna located

 with respect to the metallic structure of the vertical fin? I'm

 puzzled as to how an antenna 'buried' under the fabric can

 enjoy the necessity for a relatively 'free' view of the

 universe in all directions around the antenna. An antenna

 mounted in close proximity to the metallic structure of this

 fuselage would be first seriously detuned from it's design

 frequency and second, suffer severe distortion of radiation

 patterns. It would be interesting to see what kind of SWR

 measurements you get from such an installation.



 The drawing above calls out an antenna mounting feature

 that would offer a best-compromise location for your Comm

 antenna.



 



 

   Bob . . .

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wrmaxwell(at)bigpond.com
Guest

Posted: Wed Feb 11, 2015 3:50 pm Post subject: Frequency problem update

dalemed

Joined: 25 Dec 2007
Posts: 46

Posted: Thu Feb 12, 2015 10:31 am Post subject: Frequency problem update

Since the problem is sensitive to frequency (ground vs tower) I suspect the antenna or the way it's mounted, in which case the ferrite might be the best solution.  

Dale  [quote][b]

_________________
Dale
Zenith Zodiac CH650

Kellym

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

Posted: Thu Feb 12, 2015 11:50 am Post subject: Frequency problem update

The frequency sensitivity relates to the fact that RF feedback is 

occurring. I had this problem in a previous aircraft, which I eventually 

traced back to a cold solder joint on the RG-58 BNC coax connector at 

the radio. It worked fine on frequencies below 123.0, and as the 

frequency went higher it would give off a feedback squeal when the mike 

was keyed. New coax with properly crimped BNC connectors eliminated the 

problem. Ferrite beads just mask the problem.

On 2/12/2015 11:30 AM, Dale Medendorp wrote:

 	  Quote: 	
		  

 Since the problem is sensitive to frequency (ground vs tower) I 

 suspect the antenna or the way it's mounted, in which case the ferrite 

 might be the best solution.



 Dale



 *

 *

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

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 12, 2015 1:33 pm Post subject: Frequency problem update

At 13:49 2015-02-12, you wrote:

 	  Quote: 	
		  



The frequency sensitivity relates to the fact that RF feedback is 

occurring. I had this problem in a previous aircraft, which I 

eventually traced back to a cold solder joint on the RG-58 BNC coax 

connector at the radio. It worked fine on frequencies below 123.0, 

and as the frequency went higher it would give off a feedback squeal 

when the mike was keyed. New coax with properly crimped BNC 

connectors eliminated the problem. Ferrite beads just mask the problem.


	


    Yes. By definition, a transmission line with strong

    standing waves (high SWR) may become a poor transmission

    line and a better antenna. Since the 'distance' from

    peak to peak on a standing wave is defined by the operating

    frequency, the degree with which a degraded transmission

    line radiates (or receives) is a function of the frequency

    of interest.



    In one case, the operator reported relief from the

    effects by simply shortening a coax. He put a new

    connector on one end and decided to cut away some

    extra slack. The connector replaced was a 'good' one

    but the frequency of interest moved off to another

    value. He didn't discover the 'other' bad connector

    until later under different circumstances.



    Ferrites over a radiating line WILL reduce the

    effects . . . but it does nothing to correct the

    underlying issue . . . which may still have deleterious

    effect on system performance.



    Bad transmission lines can affect reception too

    but these are often more difficult to observe.

    In the final analysis, it's difficult to beat

    antenna installations with track records unless

    you're going to visit a capable RF lab and have

    any 'new idea' in antennas evaluated by-the-numbers.



   Bob . . .

donvansanten(at)gmail.com
Guest

Posted: Thu Feb 12, 2015 2:29 pm Post subject: Frequency problem update

Bob,

 Over the years that I have followed this list I recall you sayingÂ  "check your coax connections". I might be having a senior moment, but I can not remember you ever telling us how to check them. Is continuity all we are looking for on the conductor and the shield but not shorted together?  On Feb 12, 2015 1:40 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:[quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

 

 At 13:49 2015-02-12, you wrote:

  	  Quote: 	
		   --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

 

 The frequency sensitivity relates to the fact that RF feedback is occurring. I had this problem in a previous aircraft, which I eventually traced back to a cold solder joint on the RG-58 BNC coax connector at the radio. It worked fine on frequencies below 123.0, and as the frequency went higher it would give off a feedback squeal when the mike was keyed. New coax with properly crimped BNC connectors eliminated the problem. Ferrite beads just mask the problem.

 	
 

 Â  Â Yes. By definition, a transmission line with strong

 Â  Â standing waves (high SWR) may become a poor transmission

 Â  Â line and a better antenna. Since the 'distance' from

 Â  Â peak to peak on a standing wave is defined by the operating

 Â  Â frequency, the degree with which a degraded transmission

 Â  Â line radiates (or receives) is a function of the frequency

 Â  Â of interest.

 

 Â  Â In one case, the operator reported relief from the

 Â  Â effects by simply shortening a coax. He put a new

 Â  Â connector on one end and decided to cut away some

 Â  Â extra slack. The connector replaced was a 'good' one

 Â  Â but the frequency of interest moved off to another

 Â  Â value. He didn't discover the 'other' bad connector

 Â  Â until later under different circumstances.

 

 Â  Â Ferrites over a radiating line WILL reduce the

 Â  Â effects . . . but it does nothing to correct the

 Â  Â underlying issue . . . which may still have deleterious

 Â  Â effect on system performance.

 

 Â  Â Bad transmission lines can affect reception too

 Â  Â but these are often more difficult to observe.

 Â  Â In the final analysis, it's difficult to beat

 Â  Â antenna installations with track records unless

 Â  Â you're going to visit a capable RF lab and have

 Â  Â any 'new idea' in antennas evaluated by-the-numbers.

 

 

 

 Â  Bob . . . 

 

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

  -

 Electric-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

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

  FORUMS -

 _blank">http://forums.matronics.com

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

 b Site -

 Â  Â  Â  Â  Â  -Matt Dralle, List Admin.

 target="_blank">http://www.matronics.com/contribution

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

 

 

 

 [b]

danb

Joined: 29 Sep 2010
Posts: 7

Posted: Thu Feb 12, 2015 5:26 pm Post subject: Frequency problem update

Bob, Thanks for the good information. To answer a previous question you had...The antenna IS mounted inside of the vertical stab. I did not put a ground plane on it but rather (as mentioned earlier) took the ground to the tube frame. The only reason I configured it this way was because a buddy with the same Kitfox model mounted it this way and it has performed for him very well. With my Ham background, I knew the ideal install would be with that ground plane, however, fitting a ground plane of any size perpendicular to the antenna is not possible where the antenna is currently at. The antenna itself is not accessible...only the connections to it. I have been using a headset that has ANR capability, but I was using it without the ANR. Every time I turned the ANR feature on, I got the same RF noise. I was hoping that the new Bose headset would work but it is the same issue. The ferrite bead trick has made it operational, but like you said it is only masking the issue. I suppose I will end up mounting an antenna behind the turtledeck with a proper ground plane for the fix. Thanks to all who assisted with this problem.

Dan B. 

        From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

 To: aeroelectric-list(at)matronics.com 

 Sent: Thursday, February 12, 2015 2:28 PM

 Subject: Re: Frequency problem update

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>

At 13:49 2015-02-12, you wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com (kellym(at)aviating.com)>

The frequency sensitivity relates to the fact that RF feedback is 

occurring. I had this problem in a previous aircraft, which I 

eventually traced back to a cold solder joint on the RG-58 BNC coax 

connector at the radio. It worked fine on frequencies below 123.0, 

and as the frequency went higher it would give off a feedback squeal 

when the mike was keyed. New coax with properly crimped BNC 

connectors eliminated the problem. Ferrite beads just mask the problem.

    Yes. By definition, a transmission line with strong

    standing waves (high SWR) may become a poor transmission

    line and a better antenna. Since the 'distance' from

    peak to peak on a standing wave is defined by the operating

    frequency, the degree with which a degraded transmission

    line radiates (or receives) is a function of the frequency

    of interest.

    In one case, the operator reported relief from the

    effects by simply shortening a coax. He put a new

    connector on one end and decided to cut away some

    extra slack. The connector replaced was a 'good' one

    but the frequency of interest moved off to another

    value. He didn't discover the 'other' bad connector

    until later under different circumstances.

    Ferrites over a radiating line WILL reduce the

    effects . . . but it does nothing to correct the

    underlying issue . . . which may still have deleterious

    effect on system performance.

    Bad transmission lines can affect reception too

    but these are often more difficult to observe.

    In the final analysis, it's difficult to beat

    antenna installations with track records unless

    you're going to visit a capable RF lab and have

    any 'new idea' in antennas evaluated by-the-numbers.

   Bob . . . nbsp;  --> http://www.matronics.com/Navigator?AeroElectric-List<; http://forums.sp;            - List Contribution Web Site -

_;                     &nb://www.matronics.com/contribution" target="_blank">http://www.matronics.c===================

 [quote][b]

Kellym

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

Posted: Thu Feb 12, 2015 6:50 pm Post subject: Frequency problem update

It is NOT the location or lack of ground plane causing the feedback. It 

is most likely one of the coax connections.



On 2/12/2015 6:25 PM, danielj.billingsley(at)yahoo.com wrote:

 	  Quote: 	
		   Bob, Thanks for the good information. To answer a previous question 

 you had...The antenna IS mounted inside of the vertical stab. I did 

 not put a ground plane on it but rather (as mentioned earlier) took 

 the ground to the tube frame. The only reason I configured it this way 

 was because a buddy with the same Kitfox model mounted it this way and 

 it has performed for him very well. With my Ham background, I knew the 

 ideal install would be with that ground plane, however, fitting a 

 ground plane of any size perpendicular to the antenna is not possible 

 where the antenna is currently at. The antenna itself is not 

 accessible...only the connections to it. I have been using a headset 

 that has ANR capability, but I was using it without the ANR. Every 

 time I turned the ANR feature on, I got the same RF noise. I was 

 hoping that the new Bose headset would work but it is the same issue. 

 The ferrite bead trick has made it operational, but like you said it 

 is only masking the issue. I suppose I will end up mounting an antenna 

 behind the turtledeck with a proper ground plane for the fix. Thanks 

 to all who assisted with this problem.

 Dan B.

 ****

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

wrmaxwell(at)bigpond.com
Guest

Posted: Thu Feb 12, 2015 7:06 pm Post subject: Frequency problem update

Once you solve the         feedback problem, you will then likely start finding occasions         when your signal cannot be heard by another aircraft on certain         bearings, or that aircraft will only hear a weak signal. That         will be caused by your antenna's mounting position, being         partially shielded by the fin frame etc. When you think of it,         an antenna mounted within the tubing frame of the aircraft, even         in the fin, is essentially an antenna mounted in a Faraday Cage.

     

     Bill

     On 13/02/2015 1:48 PM, Kelly McMullen       wrote:

     

     [quote]-->       AeroElectric-List message posted by: Kelly McMullen       <kellym(at)aviating.com> (kellym(at)aviating.com)       

       

       It is NOT the location or lack of ground plane causing the       feedback. It is most likely one of the coax connections.       

       

       On 2/12/2015 6:25 PM, danielj.billingsley(at)yahoo.com (danielj.billingsley(at)yahoo.com) wrote:       

        	  Quote: 	
		  Bob, Thanks for the good information. To         answer a previous question you had...The antenna IS mounted         inside of the vertical stab. I did not put a ground plane on it         but rather (as mentioned earlier) took the ground to the tube         frame. The only reason I configured it this way was because a         buddy with the same Kitfox model mounted it this way and it has         performed for him very well. With my Ham background, I knew the         ideal install would be with that ground plane, however, fitting         a ground plane of any size perpendicular to the antenna is not         possible where the antenna is currently at. The antenna itself         is not accessible...only the connections to it. I have been         using a headset that has ANR capability, but I was using it         without the ANR. Every time I turned the ANR feature on, I got         the same RF noise. I was hoping that the new Bose headset would         work but it is the same issue. The ferrite bead trick has made         it operational, but like you said it is only masking the issue.         I suppose I will end up mounting an antenna behind the         turtledeck with a proper ground plane for the fix. Thanks to all         who assisted with this problem.         

         Dan B.         

         ****         

       	
       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

       

     [b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 12, 2015 7:19 pm Post subject: Frequency problem update

At 16:27 2015-02-12, you wrote:



 	  Quote: 	
		  Bob,

Over the years that I have followed this list I 

recall you sayingÂ  "check your coax 

connections". I might be having a senior moment, 

but I can not remember you ever telling us how 

to check them. Is continuity all we are looking 

for on the conductor and the shield but not shorted together?


	


   Certainly do the continuity check. Then, my favorite is the

   twist and tug test. The most common failure at the coax

   connector is loss of integrity at the shield. In the

   legacy solder-and-clamp connectors (UG-8 it was really

   easy fabricate a bad joint. With the crimp on connectors,

   a badly adjusted stripper can damage wires such that

   they are mechanically weakened.



   With either connector, a substantial torque moment

   on the cable as it enters the back of the connector

   should produce ZERO perceived motion.



   Bob . . .

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