Thanks Dale, all understood.
OK folks, so I repaired Elliot's R2LC board and have it running with the Harbor Freight meter. I don't have a TMCC base but am using pro-grade RF signal generator to create modulated FSK/FM signals at 455 kHz. I'm getting the same "saturated" level as Dale is getting (about 62 uA) so I think I'm good. Also, with NO 455 kHz signal in the vicinity, I read about 20uA with no antenna plugged into the connector, and about 15uA if I ground the antenna contact. That seems to square with the 3372 chip datasheet meter sensitivity. I of course can't test whether the R2LC outputs work since I can't send TMCC commands but as a signal strength meter I don't think it matters.
My next thought is a simple audible circuit that changes tone proportional to signal strength. So you can listen to the pitch go up and down with signal strength rather than (or in addition to) reading the meter. As Dale comments, this device is "only useful as relative readings" so when fussing with layout adjustments it seems having a tone going up/down might be useful so you don't have to watch the digital meter readout which might not even be in view if going thru a tunnel or across the room. Has anyone already done this? Waste of time? Comments?
