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scc_ron(at)yahoo.com
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 Posted: Tue Apr 15, 2008 5:21 am Post subject: Broken reception on my COMM |
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My Comm works fine except when I receive a stronger signal from the local tower. then the received transmission is broken and I can only hear about 1/2 the instructions. Any ideas what may be causing this?
Ron
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nuckolls.bob(at)cox.net
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| Posted: Tue Apr 15, 2008 5:50 am Post subject: Broken reception on my COMM |
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At 06:17 AM 4/15/2008 -0700, you wrote:
| Quote: | My Comm works fine except when I receive a stronger signal from the local
tower. then the received transmission is broken and I can only hear about
1/2 the instructions. Any ideas what may be causing this?
Ron
|
I presume that communication with the tower while
airborne is not a problem and that you've identified
signal strength as the apparent variable. Your receiver
may be suffering from an overload condition that's beyond
its ability to accommodate.
A receiver designer's sorta wet dream is to have the
squelch break at around 0.2 microvolts signal and produce a
readable if somewhat noisy output at 0.5 microvolts
at the antenna. When I was working in the two-way radio
business these were the benchmarks for refurbishing
and aligning a receiver.
A device with this performance level may be hard pressed
to also accept and demodulate a signal of hundreds of
microvolts. The automatic gain system within the receiver
may not have sufficient dynamic range to handle the larger
signal in close proximity to a ground based (read high power)
transmitter.
Do you carry a hand held? Perhaps ground ops is an excellent
time to pre-flight this very useful back up. This may not
be an automatic solution . . . hand helds tend to be a cut
or two below panel mounted or base station receivers and
it may be similarly afflicted with the effects of strong
signal overload . . . but it's the simplest solution and
worth trying.
If push comes to shove, you can install the formation
flying attenuator described at:
http://www.aeroelectric.com/articles/Attenuator/Formation_Flying_Attenuator_2.pdf
See also pictures at:
http://www.aeroelectric.com/articles/Attenuator/
Note that this particular design is capable of handling
the output of a 2 watt transmitter continuously. It's
fine for transmitters of 4-6 watt range but don't carry
on long winded conversations.
With this switch in the "attenuate" position, both your
incoming and outgoing signals are considerably reduced
to avoid overloading the receiver in your cockpit and
in the other aircraft's cockpit. The ground station will
have no problem hearing you either.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
| | - 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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MartinErni(at)aol.com
Guest
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| Posted: Tue Apr 15, 2008 6:05 am Post subject: Broken reception on my COMM |
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Jerry,
Read about this problem and Bob's reply. Does it sound familiar? May be this will give us a fix.
E
In a message dated 4/15/2008 9:52:13 A.M. Eastern Daylight Time, nuckolls.bob(at)cox.net writes:
| Quote: | --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)cox.net>
At 06:17 AM 4/15/2008 -0700, you wrote:
| Quote: | My Comm works fine except when I receive a stronger signal from the local
tower. then the received transmission is broken and I can only hear about
1/2 the instructions. Any ideas what may be causing this?
Ron
|
I presume that communication with the tower while
airborne is not a problem and that you've identified
signal strength as the apparent variable. Your receiver
may be suffering from an overload condition that's beyond
its ability to accommodate.
A receiver designer's sorta wet dream is to have the
squelch break at around 0.2 microvolts signal and produce a
readable if somewhat noisy output at 0.5 microvolts
at the antenna. When I was working in the two-way radio
business these were the benchmarks for refurbishing
and aligning a receiver.
A device with this performance level may be hard pressed
to also accept and demodulate a signal of hundreds of
microvolts. The automatic gain system within the receiver
may not have sufficient dynamic range to handle the larger
signal in close proximity to a ground based (read high power)
transmitter.
Do you carry a hand held? Perhaps ground ops is an excellent
time to pre-flight this very useful back up. This may not
be an automatic solution . . . hand helds tend to be a cut
or two below panel mounted or base station receivers and
it may be similarly afflicted with the effects of strong
signal overload . . . but it's the simplest solution and
worth trying.
If push comes to shove, you can install the formation
flying attenuator described at:
http://www.aeroelectric.com/articles/Attenuator/Formation_Flying_Attenuator_2.pdf
See also pictures at:
http://www.aeroelectric.com/articles/Attenuator/
Note that this particular design is capable of handling
the output of a 2 watt transmitter continuously. It's
fine for transmitters of 4-6 watt range but don't carry
on long winded conversations.
With this switch in the "attenuate" position, both your
incoming and outgoing signals are considerably reduced
to avoid overloading the receiver in your cockpit and
in the other aircraft's cockpit. The ground station will
have no problem hearing you either.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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[quote][b]
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