The conversion is not difficult, but annoying. Perfect reason for writing a program for my DM42 and free42 calculators.
A Similar situation with my spectrum analyser: Before I establish a connection I like to compute the Vrms on my 50Ohm input for the sended power in dBm. This to protect my spectrum analyzer for to high input voltages resp. to decide do I need DC blocker or do I need an attenuator or do I need no protection at all.
The following programs are doing the conversions for both cases in both directions.
Code: Select all
@ m2uV: dBm to dBuV Converter and vice versa
@
@ converting dBm to dBuV
@
@ dBuv = dBm + 90 + 20 * log(sqrt(Z0))
@
@ Frank Kirschbaum, frank.kirschbaum@gmail.com
@ 2021-04-10: Initial version
@
00 { 109-Byte Prgm }
01 LBL "m2uV"
02 MVAR "dBm"
03 MVAR "dBuV"
04 MVAR "Z0"
05 VARMENU "m2uV"
06 CF 21 @ continue programex ecution after a VIEW instruction
07 REALRES @ calculate real results only
08 STOP
09 ASTO "CONTROL" @ store the name of the unknown variable in CONTROL
10 PGMSLV ".m2uV" @ specify solver routine
11 SOLVE IND "CONTROL" @ Indirectly specify the variable to be solved
12 VIEW IND "CONTROL" @ View the solution
13 GTO "m2uV" @ return to start
14 LBL ".m2uV" @ function to solve
15 RCL "Z0"
16 SQRT
17 LOG
18 20
19 ×
20 90
21 +
22 RCL "dBm"
23 +
24 RCL- "dBuV"
25 END
Code: Select all
@ m2Vrms: dBm to VRMS Converter and vice versa
@
@ converting dBm to Vrms
@
@ V = 10^((dBm-30)/20)*sqrt(Z0)
@
@ Frank Kirschbaum, frank.kirschbaum@gmail.com
@ 2021-04-10: Initial version
@
00 { 119-Byte Prgm }
01 LBL "m2Vrms"
02 MVAR "dBm"
03 MVAR "Vrms"
04 MVAR "Z0"
05 VARMENU "m2Vrms"
06 CF 21 @ continue programex ecution after a VIEW instruction
07 REALRES @ calculate real results only
08 STOP
09 ASTO "CONTROL" @ store the name of the unknown variable in CONTROL
10 PGMSLV ".m2Vrms" @ specify solver routine
11 SOLVE IND "CONTROL" @ Indirectly specify the variable to be solved
12 VIEW IND "CONTROL" @ View the solution
13 GTO "m2Vrms" @ return to start
14 LBL ".m2Vrms" @ function to solve
15 RCL "dBm"
16 30
17 -
18 20
19 ÷
20 10↑X
21 RCL "Z0"
22 SQRT
23 ×
24 RCL- "Vrms"
25 END