Aha now I've got it..
Thanks for the tips and it was the winding phase i had incorrect..
obvious now ;-)
I will examine at the tuning aids documents too, they look very helpful.
Cheers
Rob
M0DTS
On 15/05/2011 12:42, James Moritz wrote:
Dear Rob, LF Group,
The inductance of the transformer is probably a bit on the low side
(the reactance of the total 24turn winding should be much greater than
the 68R load resistance), but should be enough to get at least
reasonably close to balance - you should be able to see at least some
reduction on the "reflect" side with 50R load connected. Check that
the phasing of the secondary winding is correct - the centre tap
should be the connection between the "start" of one winding and the
"finish" of the other.
What should happen is the RF voltage on one half of the current
transformer secondary is equal in magnitude, but opposite in phase to
the load voltage sensed by the capacitive voltage divider when the
load is 50R. The component values shown look about right to do this.
One way to check this would be to:
-Disconnect the "hot" end of the capacitive potential divider from the
TX input terminal. Note the meter readings with the TX running into
50R load.
-Disable the current transformer by shorting the 24 turn secondary and
re-connect the capacitors .Check the meter deflections with 50R load -
it should be possible to get these the same as in the first test by
adjusting the trimmer capacitor.
You can find some other ideas about LF antenna tuning aids in the file
LF_Tuning_aids.pdf at
https://sites.google.com/site/uk500khz/members-files/files
Cheers, Jim Moritz
73 de M0BMU
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