OK so you have a reel of cable and two connectors to make up the jumper between transmitter and duplexer.
The duplexer is tuned using 50 ohm test gear and the transmitter has been optimised into a 50 ohm load. Unfortunatley the output impedance of the transmitter is not 50 ohms and a length of cable to the duplexer will transform this impedance,detuning the first can in the transmit chain. A cable length can be found that minimises this effect this length can be found more easily by measurement than by calculation. I recommend a General Radio line stretcher as your next purchase from flea market/ebay. Using the stretcher an optimum electrical length can be found and copied to jumper length using the sweeper substitution method. All of this work can be done on site using a cheap sweeper and a line stretcher. Alternativley, a ferrite isolator can be put at the can end of the run, however the original posting is not in this area and isolator losses and sag make it an unattractive option. The z matcher is another option but in my practical experience it makes the jumper radiate RF.... you spend all that money on RG214/RG400 double silver plated shielding and then deliberatley mismatch it? Ian Ashford G8PWE
