I need a battery operated device for measuring signal and /or noise, sort of like a very basic spectrum analyser and would like some thoughts from you educated people (you can decide who the educated people are).
As follows
1 to 40 MHz, resolution bandwidth is not desperately narrow, could probably get away with 2.5 MHz but 1 MHz would be good. I can't connect directly to the wire so I would use a split toroid to grab the signal/noise.From the other end a wifi card in an IPAQ, data in through the serial port on the bottom. This bit is fairly easy.
-60dBm would do but -80 dBm would be better. I realise that this is what costs the money and would like it to be cheap. Absolute measurements are probably not needed as I could "calibrate" it before each use with a signal generator.
What suggestions for the bit in between the toroid secondary and the (probably PIC based) serial output stream to the IPAQ. First thoughts are to use correlation to select the input window and do the whole thing with some basic DSP algorithms and it has been years since I went there so maybe that is way off.
This is something I am just thinking about, I don't know if it is feasable at a reasonable cost and am certainly nowhere near the "building it" point. I would just like some input and possible methods. Maybe there is something out there that does this more or less off the shelf but it would need to be small. Laptop, National Instruments cards are probably not an option, too heavy.