RBDS Phase

FM does it with frequency!
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GregHahn
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RBDS Phase

Post by GregHahn » Tue Apr 11, 2017 10:46 am

Interested in hearing how you guys monitor RDS phase in order to set it in quadrature with the FM pilot. There isn't much out there on the internet that I can find. Not so much in the Audemat manual either.

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Greg Hahn
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Re: RBDS Phase

Post by TPT » Tue Apr 11, 2017 1:13 pm

Never saw anywhere where this was supposed to be a problem. Some RDS geni's generate their own sub-carrier, without reference to the pilot.

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Deep Thought
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Re: RBDS Phase

Post by Deep Thought » Tue Apr 11, 2017 6:35 pm

The only external ones I've dealt with wanted a pilot sample to work from, and generated it from that. They loop through after the stereo generator, no adjustment necessary.
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Re: RBDS Phase

Post by TPT » Wed Apr 12, 2017 7:49 am

Or an external pilot sample, such as are available from many modern processors. We feed our little Pira RDS geni from that sample off an Omnia One.
Then there are the Nautel transmitters, with an internal RDS generator--referenced to the internal stereo generator, I presume. On our NV10lt and VS2.5, we feed an externally generated composite audio, which of course, would not be synced to the internal stereo generator in the transmitter. Never had a problem.

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Re: RBDS Phase

Post by Kelly » Wed Apr 12, 2017 8:42 am

Yeah I've never heard about dealing with phasing of RDS. As everyone else mentioned, it's pretty much: Mount device, plug in power, connect to exciter, audio processor, or loop through composite audio. Insert external data as available, set injection level, done! Next, go have lunch at your favorite Mexican restaurant.
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Lefty
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Re: RBDS Phase

Post by Lefty » Wed Jun 21, 2017 8:29 pm

If you want RDS to work to its optimum you must lock it to the pilot and be 90deg out of phase.

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Re: RBDS Phase

Post by TPT » Thu Jun 22, 2017 5:51 am

Why? The RDS subcarrier is at 57 khz (3X19)--but why should the relative phase of the pilot and RDS matter?

Have two Nautels with internally generated RDS, both fed from external composite sources (Omnia 3T locally for one, Omnia One through a 25 mile STL path for the other. Never saw a problem.

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Re: RBDS Phase

Post by Lefty » Thu Jun 22, 2017 9:26 pm

I think you answered your own question :)

The 3rd Harmonic of the pilot is 57khz and without the RDS being locked to the pilot and at a phase angle of 90deg (the pic that Greghahn posted is a correct implementation of RDS) without it being locked to the pilot with correct phase angle it can cause the RDS to be interfered with.. especially on the fringe of your coverage area.. it can also cause overshoot dependant on the phase angle with obviously 0deg causing the most... and 180deg being the worst for RDS decoding

it may seem to work but its not best practice to implement RDS.

if you want to read more about it... read this http://www.radioworld.com/article/rds-i ... ation/4463

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