Today's Message Index:
----------------------
1. 05:15 AM - Nav/com 'acoustic feedback' (Miskelly, Francis G)
2. 05:58 AM - Headset plug polarity (Bill Bradburry)
3. 07:02 AM - Re: Headset plug polarity ()
4. 07:05 AM - Re: Nav/com 'acoustic feedback' (Ernest Christley)
5. 07:43 AM - Re: Headset plug polarity (Ron Quillin)
6. 08:02 AM - LCD (rd2@evenlink.com)
7. 09:01 AM - Re: Nav/com 'acoustic feedback' (Miskelly, Francis G)
8. 10:03 AM - Re: Nav/com 'acoustic feedback' (Ernest Christley)
9. 10:03 AM - Re: Nav/com 'acoustic feedback' (Matt Prather)
10. 10:38 AM - Re: LCD (Pebvjs@aol.com)
11. 12:14 PM - Re: Nav/com 'acoustic feedback' (Matt Prather)
12. 12:51 PM - Z-20 System (John Davis)
13. 01:36 PM - Re: Nav/com 'acoustic feedback' (Miskelly, Francis G)
14. 02:32 PM - Re: Nav/com 'acoustic feedback' (Matt Prather)
15. 02:58 PM - Re: LCD (rd2@evenlink.com)
16. 03:16 PM - Re: Nav/com 'acoustic feedback' (Ron Quillin)
17. 03:38 PM - emagair recommendation against Nuckoll's wiring schematic? (Erich_Weaver@URSCorp.com)
18. 04:43 PM - Re: Nav/com 'acoustic feedback' (Miskelly, Francis G)
19. 09:19 PM - Re: emagair recommendation against Nuckoll's wiring schematic? (Michael T. Ice)
Message 1
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Subject: | Nav/com 'acoustic feedback' |
The KX155 nav/com in my Glastar has 2 problems which may be related.
1. Inserting the headphone jack i have near perfect reception. However,
when i insert the microphone jack there is a loud whine suggestive of
'acoustic feedback'. Moving the boom away from my mouth reduces the
whine. With a different headset it appears as lots of static noise which
again changes with position of the boom. I've changed the aerial, power
supply and checked all the earths. It occurs with either mag and when
the generator is disconnected. It only happens when the engine is
running. The radio's been bench tested and passed as good.
2. Radio reception is good with just the headphone jack inserted.
However, insert the microphone jack and reception becomes very poor or
disappears completely. I suspect the 'acoustic feedback' is raising the
automatic squelch which is cutting off the radio station
Can anyone suggest an explanation and a solution!
Many thanks
Frank
Message 2
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Subject: | Headset plug polarity |
I am amazed at the difficulty in finding the polarity on the internet. Can
someone help me here?
What should be the polarity of the sleeve, ring, and tip on a stereo plug?
Which, ring or tip, is probably right and which is probably left on the
stereo plug?
Also what should be the polarity of the sleeve and tip on the mono plug.
How should I wire a stereo receptacle so that it could be used for both
stereo or mono?
Thanks,
Bill B
Message 3
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Subject: | Re: Headset plug polarity |
My first thought was to quickly reply, but my information is off the top of my
head and may not be correct.
My recommendation is to check your headset manufacturer's web site or give them
a call. I'm sure in a couple minutes you would have an answer.
My guess would have be tip-right, ring-left, sleeve-ground.
On a mono plug, the tip has the signal and the sleeve is the ground.
>
> From: "Bill Bradburry" <bbradburry@bellsouth.net>
> Date: 2007/08/13 Mon AM 07:57:05 EST
> To: <aeroelectric-list@matronics.com>
> Subject: AeroElectric-List: Headset plug polarity
>
>
> I am amazed at the difficulty in finding the polarity on the internet. Can
> someone help me here?
>
> What should be the polarity of the sleeve, ring, and tip on a stereo plug?
> Which, ring or tip, is probably right and which is probably left on the
> stereo plug?
>
> Also what should be the polarity of the sleeve and tip on the mono plug.
>
> How should I wire a stereo receptacle so that it could be used for both
> stereo or mono?
>
> Thanks,
> Bill B
>
>
>
>
>
Message 4
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Subject: | Re: Nav/com 'acoustic feedback' |
Miskelly, Francis G wrote:
> The KX155 nav/com in my Glastar has 2 problems which may be related.
>
> 1. Inserting the headphone jack i have near perfect reception.
> However, when i insert the microphone jack there is a loud whine
> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
> reduces the whine. With a different headset it appears as lots of
> static noise which again changes with position of the boom. I've
> changed the aerial, power supply and checked all the earths. It occurs
> with either mag and when the generator is disconnected. It only
> happens when the engine is running. The radio's been bench tested and
> passed as good.
>
> 2. Radio reception is good with just the headphone jack inserted.
> However, insert the microphone jack and reception becomes very poor or
> disappears completely. I suspect the 'acoustic feedback' is raising
> the automatic squelch which is cutting off the radio station
>
> Can anyone suggest an explanation and a solution!
> Many thanks
> Frank
Since there is a problem with multiple headset, I would check the jack
first. The symptoms seem to imply some feedback from the mic to the
audio. Look for a short or a broken ground. Beyond that, it would seem
circuitry withing the intercom is fritzed, and it gets much more
complicated.
Message 5
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Subject: | Re: Headset plug polarity |
At 05:57 8/13/2007, you wrote:
><bbradburry@bellsouth.net>
>
>I am amazed at the difficulty in finding the polarity on the internet. Can
>someone help me here?
>
>What should be the polarity of the sleeve, ring, and tip on a stereo plug?
>Which, ring or tip, is probably right and which is probably left on the
>stereo plug?
"Standards" have evolved and changed over the years, and not every
manufacturer follows them anyway, and draftsmen frequently don't know
or care how a jack is drawn and get it wrong. From the audio world:
Tip Right
Ring Left
Sleeve Common
PS-Engineering, and others, agree.
>Also what should be the polarity of the sleeve and tip on the mono plug.
Tip hot
Sleeve Common
>How should I wire a stereo receptacle so that it could be used for both
>stereo or mono?
There isn't any really good, safe and easy way and the method
selected would properly be dependent on what the signal source is,
and how well it may or may not be fault protected.
With two broken wrists in casts, I'm typing challenged. Perhaps
others can elaborate.
Ron Q.
>Thanks,
>Bill B
Message 6
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Does anyone need/can anyone use a 13" diag. screen from a NEC Versa 6230
laptop?
It's TFT color, 1024 x 768 res., works, intact, no scratches, has original
connector. Other data is no longer available (must have been disposed of
inadvertently).
If anyone would like to have it, email me, it's free for the shipping.
Rumen
do not archive
Message 7
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Subject: | Nav/com 'acoustic feedback' |
Thanks for your comments Ernest.
I've double-checked all the grounds i could find. Even took the whole
harness out (which was new) and had it double-checked. Nothing found.
If its the intercom in the radio why does it not cause the same problem
when the engine is off?
It only causes the problem when the engine is running
Kind regards
Frank
________________________________
From: owner-aeroelectric-list-server@matronics.com on behalf of Ernest
Christley
Sent: Mon 13/08/2007 15:04
Subject: Re: AeroElectric-List: Nav/com 'acoustic feedback'
<echristley@nc.rr.com>
Miskelly, Francis G wrote:
> The KX155 nav/com in my Glastar has 2 problems which may be related.
>
> 1. Inserting the headphone jack i have near perfect reception.
> However, when i insert the microphone jack there is a loud whine
> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
> reduces the whine. With a different headset it appears as lots of
> static noise which again changes with position of the boom. I've
> changed the aerial, power supply and checked all the earths. It occurs
> with either mag and when the generator is disconnected. It only
> happens when the engine is running. The radio's been bench tested and
> passed as good.
>
> 2. Radio reception is good with just the headphone jack inserted.
> However, insert the microphone jack and reception becomes very poor or
> disappears completely. I suspect the 'acoustic feedback' is raising
> the automatic squelch which is cutting off the radio station
>
> Can anyone suggest an explanation and a solution!
> Many thanks
> Frank
Since there is a problem with multiple headset, I would check the jack
first. The symptoms seem to imply some feedback from the mic to the
audio. Look for a short or a broken ground. Beyond that, it would seem
circuitry withing the intercom is fritzed, and it gets much more
complicated.
Message 8
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Subject: | Re: Nav/com 'acoustic feedback' |
Miskelly, Francis G wrote:
> Thanks for your comments Ernest.
> I've double-checked all the grounds i could find. Even took the whole harness
out (which was new) and had it double-checked. Nothing found.
> If its the intercom in the radio why does it not cause the same problem when
the engine is off?
> It only causes the problem when the engine is running
> Kind regards
> Frank
>
>
Where is your squelch set at?
Message 9
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Subject: | Re: Nav/com 'acoustic feedback' |
Ernest,
Your response kind of points to what I was thinking.. I don't think the
KX155 has any intercom, but the description of the symptoms seem like an
intercom problem. If so, I wonder if turning off the intercom aleviates
the behavior. If there isn't any intercom, then I might suspect the radio
has a problem. Plugging in the mic shouldn't have any effect until the
PTT circuitry is activated, but then you wouldn't get _any_ reception
(because the transmitter would be active)..
If the problem is related to the intercom, consider trying to find a way
to adjust the mic gain on the intercom.
Regards,
Matt-
> <echristley@nc.rr.com>
>
> Miskelly, Francis G wrote:
>> The KX155 nav/com in my Glastar has 2 problems which may be related.
>>
>> 1. Inserting the headphone jack i have near perfect reception.
>> However, when i insert the microphone jack there is a loud whine
>> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
>> reduces the whine. With a different headset it appears as lots of
>> static noise which again changes with position of the boom. I've
>> changed the aerial, power supply and checked all the earths. It occurs
>> with either mag and when the generator is disconnected. It only
>> happens when the engine is running. The radio's been bench tested and
>> passed as good.
>>
>> 2. Radio reception is good with just the headphone jack inserted.
>> However, insert the microphone jack and reception becomes very poor or
>> disappears completely. I suspect the 'acoustic feedback' is raising
>> the automatic squelch which is cutting off the radio station
>>
>> Can anyone suggest an explanation and a solution!
>> Many thanks
>> Frank
> Since there is a problem with multiple headset, I would check the jack
> first. The symptoms seem to imply some feedback from the mic to the
> audio. Look for a short or a broken ground. Beyond that, it would seem
> circuitry withing the intercom is fritzed, and it gets much more
> complicated.
>
>
Message 10
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Rumen,
I would like to have it. Let me know the shipping to ZIP 33190.
Thanks,
Ed. Sadler
http://discover.aol.com/memed/aolcom30tour
Message 11
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|
Subject: | Nav/com 'acoustic feedback' |
Does it help if you cover the mic with your hand (both sides - pull the
muff off)?
I suspect that the input stage of your intercom is being overdriven by the
acoustic noise of the engine.
Regards,
Matt-
> Thanks for your comments Ernest.
> I've double-checked all the grounds i could find. Even took the whole
> harness out (which was new) and had it double-checked. Nothing found.
> If its the intercom in the radio why does it not cause the same problem
> when the engine is off?
> It only causes the problem when the engine is running
> Kind regards
> Frank
>
> ________________________________
>
> From: owner-aeroelectric-list-server@matronics.com on behalf of Ernest
> Christley
> Sent: Mon 13/08/2007 15:04
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Nav/com 'acoustic feedback'
>
>
> <echristley@nc.rr.com>
>
> Miskelly, Francis G wrote:
>> The KX155 nav/com in my Glastar has 2 problems which may be related.
>>
>> 1. Inserting the headphone jack i have near perfect reception.
>> However, when i insert the microphone jack there is a loud whine
>> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
>> reduces the whine. With a different headset it appears as lots of
>> static noise which again changes with position of the boom. I've
>> changed the aerial, power supply and checked all the earths. It occurs
>> with either mag and when the generator is disconnected. It only
>> happens when the engine is running. The radio's been bench tested and
>> passed as good.
>>
>> 2. Radio reception is good with just the headphone jack inserted.
>> However, insert the microphone jack and reception becomes very poor or
>> disappears completely. I suspect the 'acoustic feedback' is raising
>> the automatic squelch which is cutting off the radio station
>>
>> Can anyone suggest an explanation and a solution!
>> Many thanks
>> Frank
> Since there is a problem with multiple headset, I would check the jack
> first. The symptoms seem to imply some feedback from the mic to the
> audio. Look for a short or a broken ground. Beyond that, it would seem
> circuitry withing the intercom is fritzed, and it gets much more
> complicated.
>
>
Message 12
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|
Hi All,
I'm getting ready for the electrical system in my zenith 601XL with a
Jabiru 3300.
I'm trying to keep things simple and am thinking about going with the
Z-20 Small Jabiru System. That diagram switches the main bus thru the
Master switch instead of a battery contactor. Whats the practical cutoff
in terms of current for using a contactor vs routing directly thru the
switch. Any downside to adding a contactor to this plan ? Any upsides ?
Any issues with the Z-20 plan ?
Thanks,
John Davis
Burnsville, NC
Message 13
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Subject: | Nav/com 'acoustic feedback' |
Matt
1. When i cover the mic with my hand (muff off) the character of the
feedback alters significantly but is not overall reduced. If i move the
boom away from my mouth and around to the back of my head then the
feedback reduces but doesn't disappear. Its worse (louder) the closer
the boom to my mouth. These symptoms occur on both left and right hand
headsets
2. My KX155 has an internal intercom. I haven't tried to disconnect it.
3. Plugging in the mic jack should activate the intercom and the
transmit on the radio (when PTT pressed)
4. Remember the problem only occurs when the engine is running.
5. Does anyone know how to adjust the mic gain (intercom volume control)
on the KX155? Couldn't find this info in the installation manual.
Kind regards
Frank
________________________________
From: owner-aeroelectric-list-server@matronics.com on behalf of Matt
Prather
Sent: Mon 13/08/2007 20:12
Subject: RE: AeroElectric-List: Nav/com 'acoustic feedback'
<mprather@spro.net>
Does it help if you cover the mic with your hand (both sides - pull the
muff off)?
I suspect that the input stage of your intercom is being overdriven by
the
acoustic noise of the engine.
Regards,
Matt-
> Thanks for your comments Ernest.
> I've double-checked all the grounds i could find. Even took the whole
> harness out (which was new) and had it double-checked. Nothing found.
> If its the intercom in the radio why does it not cause the same
problem
> when the engine is off?
> It only causes the problem when the engine is running
> Kind regards
> Frank
>
> ________________________________
>
> From: owner-aeroelectric-list-server@matronics.com on behalf of Ernest
> Christley
> Sent: Mon 13/08/2007 15:04
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Nav/com 'acoustic feedback'
>
>
> <echristley@nc.rr.com>
>
> Miskelly, Francis G wrote:
>> The KX155 nav/com in my Glastar has 2 problems which may be related.
>>
>> 1. Inserting the headphone jack i have near perfect reception.
>> However, when i insert the microphone jack there is a loud whine
>> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
>> reduces the whine. With a different headset it appears as lots of
>> static noise which again changes with position of the boom. I've
>> changed the aerial, power supply and checked all the earths. It
occurs
>> with either mag and when the generator is disconnected. It only
>> happens when the engine is running. The radio's been bench tested and
>> passed as good.
>>
>> 2. Radio reception is good with just the headphone jack inserted.
>> However, insert the microphone jack and reception becomes very poor
or
>> disappears completely. I suspect the 'acoustic feedback' is raising
>> the automatic squelch which is cutting off the radio station
>>
>> Can anyone suggest an explanation and a solution!
>> Many thanks
>> Frank
> Since there is a problem with multiple headset, I would check the jack
> first. The symptoms seem to imply some feedback from the mic to the
> audio. Look for a short or a broken ground. Beyond that, it would
seem
> circuitry withing the intercom is fritzed, and it gets much more
> complicated.
>
>
Message 14
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|
Subject: | Nav/com 'acoustic feedback' |
Interesting.. I wasn't aware that any KX155 has intercom. Okay. I see
the manual says it has 500ohm aux inputs, but don't see any reference to
intercom. We're talking about a Bendix/King KX-155, right? Do you have a
link to a file which describes the feature?
Does the sound vary depending on where your head/headset is sitting, or by
bending the wires around on the headset, or the wires to the jack?
Is the frequency of the whine/feedback dependent on the engine RPM? Or is
it just a steady tone?
I agree with item 3 (assuming an intercom).
Regards,
Matt-
> Matt
> 1. When i cover the mic with my hand (muff off) the character of the
> feedback alters significantly but is not overall reduced. If i move the
> boom away from my mouth and around to the back of my head then the
> feedback reduces but doesn't disappear. Its worse (louder) the closer the
> boom to my mouth. These symptoms occur on both left and right hand
> headsets
> 2. My KX155 has an internal intercom. I haven't tried to disconnect it.
> 3. Plugging in the mic jack should activate the intercom and the transmit
> on the radio (when PTT pressed)
> 4. Remember the problem only occurs when the engine is running.
> 5. Does anyone know how to adjust the mic gain (intercom volume control)
> on the KX155? Couldn't find this info in the installation manual.
> Kind regards
> Frank
>
>
> ________________________________
>
> From: owner-aeroelectric-list-server@matronics.com on behalf of Matt
> Prather
> Sent: Mon 13/08/2007 20:12
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: Nav/com 'acoustic feedback'
>
>
> <mprather@spro.net>
>
> Does it help if you cover the mic with your hand (both sides - pull the
> muff off)?
>
> I suspect that the input stage of your intercom is being overdriven by the
> acoustic noise of the engine.
>
>
> Regards,
>
> Matt-
>
>> Thanks for your comments Ernest.
>> I've double-checked all the grounds i could find. Even took the whole
>> harness out (which was new) and had it double-checked. Nothing found.
>> If its the intercom in the radio why does it not cause the same problem
>> when the engine is off?
>> It only causes the problem when the engine is running
>> Kind regards
>> Frank
>>
>> ________________________________
>>
>> From: owner-aeroelectric-list-server@matronics.com on behalf of Ernest
>> Christley
>> Sent: Mon 13/08/2007 15:04
>> To: aeroelectric-list@matronics.com
>> Subject: Re: AeroElectric-List: Nav/com 'acoustic feedback'
>>
>>
>>
>> <echristley@nc.rr.com>
>>
>> Miskelly, Francis G wrote:
>>> The KX155 nav/com in my Glastar has 2 problems which may be related.
>>>
>>> 1. Inserting the headphone jack i have near perfect reception.
>>> However, when i insert the microphone jack there is a loud whine
>>> suggestive of 'acoustic feedback'. Moving the boom away from my mouth
>>> reduces the whine. With a different headset it appears as lots of
>>> static noise which again changes with position of the boom. I've
>>> changed the aerial, power supply and checked all the earths. It occurs
>>> with either mag and when the generator is disconnected. It only
>>> happens when the engine is running. The radio's been bench tested and
>>> passed as good.
>>>
>>> 2. Radio reception is good with just the headphone jack inserted.
>>> However, insert the microphone jack and reception becomes very poor or
>>> disappears completely. I suspect the 'acoustic feedback' is raising
>>> the automatic squelch which is cutting off the radio station
>>>
>>> Can anyone suggest an explanation and a solution!
>>> Many thanks
>>> Frank
>> Since there is a problem with multiple headset, I would check the jack
>> first. The symptoms seem to imply some feedback from the mic to the
>> audio. Look for a short or a broken ground. Beyond that, it would seem
>> circuitry withing the intercom is fritzed, and it gets much more
>> complicated.
>>
>>
>>
>>
>>
>>
>>
>>
>
>
Message 15
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|
It's yours, Ed.
Email me privately with the address where to send it to. It'll be on its
way tomorrow. When you get it, look up the postage and mail me a Gold Eagle
:) (only kidding).
Rumen
do not archive
_____________________Original message __________________________
(received from Pebvjs@aol.com; Date: 01:33 PM 8/13/2007
EDT)
________________________________________________________________
Rumen,
I would like to have it. Let me know the shipping to ZIP 33190.
Thanks,
Ed. Sadler
Message 16
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|
Subject: | Nav/com 'acoustic feedback' |
At 14:29 8/13/2007, you wrote:
>Interesting.. I wasn't aware that any KX155 has intercom. Okay. I see
>the manual says it has 500ohm aux inputs, but don't see any reference to
>intercom. We're talking about a Bendix/King KX-155, right? Do you have a
>link to a file which describes the feature?
I do find a reference in the IM for a 155A/165A to an intercom level
adjustment.
Is this an A model?
Ron Q
Message 17
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Subject: | emagair recommendation against Nuckoll's wiring schematic? |
Bob et al:
Recent postings on the Vans Airforce site (see posts #44-47 at
www.tiny.cc/bb2oY) indicate that the folks at emagair do not want us to
use
the wiring method suggested for their product in your schematics (I fo
rget
the Z#). The logic for your schematic made sense to me, so I used it a
nd
dont want to re-do now unless there is a good reason. Could I impose o
n
you to talk the fine folks at Emagair and get to the bottom of this? Im
not
sure I understand the issue and Im sure you will have more insights an
d
better questions for them than I can come up with. Thank you - Lookin
g
forward to your response.
Erich Weaver
Message 18
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|
Subject: | Nav/com 'acoustic feedback' |
1. The radio is a Bendix/King KX155
2. It is approximately 1 year old. Don't know the model # but could find
out
3. It definately has an internal intercom but i've no links to describe
it
4. I didn't check whether the sound varied depending on where your
head/headset is sitting, or by
bending the wires around on the headset, or the wires to the jack but it
occurred with 3 separate headsets and on both pilot and co-pilot
outputs. Pretty sure its not a headset problem as same headsets work
fine in other planes
5. The noise gets worse with higher engine RPM but is very obvious even
at 1000 RPM. The character doesn't change - just its loudness
Many thanks
Frank
________________________________
From: owner-aeroelectric-list-server@matronics.com on behalf of Matt
Prather
Sent: Mon 13/08/2007 22:29
Subject: RE: AeroElectric-List: Nav/com 'acoustic feedback'
<mprather@spro.net>
Interesting.. I wasn't aware that any KX155 has intercom. Okay. I see
the manual says it has 500ohm aux inputs, but don't see any reference to
intercom. We're talking about a Bendix/King KX-155, right? Do you have
a
link to a file which describes the feature?
Does the sound vary depending on where your head/headset is sitting, or
by
bending the wires around on the headset, or the wires to the jack?
Is the frequency of the whine/feedback dependent on the engine RPM? Or
is
it just a steady tone?
I agree with item 3 (assuming an intercom).
Regards,
Matt-
> Matt
> 1. When i cover the mic with my hand (muff off) the character of the
> feedback alters significantly but is not overall reduced. If i move
the
> boom away from my mouth and around to the back of my head then the
> feedback reduces but doesn't disappear. Its worse (louder) the closer
the
> boom to my mouth. These symptoms occur on both left and right hand
> headsets
> 2. My KX155 has an internal intercom. I haven't tried to disconnect
it.
> 3. Plugging in the mic jack should activate the intercom and the
transmit
> on the radio (when PTT pressed)
> 4. Remember the problem only occurs when the engine is running.
> 5. Does anyone know how to adjust the mic gain (intercom volume
control)
> on the KX155? Couldn't find this info in the installation manual.
> Kind regards
> Frank
>
>
> ________________________________
>
> From: owner-aeroelectric-list-server@matronics.com on behalf of Matt
> Prather
> Sent: Mon 13/08/2007 20:12
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: Nav/com 'acoustic feedback'
>
>
> <mprather@spro.net>
>
> Does it help if you cover the mic with your hand (both sides - pull
the
> muff off)?
>
> I suspect that the input stage of your intercom is being overdriven by
the
> acoustic noise of the engine.
>
>
> Regards,
>
> Matt-
>
>> Thanks for your comments Ernest.
>> I've double-checked all the grounds i could find. Even took the whole
>> harness out (which was new) and had it double-checked. Nothing found.
>> If its the intercom in the radio why does it not cause the same
problem
>> when the engine is off?
>> It only causes the problem when the engine is running
>> Kind regards
>> Frank
>>
>> ________________________________
>>
>> From: owner-aeroelectric-list-server@matronics.com on behalf of
Ernest
>> Christley
>> Sent: Mon 13/08/2007 15:04
>> To: aeroelectric-list@matronics.com
>> Subject: Re: AeroElectric-List: Nav/com 'acoustic feedback'
>>
>>
>>
>> <echristley@nc.rr.com>
>>
>> Miskelly, Francis G wrote:
>>> The KX155 nav/com in my Glastar has 2 problems which may be related.
>>>
>>> 1. Inserting the headphone jack i have near perfect reception.
>>> However, when i insert the microphone jack there is a loud whine
>>> suggestive of 'acoustic feedback'. Moving the boom away from my
mouth
>>> reduces the whine. With a different headset it appears as lots of
>>> static noise which again changes with position of the boom. I've
>>> changed the aerial, power supply and checked all the earths. It
occurs
>>> with either mag and when the generator is disconnected. It only
>>> happens when the engine is running. The radio's been bench tested
and
>>> passed as good.
>>>
>>> 2. Radio reception is good with just the headphone jack inserted.
>>> However, insert the microphone jack and reception becomes very poor
or
>>> disappears completely. I suspect the 'acoustic feedback' is raising
>>> the automatic squelch which is cutting off the radio station
>>>
>>> Can anyone suggest an explanation and a solution!
>>> Many thanks
>>> Frank
>> Since there is a problem with multiple headset, I would check the
jack
>> first. The symptoms seem to imply some feedback from the mic to the
>> audio. Look for a short or a broken ground. Beyond that, it would
seem
>> circuitry withing the intercom is fritzed, and it gets much more
>> complicated.
>>
>>
>>
>>
>>
>>
>>
>>
>
>
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Subject: | Re: emagair recommendation against Nuckoll's wiring |
schematic?
Erich,
I had the pleasure of attending Bob's seminar this past weekend and I asked him
about this very same issue.
First the caveat. I am not an engineer and don't claim to know a whole lot about
electrical theory or application. What I am is curious and I do have an E and
a P/mag.
After reading everything I can get my hands on and studying the Z figures Z-13
and Z-33 for the Maintenance hand prop option I can detect only subtle differences.
Emag powers the mags directly from the main bus, so when you turn on the master
there is power at the mags. The switches on the panel for the emags are for P-lead
kill switches. To do maintenance (timing) all you have to do is turn on
the master and leave the panel switch off. But to check the alternator part of
the P-Mag you have to put a separate switch in line with the power supply to
the mag. When you do a run up check, you turn this switch off and if all is well
the motor keeps on humming.
Bob's design has the power go to a switch first. The positions on the switch are
down is off, middle is for internal power, up is for ships power. In the Z-33
schematic you then have to add a switch (and possibly a light) to be able to
cut the P-lead so you can do maintenance (Timing). So to do the internal alternator
check all you have to do is flick the switch to the middle position and
if all is well you can't tell the difference.
So what's the big difference. Both systems use 3 switches. Both systems do the
same thing just in slightly different ways.
Personally I can see an advantage in the Emag system where each mag has it's own
P-lead ground kill switch. Starting sequence should be pretty easy. Master on,
both switches in the up position, mash the start button.
But I am a confirmed Nuckoll's advocate and I want to see what he has to say about
this. He is still here in Alaska and touring around visiting the sights. He
has assured me that when he gets back he will dig into this and provide help.
I have sent an email to Emagair asking the same questions. Open dialog on this
question can only help us and Emagair greatly.
I have not personally heard from the guys at Emagair nor have I read anything directly
from them concerning this issue. Until I do I will keep an open mind.
Perhaps this issue is a non-event and some of the problems stem from us folks in
the field still trying to make these new mags act like the old style. For instance
how can you perform a mag drop check if there isn't one. Perhaps the answer
is who cares. I don't know but I am sure interested in how this turns out.
Please comment at will. Any dialog is appreciated.
Mike Ice
----- Original Message -----
From: Erich_Weaver@URSCorp.com
To: aeroelectric-list@matronics.com
Sent: Monday, August 13, 2007 2:36 PM
Subject: AeroElectric-List: emagair recommendation against Nuckoll's wiring schematic?
Bob et al:
Recent postings on the Vans Airforce site (see posts #44-47 at www.tiny.cc/bb2oY) indicate that the folks at emagair do not want us to use the wiring method suggested for their product in your schematics (I forget the Z#). The logic for your schematic made sense to me, so I used it and dont want to re-do now unless there is a good reason. Could I impose on you to talk the fine folks at Emagair and get to the bottom of this? Im not sure I understand the issue and Im sure you will have more insights and better questions for them than I can come up with. Thank you - Looking forward to your response.
Erich Weaver
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