I decided to get a PIRA P275R FM modulation monitor to better evaluate the local FM stations. For more information on it see: FM Broadcast Analyzer
It measures the FM modulation level, RBDS and pilot injection levels and a variety of related parameters. It is not meant to be a DX receiver. It needs to be wide band tuner for it to make accurate modulation measurements. An adjacent channel station getting close to the strength of the desired station or stronger will prevent accurate readings and often even reception. HD sidebands will prevent some parameter readings. I was curious on how the RDS injection level and phase readings compared to the ease of their being decoding.
I spent the past week logging the parameters on as many stations as possible. The following screen was referred to most often:
The pilot data can be quickly seen and any SCA can be spotted. Particularly for weaker signals, getting the correct input level is important. Too little might not be enough to obtain readings. Too much and interference and/or overload from a stronger nearby signal could do the same. I used a step attenuator to get the best reception as shown on the MPX spectrum display. I logged the SCA data and used my HD receivers to log the number of HD channels being transmitted as well as if they were also transmitting Artist Experience screens. While not a large number, there were more SCA’s found than expected. A few used it to provide readings to the studio site. An example of a Radio Talking Book SCA ID is attached. The above screen shows the recommended pilot parameters. And while the monitor provided the deviation levels in kHz, I converted them to percentages in my report since that’s how the FCC limits are defined.
Given the equipment limitations mentioned, I felt good in getting data on 83 different stations. My highly directional antennas helped. Incomplete data was obtained on a fair number of stations due to HD and other interference and/or too weak signals. For some of the stations I highlighted the missing measurement in yellow along with the likely cause. The HD evaluation was done just before the modulation monitor was received. There was a bit of a tropo opening then which made an HD reception possible while the later analog measurements were impossible. Due to a strong local station, two HD stations blended into a different analog station with changing propagation.
Two of the other modulation monitor screens are shown below as well as two more at the end of the report.
Now the measurements:
It measures the FM modulation level, RBDS and pilot injection levels and a variety of related parameters. It is not meant to be a DX receiver. It needs to be wide band tuner for it to make accurate modulation measurements. An adjacent channel station getting close to the strength of the desired station or stronger will prevent accurate readings and often even reception. HD sidebands will prevent some parameter readings. I was curious on how the RDS injection level and phase readings compared to the ease of their being decoding.
I spent the past week logging the parameters on as many stations as possible. The following screen was referred to most often:
The pilot data can be quickly seen and any SCA can be spotted. Particularly for weaker signals, getting the correct input level is important. Too little might not be enough to obtain readings. Too much and interference and/or overload from a stronger nearby signal could do the same. I used a step attenuator to get the best reception as shown on the MPX spectrum display. I logged the SCA data and used my HD receivers to log the number of HD channels being transmitted as well as if they were also transmitting Artist Experience screens. While not a large number, there were more SCA’s found than expected. A few used it to provide readings to the studio site. An example of a Radio Talking Book SCA ID is attached. The above screen shows the recommended pilot parameters. And while the monitor provided the deviation levels in kHz, I converted them to percentages in my report since that’s how the FCC limits are defined.
Given the equipment limitations mentioned, I felt good in getting data on 83 different stations. My highly directional antennas helped. Incomplete data was obtained on a fair number of stations due to HD and other interference and/or too weak signals. For some of the stations I highlighted the missing measurement in yellow along with the likely cause. The HD evaluation was done just before the modulation monitor was received. There was a bit of a tropo opening then which made an HD reception possible while the later analog measurements were impossible. Due to a strong local station, two HD stations blended into a different analog station with changing propagation.
Two of the other modulation monitor screens are shown below as well as two more at the end of the report.
Now the measurements:
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