Power Mike not working on radio

I bought a PCM 1000 power microphone to connect to my Cobra 29 LTD classic.

When I plug it in I get received when I key it up the needle swings and I get a lot of squill I get talkback over my speaker and when I turn down my mic gain and the gain on the microphone I get hum any thoughts or suggestions would be very helpful thank you. By the way the radio normally does not have TalkBack at all.