) writes:
I have a National NC 300 receiver,it has a XCU 303 calibrator that was
made for NC 303...It works fine as a marker, but it has extra tube
(12AT7) and an antenna input connector ...I would like to see the 303
manual to see what it says about this calibrator..Any help on this?
thanks Harold W4PQW

I don't have any famliarity with that, so this is a guess. If the receiver
doesn't tune one of the WWV frequencies, maybe there is a converter in there
so you can receive WWV?

Michael VE2BVW