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KQRS RDBS Alternate Frequency Issue

donatj

donatj

My radio in my 2005 Chrysler Crossfire won't stay tuned to KQRS, and keeps tuning to NPR. Been doing this for 10+ years since I got it.

I mentioned it on hacker news, and a commenter told me it might be the alt frequency. Poking around with SDR in Gqrx it looks like it indeed has an alt frequency of 91.1

In my Googling, I can't find any re-broadcasters of KQRS on 91.1 so I'm guessing this is just an error?

I'm not very experienced with SDR, and this is the first I'm hearing about RDBS even existing, so I'm hoping for a sanity check here.
Seems like more people would be having this problem if it wasn't just a problem with my radio?

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Yup. AF is designed to steer radios to an "Alternate Frequency" carrying the same programming. It's used far more commonly in Europe than the US due to the way they operate transmitter sites. Part of the problem in the US is that receivers handle it really inconsistently. Some ignore it, some will honor it, and others go bonkers when it is turned on. It's also tied to the PI code. In Europe these groups of frequencies broadcast the same PI code. In the US, each station has its own PI code so it sort of "breaks" the AF functionality.

I'm not sure why KQRS would have KNOW listed as an AF, but I suspect their RDS generator has just lost its mind and populated a field that isn't supposed to be populated. I've had it happen to a couple of mine as well and ended up replacing them.
 
From a former Minneapolis broadcast engineer

"I suspect they're running an Audemat FMB80 that lost its mind at some point. Most car radios in the US ignore AF since it's really not possible to implement due to the way we use PI codes and the PS field."
 
Hmmm...I can't seem to reproduce this. With my own RDS decoder and examining the raw RDS data, I'm only seeing it specifying that there aren't any alternate frequencies. More specifically, I'm just seeing it send "224" and "205" AF commands over and over, which specifies that there are no AFs listed. I even tried testing recordings from my archives dating back a year and a half ago in case it was fixed, but they show the same thing.

Does the auto-switching only happen sometimes, or is it a constant thing? Perhaps the commands are intermittently sent. Does it still show 91.1 as an alternate frequency in your SDR software right now?

Thanks!
 
I'm not seeing it now either, I think they fixed it! I actually emailed them the same day I made my post. They never sent me anything back, but I'm not seeing it being broadcast either.
 
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