Author Topic: Lexus car radio issue  (Read 4927 times)

radiowavesokc

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Lexus car radio issue
« on: November 29, 2012, 08:20:15 pm »
Hi.  I have an odd situation happening when I try to add RDS to one of my sites.  I have a listener with a Lexus 2004 car radio that is suddenly getting some audio clip/drop outs while I'm encoding RDS.  I have at first tried a Inovonics encoder and now a Pira32 encoder.  We have an Orban 8100A XT/2 processor feed to the transmitter via a composite STL.  I have the encoder at the transmitter site.   I am sampling the composite for the stereo pilot lock via just a BNC splitter right off the back of the STL receiver.   The output of the RDS encoder is wired to the SCA input of the exciter.  The exciter is a Harris THE-1.   I have ensured that I am not in loop mode where the MPX is being passed through the RDS encoder.   

What the heck am I doing wrong?

Thanks!

PR

Jan

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Re: Lexus car radio issue
« Reply #1 on: November 29, 2012, 09:37:33 pm »
The car radio is probably searching for alternative frequencies for your station. It stops playing your station for a while in order to quickly tune to other frequencies. Your audio broadcast is still continuous.

What you can try?

1) Maybe your RDS signal is transmitted at low modulation level (2 kHz or less) so that the receiver considers the reception as bad and errorneous and tries searching for better frequency.
2) If your station has only one transmitter, the second PI digit must be zero (x0xx). The PI is set to FFFF from factory on the encoder!
3) If your station has more transmitters, make sure only the nearest alternative frequencies are placed in AF list on each RDS encoder.
4) Maybe you've changed your PI after the listener stored your station into the receiver's preset memory.  In that case the listener must manually tune and store the station into the preset memory again otherwise the receiver tries to find the original station that was first stored.

radiowavesokc

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Re: Lexus car radio issue
« Reply #2 on: November 29, 2012, 10:19:03 pm »
The car radio is probably searching for alternative frequencies for your station. It stops playing your station for a while in order to quickly tune to other frequencies. Your audio broadcast is still continuous.

I've taken all the other AFs out of this station's list.  All that remains is the actual frequency the encoder is on now.  The listener confirmed that the drop-out still occurs.


What you can try?

1) Maybe your RDS signal is transmitted at low modulation level (2 kHz or less) so that the receiver considers the reception as bad and errorneous and tries searching for better frequency.

I'm running about 3.75% RDS level.  That's 2.8k deviation.  I'll try increasing it and testing with the listener to see if more level cures the issue.

2) If your station has only one transmitter, the second PI digit must be zero (x0xx). The PI is set to FFFF from factory on the encoder!

My PI generated is 2158 (hex).  I'm in the US.  Should I still try changing it to somehting with a 0 on the second digit to ensure that's not tricking the Lexus radio?


3) If your station has more transmitters, make sure only the nearest alternative frequencies are placed in AF list on each RDS encoder.

To test things, I've actually changed the PI to the real call sign of this transmitter.  On both the mothership that's not having the issue and this transmitter site I've change the AF to only list that transmitter frequency. The result is still the same (dropout issue)


4) Maybe you've changed your PI after the listener stored your station into the receiver's preset memory.  In that case the listener must manually tune and store the station into the preset memory again otherwise the receiver tries to find the original station that was first stored.

I have had the listener tune his radio up to another station via the dial and then back down to me.  the drop-out still occurs.  Maybe there is still something left in the memory of the radio that might be affecting things?

Thanks!

PR



Jan

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Re: Lexus car radio issue
« Reply #3 on: November 30, 2012, 08:19:08 am »
PI meaning is different for European and US standard. There's everything correct on the RDS encoder but maybe the car radio is set to European standard, so that PI 2158 means that there are different AF's (no matter if they are placed in AF list or not).

The final solution must be made on the receiver's side. Switch it to US mode (if possible), turn off any searching. There's not only AF searching. The car radio may also periodically tune all preset stations and search for traffic announcement. If there's some user manual, it should help. Or some kind of reset?

Many receiver's functions and features are not defined in RDS/RBDS standard, so they cannot be affected from the RDS encoder's side. Only make sure you've set TP=1, TA=0, PTY>0.

radiowavesokc

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Re: Lexus car radio issue
« Reply #4 on: November 30, 2012, 05:59:36 pm »
Thanks!

radiowavesokc

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Re: Lexus car radio issue
« Reply #5 on: December 03, 2012, 08:33:56 pm »
Ok.  I've tried different PIs than my primary station in the market. I've tried it with a 0 in the second digit.  I've tried both level input jumper settings for the pilot sample.  I've tried both looping through the encoder and side-chaining it.  It all still has the same result with the listener with the Lexus.  The audio still clips.  I'm at a loss.

I've also looked at the baseband demodulated signal on the mod monitor at the station to see what it going over the air.  It looks to me to be good, clean quadrature modulation of the RDS signal. 

Some other odd clues are that this same Lexus car listener is able to listen to our other signal when he is in the other part of town with no issues.  It's using a different audio processor and overall chain.  The one he is able to listen to properly is using an Orban 2200.  The station he is not able to listen to properly is using a 8100XT/2. 

I have tried an Inovonics RDS encoder on the troublesome station before with the same result.  I'm quite sure it's not a actual problem with the encoder by something I've got in my airchain that's fighting it. 

Any other ideas?

Thanks!

Jan

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Re: Lexus car radio issue
« Reply #6 on: December 03, 2012, 10:22:40 pm »
It seems to me the car radio still looks for the original station that has been received on that frequency first time (and probably stored to preset memory).

Stations are recognized by PI. Frequencies are usually stored into preset memory with PI and AF list. The receiver now detects another PI than what has been received first time on that frequency so it tries to find the original station. It may be hard to rectify it. It may be a bug in the receiver as well.

In my opinion there's currently no way how to solve it on the transmitter's side. It has nothing to do with broadcast equipment brand name. Some kind of the receiver's reset is probably necessary. If you find a solution or get some news, please let us know!

radiowavesokc

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Re: Lexus car radio issue
« Reply #7 on: December 04, 2012, 10:52:36 pm »
Thanks.