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nuckolls.bob(at)aeroelect
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 Posted: Tue Nov 23, 2010 9:23 am Post subject: Noises in transmitted signals |
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At 09:18 AM 11/23/2010, you wrote:
G`day Bob
I am wondering if you could help me with connecting my radio. I
have replaced an older Terra 960 navcom and PM 3000 intercom with
a new ICOM A210. I just used the original wiring to the PTT and
mic/headphone sockets. I eliminated the PM3000 intercom and am just
using the "built-in" intercom in the A210. None of these wires are shielded.
I have been using this setup for the past couple of months but the tower
tells me my readability is usually 3 with quite a bit of background noise.
I have a KitFox with a Rotax 912UL (80HP). I am using just one
coax lead from the original RAMI AV-534 VHF Antenna 118-136 MHz.
The other lead is just taped up.
I now want to make up a new harness and hopefully improve
readability/background noise.
You're struggling with the same problem that
tens of thousands of technicians have faced since
DeForest lit up his first audion.
The term "background noise" is indeterminate.
It could be ignition, wind noise, alternator
noise coming in through the bus, noise from
another accessory getting into signal pathways
(ground loops), etc.
EACH of these noise sources has its own peculiar
characteristic that the moderately experienced
technician will recognize IF he heard it . . . but
tower operators are not generally noteworthy
for their technical acumen nor are they expected
to be.
On many occasions, I've been amazed at a tower
operator's ability to get intelligence from some
of the worst sounding radios. I'm similarly
amazed at their patience when working with an
airplane plagued with trashy signals.
When is this noise noted? Are you in flight? On the
ground? Engine running?
Get a friend to help you. Have them sit in
the cockpit and give you the 1,2,3,4 routine
on a locally unused frequency while you stand
off with a hand held (ear phones on it if
you can) so YOU can listen to YOUR radio and
described what you hear. You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
Not only do you need to know the character of
the noise but the conditions under which it
occurs. After you get an auditory sample, describe
the nature of the noise and the conditions under
which it does or does not happen.
1. I was planning on using 22ga. shielded for all wiring.
I've never fixed a noise problem by adding shielded
wires to a harness that were not already in
place and in accordance with the manufacturer's
wiring diagrams.
2. Reinstalling the PM3000 intercom
Depends on what kind of noise and how it's
getting in . . . I wouldn't discount this idea
to zero . . . but it's quite low and probably
not necessary.
3. Possibly bringing the radio power feed with a
dedicated wire directly back to the battery. Would
this help with the noise issue??? Just my own idea!!
I'm a bit short tempered with folks who put
out products for airplanes and then suggest that
THEIR product performs "best" when wired directly
to the ship's battery. Either they did their
homework and the device can be installed like
everybody else's products . . . or they are
admitting a combination of ignorance or hiding
a known shortcoming in the product's design.
The Icom products do not suffer from the effects
of this human shortcoming . . . so no, you don't
need to move the power supply wires. We MIGHT
need to fix a noise source that comes in on those
wires but that's part of the investigation/
identification task described above.
Some years ago I published a diagram for hooking
a tape recorder to the output of a hand held so
that folks could record their own signals
single-handed. Nowadays, this probably needs
to be some sort of connection to an MP3 player
with dictation features.
You can set the hand held out away from the
airplane and rubber-band a dictation machine
to the speaker grille. In any case, THAT is
where you start before you chopping out any
wires.
Bob . . .
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rjquillin(at)cox.net
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| Posted: Tue Nov 23, 2010 9:37 am Post subject: Noises in transmitted signals |
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At 09:19 11/23/2010, you wrote:
| Quote: | You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
|
Would this be advisable if one also wished to transmit and talk to the operator in the aircraft?
I'm thinking not a good idea, except for receive only...
Ron Q. [quote][b]
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VIXEN
Joined: 23 Nov 2009
Posts: 35
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| Posted: Tue Nov 23, 2010 11:56 am Post subject: Noises in transmitted signals |
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Thanks for the reply Bob.
Sorry about the "background" noise description. This noise is not there when the engine is shut down. It is there when when the engine is running. Seems to get more noticeable as engine RPM increases. It makes no difference if A/C is stationary, taxiing,or flying.
I ran the old radio on a separate wheel-chair battery for a few flights and it seemed to be much better. I have not tried it with this one.
1. The original Terra 960 also had the same issues. My thinking was that by rewiring with shielded wire (according to the ICOM diagram) would help!!
2. Also. would the PM3000 not be a better intercom than the" built in" in the ICOM?? Isn`t shielded wire going to just generally going to improve the situation??
I will experiment with listening on the portable as soon as it warms up a bit. We are experiencing an unusual cold spell today and tomorrow (-12C) this morning!!!!
Cheers
Don
On Tue, Nov 23, 2010 at 9:19 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
At 09:18 AM 11/23/2010, you wrote:
G`day Bob
I am wondering if you could help me with connecting my radio. I
have replaced an older Terra 960 navcom and PM 3000 intercom with
a new ICOM A210. I just used the original wiring to the PTT and
mic/headphone sockets. I eliminated the PM3000 intercom and am just
using the "built-in" intercom in the A210. None of these wires are shielded.
I have been using this setup for the past couple of months but the tower
tells me my readability is usually 3 with quite a bit of background noise.
I have a KitFox with a Rotax 912UL (80HP). I am using just one
coax lead from the original RAMI AV-534 VHF Antenna 118-136 MHz.
The other lead is just taped up.
I now want to make up a new harness and hopefully improve readability/background noise.
You're struggling with the same problem that
tens of thousands of technicians have faced since
DeForest lit up his first audion.
The term "background noise" is indeterminate.
It could be ignition, wind noise, alternator
noise coming in through the bus, noise from
another accessory getting into signal pathways
(ground loops), etc.
EACH of these noise sources has its own peculiar
characteristic that the moderately experienced
technician will recognize IF he heard it . . . but
tower operators are not generally noteworthy
for their technical acumen nor are they expected
to be.
On many occasions, I've been amazed at a tower
operator's ability to get intelligence from some
of the worst sounding radios. I'm similarly
amazed at their patience when working with an
airplane plagued with trashy signals.
When is this noise noted? Are you in flight? On the
ground? Engine running?
Get a friend to help you. Have them sit in
the cockpit and give you the 1,2,3,4 routine
on a locally unused frequency while you stand
off with a hand held (ear phones on it if
you can) so YOU can listen to YOUR radio and
described what you hear. You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
Not only do you need to know the character of
the noise but the conditions under which it
occurs. After you get an auditory sample, describe
the nature of the noise and the conditions under
which it does or does not happen.
1. I was planning on using 22ga. shielded for all wiring.
I've never fixed a noise problem by adding shielded
wires to a harness that were not already in
place and in accordance with the manufacturer's
wiring diagrams.
2. Reinstalling the PM3000 intercom
Depends on what kind of noise and how it's
getting in . . . I wouldn't discount this idea
to zero . . . but it's quite low and probably
not necessary.
3. Possibly bringing the radio power feed with a
dedicated wire directly back to the battery. Would
this help with the noise issue??? Just my own idea!!
I'm a bit short tempered with folks who put
out products for airplanes and then suggest that
THEIR product performs "best" when wired directly
to the ship's battery. Either they did their
homework and the device can be installed like
everybody else's products . . . or they are
admitting a combination of ignorance or hiding
a known shortcoming in the product's design.
The Icom products do not suffer from the effects
of this human shortcoming . . . so no, you don't
need to move the power supply wires. We MIGHT
need to fix a noise source that comes in on those
wires but that's part of the investigation/
identification task described above.
Some years ago I published a diagram for hooking
a tape recorder to the output of a hand held so
that folks could record their own signals
single-handed. Nowadays, this probably needs
to be some sort of connection to an MP3 player
with dictation features.
You can set the hand held out away from the
airplane and rubber-band a dictation machine
to the speaker grille. In any case, THAT is
where you start before you chopping out any
wires.
Bob . . .
===========
om" target="_blank">www.aeroelectric.com
ooks.com" target="_blank">www.buildersbooks.com
et="_blank">www.homebuilthelp.com
="_blank">http://www.matronics.com/contribution
le, List Admin.
===========
-List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
===========
http://forums.matronics.com
===========
[b]
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VIXEN
Joined: 23 Nov 2009
Posts: 35
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| Posted: Tue Nov 23, 2010 12:04 pm Post subject: Noises in transmitted signals |
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On Tue, Nov 23, 2010 at 9:32 AM, Ron Quillin <rjquillin(at)cox.net (rjquillin(at)cox.net)> wrote:
[quote] At 09:19 11/23/2010, you wrote:
| Quote: | You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
|
Would this be advisable if one also wished to transmit and talk to the operator in the aircraft?
I'm thinking not a good idea, except for receive only...
Ron Q. | Quote: |
_blank">www.aeroelectric.com
.com" target="_blank">www.buildersbooks.com
="_blank">www.homebuilthelp.com
_blank">http://www.matronics.com/contribution
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
tp://forums.matronics.com
|
[b]
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Tue Nov 23, 2010 1:46 pm Post subject: Noises in transmitted signals |
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Ron: Removing the rubber duck antenna reflects close to 100% of the power out of the final RF tr5ansistors back on themselves... To the radio it is equivalent to leaning into a left hook.
Never try using a radio without the appropriate load on it.
If you want to try this you can wire a light bulb of sufficient wattage across the antenna terminals. Don’5t be surprised if the light bulb glows when the PTT is keyed.
Noel
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Ron Quillin
Sent: November 23, 2010 2:02 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: Noises in transmitted signals
At 09:19 11/23/2010, you wrote:
You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
Would this be advisable if one also wished to transmit and talk to the operator in the aircraft?
I'm thinking not a good idea, except for receive only...
Ron Q. 01234567890123456
[quote][b]
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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rjquillin(at)cox.net
Guest
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| Posted: Tue Nov 23, 2010 2:16 pm Post subject: Noises in transmitted signals |
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At 13:38 11/23/2010, you wrote:
| Quote: | Ron: Removing the rubber duck antenna reflects close to 100% of the power out of the final RF tr5ansistors back on themselves... To the radio it is equivalent to leaning into a left hook.
Never try using a radio without the appropriate load on it. |
Precisely, that was the point of my post.
Don't fry your RF output stage.
Bob's comment suggested removal of the antenna.
OK for RX only, bad juju for XMIT.
[quote]
If you want to try this you can wire a light bulb of sufficient wattage across the antenna terminals. Don’5t be surprised if the light bulb glows when the PTT is keyed.
Noel
From: owner-aeroelectric-list-server(at)matronics.com [ mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)] On Behalf Of Ron Quillin
Sent: November 23, 2010 2:02 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: Noises in transmitted signals
At 09:19 11/23/2010, you wrote:
You might take the
rubber duck off the hand held so that you can
stand say 50 feet away but not overload the hand
held receiver.
Would this be advisable if one also wished to transmit and talk to the operator in the aircraft?
I'm thinking not a good idea, except for receive only...
Ron Q.
[b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Nov 23, 2010 2:49 pm Post subject: Noises in transmitted signals |
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| Quote: | Would this be advisable if one also wished to transmit and talk to the operator in the aircraft?
I'm thinking not a good idea, except for receive only... |
Correct . . . there is some risk to transmitting on
an unloaded transmitter . . . but not much. All the
panel mounted radios built by the 'big guys' are
protected against infinite SWR. Hand helds are still
more at risk for situations where the antenna is in
close proximity to conductive objects, wrong antenna
installed or simply left disconnected. I haven't
heard of a disconnected-antenna-meltdown in years.
When the first solid state radios came out, it WAS
a major concern.
Aha! Here's a chance to plug a AEC DIY project one
can do in a few minutes on the workbench after a
trip to Radio Shack.
http://aeroelectric.com/Pictures/Tools/RF_Antenna_Test_Tools/DummyLoad.jpg
Stick one of these on the antenna jack for the test
hand-held and all will be right with the world even
if you decide to transmit.
Bob . . . [quote][b]
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N20DG
Joined: 02 Jan 2008
Posts: 61
Location: lancaster, texas
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| Posted: Tue Nov 23, 2010 4:18 pm Post subject: Noises in transmitted signals |
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Back in the '50's we called that a dummy load for testing the rig
D
In a message dated 11/23/2010 3:48:46 P.M. Central Standard Time, noelloveys(at)yahoo.ca writes:
| Quote: |
If you want to try this you can wire a light bulb of sufficient wattage across the antenna terminals. Don’5t be surprised if the light bulb glows when the PTT is keyed. |
[quote][b]
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Wed Nov 24, 2010 4:44 pm Post subject: Noises in transmitted signals |
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Hams ( amateur operators ) still do!
Noel
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of RGent1224(at)aol.com
Sent: November 23, 2010 8:45 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: Noises in transmitted signals
Back in the '50's we called that a dummy load for testing the rig
D
In a message dated 11/23/2010 3:48:46 P.M. Central Standard Time, noelloveys(at)yahoo.ca writes:
| Quote: |
If you want to try this you can wire a light bulb of sufficient wattage across the antenna terminals. Don’5t be surprised if the light bulb glows when the PTT is keyed. |
01234567890123456
[quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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