Becker AR-4201 Design Fault?

[John Carlyle]

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

[[email protected]]

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

[John Carlyle]

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

[[email protected]]

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

[noel.wade]

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

[SkyHiCO]

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.

[[email protected]]

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.

[Vaughn Simon[_2_]]

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

[Charlie M. (UH & 002 owner/pilot)]

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.

[[email protected]]

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.

[2G]

On Monday, July 11, 2016 at 4:11:33 PM UTC-7, wrote:
> 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.

You can put a 50 ohm terminator on your antenna input to the radio and see if the noise stops. If it does you are probably receiving it from an external source. If it doesn't it MAY be generated internally, or it may be conducted from an external source thru the power leads. You can isolate that by powering the radio from a separate power source than the rest of the glider..

Tom

[John Carlyle]

SkyHiCO, drguyacheson, Vaughn, 2G, thank you all for your input.

SkyHiCO, drguyacheson, I'm relieved to learn that I'm not alone. I wonder if there are more pilots having noise with AR4201 radios? Please post to this thread if you are getting noise on 123.5 MHz.

Vaughn, thanks for giving the problem a name. One of the Google hits I found says a birdie usually sounds "like unmodulated carriers -- signals with "dead air." Occasionally they are modulated by clicks, humming sounds, or audible tones." The humming sound fits what I hear.

Tom, your idea of disconnecting the antenna is nice. I know that the 123.5 MHz noise I hear is not coming through the power leads, since I hear it on a radio powered by a battery that feeds no other instruments.

-John, Q3

[[email protected]]

I want to opine that this noise issue is not a design fault of the radio. It is the result of all the various sources of signal radiation from all of our devices.
Perhaps, the issue is the overall design of connectors for our devices. Seems like they should all have shielded cables and connectors to prevent the radiation of electromagnetic signals.
Is that why the Butterfly systems have such special cable connectors?

[John Carlyle]

drguyacheson, in your case I think that's correct. In my case, it's not - I have connected an AR4201 to a battery, an antenna and a speaker and turned it on in the middle of my back yard, and I heard noise on 123.5 MHz. I never attempted to take this lash-up for a drive to sample different environments, because it replicated what I'd heard in the air in 3 different planes with 3 different AR4201 radios in widely spread geographic locations. I think Vaughn is correct - it's a birdie coming from the internal oscillator in the radio. That's why I'd like more AR4201 users to tune to 123.5 MHz and post if they hear noise.

-John, Q3

On Tuesday, July 12, 2016 at 9:46:36 AM UTC-4, wrote:
> I want to opine that this noise issue is not a design fault of the radio. It is the result of all the various sources of signal radiation from all of our devices.
> Perhaps, the issue is the overall design of connectors for our devices. Seems like they should all have shielded cables and connectors to prevent the radiation of electromagnetic signals.
> Is that why the Butterfly systems have such special cable connectors?

[[email protected]]

Nice trouble shooting.

[JS]

On Tuesday, July 12, 2016 at 6:56:14 AM UTC-7, John Carlyle wrote:
> drguyacheson, in your case I think that's correct. In my case, it's not - I have connected an AR4201 to a battery, an antenna and a speaker and turned it on in the middle of my back yard, and I heard noise on 123.5 MHz. I never attempted to take this lash-up for a drive to sample different environments, because it replicated what I'd heard in the air in 3 different planes with 3 different AR4201 radios in widely spread geographic locations. I think Vaughn is correct - it's a birdie coming from the internal oscillator in the radio. That's why I'd like more AR4201 users to tune to 123.5 MHz and post if they hear noise.
>
> -John, Q3
>
> On Tuesday, July 12, 2016 at 9:46:36 AM UTC-4, wrote:
> > I want to opine that this noise issue is not a design fault of the radio. It is the result of all the various sources of signal radiation from all of our devices.
> > Perhaps, the issue is the overall design of connectors for our devices. Seems like they should all have shielded cables and connectors to prevent the radiation of electromagnetic signals.
> > Is that why the Butterfly systems have such special cable connectors?

Only AR4201 123.5MHz oddness I can think of: No oscillation, but sounded like the squelch was turned off. No problem on other frequencies.
Jim

[[email protected]]

Did the noise go away when you disconnected the antenna? Didn't see the answer, sorry if this is repeditive.
JJ

[John Carlyle]

JJ, I haven't tried that experiment yet. Need to find a 50 ohm terminator and then get out to the airport where the glider is stored. I'll post the results.

-John, Q3

On Wednesday, July 13, 2016 at 9:46:03 AM UTC-4, wrote:
> Did the noise go away when you disconnected the antenna? Didn't see the answer, sorry if this is repeditive.
> JJ

[bumper[_4_]]

On Wednesday, July 13, 2016 at 7:03:39 AM UTC-7, John Carlyle wrote:
> JJ, I haven't tried that experiment yet. Need to find a 50 ohm terminator and then get out to the airport where the glider is stored. I'll post the results.


You wouldn't need a 50 ohm terminator (dummy load) if you don't transmit. You are only seeing if the interference is RF, coming into the radio via antenna or coax. Disconnecting the coax at the back of the radio should do. If that does eliminate the noise, then a hand held radio with squelch turned down might be useful in locating source.

If it does not eliminate the interference when powered from aircraft buss, turn other stuff off one by one to try to find guilty device. Install ferrites on wiring. If it's still present when powered up from a battery (no other devices turned on) then for sure it's internal.

LNAV would generate a lot of noise and break squelch on some frequencies. Ferrites on LNAV wiring solved problem for me. Best if there's enough wiring slack to go through the ferrite hole more than once - though once will often do.

bumper

[John Carlyle]

Well, I was wrong. The Becker AR4201 radio that’s in my current glider is not generating noise internally on 123.50 MHz. The noise is coming from a GPS in the glider.

In my first glider, I heard noise on 123.50 MHz from the AR4201. The noise was only on that frequency, though, and I sold that glider before I got around to tracking down the source of the noise.

In my second glider, when I heard noise again on 123.50 MHz from its AR4201, I removed the radio from the glider and connected it only to an antenna and a speaker. I heard noise on 123.50 MHz with the antenna disconnected, so I knew it had to be coming from inside the radio. Naturally I figured that the AR4201 had been the source of the noise I'd heard in my first glider, too.

In my third glider, when I also heard noise on 123.50 MHz from its AR4201, I pulled all the fuses except for the radio. The noise was still there, so I believed it was again inside the radio. Strike 3 against Becker? No. Crucially, I had not disconnected the antenna. Yesterday I did disconnect the antenna and surprise, surprise, there was no noise. I obviously goofed during my previous trouble shooting on this glider! But what was the problem?

While reconnecting the antenna, I noticed a green blinking LED on my Cambridge GPS 25. What the heck? It turned out some genius at the factory had wired the GPS 25 to power without going through the panel fuses! When I unplugged the power lead from the GPS 25, the radio became noise free on 123.50 MHz with the antenna connected. Time for ferrites on the GPS 25, and time to exonerate Becker...

Thanks to everyone who wrote in on this thread. I appreciate your helping me to find the source of my noise problem.

-John, Q3

[Charlie M. (UH & 002 owner/pilot)]

Glad you found the issue and resolved it (sorta).
Thanks for the follow-up, may help others down the road!

[[email protected]]

The way I like to trouble shoot a radio that is breaking squelch is to turn on only the radio with no squelch.......wide open, so that it gives all background noise. Then I turn on all other electrical equipment, one at a time. Think of it as filling a dam, noise from each unit adds to the overall water level. When the dam is full it spills over or breaks squelch. All equipment will add a little background noise, but some add tremendous amounts. The Cambridge GPS is about the worst offender I have run across. You can try moving the GPS as far away from radio antenna as possible, do this with radio on as you listen to the background noise in different positions. Best bet may be to get another GPS. Grounding everything to ships ground may help, shielding and ferrit's may also help.
Good luck,
JJ

[John Carlyle]

JJ, That's a good technique for finding noise generators, thanks for sharing. You know the glider, so you'll remember that the GPS is on the parcel shelf. That means the radio antenna cable and the GPS output run together for almost 10 feet. I was always going to replace the L-Nav and Gps-Nav, that may happen sooner now.

-John, Q3

On Friday, July 22, 2016 at 6:34:05 PM UTC-4, wrote:
> The way I like to trouble shoot a radio that is breaking squelch is to turn on only the radio with no squelch.......wide open, so that it gives all background noise. Then I turn on all other electrical equipment, one at a time. Think of it as filling a dam, noise from each unit adds to the overall water level. When the dam is full it spills over or breaks squelch. All equipment will add a little background noise, but some add tremendous amounts.. The Cambridge GPS is about the worst offender I have run across. You can try moving the GPS as far away from radio antenna as possible, do this with radio on as you listen to the background noise in different positions. Best bet may be to get another GPS. Grounding everything to ships ground may help, shielding and ferrit's may also help.
> Good luck,
> JJ

[2G]

On Friday, July 15, 2016 at 1:19:23 AM UTC-7, bumper wrote:
> On Wednesday, July 13, 2016 at 7:03:39 AM UTC-7, John Carlyle wrote:
> > JJ, I haven't tried that experiment yet. Need to find a 50 ohm terminator and then get out to the airport where the glider is stored. I'll post the results.
>
>
> You wouldn't need a 50 ohm terminator (dummy load) if you don't transmit. You are only seeing if the interference is RF, coming into the radio via antenna or coax. Disconnecting the coax at the back of the radio should do. If that does eliminate the noise, then a hand held radio with squelch turned down might be useful in locating source.
>
> If it does not eliminate the interference when powered from aircraft buss, turn other stuff off one by one to try to find guilty device. Install ferrites on wiring. If it's still present when powered up from a battery (no other devices turned on) then for sure it's internal.
>
> LNAV would generate a lot of noise and break squelch on some frequencies. Ferrites on LNAV wiring solved problem for me. Best if there's enough wiring slack to go through the ferrite hole more than once - though once will often do.
>
> bumper

The terminator is necessary to keep the radio from receiving anything on the antenna input. An unterminated input will function as a poor antenna. You can make a terminator with a BNC cable and a 50 ohm resistor soldered between the center conductor and the shield. Or you can buy one at:

http://www.trianglecables.com/product/BNC-Male-Terminator-5-Watt-50-Ohm.aspx?utm_source=google&utm_medium=merchant&utm_campaign=380&gclid=CjwKEAjwlZa9BRCw7cS66eTxlCkSJAC-ddmwv4-odgMLYxZKEAyfZoWJQnS2yBQKPfJFUbizjXWMCRoC5vrw_wcB

This is the only way to resolve the issue presented.

Tom