Complete: Field Strength Meter

Well, with a combination of an hour last night and a couple today my Field Strength Meter (FSM) is complete and operational. I'd say three quarters of all time spent on it was just on the enclosure, the actual circuit is very simple and only takes (as the magazine suggested) 30 minutes or so to assemble – once the enclosure is done.

It works a treat and easily exhibits full scale deflection with just the 5W from my handheld – good that it's got the potentiometer to adjust the sensitivity. I'm now looking forward to trying some experiments with it for which I have the 2m whip from my FT-817 attached as the receiving antenna – but could be interesting to hook it up to my 40m dipole etc and try some things….

Actually, one thing I was thinking of trying is building some external band pass filters (because being your basic FSM it has no filter in the circuit at all). I'd basically build these inside small aluminium boxes with two male BNC connectors so that I could just plug them in and try them out. I'd build one for each band, and maybe even try some different designs, could be a fun experiment to see the impact.

Oh, and just as a reminder, the design is that from the March 2010 edition of Australian Amateur Radio magazine. There's also a theoretical design in the Radio Theory Handbook, but it is somewhat more complicated and potentially for no real benefit – but who knows.

One last thing, I'm now interested to see how I go about turning this into a calibrated FSM maybe to take readings in dB or uV. Maybe I could then use such a thing to give me a reading of local noise levels etc and as a better comparison for antennas. Further, I'd like to learn how to implement an LED/LCD 7 segment display or maybe even a LCD dot matrix display – could be a great project to learn it with. We'll see – got a few other things to do first. 😉

Fsm_001Fsm_002

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