Becker AR-4201 Design Fault?

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

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

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?

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?

Nice trouble shooting.

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

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

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

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

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