[BC] AM Modulation Monitor Off Air Monitoring

[Miltron]

You could not be more correct when you say it needs to be linear !
This reminds me of the account told to me by Bob Lambert decades ago of his trip to do an annual proof on a small town station owned by a ham who had enough technical savvy to keep things fixed but get into trouble if he strayed too far.
He bragged that he had devised a way to see modulation at the studio on a 'scope (tapped into the IF of a radio).
He was shocked and dismayed when Bobby showed him the drastic difference between modulation shown by the IF and the actual RF at the xmtr.........
M

-----Original Message-----
>From: RichardBJohnson at comcast.net

>You need about a watt of RF to run a monitor. In the "olden days," we would build a TRF "tuned RF" amplifier with a carefully shielded front-end, that would amplify about a milivolt from an outside random-wire antenna to the required 7 to 10 VRMS needed for the monitor. It needed to be linear, and could not use AGC, which would introduce apparent carrier-shift with asymmetrical modulation.
>
>Since some monitors do not care about the input frequency, one could amplify the 455 kHz IF of a conventional superheterodyne receiver using the same kind of linear amplifier.[snip]