Comm noise

[John[_9_]]

I flew yesterday with an owner who pointed out that he is getting a
type of crackling noise over both comm radios. The noise is most
prevalent when receiving from more distant and weaker transmitters
like other aircraft and not noticeabl when receiving from closer more
powerful transmitters i.e. the tower.

The owner has operated the aircraft with every other system turned off
including the alternators and has operated on individual magnetos with
no change. The most recent change to equipment was an audion panel
installation. The noise is not rythmic like ignition noise and does
not rise and fall with engine settings like some alternator noise. It
is not as intense as the white noise when checking squelch. It is a
type of random crackling like noise.

Any thoughts?

John Dupre'

[darthpup]

Solar activity...Sun spots...solar flares....
Signal to noise ratio...
typical for any radio receiver.

[RST Engineering]

Aircraft type? Does it on the ground? In air only, slowflight as well as
cruise speed?

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"John" > wrote in message
...
>I flew yesterday with an owner who pointed out that he is getting a
> type of crackling noise over both comm radios. The noise is most
> prevalent when receiving from more distant and weaker transmitters
> like other aircraft and not noticeabl when receiving from closer more
> powerful transmitters i.e. the tower.
>
> The owner has operated the aircraft with every other system turned off
> including the alternators and has operated on individual magnetos with
> no change. The most recent change to equipment was an audion panel
> installation. The noise is not rythmic like ignition noise and does
> not rise and fall with engine settings like some alternator noise. It
> is not as intense as the white noise when checking squelch. It is a
> type of random crackling like noise.
>
> Any thoughts?
>
> John Dupre'

[Orval Fairbairn[_2_]]

In article
>,
John > wrote:

> I flew yesterday with an owner who pointed out that he is getting a
> type of crackling noise over both comm radios. The noise is most
> prevalent when receiving from more distant and weaker transmitters
> like other aircraft and not noticeabl when receiving from closer more
> powerful transmitters i.e. the tower.
>
> The owner has operated the aircraft with every other system turned off
> including the alternators and has operated on individual magnetos with
> no change. The most recent change to equipment was an audion panel
> installation. The noise is not rythmic like ignition noise and does
> not rise and fall with engine settings like some alternator noise. It
> is not as intense as the white noise when checking squelch. It is a
> type of random crackling like noise.
>
> Any thoughts?
>
> John Dupre'

I had a similar problem years ago, with one of those cheap whip
antennas. I switched to a high-quality antenna and got rid of the
problem.

It appears that moisture had somehow entered the material surrounding
the metal antenna and was causing arcing.

--
Remove _'s from email address to talk to me.

[John[_9_]]

On Aug 28, 3:12*pm, "RST Engineering" > wrote:
> Aircraft type? *Does it on the ground? *In air only, slowflight as well as
> cruise speed?
>
> Jim
>
> --
> "It is the mark of an educated mind to be able to entertain a thought
> without accepting it."
> * * * * --Aristotle
>
> "John" > wrote in message
>
> ...
>
>
>
> >I flew yesterday with an owner who pointed out that he is getting a
> > type of crackling noise over both comm radios. *The noise is most
> > prevalent when receiving from more distant and weaker transmitters
> > like other aircraft and not noticeabl when receiving from closer more
> > powerful transmitters i.e. the tower.
>
> > The owner has operated the aircraft with every other system turned off
> > including the alternators and has operated on individual magnetos with
> > no change. *The most recent change to equipment was an audion panel
> > installation. *The noise is not rythmic like ignition noise and does
> > not rise and fall with engine settings like some alternator noise. *It
> > is not as intense as the white noise when checking squelch. *It is a
> > type of random crackling like noise.
>
> > Any thoughts?
>
> > John Dupre'- Hide quoted text -
>
> - Show quoted text -

F33 Bonanza. Slow as well as cruise flight. I was only told about it
once we were airborne and didn't think to listen othewise.

John Dupre'

[John[_9_]]

On Aug 28, 4:55*pm, Orval Fairbairn >
wrote:
> In article
> >,
>
>
>
>
>
> *John > wrote:
> > I flew yesterday with an owner who pointed out that he is getting a
> > type of crackling noise over both comm radios. *The noise is most
> > prevalent when receiving from more distant and weaker transmitters
> > like other aircraft and not noticeabl when receiving from closer more
> > powerful transmitters i.e. the tower.
>
> > The owner has operated the aircraft with every other system turned off
> > including the alternators and has operated on individual magnetos with
> > no change. *The most recent change to equipment was an audion panel
> > installation. *The noise is not rythmic like ignition noise and does
> > not rise and fall with engine settings like some alternator noise. *It
> > is not as intense as the white noise when checking squelch. *It is a
> > type of random crackling like noise.
>
> > Any thoughts?
>
> > John Dupre'
>
> I had a similar problem years ago, with one of those cheap whip
> antennas. I switched to a high-quality antenna and got rid of the
> problem.
>
> It appears that moisture had somehow entered the material surrounding
> the metal antenna and was causing arcing.
>
> --
> Remove _'s *from email address to talk to me.- Hide quoted text -
>
> - Show quoted text -

I did notice that the upper antenna is loosing some of its coating and
the exposed areas look corroded. I would replace the antenna for that
reason alone but the owner wants some more confirmation than looks.
The lower antenna (bent whip) doesn't appear corroded although the
whip portion is slightly bent.

John Dupre'

[Orval Fairbairn[_2_]]

In article
>,
John > wrote:

> On Aug 28, 4:55*pm, Orval Fairbairn >
> wrote:
> > In article
> > >,
> >
> >
> >
> >
> >
> > *John > wrote:
> > > I flew yesterday with an owner who pointed out that he is getting a
> > > type of crackling noise over both comm radios. *The noise is most
> > > prevalent when receiving from more distant and weaker transmitters
> > > like other aircraft and not noticeabl when receiving from closer more
> > > powerful transmitters i.e. the tower.
> >
> > > The owner has operated the aircraft with every other system turned off
> > > including the alternators and has operated on individual magnetos with
> > > no change. *The most recent change to equipment was an audion panel
> > > installation. *The noise is not rythmic like ignition noise and does
> > > not rise and fall with engine settings like some alternator noise. *It
> > > is not as intense as the white noise when checking squelch. *It is a
> > > type of random crackling like noise.
> >
> > > Any thoughts?
> >
> > > John Dupre'
> >
> > I had a similar problem years ago, with one of those cheap whip
> > antennas. I switched to a high-quality antenna and got rid of the
> > problem.
> >
> > It appears that moisture had somehow entered the material surrounding
> > the metal antenna and was causing arcing.
> >
> > --
> > Remove _'s *from email address to talk to me.- Hide quoted text -
> >
> > - Show quoted text -
>
> I did notice that the upper antenna is loosing some of its coating and
> the exposed areas look corroded. I would replace the antenna for that
> reason alone but the owner wants some more confirmation than looks.
> The lower antenna (bent whip) doesn't appear corroded although the
> whip portion is slightly bent.
>
> John Dupre'

That would do it on the upper antenna -- especially if it has flown
through rain. Is the antenna airfoil-shaped or one of theose
wrapped-metal, round ones? I had the latter and it eventually succombed
to moisture.

--
Remove _'s from email address to talk to me.

[John[_9_]]

On Aug 29, 10:11*am, Orval Fairbairn >
wrote:
> In article
> >,
>
>
>
>
>
> *John > wrote:
> > On Aug 28, 4:55*pm, Orval Fairbairn >
> > wrote:
> > > In article
> > > >,
>
> > > *John > wrote:
> > > > I flew yesterday with an owner who pointed out that he is getting a
> > > > type of crackling noise over both comm radios. *The noise is most
> > > > prevalent when receiving from more distant and weaker transmitters
> > > > like other aircraft and not noticeabl when receiving from closer more
> > > > powerful transmitters i.e. the tower.
>
> > > > The owner has operated the aircraft with every other system turned off
> > > > including the alternators and has operated on individual magnetos with
> > > > no change. *The most recent change to equipment was an audion panel
> > > > installation. *The noise is not rythmic like ignition noise and does
> > > > not rise and fall with engine settings like some alternator noise. *It
> > > > is not as intense as the white noise when checking squelch. *It is a
> > > > type of random crackling like noise.
>
> > > > Any thoughts?
>
> > > > John Dupre'
>
> > > I had a similar problem years ago, with one of those cheap whip
> > > antennas. I switched to a high-quality antenna and got rid of the
> > > problem.
>
> > > It appears that moisture had somehow entered the material surrounding
> > > the metal antenna and was causing arcing.
>
> > > --
> > > Remove _'s *from email address to talk to me.- Hide quoted text -
>
> > > - Show quoted text -
>
> > I did notice that the upper antenna is loosing some of its coating and
> > the exposed areas look corroded. *I would replace the antenna for that
> > reason alone but the owner wants some more confirmation than looks.
> > The lower antenna (bent whip) doesn't appear corroded although the
> > whip portion is slightly bent.
>
> > John Dupre'
>
> That would do it on the upper antenna -- especially if it has flown
> through rain. Is the antenna airfoil-shaped or one of theose
> wrapped-metal, round ones? I had the latter and it eventually succombed
> to moisture.
>
> --
> Remove _'s *from email address to talk to me.- Hide quoted text -
>
> - Show quoted text -

Wrapped metal round antenna with a tear shaped base.

[RST Engineering]

Orval, you are chasing your tail. If it does it on BOTH radios, the
probability of a dual identical fault is practically zero, especially if the
noise on #1 correlates with the noise on #2.

Sure, go ahead and shotgun the thing and then come back in here lamenting
that you spent $X amus on the problem and it is still there.

I've never seen a "wrapped metal" com antenna in my career. Can you point
me to a manufacturer and model so I can see for myself. Most of what looks
like "wrapped metal" is in fact a fiberglass soda straw with either braid or
foil inside the straw.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"Orval Fairbairn" > wrote in message
...
> In article
> >,
> John > wrote:
>
>> On Aug 28, 4:55 pm, Orval Fairbairn >
>> wrote:
>> > In article
>> > >,
>> >
>> >
>> >
>> >
>> >
>> > John > wrote:
>> > > I flew yesterday with an owner who pointed out that he is getting a
>> > > type of crackling noise over both comm radios. The noise is most
>> > > prevalent when receiving from more distant and weaker transmitters
>> > > like other aircraft and not noticeabl when receiving from closer more
>> > > powerful transmitters i.e. the tower.
>> >
>> > > The owner has operated the aircraft with every other system turned
>> > > off
>> > > including the alternators and has operated on individual magnetos
>> > > with
>> > > no change. The most recent change to equipment was an audion panel
>> > > installation. The noise is not rythmic like ignition noise and does
>> > > not rise and fall with engine settings like some alternator noise. It
>> > > is not as intense as the white noise when checking squelch. It is a
>> > > type of random crackling like noise.
>> >
>> > > Any thoughts?
>> >
>> > > John Dupre'
>> >
>> > I had a similar problem years ago, with one of those cheap whip
>> > antennas. I switched to a high-quality antenna and got rid of the
>> > problem.
>> >
>> > It appears that moisture had somehow entered the material surrounding
>> > the metal antenna and was causing arcing.
>> >
>> > --
>> > Remove _'s from email address to talk to me.- Hide quoted text -
>> >
>> > - Show quoted text -
>>
>> I did notice that the upper antenna is loosing some of its coating and
>> the exposed areas look corroded. I would replace the antenna for that
>> reason alone but the owner wants some more confirmation than looks.
>> The lower antenna (bent whip) doesn't appear corroded although the
>> whip portion is slightly bent.
>>
>> John Dupre'
>
> That would do it on the upper antenna -- especially if it has flown
> through rain. Is the antenna airfoil-shaped or one of theose
> wrapped-metal, round ones? I had the latter and it eventually succombed
> to moisture.
>
> --
> Remove _'s from email address to talk to me.

[Orval Fairbairn[_2_]]

In article
>,
John > wrote:

> On Aug 29, 10:11*am, Orval Fairbairn >
> wrote:
> > In article
> > >,
> >
> >
> >
> >
> >
> > *John > wrote:
> > > On Aug 28, 4:55*pm, Orval Fairbairn >
> > > wrote:
> > > > In article
> > > > >,
> >
> > > > *John > wrote:
> > > > > I flew yesterday with an owner who pointed out that he is getting a
> > > > > type of crackling noise over both comm radios. *The noise is most
> > > > > prevalent when receiving from more distant and weaker transmitters
> > > > > like other aircraft and not noticeabl when receiving from closer more
> > > > > powerful transmitters i.e. the tower.
> >
> > > > > The owner has operated the aircraft with every other system turned off
> > > > > including the alternators and has operated on individual magnetos with
> > > > > no change. *The most recent change to equipment was an audion panel
> > > > > installation. *The noise is not rythmic like ignition noise and does
> > > > > not rise and fall with engine settings like some alternator noise. *It
> > > > > is not as intense as the white noise when checking squelch. *It is a
> > > > > type of random crackling like noise.
> >
> > > > > Any thoughts?
> >
> > > > > John Dupre'
> >
> > > > I had a similar problem years ago, with one of those cheap whip
> > > > antennas. I switched to a high-quality antenna and got rid of the
> > > > problem.
> >
> > > > It appears that moisture had somehow entered the material surrounding
> > > > the metal antenna and was causing arcing.
> >
> > > > --
> > > > Remove _'s *from email address to talk to me.- Hide quoted text -
> >
> > > > - Show quoted text -
> >
> > > I did notice that the upper antenna is loosing some of its coating and
> > > the exposed areas look corroded. *I would replace the antenna for that
> > > reason alone but the owner wants some more confirmation than looks.
> > > The lower antenna (bent whip) doesn't appear corroded although the
> > > whip portion is slightly bent.
> >
> > > John Dupre'
> >
> > That would do it on the upper antenna -- especially if it has flown
> > through rain. Is the antenna airfoil-shaped or one of theose
> > wrapped-metal, round ones? I had the latter and it eventually succombed
> > to moisture.
> >
> > --
> > Remove _'s *from email address to talk to me.- Hide quoted text -
> >
> > - Show quoted text -
>
> Wrapped metal round antenna with a tear shaped base.

Yup -- That's the kind that I replaced! Apparently, they last only so
long, then they get wet inside.

--
Remove _'s from email address to talk to me.

[Morgans[_2_]]

"RST Engineering" > wrote

> Orval, you are chasing your tail. If it does it on BOTH radios, the
> probability of a dual identical fault is practically zero, especially if
> the noise on #1 correlates with the noise on #2.
>
> Sure, go ahead and shotgun the thing and then come back in here lamenting
> that you spent $X amus on the problem and it is still there.

I'm with you, on this point.

Do you have any ideas on what possible things to look at (to trouble-shoot
it) to figure out what the real problem is, yet?
--
Jim in NC

[RST Engineering]

Sure. Does it do it with just the master switch on, sitting on the ground,
engine off. Engine on and idle. Engine on taxiing. Engine on runup.
Engine on takeoff roll. Engine on climbout...

What is the LEAST active thing the airplane is doing when it starts. Does
it always happen, say, ten minutes into the flight? Or does it do it on the
ground in the same ten minutes? Does it start in the air and continue after
landing?

An hour's logical troubleshooting can save dozens of hours shotgunning the
problem.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"Morgans" > wrote in message
...
>
> "RST Engineering" > wrote
>
>> Orval, you are chasing your tail. If it does it on BOTH radios, the
>> probability of a dual identical fault is practically zero, especially if
>> the noise on #1 correlates with the noise on #2.
>>
>> Sure, go ahead and shotgun the thing and then come back in here lamenting
>> that you spent $X amus on the problem and it is still there.
>
> I'm with you, on this point.
>
> Do you have any ideas on what possible things to look at (to trouble-shoot
> it) to figure out what the real problem is, yet?
> --
> Jim in NC
>

[David Lesher]

"RST Engineering" > writes:

>Orval, you are chasing your tail. If it does it on BOTH radios, the
>probability of a dual identical fault is practically zero, especially if the
>noise on #1 correlates with the noise on #2.



Do the two radios have separate antennas, or do they share a single point
of failure?


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[Peter Clark]

Wouldn't taking a meter to the coax where it attaches to the radio
tray tell whether the cable and/or antenna has a problem?

On Sat, 30 Aug 2008 08:22:33 -0700, "RST Engineering"
> wrote:

>Sure. Does it do it with just the master switch on, sitting on the ground,
>engine off. Engine on and idle. Engine on taxiing. Engine on runup.
>Engine on takeoff roll. Engine on climbout...
>
>What is the LEAST active thing the airplane is doing when it starts. Does
>it always happen, say, ten minutes into the flight? Or does it do it on the
>ground in the same ten minutes? Does it start in the air and continue after
>landing?
>
>An hour's logical troubleshooting can save dozens of hours shotgunning the
>problem.
>
>Jim

[RST Engineering]

Have you ever seen two com radios sharing a single antenna? Tell me how you
do it without the transmitter of #1 blowing up the receiver of #2. Unless
you are talking about dual Genave A-200s/Escort 110s and the ilk that used
two antenna inputs, one for the transmitter and one for the receiver.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"David Lesher" > wrote in message
...
> "RST Engineering" > writes:
>
>
> Do the two radios have separate antennas, or do they share a single point
> of failure?
>
>
> --
> A host is a host from coast to
> & no one will talk to a host that's close........[v].(301) 56-LINUX
> Unless the host (that isn't close).........................pob 1433
> is busy, hung or dead....................................20915-1433

[RST Engineering]

The odds of finding the problem that way lie somewhere between the odds of
winning an argument with an umpire and an argument with your wife.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"Peter Clark" > wrote in message
...

> Wouldn't taking a meter to the coax where it attaches to the radio
> tray tell whether the cable and/or antenna has a problem?

[john smith]

In article >,
"RST Engineering" > wrote:

> The odds of finding the problem that way lie somewhere between the odds of
> winning an argument with an umpire and an argument with your wife.

I'll take my chances with the umpire.

[David Lesher]

"RST Engineering" > writes:

>Have you ever seen two com radios sharing a single antenna? Tell me how you
>do it without the transmitter of #1 blowing up the receiver of #2. Unless
>you are talking about dual Genave A-200s/Escort 110s and the ilk that used
>two antenna inputs, one for the transmitter and one for the receiver.

I thought Nav antennas were typically shared. I mention this because I
have seen non-aircraft multi-antenna multi-front-end receivers where
weirdness on one antenna appeared to be on the other.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[Mike[_22_]]

"David Lesher" > wrote in message
...
> "RST Engineering" > writes:
>
>>Have you ever seen two com radios sharing a single antenna? Tell me how
>>you
>>do it without the transmitter of #1 blowing up the receiver of #2. Unless
>>you are talking about dual Genave A-200s/Escort 110s and the ilk that used
>>two antenna inputs, one for the transmitter and one for the receiver.
>
> I thought Nav antennas were typically shared. I mention this because I
> have seen non-aircraft multi-antenna multi-front-end receivers where
> weirdness on one antenna appeared to be on the other.

A Nav only antenna doesn't transmit, which is why they can be shared easily.
It's possible to share comm antennas, but you need either a transmit switch
or duplexer of some type to protect the receiver.

[RST Engineering]

First of all, the OP said it was his COM radio that was affected; NAV wasn't
mentioned.

Second, to use the correct terms, Nav antennas are isolated in a splitter
where a defect in one radio does not affect the other. Google "Wilkinson
splitter" for a technical description. "Shared" doesn't convey the full
effect of what has to happen; that implies that you just run both radios to
a single antenna without any isolation device in the path.

Jim

--
"It is the mark of an educated mind to be able to entertain a thought
without accepting it."
--Aristotle


"David Lesher" > wrote in message
...
>
> I thought Nav antennas were typically shared. I mention this because I
> have seen non-aircraft multi-antenna multi-front-end receivers where
> weirdness on one antenna appeared to be on the other.
>
> --
> A host is a host from coast to
> & no one will talk to a host that's close........[v].(301) 56-LINUX
> Unless the host (that isn't close).........................pob 1433
> is busy, hung or dead....................................20915-1433

[RST Engineering]

Yup, and typically you shut one transceiver off (in the RF sense) and
connect the antenna directly to the other transceiver with a switch. Both
this technique and the duplexer are rather difficult to achieve when you are
talking ten watt transceivers being isolated in a small device from a
microvolt receiver. For years hams have used coaxial switches to switch
antennas between HF rigs, but doing it at VHF presents its own set of
technical problems. Google Dow-Key to see the moosieness (?) of a coax
switch.

Jim


>
> A Nav only antenna doesn't transmit, which is why they can be shared
> easily. It's possible to share comm antennas, but you need either a
> transmit switch or duplexer of some type to protect the receiver.

[Mike[_22_]]

"RST Engineering" > wrote in message
m...
> Yup, and typically you shut one transceiver off (in the RF sense) and
> connect the antenna directly to the other transceiver with a switch. Both
> this technique and the duplexer are rather difficult to achieve when you
> are talking ten watt transceivers being isolated in a small device from a
> microvolt receiver. For years hams have used coaxial switches to switch
> antennas between HF rigs, but doing it at VHF presents its own set of
> technical problems. Google Dow-Key to see the moosieness (?) of a coax
> switch.

The FAA does it on the other end on the same frequencies. The actual device
that does it is not very large either. It's about 2-3" square and about an
inch tall. I've never seen it on an airborne application, but that's not to
say it isn't practical or even that it hasn't been done. Personally I
wouldn't want it as it just gives you another few single points of failure.
I'd rather have two antennas and two sets of cables.

[David Lesher]

"Mike" > writes:

>I'd rather have two antennas and two sets of cables.


Agreed, especilly for a hand-held. Add an antenna for it, period.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

[Morgans[_2_]]

"RST Engineering" > wrote

> Google Dow-Key to see the moosieness (?) of a coax switch.

I see all kind of neat products there, but I still don't understand what you
are getting at, as far as moosieness (whatever that term is or implies) and
its relation to a coax switch.

I know I shudder every time I contemplate having to make up a well and
properly shielded connection. I would assume that is the direction you are
going, with trying to keep the correct clearances between the conductor and
the shield, with all of the components in a switch, and still be well
shielded.

Or not? <g>
--
Jim in NC