RMS or P-P Voltage for modulation alignment

[Realred]

Most alignment instructions call for a 1khz tone at 30mv injected into mic input. I've always assumed it was RMS but I saw a video the other day where the guy's sig gen was clearly visible and set for 30mv p-p. Just wondering.

 

[Pez]

Good question. I have worked with radios that specify either P-P or RMS. And many that don't specify at all. And not all radios require the same level.
In practice, I always start with 50mV P-P (35mV RMS) and go up and down from there to see where the input level is happy. I will always check the manual if I have the information in front of me, but it's not usually that critical when you are in the ballpark. 8 out of 10 times, 50mV P-P does the job nicely. But as is the case with these things, YMMV.

When it comes to 2-tone SSB tests, the variance can be even wider and you will be up and down with both tone levels, to balance the pips (TOI/IMD tests). Again, it all depends on how the DUT is performing at the time. The info in the book is a starting point.

73

 

[Shadetree Mechanic]

The B&K 1040 Service Master test set has the user keying the microphone that is held to a speaker that plays the tone, so I don't think it's that critical. Just so long as the signal isn't so big as to "push" the radios limiter like a power mic sometimes can.

 

[Realred]

Thanks for the replies. Seeing the B&K 1040 procedure does illustrate the uncritical nature of that procedure I guess. It just bugs me that they would specify an actual number but then leave me hangin'.