[Antennas] Dentron Tuner Help

2002年7月07日 13:21:10 -0400

I'm trying to repair the wattmeter section in this tuner for a good
friend. He bought the tuner some time ago and the FWD meter didn't work.
I brought the tuner to the house and replaced the 2 diodes in the RF
sensing unit. Also found both air variables run out to their stops. Now
Dentron uses a strange way for the 2 resistors 1 is 43 ohm and the other
is a 10 ohm. You would assume the 2 would be of equal value ? The 43 is
in the FWD part of the circuit the 10 in the REFL. Well I have the unit
repaired and the FWD meter calibrated...all OK....so far. So I reverse
the input-output coax's and try to calibrate the REFL. This is where I
am completely stumped. In every other wattmeter I have built I just
calibrated the REFL to 100 watts or whatever scale I was using and it
worked just fine when the cables where put back to normal. Not in this
animal...the REFL meter now reads 100 watts when it should be reading
whatever the REFL power really is. I finally just left the cables as
they should be, and adjusted the REFL for what it really is, I put the
rig on 20 and the antenna on 40, applied just enough RF to get a 5 watt
REFL reading on my meter and adjusted the pot in the Dentron for the
same reading. Now my question is, does anyone know or have any
experience with the MT3000A meter circuit or a similar animal ? And if
you do, just how in the heck do you calibrate the wattmeter ???????
TIA...73
Ed W3NR