From: "Jeff DePolo WN3A" <[EMAIL PROTECTED]>:> > >Even pass cavities don't necessarily attenuate harmonics produced by a >circulator sufficiently. A 1/4 wave cavity will have a very good pass >response at 3/4 wave (3rd harmonic).
A long time ago I tuned a 10" diameter Motorola pass can to a 2 meter freq., then tried using it at exactly 3x. Wasn't even close. Apparently overmoding or some capacitive effect pulled the higher-order resonance. Perhaps some evening I'll try that experiment again & see how far down the 3rd harmonic response is. If it was due to overmoding then it's possible that this effect will not be present on the narrower (4 to 6") VHF cavities. >Even at other harmonics, or between >harmonics, a bandpass cavity isn't necessarily going to give you adequate >attenuation of the harmonics. A pass can is always good practice on any >transmitter, but a one-stop-shopping cure for isolator harmonics it is not. I thought that a pass cavity would have maximum attenuation at even multiples of resonance. The only real issue should then be the 3rd & maybe 5th harmonic of the isolator output. Bob NO6B Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
