I'm making a near-field probe to to search for GNSS (GLONASS) blocking signals on my PCB. 

According to <http://www.eryptick.net/unisold/loop.html> the wire length for a loop should be 1/3 the wavelength to be resonant and avoid a tuning capacitance to resonate out the wire's inductance, so my loop is this length. 

It's single ended so the end of the loop is grounded (I've also tried open ended).

I'm using an aluminium wire for the loop which is soldering into the barrel of a BNC male-to-male adapter then feeding this to a spectrum analyser.

However it doesn't seem to work at all — it's been a while since I made one of these and I have a feeling I'm doing something silly

Does any of the above seem incorrect?