Hello Markus and Rick!
I have only just acquainted myself with your messages.
(Just going out from hospital, big blood pressure problem...)
Thanks a lot for precious information, of what make fun still!
I recovered some ferrites N87 types which should work in 137 KHZ.
Another subject interests me, it is the possibility of transmitting with a big spool of several turns (a bit as WD2XDW). But EIRP is much weaker than with a vertical aerial, then it is necessary to "push more" in power!
Thanks in advance!
- 73: Jeff / F6CWN