[Johnson] 250-28 calibrator questions

[jeremy-ca]

I just picked one of these up and plan to use it with the HQ129X & Viking I.

A schematic/instruction sheet would help as Ive a few questions.
-  Why 2 filament leads instead of grounding one side?

- Would a 1 MHz xtal work in that circuit?

- Any problem using coax to a T connector? Or would it load the circuit down 
too much. Im going to use a ferrite 4:1  balun on the 129X so I can use coax 
fed antennas; that will be different than the home made 600 Ohm line I used 
in the 50's!

Carl
KM1H