Total posts : 45366
“just a matter of building the antenna and calibrating it to my scope using the known signal source”
That is one approach, but in that case it wouldn’t matter what the receive antenna was, or whether or not it used the right balun — as long as the receive system used the same hardware configuration and test procedure during both the reference “calibration,” and when checking the system under test.
Another possible concern is that the reference source used in this process could produce less than 250 µV/m at a distance of three meters, which would be compliant with FCC 15.239, but not at the upper limit.
Unfortunately, the only way to measure fields ~accurately is to use equipment designed and calibrated to do that.