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Thanks for the RDS Help

Readers like Alan Jurison’s data series in Radio World.

Thanks for the RDS Help

I just finished all four of Alan Jurison’s articles on RDS and they were a big help.

I live in a city of 30,000, Alaska’s capital, and I don’t believe any station here has ever had RDS, so I’m very excited to have our RT+ working and our station feeding our listeners more than just audio.

Dominick Pannone
Alaska Broadcast Communications
Juneau, Alaska

How Could You Not Know?

I enjoyed your Radio World article on RDS injection.

I have to agree 100 percent. My former assistant and I did nearly identical tests in Reno, Nev., and had identical results. We at that time ended up setting all of our FMs to 6 percent injection in quadrature with the 19 kHz pilot. We were running RT+ at the time via home-brew RT+ compiler units that my assistant built.

It was a fun project. We went so far as to go to each car dealership and test car radios, and found extreme differences in RDS-capable radios. We also tested the Zune and Nano with results identical to the author’s.

In Reno I see as low as 2.5 percent injection on some stations, with the highest being 6 percent. My wife has a 2002 Nissan Pathfinder and it will recognize the existence of RDS with as little as 1 percent injections, but will not decode PS at all unless there is 4 percent injection.

It is amazing to me that a broadcast engineer could sleep at night without knowing his RDS injection level. How could you put something on the air and not know? But you are right; it happens often. Absolutely amazing!

Yet if you listen to the average FM station’s audio, it is much easier to believe. If they can’t get the audio right, why would anything else be right?

Thank you for the cool series of articles.

Ian Perry
Chief Engineer
The Pilgrim Radio Network
Carson City, Nev.

You can read all the articles in Alan Jurison’s series “Get the Most Out of RDS” online.

Let’s Do Lunch

I really enjoyed reading Alan Jurison’s article on RDS/RBDS subcarrier injection levels.

As a designer of RDS/RBDS encoders, I’d like to reinforce his findings about how touchy some tuners are about the level, and really appreciate seeing his attention to detail when testing different radios.

I cannot emphasis enough that you must set these appropriately to get the most out of your RDS/RBDS signal. The subcarrier level is relative to the entire composite signal, so it’s not something we can set precisely from the factory; we must rely on the customer to do it on site.

Sadly, I find that a lot of broadcasters don’t have the right equipment available to measure their subcarrier, and never think to ask the engineer down the road to check for them. Trading lunch for a level check is a great solution!

I encourage everyone to double-check your levels, just like you do for your main signal.

Tom Pittenger
Embedded Systems Design Engineer
Inovonics, Inc.
Felton, Calif.