I again find myself being temped by this unit:
http://www.radioassociates.com/
Although I have access to a Belar mod monitor, it's not exactly frequency agile and I'd need the matching RF amp, etc to really get much use out of it in part 15 work.
It appears that with the Part 15 module this would not only work, but when used with the IF of a radio could also be used to check modulation of virtually any station, part 15 or full power, which of course makes it useful in my commercial radio as well as part 15 work. it looks to be about a $400 investment with the unit and the Part 15 module. Much cheaper than a more traditional unit.
Anyone seen this in real life? Comments from other engineering types?
Tim in Bovey
The description for the AMM-SD1 Off Air RF Pickup Unit offered for Part 15 AM use on that website at http://www.radioassociates.com/part15.htm states that "100mV (minimum) of carrier signal is required" at the input connector of that pickup unit.
Such a minimum r-f voltage would be difficult to produce by a receive antenna located more than several meters away from the transmit antenna of an unlicensed Part 15 AM setup truly compliant with FCC §15.219, and even less so for a setup truly compliant with §15.209.
Also, the description of the AMM-SD1 does not include any specifications for its r-f bandwidth/tuning capabilities.
Lacking the existence of such capabilities, then the modulation levels displayed by that software on a PC screen could be polluted by other sources producing fields that were NOT rejected by the receive antenna and/or the AMM-SD1.
My impression when I read "The off-air interface covers the frequency range from 400kHz to 1750kHz and requires 100mV (minimum) of carrier to operate. This is easy to obtain by simply locating a wire or other antenna near to, or in the vicinity of the transmitter or transmitting antenna, and connecting this wire either directly or through a piece of feedline to the AMM-SD1 off-air RF pickup." was that the antenna used for grabbing signal for the unit would be located adjacent to, or within a foot or two of the transmitting antenna.
It also says this pickup can be used with the IF output of a communications receiver which can then be used to monitor any station that you can receive on that receiver.
As I have access to freshly calibrated commercial Mod Monitors, AND I have access to not only my Part 15, but a shack full of ham gear including lots of AM stuff, and several commercial radio stations where I can use this and compare results to known accurate professional monitors, I could be in a position to do some testing.
Tim in Bovey