BCD396T Audio clipping on AM aircraft?

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Hi, Anybody else have this problem? I have audio clipping with momentary drop in the S-meter during peak audio transients that are even slightly loud or overmodulated. The scanner will mute syllables and sometimes entire words. It occurs more on ATC transmissions than pilot transmissions. Some ATIS recordings such as the Van Nuys Airport ATIS sounds completely chopped up. I have searched everywhere for a solution.

Any suggestions? Settings? Please help?

Great scanner otherwise, thanks Uniden!

 

[Dubbin]

You don't happen to have close call, a priority or weather alert turned on do you?

 

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nope, none of those is on, it only occurs during the audio peaks on certain loud controllers are talking. Thanks for the input though.

 

[nd5y]

I get that occasionally on mine. It is due to the transmitter being overmodulated. There is nothing you can do about it.

 

[KD4UXQ]

Probably the receiver is saturated

The indication that the signal strength meter drops and the audio is sometimes muted along with the distortion indicates that the receiver front end is being saturated or overloaded by the received signal. The signal overload essentially shuts down the front end of the receiver when too strong. And the fact that aircraft which are often farther away and also have a lower ERP than the air field operations transmitters do not give you problems, reinforces the assumption.

I am guessing you are right under the transmitter sight or using some type of external antenna with gain over the supplied antenna because I use my 396 to monitor our Control Tower in the 235th ATC in New London NC and I don't have as much of the problem, but if I am very close to the transmitter sight the audio is distorted and sounds like receiver saturation to me even with the supplied antenna. Your description certainly sounds like receiver saturation. Try reducing signal gain in your antenna system or using the attenuator in the radio. In fact if it is receiver saturation the attenuator should correct it, but it will also reduce your reception ability of aircraft farther away.

 

[k5xs]

Amen

It sounds to me like receiver overload. Try attenuating the signal.

Let us know if that helps!

 

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It sounds to me like receiver overload. Try attenuating the signal.

Let us know if that helps!

Yes, you guys are on to something, thanks, the clipping DOES occur when I am near the airport, and yea it does follow the symptoms of front end overload. I did try the attenuator, that didn't help, I am using an external antenna on the car. I will try the rubber duck tomorrow, when I drive near the airport, and see what happens.

 

[ka3jjz]

You might also try adjusting the analog AGC settings. I've noted no real issues with clipping, and I have numerous air freqs in my 396. These settings are available when in the hidden menu mode in version 2.0x firmware, and in version 3.0x, you don't need to get into hidden menu mode to access them.

73 Mike

 

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Problem solved. I tried the rubber duck on my drive yesterday, that didn't work, just made the signals very weak, but clipping continued. Then it hit me, check the dang SQUELCH! :roll: It was at 7, reducing SQUELCH to 3 did the trick, clipping stopped. Interesting, since most radios squelch does nothing on strong signals, so I didn't even associate it at first. The s-meter dropping and clipping at peaks threw me off too. I'm relieved it was an easy fix, and nothing was broken. Thanks for your input guys!