RDS encoding issue

[OKCRadioGuy]

Hi. Our station has a strange issue when trying to impliment RDS. I've tried two different RDS encoders and get an odd result. (one from one company and one from another) A guy that has a Lexus car radio (he thinks 2004 model) is experiencing audio clips every so often when I have RDS running. Our audio processor is an Orban 8100A XT/2. I'm sampling the composite signal from the 8100 via a composite STL link for the RDS to lock onto. The output is wired over to the exciter SCA input. I've ensured that I'm not passing the rest of the composite through the RDS encoder (looped mode). Does anyone have ideas on what the heck is wrong with things that would cause the Lexus radio to get some audio drop outs? Thanks!

 

[chriscollins]

I have never seen such an issue on any of the RDS encoders I've setup. It could be possible he has a defective chip that has problems with RDS... Perhaps he could listen to another encoded station to see if he has the same problem.

You could also manually set the RDS injection, etc and remove the pilot sample, to see if that fixes the problem.

 

[OKCRadioGuy]

I haven't tried removing the pilot sample and letting it free-run just yet. That might be a good test. The really odd thing is this guy also occationally listens to our other transmitter on the other end of the metro when he's in that part of coverage and has no issue with it. I'm beginning to think it's something odd with my audio airchain or hookup with the troublesome station. I've actually tried two different RDS encoders with this same odd result.

 

[WNTIRadio]

Have you checked the pilot level, frequency and phase after it goes through the composite STL?

What model of composite STL are you using?

Is there another alternate frequency programmed in that his radio is reacting to?

You want "sidechain mode" not looped mode if you're not passing the entire baseband through the RDS encoder. Sidechain mode strips out the pilot for lock and only sends the 57kHz out of the output port.

What's your injection level on the RDS?

 

[mm11]

I have a Blaupunkt San Francisco CD70 that will occasionally briefly mute the audio of a station when (I think) it gets multipath. Is this what you are hearing? If I take the radio out of RDS mode it is fine. Of course this drove me nuts for a while after I put the radio in because I'm hearing the stations that I engineer drop out so I thought of problems that weren't related to the radio. The radio has some other quirks too and has been discontinued but I love it for the automatic equalization. I can plug in a reference mic and the radio will play a series of noise in each channel and then automatically set a correction equalization. It sounds great. RDS radios are not consistent in how they display or work across different manufacturers. I'm sure there are other radios that have quirks like mine. The trick to setting up RDS is to have a well known reference tuner that also will display the Radio Text field. A Denon TU-1500RD works for me. Get RDS working well on something like that and forget about the Lexus radio.

 

[OKCRadioGuy]

Have you checked the pilot level, frequency and phase after it goes through the composite STL?

I've used our MicroGen to look at the level coming out of the transmitter for both pilot and RDS. 9.0% for Pilot and about 3.8% for the RDS. I haven't taken a scope up there to see if I see something visibly odd going on.

What model of composite STL are you using?

TFT 9300 series composite.

Is there another alternate frequency programmed in that his radio is reacting to?

At first I thought that might very well be just it. So I de-programmed everything other than the frequency that the station is on into the AF list. I've also turned off both flags for traffic and even changed the PI to the real station call sign instead of the main station's callsign.

You want "sidechain mode" not looped mode if you're not passing the entire baseband through the RDS encoder. Sidechain mode strips out the pilot for lock and only sends the 57kHz out of the output port.

I need to double-check that it isn't passing some MPX but, according to the directions, I have the jump in the right place to not pass MPX.

What's your injection level on the RDS?

3.8%


Thanks!

 

[OKCRadioGuy]

The place I was sampling the levels was off-air through the transmitter, etc.

 

[w9wi]

Here's a WAY outside the box thought... if it's only affecting certain radios...

Is it possible you have any alternate frequencies (AF) programmed in the box?

Theory being, your signal fades a bit, the radio decides to check your other frequency (that doesn't actually exist), finds nothing, and goes back to the original (correct) frequency.

 

[OKCRadioGuy]

Hi. I've taken the other AFs out and only have the station's frequency in the list now. Thanks!

 

[mm11]

Here's a WAY outside the box thought... if it's only affecting certain radios...

Is it possible you have any alternate frequencies (AF) programmed in the box?

Theory being, your signal fades a bit, the radio decides to check your other frequency (that doesn't actually exist), finds nothing, and goes back to the original (correct) frequency.

A good thought. Perhaps that's what is occurring with my radio but it never seemed consistent enough for me to believe it. I've played around with AF on two different class A simulcasts that don't overlap very much. I do have the AFs programmed in the RDS generators but my experience with AF is that the main and alternate must have a strong RDS presence before it will switch. I found that the AF switch will not work on the fringe of the RDS coverage area so in our case it doesn't work at all. Perhaps it would if I turned the injection level way up but I wouldn't want to compromise the main channel modulation level. I've driven around Italy and watched the AF switching where it works well. In all of the hand-offs both stations still had a good solid signal.

 

[OKCRadioGuy]

Yeah. That's the key for sure with a good hand-off. In my case I do have quite a bit of overlap so it should hand-off well in most cases if I can figure out how to get past this Lexus oddity...