On 1/18/2014 8:23 AM, Phil & Debbie Salas wrote:
Take a look at the measured KAT500 isolation numbers in the “Product Reviews” section of my website atwww.ad5x.com. The isolation varies based on the ports chosen, and the frequency band. As an example, the isolation on 20 meters has a worst-case value of 36dB between ports 2-3 (when 3 is selected), and a best case value of 65dB between ports 3-1 with port 1 selected.
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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
