Is that BTW?
Yes - dear oh dear - pot calling kettle black


It appears to have a flat section of line that is parallel to the coax
centre conductor and is presumably capacitively and inductively
coupled, and it uses some form of frequency compensation to give it
broadband response. You rotate the sampler element for measurement of
the opposite direction.

Have played with that type of Bird. Worked well as I recall. Have also
made a Bruene type - fairly constant readings over wide frequency range.
Yes 40m is a bit ordinary at the mo for short distance.
Cheers,
Alan