On Jun 2, 2007, at 5:43 PM, Gary Schafer wrote: > Mostly correct but an isolator could be thought of as a device to > "clean up > a transmitter" too. An isolator provides a flat 50 ohm load to the > transmitter no matter what kind of load the antenna or duplexer may > present. > Sometimes transmitters get a little "squirrelly" and generate spurs > when not > seeing a flat 50 ohms.
True, but you'd better find out why your antenna system overall isn't presenting a 50 ohm load to the transmitter in that case anyway. The isolator is just covering up the real problem. Although I will admit, it's sure nice to let it do that "cover up" function until you have time to figure it out. And yes, with some setups including the duplexer and everything else, sometimes you just can't get it quite right and the isolator might then be considered to be "cleaning up the transmitter" in the most broad sense. I just didn't want people getting the impression that an isolator does any shaping of the RF output of the transmitter. The secondary effect of keeping a transmitter than doesn't like non-50-ohm loads from going crooked on you, is useful... but not a "fix" for a transmitter that really has problems. In fact, as you re-iterated... it creates harmonics that need to be properly filtered. -- Nate Duehr, WY0X
