“Yes, BUT -- these are passive networks, and the response of all passive networks depends upon the source Z and the load Z at each port. I'll bet your measurements were for 50 ohm sources and 50 ohm loads. Real world antennas differ widely from 50 ohms even when they are close to resonance on the bands of interest, and by a lot more when they are resonant on other bands. And if that isn't enough, source and load Z are transformed by transmission lines between the antenna, the device (the KAT), and the load (the RX). We run into exactly the same issues when measuring bandpass filters, a lot of which I published a year or so ago in NCJ. Our measurements look great, we do them very carefully, but hook real antennas and equipment to these networks and the results can be very different.73, Jim K9YC”
Jim - You are absolutely correct. Antennas resonant on different bands should improve things. My measurements were made in a 50 ohm system. However, without knowing what the other antennas are, a 50 ohm system measurement at least gives a feel for the isolation. In my case, I have two different antennas resonant on some of the same bands (vertical and dipole), and a 6-meter beam. So the 50 ohm measurement makes sense for the same-band antennas. Putting these two antenna on Ports 1 & 3 improves isolation quite a bit (over Ports 1/2 or 2/3). And the 6-meter beam on Port 2 will have more isolation between the antenna on Ports 1 and 3 since it is not resonant on the HF bands. Phil – AD5X ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
