Author Topic: Deviation MAX appears to be wrong.  (Read 3853 times)


  • Newbie
  • *
  • Posts: 2
Deviation MAX appears to be wrong.
« on: October 03, 2012, 05:48:57 pm »
We have a Pira 75 and are using the control software.
In the software under Deviation MAX (the one that constantly changes, not the one in the Accumulated Distribution Plot) our station only ever shows 74kHz. However we have a mod monitor connected directly to the output of the transmitter, a BelAir, and it's showing us at 110%(82kHz). We also have an Inovonics 630 using an Antenna at our studios and it too is indicating 110%.
Is there something I need to adjust in the Pira so it's more accurate for us?


  • Hero Member
  • *****
  • Posts: 612
Re: Deviation MAX appears to be wrong.
« Reply #1 on: October 04, 2012, 09:08:50 am »
In terms of FM deviation measurement the PIRA75 is a class better device than your other equipment. Its precision is guaranteed by principle of operation and pure DSP processing. There's nothing to adjust. See complete explaination at

The Inovonics 630 is a pretty old device. FM deviation measurement is not the main purpose of this device as it is a FM Relay Receiver. Due to limited precision, this kind of equipment is factory adjusted to show higher deviation (= has only positive inaccuracy) to ensure that the transmission equipment is never overmodulating. Thus it cannot be used for reference measurements. Simple analogue FM deviation measurement plugin with LED bar and unknown method of processing cannot be compared to fullfeatured DSP equipment.