I think this is a wonderful tool and it's a shame that nothing similar and compact is produced at the moment. I read the very interesting article about the function of the HP547A in the HP journal of Dec. 1976 (linked somewhere in here) and I studied the schematic. HP basically gives the design away with this extensive documentation, the only hard part is the pick up coil. They have a nice drawing that shows how it is basically done and the article explains what the designed took into consideration for optimal performance. Getting a suitable ferrite core is not easy and they also don't tell you what properties the inductor needs to have. I'm no expert on inductors or electric fields, nonetheless I tried my luck and solder a small SMD inductor with 1.5uH (TDK VLS252012T-1R5N1R4) that I had lying around together with a 47R resistor in parallel to a piece of RG178. I'm not sure if the 47R is necessary but I thought it couldn't hurt and would most likely help with refelction on the coax.
I then used a scope and a signal generator to test the setup and it worked astonishingly well!
I set the signal generator to generate positive pulses with 1Mhz and 2.5Vpp. I connected a short banana cable to it, forming a short circuit current path, and held the probe against the cable.
It worked much better than expected! It does all the tricks you would expect from this kind of probe. It is not sensitive to e fields, it is detecting the polarity of h fields correctly (inverted output it turned 180°), it shows next to no output if turned 90°.
I estimate the current in the test lead to be about 50mA - 100mA. The signal of the probe shows up as a 5mVp pulse. The input of the scope is set to 50Ohm for obvious reasons.
What do you think about these results?
Do you have any ideas how this setup could be improved?
Best Regards!