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dan(at)azshowersolutions.
Guest

Posted: Wed Jul 06, 2011 5:22 pm Post subject: PTT buzz

Well, my ghost is still in the plane. I was able to roll the plane completely out of the garage last weekend and it still had the nasty oscillating buzz as the PTT button was pressed to operate my Garmin SL40. Again, this is without the engine running and just operating on my 12V battery. The TX light comes on (on the radio), the transmit light turns red on the intercom, and when someone else calls I can hear loud and clear. 

In trying to troubleshoot I was doing searches on other blogs and found a possible reason I'd like to bounce off of this list. One other person had a buzz happening similar to mine (using the same radio) and found after great deliberation that the connection to his antenna was poor. He said he bought a "cheapo" antenna (yes I did this) and did a poor-man's termination using a ring terminal on the threaded antenna bottom and then running the outer coax wire to ground. He had an EE stop by and quickly found this as being a problem. he purchased a "quality" antenna with a BNC connector, hooked it up, and said problem solved. 

My question is this...before I go and lay down over $100 for an antenna, does anyone concur with this as a possible problem? I would also like to know if there is a BNC connector (or proper terminator)designed to hook up to an antenna with just the threads on the bottom. Thanks

Dan B

--- On Tue, 6/21/11, Dan Billingsley <dan(at)azshowersolutions.com> wrote:

 	  Quote: 	
		   From: Dan Billingsley <dan(at)azshowersolutions.com>

 Subject: Re: PTT buzz

 To: aeroelectric-list(at)matronics.com

 Date: Tuesday, June 21, 2011, 6:29 PM

 I didn't turn the lights off but I

 was able to roll the plane out from under the lights a ways.

 When I did that, the noise became less prominent. I will

 need to wait until I have an extra hand to roll the plane

 all the way out of the garage (The slope + gravity= plane in

 street). One of the guys I talked to today had a good point

 about when I key the mic inside the closed space I have

 quite a bit RF dancing back and forth in there. Would it be

 reasonable to say it could be some feedback interference as

 well?

 Dan

 --- On Tue, 6/21/11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com>

 wrote:

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

 > Subject: Re: PTT buzz

 > To: aeroelectric-list(at)matronics.com

 > Date: Tuesday, June 21, 2011, 2:45 PM

 > --> AeroElectric-List message

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

 > 

 > At 04:18 PM 6/21/2011, you wrote:

 > > 

 > Billingsley <dan(at)azshowersolutions.com>

 > > 

 > > I think I found the ghost...When I first heard it

 it

 > sounded like AC cycling (the noise was very

 consistant).

 > AFter going thru this symptom with a few

 folks...Garmin

 > techs saying they never heard of it b-4...

 > > I was scratching my head and looked up. The

 antenna

 > was hovering  between two floursent lights in the

 > garage...it WAS AC!

 > > Dan

 > 

 >    Hmmmm . . . good hypothesis. If you turn

 > off the lights

 >    does the buzz go away?

 > 

 > 

 >   Bob . . . 

 > 

 >

 > AeroElectric-List Email Forum -

 browse

 Un/Subscription,

 Chat,

 > FAQ,

 >

 >    - MATRONICS WEB FORUMS -

 Forums!

 >

 > List Contribution Web Site -

 >               -Matt

 > Dralle, List Admin.

 >

 > 

 > 

 > 

 >

longg(at)pjm.com
Guest

Posted: Thu Jul 07, 2011 5:01 am Post subject: PTT buzz

Dan,



Maybe a silly question, but have you tried another radio in its place? Had it bench tested lately?



--

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Thu Jul 07, 2011 5:29 am Post subject: Re: PTT buzz

Dan,



Of course, I concur. Here's why:



Coaxial cables are classed as high frequency waveguides because the energy transmitted in them is almost entirely within the insulation. An amazing demonstration of this is that the group wave velocity is exactly equal to the speed of the electromagnetic wave in the particular material out of which the insulation is made. The importance of this is directly proportional to frequency. For audio purposes it matters little. Above a Megahertz it becomes critical.



"Pigtails" where the coax shield is twisted into a lead and both the inner conductor and twisted-up-shield lead are treated as separate wires is deadly to signals above a Megahertz. The shield should be terminated by any method that does not increase the impedance of the shield or the inner conductor. There are many ways to do this, but they all use some collar arrangement to terminate the messy coax shield. Any coax catalog has lots of solutions--use them.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

ceengland(at)bellsouth.ne
Guest

Posted: Thu Jul 07, 2011 5:36 am Post subject: PTT buzz

Hi Dan,

Any chance that someone in your area could just loan you a BNC type 

antenna & coax for it? If so, you could just substitute. On 2nd thought, 

how about a 'rubber ducky' off a handheld? You'd still need a BNC to BNC 

cable, and a Male-Male BNC adapter to hook up the antenna, but that 

should be easier & cheaper than a $100 antenna.

If you can't come up with a local solution, I might have one and a cable 

in my collection I could ship to you for testing.

Another (long shot) idea is, are you running off a bench power supply, 

or the plane's battery? If a bench supply, I wonder if RF could be 

getting into the supply. Bob might be better able to address that 

possibility.

Charlie

On 07/06/2011 08:19 PM, Dan Billingsley wrote:

 	  Quote: 	

 Well, my ghost is still in the plane. I was able to roll the plane completely out of the garage last weekend and it still had the nasty oscillating buzz as the PTT button was pressed to operate my Garmin SL40. Again, this is without the engine running and just operating on my 12V battery. The TX light comes on (on the radio), the transmit light turns red on the intercom, and when someone else calls I can hear loud and clear.

 In trying to troubleshoot I was doing searches on other blogs and found a possible reason I'd like to bounce off of this list. One other person had a buzz happening similar to mine (using the same radio) and found after great deliberation that the connection to his antenna was poor. He said he bought a "cheapo" antenna (yes I did this) and did a poor-man's termination using a ring terminal on the threaded antenna bottom and then running the outer coax wire to ground. He had an EE stop by and quickly found this as being a problem. he purchased a "quality" antenna with a BNC connector, hooked it up, and said problem solved.

 My question is this...before I go and lay down over $100 for an antenna, does anyone concur with this as a possible problem? I would also like to know if there is a BNC connector (or proper terminator)designed to hook up to an antenna with just the threads on the bottom. Thanks

 Dan B

 --- On Tue, 6/21/11, Dan Billingsley<dan(at)azshowersolutions.com>  wrote:

> From: Dan Billingsley<dan(at)azshowersolutions.com>

> Subject: Re: PTT buzz

> To: aeroelectric-list(at)matronics.com

> Date: Tuesday, June 21, 2011, 6:29 PM

> I didn't turn the lights off but I

> was able to roll the plane out from under the lights a ways.

> When I did that, the noise became less prominent. I will

> need to wait until I have an extra hand to roll the plane

> all the way out of the garage (The slope + gravity= plane in

> street). One of the guys I talked to today had a good point

> about when I key the mic inside the closed space I have

> quite a bit RF dancing back and forth in there. Would it be

> reasonable to say it could be some feedback interference as

> well?

> Dan

>

> --- On Tue, 6/21/11, Robert L. Nuckolls, III<nuckolls.bob(at)aeroelectric.com>

> wrote:

>

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

>> Subject: Re: PTT buzz

>> To: aeroelectric-list(at)matronics.com

>> Date: Tuesday, June 21, 2011, 2:45 PM

>> -->  AeroElectric-List message

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

>>

>> At 04:18 PM 6/21/2011, you wrote:

>>> 

>> Billingsley<dan(at)azshowersolutions.com>

>>> I think I found the ghost...When I first heard it

> it

>> sounded like AC cycling (the noise was very

> consistant).

>> AFter going thru this symptom with a few

> folks...Garmin

>> techs saying they never heard of it b-4...

>>> I was scratching my head and looked up. The

> antenna

>> was hovering  between two floursent lights in the

>> garage...it WAS AC!

>>> Dan

>>     Hmmmm . . . good hypothesis. If you turn

>> off the lights

>>     does the buzz go away?

>>

>>

>>    Bob . . .

>>

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 07, 2011 5:47 am Post subject: PTT buzz

At 08:19 PM 7/6/2011, you wrote:

 --> AeroElectric-List message posted by: Dan Billingsley <dan(at)azshowersolutions.com>



 Well, my ghost is still in the plane. I was able to roll the plane completely out of the garage last weekend and it still had the nasty oscillating buzz as the PTT button was pressed to operate my Garmin SL40. Again, this is without the engine running and just operating on my 12V battery. The TX light comes on (on the radio), the transmit light turns red on the intercom, and when someone else calls I can hear loud and clear. 

 In trying to troubleshoot I was doing searches on other blogs and found a possible reason I'd like to bounce off of this list. One other person had a buzz happening similar to mine (using the same radio) and found after great deliberation that the connection to his antenna was poor. He said he bought a "cheapo" antenna (yes I did this) and did a poor-man's termination using a ring terminal on the threaded antenna bottom and then running the outer coax wire to ground. He had an EE stop by and quickly found this as being a problem. he purchased a "quality" antenna with a BNC connector, hooked it up, and said problem solved. 



 My question is this...before I go and lay down over $100 for an antenna, does anyone concur with this as a possible problem? I would also like to know if there is a BNC connector (or proper terminator)designed to hook up to an antenna with just the threads on the bottom. Thanks



    DIY antennas have been successfully installed

    on lots of OBAM aircraft. Back in the early days

    of VHF comm radios in airplanes, virtually all

    the antennas were built at the airframe factory,

    not purchased.  



    Build one of these from RadioShack parts:



 [img]cid:.0[/img]



     Stick it on the back of your comm transceiver in place

     of the antenna coax.  See if the 'buzz' goes away. Keep

     the test transmissions short . . . a few seconds. This

     load is only good for 2W continuous so your transceiver's

     output represents an potential 'overload' condition but

     short test transmissions wont hurt it.



     If the noise goes away, then quality of the feedline

     and antenna system is suspect. It could be a poorly

     installed connector at the transceiver end, at some

     intermediate joint, or the antenna end. The fact that

     you have a DIY antenna is not an automatic recipe for

     failure but it does put some extra-ordinary requirements

     on the fabricator for quality of the made-up joints.



     You could fabricate an antenna using one of these

     coax-connector-to-rod adapters that are common to

     the CB radio accessories market. One such article is

     Radio Shack 219-0961



 [img]cid:.1[/img]



     This product is designed to accept the PL-259

     "UHF" style connector and an antenna rod fitted

     with a 3/8-24 threaded end. Note that this product

     comes with an internal tooth star washer to

     effect good electrical connection between coax

     shield and the aircraft skin. This washer needs

     to be exactly centered in the final make up of

     the joint.



 [img]cid:.2[/img]



     You can install this style connector directly on the

     end of your coax but it's a bit of a chore



  http://tinyurl.com/2lwyc 



     You'll also need a step-down adapter



 [img]cid:.3[/img]



     to mate the smaller RG-400 style coax with the

     larger connector.



     Alternatively, you can install a BNC connector

     on the end of your coax and use a BNC-UHF

     adapter on the antenna mount.



 [img]cid:.4[/img]



    Steer clear of any coax connector that is

    not crimped or soldered. "Twist on" or other

    "solderless" connectors are to be avoided.



    Many folks have discovered that $100 for a pre-assembled

    antenna is not too bad a deal. You can spend a goodly

    chunk of $time$ fabricating your own antenna. It's

    not difficult but it's not a trivial exercise either.



 

 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 07, 2011 6:16 am Post subject: PTT buzz

Above a Megahertz it becomes critical.



"Pigtails" where the coax shield is twisted into a lead and both the 

inner conductor and twisted-up-shield lead are treated as separate 

wires is deadly to signals above a Megahertz. The shield should be 

terminated by any method that does not increase the impedance of the 

shield or the inner conductor.



   I think the terms 'deadly' and 'critical' are not

   appropriate here. Yes, as soon as you break out a

   shield and center conductor from a coax cable,

   the resulting conductors are no longer 'coax' and

   they become part of the antenna.



   No, they are not 'ideal' connections between

   the coax and antenna elements. But their effects

   on overall performance is impossible to simply

   observe and can only be measured with pretty

   sophisticated equipment.



   There was some discussion a few years back

   about the value of adding the ferrite beads

   over feed line attached to an embedded foil

   VOR antenna. See the "foil antenna" series

   photos at:



http://aeroelectric.com/Pictures/Antenna

   I did some work in the RF lab and found

   that it took a couple dozen beads to

   drive the 'deleterious effects' of antenna-to-

   feedline mismatch to immeasurable levels. At the

   same time, having NO beads installed produced

   no observable value.



   The observable effects for DIY departures from

   idea are likely to be the result of poor

   connection, i.e. loss of gas tight connection

   between two components . . . not for having violated

   the sanctity of a coaxial feedline.



   The exposed center conductor and shield pigtails

   simply become part of the antenna's complex

   impedance. Careful measurements would show that

   the trimmed antenna length will be a tad shorter

   because of exposed feedline pigtails . . . but

   the time it takes to "trim for perfection" will

   not make the radio perform batter in any way

   you can observe.



   Bob . . .

dan(at)azshowersolutions.
Guest

Posted: Thu Jul 07, 2011 6:31 am Post subject: PTT buzz

Thank You all for your thoughtful inputs...I think a good place to start will be building that dummy load Bob. Thank you and I will keep the list informed of my progress.

Dan



--- On Thu, 7/7/11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:



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

 Subject: Re: Re: PTT buzz

 To: aeroelectric-list(at)matronics.com

 Date: Thursday, July 7, 2011, 8:12 AM

 --> AeroElectric-List message

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

 

 Above a Megahertz it becomes critical.

 

 "Pigtails" where the coax shield is twisted into a lead and

 both the inner conductor and twisted-up-shield lead are

 treated as separate wires is deadly to signals above a

 Megahertz. The shield should be terminated by any method

 that does not increase the impedance of the shield or the

 inner conductor.

 

   I think the terms 'deadly' and 'critical' are not

   appropriate here. Yes, as soon as you break out a

   shield and center conductor from a coax cable,

   the resulting conductors are no longer 'coax' and

   they become part of the antenna.

 

   No, they are not 'ideal' connections between

   the coax and antenna elements. But their effects

   on overall performance is impossible to simply

   observe and can only be measured with pretty

   sophisticated equipment.

 

   There was some discussion a few years back

   about the value of adding the ferrite beads

   over feed line attached to an embedded foil

   VOR antenna. See the "foil antenna" series

   photos at:

 

 http://aeroelectric.com/Pictures/Antenna

 

 

   I did some work in the RF lab and found

   that it took a couple dozen beads to

   drive the 'deleterious effects' of antenna-to-

   feedline mismatch to immeasurable levels. At the

   same time, having NO beads installed produced

   no observable value.

 

   The observable effects for DIY departures from

   idea are likely to be the result of poor

   connection, i.e. loss of gas tight connection

   between two components . . . not for having

 violated

   the sanctity of a coaxial feedline.

 

   The exposed center conductor and shield pigtails

   simply become part of the antenna's complex

   impedance. Careful measurements would show that

   the trimmed antenna length will be a tad shorter

   because of exposed feedline pigtails . . . but

   the time it takes to "trim for perfection" will

   not make the radio perform batter in any way

   you can observe.

 

 

 

   Bob . . . 

 

 AeroElectric-List Email Forum -

 FAQ,

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Thu Jul 07, 2011 10:13 am Post subject: PTT buzz

Dan, If you have a 121.5 ELT use the portable antenna from it.



Rick Girard



On Thu, Jul 7, 2011 at 9:27 AM, Dan Billingsley <dan(at)azshowersolutions.com (dan(at)azshowersolutions.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Dan Billingsley <dan(at)azshowersolutions.com (dan(at)azshowersolutions.com)>

  

 Thank You all for your thoughtful inputs...I think a good place to start will be building that dummy load Bob. Thank you and I will keep the list informed of my progress.

 Dan

 

 --- On Thu, 7/7/11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

 

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

 > Subject: Re: Re: PTT buzz

 > To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)

 > Date: Thursday, July 7, 2011, 8:12 AM

 

 	  Quote: 	
		   --> AeroElectric-List message

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


 >

 > Above a Megahertz it becomes critical.

 >

 > "Pigtails" where the coax shield is twisted into a lead and

 > both the inner conductor and twisted-up-shield lead are

 > treated as separate wires is deadly to signals above a

 > Megahertz. The shield should be terminated by any method

 > that does not increase the impedance of the shield or the

 > inner conductor.

 >

 >   I think the terms 'deadly' and 'critical' are not

 >   appropriate here. Yes, as soon as you break out a

 >   shield and center conductor from a coax cable,

 >   the resulting conductors are no longer 'coax' and

 >   they become part of the antenna.

 >

 >   No, they are not 'ideal' connections between

 >   the coax and antenna elements. But their effects

 >   on overall performance is impossible to simply

 >   observe and can only be measured with pretty

 >   sophisticated equipment.

 >

 >   There was some discussion a few years back

 >   about the value of adding the ferrite beads

 >   over feed line attached to an embedded foil

 >   VOR antenna. See the "foil antenna" series

 >   photos at:

 >

 > http://aeroelectric.com/Pictures/Antenna

 >

 >

 >   I did some work in the RF lab and found

 >   that it took a couple dozen beads to

 >   drive the 'deleterious effects' of antenna-to-

 >   feedline mismatch to immeasurable levels. At the

 >   same time, having NO beads installed produced

 >   no observable value.

 >

 >   The observable effects for DIY departures from

 >   idea are likely to be the result of poor

 >   connection, i.e. loss of gas tight connection

 >   between two components . . . not for having

 > violated

 >   the sanctity of a coaxial feedline.

 >

 >   The exposed center conductor and shield pigtails

 >   simply become part of the antenna's complex

 >   impedance. Careful measurements would show that

 >   the trimmed antenna length will be a tad shorter

 >   because of exposed feedline pigtails . . . but

 >   the time it takes to "trim for perfection" will

 >   not make the radio perform batter in any way

 >   you can observe.

 >

 >

 >

 >   Bob . . .

 >

 



 	  Quote: 	
		   AeroElectric-List Email Forum -

 > FAQ,
	


 >    - MATRONICS WEB FORUMS -

 > List Contribution Web Site -

 >               -Matt

 > Dralle, List Admin.

 

 	  Quote: 	
		  

 >
	


 >

 >

 

 

 ===========

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

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

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

 ===========

 

 

 

 



	


-- 

Zulu Delta

Mk IIIC

Thanks, Homer GBYM

It isn't necessary to have relatives in Kansas City in order to be unhappy.

   - Groucho Marx



 

  [quote][b]

_________________
The smallest miracle right in front of you is enough to make you happy....

dan(at)azshowersolutions.
Guest

Posted: Thu Jul 07, 2011 5:20 pm Post subject: PTT buzz

ok...the saga continues. AFter getting home today I disconnected the coax from behind the SL40 and attached the rubber anntenna off of my HT. The sound is different...it is no longer a buzz but it sounds as if it is turning itself on and off when the PTT is depressed...a pulse of sorts approx two cycles per second. Some have e-mailed and said to try turning the squelch down...check. I was also told to turn the side tone to zero...check. no luck so far. So it seems to possibly be either in the radio or a mis-guided wire going to the intercom. Double checking wires tomorrow. Throw out the ideas if you get one.

Thanks, Dan



--- On Thu, 7/7/11, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:



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

 Subject: Re: Re: PTT buzz

 To: aeroelectric-list(at)matronics.com

 Date: Thursday, July 7, 2011, 8:12 AM

 --> AeroElectric-List message

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

 

 Above a Megahertz it becomes critical.

 

 "Pigtails" where the coax shield is twisted into a lead and

 both the inner conductor and twisted-up-shield lead are

 treated as separate wires is deadly to signals above a

 Megahertz. The shield should be terminated by any method

 that does not increase the impedance of the shield or the

 inner conductor.

 

   I think the terms 'deadly' and 'critical' are not

   appropriate here. Yes, as soon as you break out a

   shield and center conductor from a coax cable,

   the resulting conductors are no longer 'coax' and

   they become part of the antenna.

 

   No, they are not 'ideal' connections between

   the coax and antenna elements. But their effects

   on overall performance is impossible to simply

   observe and can only be measured with pretty

   sophisticated equipment.

 

   There was some discussion a few years back

   about the value of adding the ferrite beads

   over feed line attached to an embedded foil

   VOR antenna. See the "foil antenna" series

   photos at:

 

 http://aeroelectric.com/Pictures/Antenna

 

 

   I did some work in the RF lab and found

   that it took a couple dozen beads to

   drive the 'deleterious effects' of antenna-to-

   feedline mismatch to immeasurable levels. At the

   same time, having NO beads installed produced

   no observable value.

 

   The observable effects for DIY departures from

   idea are likely to be the result of poor

   connection, i.e. loss of gas tight connection

   between two components . . . not for having

 violated

   the sanctity of a coaxial feedline.

 

   The exposed center conductor and shield pigtails

   simply become part of the antenna's complex

   impedance. Careful measurements would show that

   the trimmed antenna length will be a tad shorter

   because of exposed feedline pigtails . . . but

   the time it takes to "trim for perfection" will

   not make the radio perform batter in any way

   you can observe.

 

 

 

   Bob . . . 

 

 AeroElectric-List Email Forum -

 FAQ,

    - MATRONICS WEB FORUMS -

 List Contribution Web Site -

               -Matt

 Dralle, List Admin.

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 07, 2011 6:08 pm Post subject: PTT buzz

At 08:16 PM 7/7/2011, you wrote:

 	  Quote: 	
		  

<dan(at)azshowersolutions.com>



ok...the saga continues. AFter getting home today I disconnected the 

coax from behind the SL40 and attached the rubber anntenna off of my 

HT. The sound is different...it is no longer a buzz but it sounds as 

if it is turning itself on and off when the PTT is depressed...a 

pulse of sorts approx two cycles per second. Some have e-mailed and 

said to try turning the squelch down...check. I was also told to 

turn the side tone to zero...check. no luck so far. So it seems to 

possibly be either in the radio or a mis-guided wire going to the 

intercom. Double checking wires tomorrow. Throw out the ideas if you get one.

Thanks, Dan


	


   This is not a meaningful test. A rubber duck is a RADIATING

   device that floods the wiring behind the panel with RF

   energy. If the feedline is radiating due to bad termination,

   then the symptoms you're seeing may well be indiciative of

   a cockpit flooded with RF. Changing the radiator from a bad

   coax to an antenna mounted right to the back of the radio

   is not likely to yield useful information.



   You need to do the dummy load thing first.

   Bob . . .

dan(at)azshowersolutions.
Guest

Posted: Fri Jul 08, 2011 2:56 am Post subject: PTT buzz

 	  Quote: 	
		     This is not a meaningful test. A rubber duck is a

 RADIATING

   device that floods the wiring behind the panel with

 RF

   energy. If the feedline is radiating due to bad

 termination,

   then the symptoms you're seeing may well be

 indiciative of

   a cockpit flooded with RF. Changing the radiator

 from a bad

   coax to an antenna mounted right to the back of the

 radio

   is not likely to yield useful information.

 

   You need to do the dummy load thing first.

 

 

   Bob . . . 

 Roger That

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dan(at)azshowersolutions.
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Posted: Sat Jul 09, 2011 6:01 am Post subject: PTT buzz

I built the dummy load as per Bob's direction, removed the coax from the back of the radio and installed the dummy BNC...turned things on, hit PTT...no joy. I still get the buzz. Now, that means this primary culpret is within my system. Either between my radio (SL40), my intercom 

(PM 1000 II), or the Approach Fast Stack (http://approachfaststack.com/) hub that interfaces the two. Another potential goober could be with my wire runs to the headset jacks. Approach did a nice job of these using shielded wires, however, they were too short (my bad guestimate)as my termination point is behind the co-pilot. I ended up splicing these wires using a Cat-5 wire bundle to the termination point.

I was quite careful when doing this splice, however, I wonder if the lack of shielded wires could be hurting me. Any thoughts of where to start would be welcome. 

Thanks,

Dan B



 	  Quote: 	
		   > ok...the saga continues. AFter getting home today I

 disconnected the coax from behind the SL40 and attached the

 rubber anntenna off of my HT. The sound is different...it is

 no longer a buzz but it sounds as if it is turning itself on

 and off when the PTT is depressed...a pulse of sorts approx

 two cycles per second. Some have e-mailed and said to try

 turning the squelch down...check. I was also told to turn

 the side tone to zero...check. no luck so far. So it seems

 to possibly be either in the radio or a mis-guided wire

 going to the intercom. Double checking wires tomorrow. Throw

 out the ideas if you get one.

 > Thanks, Dan

 

   This is not a meaningful test. A rubber duck is a

 RADIATING

   device that floods the wiring behind the panel with

 RF

   energy. If the feedline is radiating due to bad

 termination,

   then the symptoms you're seeing may well be

 indiciative of

   a cockpit flooded with RF. Changing the radiator

 from a bad

   coax to an antenna mounted right to the back of the

 radio

   is not likely to yield useful information.

 

   You need to do the dummy load thing first.

 

 

   Bob . . . 

 

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dalamphere(at)comcast.net
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Posted: Sat Jul 09, 2011 6:47 am Post subject: PTT buzz

Dan,



This may be totally unuseful, but if you have the aux jacks installed 

between the PS1000 (per PS's instructions) and radio, have you tried 

disconnecting the intercom and plugging your headset and mike jacks into 

those and tried the same experiment (with the dummy load)??



FWIW



Dave



---

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jul 09, 2011 9:08 am Post subject: PTT buzz

At 08:58 AM 7/9/2011, you wrote:

 	  Quote: 	
		  

<dan(at)azshowersolutions.com>



  I built the dummy load as per Bob's direction, removed the coax 

 from the back of the radio and installed the dummy BNC...turned 

 things on, hit PTT...no joy. I still get the buzz.


	


   Okay, good data.



   Describe the "buzz" . . . what does it sound like?

   When listening to the 'buzzing' transmitter on

   another radio, is the same noise heard there too

   or is it just in your own headset?  Does the intercom

   have an auto-bypass function? In other words, if you

   power down just the intercom, does the mic and phones

   wiring default to direct connection with the transceiver?



   If so, does the buzz go away in default mode?



   Bob . . .

enginerdy(at)gmail.com
Guest

Posted: Sat Jul 09, 2011 12:15 pm Post subject: PTT buzz

As Dave suggested, try a headset out in the 'aux jacks' that are directly connected to the radio (you did install them per the PS installation manual, right?  Or as Bob suggested, putting the intercom in bypass mode. The PM1000 II should do that when turned off. This should cut the problem in half. Here are two troubleshooting approaches that might work, given the result:



1) Headset directly into the radio is noisy:

Have you checked the supply voltage across the radio while transmitting and while not transmitting? That is, with the meter probing the supply voltage *at the radio*, grounded to the power ground *at the radio*. Transmitting is a high-power activity, so it's possible that it's causing a big voltage sag that the radio doesn't appreciate. This could be due to wire resistance in both the supply AND ground wires. What is important is what the radio 'sees' while transmitting.



2) Headset directly into the radio is clean:

Another possibility is that the power ground to the radio isn't significant enough, causing a noise voltage to be 'seen' on the audio at the intercom. This is difficult to explain, but you could experiment by connecting an extra ground wire at the radio and finding an additional ground point: the avionics ground, the intercom power ground, one of the fast stack commons... This would help the power supply electrons get to where they want to go without 'pushing' other signals around.



Just to double-check, but you're not doing the test while connected to a battery charger?



--Daniel



On Jul 9, 2011, at 8:58 AM, Dan Billingsley wrote:



 	  Quote: 	
		   

 

 I built the dummy load as per Bob's direction, removed the coax from the back of the radio and installed the dummy BNC...turned things on, hit PTT...no joy. I still get the buzz. Now, that means this primary culpret is within my system. Either between my radio (SL40), my intercom 

 (PM 1000 II), or the Approach Fast Stack (http://approachfaststack.com/) hub that interfaces the two. Another potential goober could be with my wire runs to the headset jacks. Approach did a nice job of these using shielded wires, however, they were too short (my bad guestimate)as my termination point is behind the co-pilot. I ended up splicing these wires using a Cat-5 wire bundle to the termination point.

 I was quite careful when doing this splice, however, I wonder if the lack of shielded wires could be hurting me. Any thoughts of where to start would be welcome. 

 Thanks,

 Dan B

dan(at)azshowersolutions.
Guest

Posted: Sat Jul 09, 2011 5:25 pm Post subject: PTT buzz

 	  Quote: 	
		   

   Okay, good data.

 

   Describe the "buzz" . . . what does it sound like?

The buzz has changed in pitch since removing the antenna. It used to be a medium pitch (as far as notes go say a C)and oscillating. Now that the dummy load is in place the buzz dropped to say a G (much lower) almost a growel. I don't want to hold the key down too long (to determine if still oscillating) as I don't want to overload the dummy...You pick which dummy as it can go either way at this point :>)
	


 	  Quote: 	
		     When listening to the 'buzzing' transmitter on

   another radio, is the same noise heard there too

   or is it just in your own headset?

When the antenna was connected, yes, I did transmit the buzz as the wife heard it on the HT. I would hear her loud and clear and she reported the buzz.
	


  Does the

 	  Quote: 	
		   intercom

   have an auto-bypass function? In other words, if

 you

   power down just the intercom, does the mic and

 phones

   wiring default to direct connection with the

 transceiver?

Although the other guys here have indicated this intercom should have a bypass, I just went out and turned off the intercom and tried it. I cannot hear myself talk and hear nothing when I key the mic. I have gone into the radio and turned down several things, so tomorrow I will look into this a bit further. I did have the FastStack designed to operate a comm 2 (so it has another out). My plan was to eventually run my hand held as a backup and they gave me a switch to go back and forth. I have tried taking my Comm1 harness out of the comm1 jack and moved it to Comm 2. I flipped the switch and still got the buzz.
	


 	  Quote: 	
		   

   If so, does the buzz go away in default mode?

Will get back to you tomorrow on this one when I explore a bit more.
	




Thanks for the help,

Dan

 	  Quote: 	
		   

   Bob . . .

 

 

 

 

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dan(at)azshowersolutions.
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Posted: Sat Jul 09, 2011 5:30 pm Post subject: PTT buzz

Daniel, thanks for the ideas. I will be trying them tomorrow. Today I was chasing parts (this I'm convinced is = to 3/4 of the build). No, not connected to a charger...the battery shows full charge.

Dan B

--- On Sat, 7/9/11, Daniel Hooper <enginerdy(at)gmail.com> wrote:

 	  Quote: 	

 As Dave suggested, try a headset out in the 'aux jacks'

 that are directly connected to the radio (you did install

 them per the PS installation manual, right?  Or as Bob

 suggested, putting the intercom in bypass mode. The PM1000

 II should do that when turned off. This should cut the

 problem in half. Here are two troubleshooting approaches

 that might work, given the result:

 1) Headset directly into the radio is noisy:

 Have you checked the supply voltage across the radio while

 transmitting and while not transmitting? That is, with the

 meter probing the supply voltage *at the radio*, grounded to

 the power ground *at the radio*. Transmitting is a

 high-power activity, so it's possible that it's causing a

 big voltage sag that the radio doesn't appreciate. This

 could be due to wire resistance in both the supply AND

 ground wires. What is important is what the radio 'sees'

 while transmitting.

 2) Headset directly into the radio is clean:

 Another possibility is that the power ground to the radio

 isn't significant enough, causing a noise voltage to be

 'seen' on the audio at the intercom. This is difficult to

 explain, but you could experiment by connecting an extra

 ground wire at the radio and finding an additional ground

 point: the avionics ground, the intercom power ground, one

 of the fast stack commons... This would help the power

 supply electrons get to where they want to go without

 'pushing' other signals around.

 Just to double-check, but you're not doing the test while

 connected to a battery charger?

 --Daniel

 On Jul 9, 2011, at 8:58 AM, Dan Billingsley wrote:

 > 

 Billingsley <dan(at)azshowersolutions.com>

 > 

 > I built the dummy load as per Bob's direction, removed

 the coax from the back of the radio and installed the dummy

 BNC...turned things on, hit PTT...no joy. I still get the

 buzz. Now, that means this primary culpret is within my

 system. Either between my radio (SL40), my intercom 

 > (PM 1000 II), or the Approach Fast Stack (http://approachfaststack.com/) hub that interfaces the

 two. Another potential goober could be with my wire runs to

 the headset jacks. Approach did a nice job of these using

 shielded wires, however, they were too short (my bad

 guestimate)as my termination point is behind the co-pilot. I

 ended up splicing these wires using a Cat-5 wire bundle to

 the termination point.

 > I was quite careful when doing this splice, however, I

 wonder if the lack of shielded wires could be hurting me.

 Any thoughts of where to start would be welcome. 

 > Thanks,

 > Dan B

 > 

 > 

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tim2542(at)sbcglobal.net
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Posted: Sat Jul 09, 2011 9:49 pm Post subject: PTT buzz

Just a quick note Dan, the intercom will only default Comm 1.  If this 

is com 2 it will not work with the Audio panel power off.

FWIW, TIm

 	  Quote:

dan(at)azshowersolutions.
Guest

Posted: Sun Jul 10, 2011 5:04 am Post subject: PTT buzz

 	  Quote: 	
		   

 Just a quick note Dan, the intercom will only default Comm

 1.  If this 

 is com 2 it will not work with the Audio panel power off.

 FWIW, TIm

 >

 

 Thanks Tim...good to know that.

Dan
	


 	  Quote: 	
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Posted: Sun Jul 10, 2011 8:11 am Post subject: PTT buzz

So I believe I may have narrowed it down to two possibilities if not both of 

them adding to the issue...

1. I turned the intercom off and tried to transmit...I still got the buzz and it 

is oscillating. My wife heard it broadcast on the HT and I heard her loud and 

clear when she talked to me. I have not measured the voltage across the radio as 

it is being keyed yet, however, my Dynon 100 indicates I my system voltage 

(BATT) is at 11.3V. So Daniel, this may be part of it.

2. As I was reading the Intercom install manual I found this entry interesting:

     Electrical Noise IssuesWARNING: You must use separate shielded cables for 

the microphone and headphone jacks. Combining

these two wires WILL cause loud oscillations and degrade

the intercom function. The oscillation is caused

by the cross-coupling between the large headphone

signal and the small microphone signal.

 

So, realizing that the intercom is currently bypassed, should this warning still 

be of concern? Remember I mentioned in a previous post that the headphone and 

mic jacks were sent too short, so I cut them off behind the panel and spliced 

them with Cat-5 cable. These jacks terminate behind the co-pilot.



---

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