Pira.cz Technical Forum

Radio Data System (RDS) => P132, P164, P232(U) and P332 RDS Encoders => Topic started by: Gordon_Waters on May 08, 2018, 09:46:48 am

Title: P132 Introducing Static on the FM Transmission
Post by: Gordon_Waters on May 08, 2018, 09:46:48 am

Hi,

Just install the P132 and notice that there is now slight static / distortion of our transmission.
What would cause this ?
What can I do about it.

I have a encoder & transmitter  with single MPX connector so using it in loop mode
.


Thanks

Title: Re: P132 Introducing Static on the FM Transmission
Post by: Jan on May 08, 2018, 11:24:35 am

Did you adjust RDS level?

What's the RDS modulation level reading on your FM analyzer?

Title: Re: P132 Introducing Static on the FM Transmission
Post by: Gordon on May 09, 2018, 12:42:31 am

Hi,

Thanks for your reply.

I do not have a FM analyzer, so do not know. I guess I need to get hold of one and find out.

I Did turn it back form the 4000 to 3000, but didn't notice anything. Although I was not sre that this would achive anything.

Gordon

Title: Re: P132 Introducing Static on the FM Transmission
Post by: Jan on May 09, 2018, 05:59:10 am

Do you mean 4000 mV pp ?

In loopthrough mode, the RDS level should never exceed 350 mV pp ! (LEVEL=22)

For example:
assuming your FM transmitter requires 5000 mV pp for 75 kHz FM deviation
and desired RDS modulation level is 3 kHz,
the RDS level must be (3/75) * 5000 = 200 mV pp (LEVEL=13)

Title: Re: P132 Introducing Static on the FM Transmission
Post by: Gordon_Waters on May 11, 2018, 12:57:13 am

Thanks, With some testing I have dropped it back to 203mV. The static is certainly not as noticeable, but it's still there slightly.

It's like the station is not quite turned in.

Title: Re: P132 Introducing Static on the FM Transmission
Post by: Jan on May 11, 2018, 11:51:51 am

In correct configuration the RDS encoder is absolutely inaudible.

Does the noise disappear if you disconnect power supply from the RDS encoder?
Does the noise disappear if you set the LEVEL to 0?
Are you using original power supply or own power supply? It the voltage 12 V DC?
What's your transmission equipment brand name and model? (both the stereo encoder and the transmitter)