Because of the folding back of the currents I would not expect the 4:1
step up transformer to be a stirling performer at common mode
rejection...
The best way to approach this is to use the 4:1 transformer balun
strictly as a transformer, then add a 1:1 choke balun in series with
it...
Personally I would wind the coax into a solenoidal choke balun
immediately below the 4:1 transformer being thrifty and all that and
call it good...




denny / k8do