Ground referencing the signal received from a simple wire antenna

[nathanpc]

I'm fascinated by RF, low frequencies, nothing even near the GHz range yet, but I plan to get there one day. I was playing around building a simple envelope detector for a 1MHz carrier modulated with 700Hz coming from my function generator, it worked beautifully until I decided to test it receiving the same signal wirelessly.

I attached a wire to the output of the function generator and cranked up the voltage (it's still a very weak signal so I wasn't interfering with anyone's reception) a bit just to make sure I would receive something. I tested it by attaching another wire to my oscilloscope probe and sure enough I got about a volt peak to peak with the wires very close to each other.

So I attached the wire antenna to the input of my envelope detector and the oscilloscope probe to the output. Interestingly enough I wasn't getting the 700Hz, but instead I was getting the full received signal, it passed right through the envelope detector. First I thought it may have been receiving the signals there too but as soon as I removed the antenna from the detector the signal vanished.

After troubleshooting for a while (you learn a lot when things don't work, Dave is right) I noticed that when I had the function generator connected directly to the envelope detector and removed the ground lead I would get exactly the same result as I had with the wire antenna, so I realized it must be the fact that the signal being received by the antenna is not ground referenced to the detector circuit (please tell me if my conclusion about the issue is wrong).

I Googled about how to ground reference a signal from an antenna, but all I got was how to do it in respect to mains earth in large tower antennas. Could anyone help me on how to ground reference a simple wire antenna in this case?