Antenna Switch Loss & Isolation Evaluation

A quick look at an older HF multiport Antenna Selection Switch measuring Insertion Loss and Port-to-Port Isolation. Since 100W = 50dBm, for most situations we would like to see 50dB or better loss between any selected port and all other ports so that no more than 0dBm (1mW) is seen at unselected ports. The switch we are evaluating in this video seems to have good enough isolation at HF but starts to degrade by 50MHz and is not very useful at either 2m or 220MHz due to poor port isolation. The unit also has a 10dB suck out at 325 MHz thus should not be used above this frequency in any case. Apparently Heathkit specified this unit as able to handle 1KW at less than 1.1:1 VSWR up to 250 MHz but I stick by my recommendation to use it only to 50 MHz unless port-to-port isolation isn't particularly important for your application. An example of such a use might be to switch between a Two Meter vertical antenna for FM operation and a horizontal beam for for SSB operation. There is no particular need for high port-to-port isolation in this case since it is likely that there will be additional isolation of 10-30dB due to cross polarization between the antennas. See http://www.manualslib.com/manual/4667... for an online copy of the manual for this unit.