[Hamlib-developer] S-meter reading - flrig/IC-7300

[Philip R. <gm...@bt...>]

I have noticed a discrepancy when displaying the S-meter reading read 
from IC-7300 using flrig and hamlib.


I have looked at the code at each stage.

The Icom CI-V has:

Read S-meter level
*(0000=S0, 0120=S9, 0241=S9+60dB)

Flrig converts this into percentage full-scale deflection (S9+60) 
(IC7300.cxx l. 1670):

mtr =(int)ceil(mtr /2.41);

and the display on flrig and the actual IC-7300, as far as I can tell, 
look pretty much the same.

Hamlib seems to interpret this (flrig.c ll.2388+) as dB above S0.

    case RIG_LEVEL_STRENGTH:
         val->i = atoi(value) - 54;
         //if (val->i > 0) val->i /= 10;
         rig_debug(RIG_DEBUG_TRACE, "%s: val.i='%s'(%d)\n", __func__, 
value, val->i);
         break;

and converts this to dB above S9 per the comment in rig.h L. 1080.

#define RIG_LEVEL_STRENGTH   CONSTANT_64BIT_FLAG(30)      /*!< \c 
STRENGTH -- Effective (calibrated) signal strength relative to S9, arg 
int (dB) */


However its not - it's out by about 10%.

My app then interprets this per the hamlib definition, which seems to 
the only specified value and I display a version which is several dB 
lower then that displayed on the rig or on flrig. I couldn't find in the 
flrig documentation what rig.get_smeter should return. Looking at 
rig.get_Sunits and rig.get_DBM it looks like a value of 50 is S9, 100 is 
S9+60 and linearly interpolated over 0-50 and 50-100.


I don't know if this is a general problem across all rigs. Is FSD on the 
flrig S-meter always S9+60? Or will it vary by rig?


It's not a major issue in the grand scheme of things. I was just curious 
why I seemed to be displaying a lower value than flrig was. It's not an 
accurate value anyway, just wondered why it was different.


73 Phil GM3ZZA