On the recommendation of this forum i have bought myself an AIM 4170C antenna analyser. looks a nice bit of kit I am new to amateur radio and have an immediate question. At the moment i have a 25 feet high horizontal quad loop of about 490 feet in length. It feeds off a corner into my bungalow through an upper window, via 450 ohm (I think...) one inch wide ladder line. This goes straight to the two screw terminals on the back of my Yaesu FC-902 ATU, and the ATU then goes to my FT-902DM transceiver. The analyser has a SO-239 socket on it for connection to the DTU. How should I be connecting it to my antenna system? I think I may need something like a 4 ; 1 balun at the house end of the ladder line, then connect the analyser via a short piece of co-ax to the balun, which in turn is connected to either "side" of the loop antenna ladder line? Or have I got this wrong? Is there an easy way to connect the ladder line so it terminates in a PL-259 plug, or is this an incorrect way of measuring things? I wiah to use the loop on HF multi band and in particular see if it can be optimised for either 160 metres or for PSK31 digi modes on either 20 metres or 17 metres. At the moment the AIM 4170C is probably 100 times more complicated than I am comfortable with, but I thought buying something really basic may be false economy in the longer term, as I feel I could get quite into this hobby Thanks.