This is my first radio that decodes RDS so I have a few questions about how it works.

1. Is it only FM? I've not found an AM stations with it.
2. Why does it sometimes stay on and sometimes flash?
3. I've heard that if your radio supports this, it monitors all frequencys for it all the time so that reguardless of the station your listening to, if a traffic report is played, the tuner would play that and then go back to your music. Is this the way it works?
4. If I tune to one particular FM station where the RDS lits up, I get a clock in the lower right hand corner. After I get the clock, it stays on reguardless of which station I change to. Even if I switch to AM. It's there until I turn the radio off and then I have to go to that one station again to get it back. Why is this?
5. When I have the clock, why does the top dot in the colon flash?


Thanks for your help.

Steve

Is it only FM? I've not found an AM stations with it.

Good question. Don't know. It's either: a) RDS is FM-only, or b) None of your local AM stations are broadcasting RDS.

Why does it sometimes stay on and sometimes flash?

Does it flash steadily or intermittently? If intermittently, I would assume it is due to signal strength and the signal is dropping in and out.

I've heard that if your radio supports this, it monitors all frequencys for it all the time so that reguardless of the station your listening to, if a traffic report is played, the tuner would play that and then go back to your music. Is this the way it works?

This is called TA (Traffic Announce), and it is not in the current version of the software. A future release of the software will be TA-capable (although I don't know if it will be in 2.0 or not).

I don't know where you live, but your local radio stations would also have to broadcast the necessary TA information in order for it to work.

If I tune to one particular FM station where the RDS lits up, I get a clock in the lower right hand corner.

Wow, I've never seen the RDS clock on mine. That's cool. I guess none of my local stations broadcasts an RDS clock.

It's there until I turn the radio off and then I have to go to that one station again to get it back. Why is this?

Because, until you tune to a station that broadcasts an RDS clock, the player can't get the clock signal.

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Tony Fabris

In reply to:

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This is my first radio that decodes RDS so I have a few questions about how it works.

1. Is it only FM? I've not found an AM stations with it.
   
2. Why does it sometimes stay on and sometimes flash?
   
3. I've heard that if your radio supports this, it monitors all frequencys for it all the time so that reguardless of the station your listening to, if a traffic report is played, the tuner would play that and then go back to your music. Is this the way it works?
   
4. If I tune to one particular FM station where the RDS lits up, I get a clock in the lower right hand corner. After I get the clock, it stays on reguardless of which station I change to. Even if I switch to AM. It's there until I turn the radio off and then I have to go to that one station again to get it back. Why is this?
   
5. When I have the clock, why does the top dot in the colon flash?

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I don't have my tuner yet, but I've learnt a little about RDS:

1. RDS is broadcast on FM only. There's provision in the spec to define a version of RDS for AM, but it's never likely to happen.
   
2. Based on experience with other tuners, flashing generally indicates a weak RDS signal, usually while the tuner attempts to find the program on alternative frequencies (AF).
   
3. You get the effect of monitoring all frequencies, exactly as you describe. The way it works is that the radio stations cooperate (yes, really) and when one station is broadcasting traffic anouncements (TA) the other stations that send traffic programming (TP) tell the tuner which station to go to. When the station turns off the TA switch (supposed to be at the end of the announcements, but some are naughty and want you to listen to their adverts as well), the tuner goes back to what it was doing.

   This functionality is not in the empeg player yet, but promised for v2.0. Mine's not going into the car until that happens, because that's the one feature I can't live without - I do 8-12 hours on a Friday night reasonably often, and it's important to know which route to take.
   

4. I don't know about the empeg's clock display - I guess it doesn't display the clock until it has synchronised.
   
5. I guess the colon flashes because you can't hear it tick when you've got your music on loud. I don't know the empeg, but many consumer clocks flash the upper dot in the first half of the minute, and the lower one in the other half. Perhaps it's doing this?
   

And a question of my own:

How do you tell the empeg which time zone to use to convert UTC from RDS into local time? (RDS does use UTC, doesn't it?)

Somebody else will no doubt add in the empeg-specific bits for me...

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Toby Speight

It's FM only. It's modulated in above the L-R, at something like 38 (or is it 57?) kHz. FM's multiplex goes something like this (from DC): L+R, 19kHz pilot, L-R, RDS (at 1187bps).

If the icon flashes, this means that sync has been lost due to corruption of the datastream. There's a lot of error correction in there (10 bits of CRC per 16 bits of data) but sync does get lost sometimes.

It doesn't monitor all frequencies for traffic announcements. EON (enhanced other networks) means that stations feed each other RDS information and your station may signal to your tuner that a partner/local station is now transmitting traffic info and then the switch can happen for the duration of the bulletin.

AF lists do involve monitoring a set of other frequencies to allow auto switch to a stronger transmitter of the same station you're listening to.

Both TA and AF are standard in europe, but seeing how patchy RDS is in the USA I doubt you'll have a lot of use for them there (yet).

An RDS clock signal will bring up the clock (even on a mk1). If the signal is lost the empeg keeps updating it with elapsed time. It doesn't currently correct/set the internal empeg clock, though this may happen in the future.

Hugo

In reply to:

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An RDS clock signal will bring up the clock (even on a mk1). If the signal is lost the empeg keeps updating it with elapsed time. It doesn't currently correct/set the internal empeg clock, though this may happen in the future.

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Only with the user's permission, I hope. I don't want broken radio stations mucking about with my clock all the time...

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Toby Speight

ISTR the RDS station transmits the UTC offset it is using too.

We'll make auto-set an option, and also give the capability to ignore silly-looking differentials.

Hugo

Yeah, my TV set is like that. Supposedly, it can set its internal clock from the local PBS station, but the local PBS station is always wrong.

___________
Tony Fabris

In reply to:

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ISTR the RDS station transmits the UTC offset it is using too.

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Good point - the user doesn't need to configure anything

Bad point - at daylight-savings changes, you don't get the new offset until you use the tuner. Also cross-border changes (in Australia and US, no language change at the borders, so likely to listen to cross-border stations...)

In reply to:

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We'll make auto-set an option, and also give the capability to ignore silly-looking differentials.

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Very sensible - I like that.

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Toby Speight - 040103385

We had a video recorder (still do) that got its time from the teletext signal on the video feed. It worked great until we acquired a French housemate - she often watched the French station TV5 on our cable TV feed, and it's simply re-broadcast in the original timezone (CET, I think) an hour out from the UK point of view. So often, we ended up recording something an hour earlier than we wanted.

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Toby Speight - 040103385

Good idea to make the clock auto-setting user configurable. I have only one radio station here in Fort Lauderdale that broadcasts the clock data on RDS. When I tune to that station, I get the clock display in the lower right corner of my screen. I am also using Kit's clock hack, which displays in the lower left corner of my screen.

The interesting thing is that there is a 25 minute difference between the two clocks. Kit's displays the time as set via the menus, and the RDS displays some weird offset...

-Trevor

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