Paul, If you use a 50 ohm coax between the CP1 and the 'scope, you should use a 50 ohm termination right at the 'scope to achieve proper patterns and voltage readings on the 'scope - the in-line type terminators work best in this situation, and you would not use the CP1 built-in termination for this situation since the termination is at the 'scope input.
A good method IMHO is to use a 10X probe (properly calibrated) on the 'scope and place the termination right at the place where the scope probe is placed - remember that this only works correctly with a 10x probe on the scope. If you place the 10x probe across the CP1 50 ohm terminator (with the built-in terminator switched in), then the 'scope should read correctly. The 'rule of thumb' (if I can generalize) in all cases of RF power (or voltage) measurement is to attach the termination at the far end of any coax used for the connection(s) - if the terminations is applied at any other point in the system then erroneous readings are likely to result. This is just like antenna feedline considerations - if you connect an unterminated chunk of feedline to an antenna, it will act as an inductor or capacitor (depending on the length) and modify the voltage at the attachment point as well as at the far end of the stub. When doing RF measurements be certain you have not created random stubs in the measurement connections. 73, Don W3FPR > -----Original Message----- > > I am not sure I understand the procedure for terminating the > sampling ports. > If a port is unused it says to terminate it into the internal 50 > ohm load to > maintain balance. This makes sense. But if I connect a port (or ports) > through a short piece of 50 ohm coax to a scope which has a high impedance > input, is this port properly terminated? > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
