P275 measurements

[jasonrkgvlkikt@gmail.com]

I have had the chance to compare the performance of my P275 to several FM Signal analyzers which cost a LOT more.. and I can tell you without a doubt the P275 delivers repeatable and reliable measurements based on YOUR ability to use it right.

Now, I would like to know if I can write a script, or such, that allows me to measure the pilot FREQUENCY (and if I can, also measure on the RDS or other subcarriers) in addition to seeing the pilot display in the MPX screen.  I can see it at about 19k, or 38, or 57.. the P257 does the math and I can convert it to percent.. but how to get the pilot FREQUENCY out of the mix?

  I've tried rolling the mouse through, I see X and Y values change, but I'd like to know if there is a way to get those frequencies reasonably measured by pointing and clicking, or running a script.

The values I get right now for modulation, RDS level, Pilot level are close (within a few fractions of a percent) of what I see on devices costing many times what the P275 costs.. which is fine because it is REPEATABLE and reliable. 

[Jan]

Here's a simple script you can use:

Code: [Select]

send(MEM 1B0C?v)
set(pltfreq,%lastmemvalue)
if (%pltfreq=0)
  goto(pilot_none)
  endif
if (%pltfreq<7367)
  goto(pilot_failed)
  endif
if (%pltfreq>7368)
  goto(pilot_failed)
  endif
goto(pilot_ok)

pilot_none:
textwindow.addline(No pilot or poor signal)
goto(pilot_end)

pilot_failed:
textwindow.addline(Pilot frequency failed)
goto(pilot_end)

pilot_ok:
textwindow.addline(Pilot frequency OK)

pilot_end:

Remarks:
The script reads internal undocumented register and works with firmware version 2.2 r6, operation with previous or future firmware is not guaranteed.
Value of 7367 covers a range from 18.997,5 to 19.000,0
Value of 7368 covers a range from 19.000,0 to 19.002,5
Unlike a frequency counter, the P275 does not contain TCXO so any frequency measurements are limited to accuracy of about +/- 0.005% (that is +/- 1 Hz for the pilot)
The P275 contains 19kHz NCO for the pilot recovery. Internally the pilot frequency is held with 32-bit precision. Higher word is at address 0x1B0C, lower word at address 0x1942. These addresses may differ accross the firmware versions.
We will consider adding a special command for getting the pilot frequency directly.