The AM Forum

  Or for anyone else who might know the answer, but I'm thinking it's a Steve thing: The Mod Monitor's software must base its modulation percentage determination on the carrier level, but does it continually update that throughout the transmission, or does it only look at the carrier level at the start of the transmission? If the carrier level were to increase or decrease during the transmission, does the software take that into account?
 

Good question.  Have been wondering about that myself.

  Here's the reason I ask: I use, and really like, my Steve-O-Meter, as well as an LP-100. When I run my K7DYY, the peak reading on the LP-100 agrees quite closely with what the REA Mod Monitor indicates—right around 4x the carrier when the Mod Monitor is showing 100% positive modulation. When I run my DX-60B—with Steve's modification for pure screen modulation—however, the two instruments part company a bit, with the LP-100 indicating significantly less than 4x the carrier while the Mod Monitor is showing a solid 100% positive or higher.
  One thing I note is that, with the LP-100 set to read peak, its display immediately shows 14 watts of carrier before I start modulating, but then, once I stop talking, while keeping the transmitter keyed, the LP-100's display drops to 10.5 watts as soon as the peak-hold times out. If I change the power mode on the LP-100 to "tune," which gives a pretty much instantaneous reading with no peak-hold, it tells me that my carrier is, in fact, 10.5 watts. That 14 watt initial reading in peak mode is, apparently, a brief spike generated by the DX-60B at the start of transmission, which the LP-100 catches and holds. Now, if the Mod Monitor's software is grabbing that initial 14 watt spike and basing its calculations on that, while the actual carrier is really only 10 watts, that would explain the discrepancy in the Mod Monitor vs LP-100 readings. The K7DYY has no such spike, and its Mod Monitor and LP-100 readings agree, so that's why I'm suspecting that the Mod Monitor might be basing its calculations on the carrier it sees right at the start of transmission.
  Edit: I do realize that the human voice as a wave-form, and its characteristics, are extremely complex, and expecting precise readings is tantamount to nailing jelly to a tree, but I'm not expecting exact readings; just wondering why I'm getting better agreement with the DYY than with the DX-60B.

An easy way to help determine the DX-60 discrepancy is to start the REA software AFTER your transmitter is keyed..

If then, the peak/watts and percentage agree then you are spot on with the RF carrier spike “lock” that would explain your observations..

Interesting!

  That is a creative suggestion.  I will try that! Thanks.

I believe the algorithm analyzes in real time, constantly analyzing the total envelope.

Ya know, if you have a question to a member and they don't hang out on AMfone 24/7, you can always send them a PM.

  I do indeed know that, but I figured that not only does Steve view and post here regularly, but posing the question in the forum could be educational for all the other inquiring minds who might like to know the answer. Steve's Mod Monitor is deservedly popular—many of us use it all the time. It's certainly one of my favorite shack accessories.

It really doesn't make any difference to me; it's your query. Your email could just ask him to come to the board and answer the question for all.
As far as posting regularly, he has only post 8 times so far here in 2024: 12/24 (Merry Xmas thread), 12/11, 10/25, 10/20, 7/23, 7/19, 6/3, 2/27
He's probably also getting ready to "sunbird" to Florida shortly. Pickle is calling!