Not sure if it has been posted yet, but there is a good technical write up of previous North Korean satellites here:

http://38north.org/2012/09/nhansen091212/

Some sites suggest 450 to 470Mhz is likely band. Ideally would need a very high gain setup with a wideband SDR dongle to see any transmissions. If they wanted they could turn all transmitters off unless commanded or else only when the GPS says they are within range of the ground station. Note the article linked is only the older satellites.

I don't believe there was any public reception of actual emissions from previous models. It does look likely UHF will be used. In this day and age if it does emit on UHF constantly someone probably will detect it and share. with possibly 6 UHF antennas there may be multiple downlinks. I will buy a pint for whoever decodes the GPS location downlink first!