Great investigation. Looking forward to the next part as I'm in the process myself of starting to use AD8307 in an Arduino application. Keep up the good work Charlie and thank you for sharing!
Cheers Harry. I think I will definitely go with the Tandem Match Coupler. Just trying ti determine now which toroid to use. The original used T50-3. I don't have any of those. Maybe a T50-2. I note others use FT50-43 too.
Hi Charlie, if your looking into using the AD8307, some of the designd I've looked at in the past seem to use a tandem match coupler that I think will do away with the need for the sence diodes. You should be able to measure very low power levels with that configuration I think....
Hi Brian. I've just ordered 20x AD8307 in SOP8 format for NZD5, so that's not too bad. No idea if they will work at that price! I think the tandem match is a nice idea, as well as the Bruene coupler. I will have to do some more research as I expect the tandem will need some diode to generate DC (I would have thought). It was certainly well worth exploring the other coupler and signal conditioning circuit.
Yes I certainly will. I believe the Stockton bridge (named after David Stockton, G4ZNQ) is the same topology as the Tandem coupler, which was popularized by John Grebenkemper. I think it will work fine. Thanks again.
I know this is a very old video, but the log amp schematic has the op-amp inputs (+,-) reversed….the + inputs need grounding, and the - inputs are the current summing nodes. If connected as shown, your results are meaningless. Also it isn’t mentioned that inputs need to be connected to produce a negative input voltage with the logging diodes oriented a shown…this is determined by the orientation of the detector diodes.
