would be nice if makers of certified tx's would add a sample output for modulation monitoring using pro meters such as belar amm-1
How would this help a prospective customer?
Neil
Not sure, but I'd guess the meters would be helpful to know how much modulation-before-distortion (causing splatter into adjacent freqs) can be accommodated by the system.
Indeed, it would take more power to drive a Bellar mod monitor than a certified Part 15 transmitter's final amp puts out! You can hear loudness, distortion and splatter with your ears. Use 'em and save your money!
It would need a calibrated pre-amplifier to boost up the low level signal, and without loading down that low level signal output, in order to properly obtain an accurate measurement on the pro monitor units.
But the idea of having a sampling port is a good one, and the Part 15 TX makers could also build a modulation monitor that works with the low power level of their TX's.
We are working in the low power realm thus it makes sense to use testing gear built for that low power realm. Simply cranking up the RF gain for driving high-level monitoring gear wont cut it, at least not without proper calibrated amplifiers.
Overall I think the suggestion is a worthy one. Some Part 15 operators follow the same steps and procedures as Part 73 engineers do, nothing wrong with that. In fact, it makes for good engineering practices. But I believe that there should be a line of testing gear built by these Part 15 transmitter makers to add to their product line for the world of Part 15 broadcasting.
RFB
The only mfr I know of in Part 15 stuff that provides a meter for resonance matching is the Talking House external ATU.
But what is really needed is a inexpensive FSM, built and calibrated specifically for AM-band testing, digital number readout. I've played around with some simple circuits to start with, based on some I've seen, but I'm a ways from what I want.
"what is really needed is a inexpensive FSM, built and calibrated specifically for AM-band testing"
I agree. Question would be, could it be built so that it maintains within a reasonable tolerance to accuracy.
It would not have to have exact specs of a Potomac or even a 120E, and cannot be expected to have their level of accuracy. But a FSM for Part 15 is indeed a valuable and must have tool to Part 15 stations.
There should be one for LW, AM, SW and FM.
Ok all you Part 15 kit and certified TX makers, start hitting the drawing boards! 😉
RFB