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Curious what would cause KWAV 96.9 stereo pilot to fail / oscillate like this?

pclover

pclover

Perhaps people have seen this behavior before. Curious what would cause a stereo pilot to oscillate like this?

No, It's not a SDR failure because no other station and only this station has issues on all my radios.

They've had stereo problems for several months but seem in no hurry to fix it. No reply to emails.

Right now it's really bad and radios keep dropping in out of stereo. On several of my radios there stereo light will keep flipping on and off. Kind of odd given it's a flagship station for this area.

streamable.com

Watch SDR Console, 97.250 MHz, 2025-06-23 12h07m08s | Streamable

Watch "SDR Console, 97.250 MHz, 2025-06-23 12h07m08s" on Streamable.
streamable.com
 
pclover said:
Perhaps people have seen this behavior before. Curious what would cause a stereo pilot to oscillate like this?
Click to expand...
By definition stereo pilots oscillate. That's the nature of sine waves.

Assuming the capture you took is accurate and not the product of a receive phenomenon, there could be a circuitry failure in the stereo generator (which is usually within the audio processor). Without knowing what equipment they have, it's hard to be more precise than that.

One possibility would be a dry capacitor, which could allow the audio to mix with the stereo pilot by leaking some amount of signal through the power subsystem of the stereo generator.

For many station owners, engineering problems aren't problems until they create an off-air emergency.
 
I had this happen at my station. It happens when both your transmitter and audio processor generate 19 kHz pilot and you are seeing two pilot signals beating against each other producing that slow up and down level oscillation due to slight frequency difference between them. Basically it's a configuration mistake.
 
Last edited:
Yes, a common problem which I see frequently. There should only ever be one pilot active and it must be the one from the in use stereo encoder which is usually in the audio processor. Most likely the unwanted pilot is coming from the exciter which could be selected to stereo mode instead of MPX/composite. Having two pilots active will look like the pilot phase is changing to the receiver which has odd affects on the stereo image such as the image sweeping from one side to the other.

You can have a similar problem with RDS/RBDS.
 
I’m not too familiar with the engineering part, but I’ve seen some stations stereo light turn off when they play mono content. I think it’s called “auto pilot”. I believe it’s supposed to help with reception in fringe areas. But if the stereo light is blinking when stereo content is playing, there must be a problem.
 
My aunt who lives in the Santa Cruz area gets 2 stations on 96.9, the other station being KEPT from Hayward. Think their transmitter is near Niles causing the signal to hit into Santa Cruz.
 


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