Becker AR-4201 Design Fault?

Has anyone else who uses a Becker AR-4201 radio experienced background noise only on 123.5 MHz?

I thought there was interference being generated in my geographic area or in my plane, but I’ve now heard noise on 123.5 in 3 different gliders using 3 different AR-4201s. A friend using a Dittel FSG71M experienced no noise at all last weekend for 3 hours when I was getting background noise, which is when I knew I had a problem.

I can raise the squelch to eliminate the noise on 123.5, but then all other frequencies have less sensitivity, so that’s not a solution.

-John, Q3

What other equipment are you running? I have seen the Cambridge model-20 GPS running the SN-10 generate enough noise to break squelch on just one frequency. Fix was to move antenna lead as far away from offending equipment as possible.
JJ

Hi, JJ,

On the ground I can turn everything off except the radio and get the noise. This has been the case for all 3 gliders. The noise doesn’t sound like the usual squelch static, it’s more like a heavy diesel engine at idle but varying over a couple of hundred rpms over a 5 to 10 second period. I’ve duplicated it using a test harness in my home electronic shop. That’s why I think the source of the noise lies in the Becker AR4201 design.

-John, Q3


On Saturday, July 9, 2016 at 8:04:41 PM UTC-4, wrote:
What other equipment are you running? I have seen the Cambridge model-20 GPS running the SN-10 generate enough noise to break squelch on just one frequency. Fix was to move antenna lead as far away from offending equipment as possible.
JJ

That is weird.......but I doubt it is in the radio because it only happens on 123.5. Bet you have something on that freq or a harmonic of 123.5. I remember hearing music on 123.3 in the California Central Valley, but only in certain areas. I remember flying my primitive RC model on 27 Meg's, near the base comm center. I was transmitting a series of beeps ( one beep for left, two beeps for right, when an airman came running out of the comm center shouting I was all over 243 emergency freq. I didn't believe it, so he invited me to come in and listen........ Sure enough, I was loud and clear on 243 which is the ninth harmonic of 27 Meg's)
Good luck,
JJ

John - I've seen fluorescent lights in my workshop cause static on specific frequencies. Check if turning the lights off (both in & nearby) makes the problem go away.

--Noel

On Saturday, July 9, 2016 at 3:01:31 PM UTC-6, John Carlyle wrote:
Has anyone else who uses a Becker AR-4201 radio experienced background noise only on 123.5 MHz?

I thought there was interference being generated in my geographic area or in my plane, but I’ve now heard noise on 123.5 in 3 different gliders using 3 different AR-4201s. A friend using a Dittel FSG71M experienced no noise at all last weekend for 3 hours when I was getting background noise, which is when I knew I had a problem.

I can raise the squelch to eliminate the noise on 123.5, but then all other frequencies have less sensitivity, so that’s not a solution.

-John, Q3

Happened to me this weekend at Moriarty.

I flew for several years with Becker/C302/Oudie/transponder with no radio issues. Upgraded to S80 and had significant feedback/noise on 123.5. We started placing magnets around various connecting wires/cables. The noise moved to 123.3 on one combination. With moving the magnets from the center of the connecting cables to the ends we eliminated all the radio noise/feedback.

On 7/9/2016 5:01 PM, John Carlyle wrote:
Has anyone else who uses a Becker AR-4201 radio experienced background noise only on 123.5 MHz?

I thought there was interference being generated in my geographic area or in my plane, but I’ve
now heard noise on 123.5 in 3 different gliders using 3 different
AR-4201s. A friend using a Dittel
FSG71M experienced no noise at all last weekend for 3 hours when I was
getting background noise, which is when I knew I had a problem.

I can raise the squelch to eliminate the noise on 123.5, but then all other frequencies have less sensitivity, so that’s not a solution.

-John, Q3

Assuming that you have eliminated all possibility of interference from
external sources, and supported by your evidence of seeing the same
behavior on three other radios of the same model, I would guess that the
problem is a frequency synthesizer "birdie". Which is indeed a design
problem.

Google will give you a few references if search "frequency synthesizer
birdie", including this one: http://tinyurl.com/radiobirdie

But now I feel like the doctor who names your malady but offers no help
for it. Your only shot is to go back to the manufacturer. They may be
able to tweak your radio to get rid of it.

Vaughn

I will "assume" you mean ferrites (which can kill/control outside electrical noise). They come in different sizes and shapes, "solid" or split (split makes it easier to add to existing wire runs).
An EE can comment, but I also believe they are sized/shaped depending on the frequency you're trying to kill.

Ferrite.
That was the word I was searching for.
They solved the problem but it took a significant amount of trials to solve the noise. The problem has stayed fixed for many months.