Portland TSA Off of IWN?

A while back I discovered that the TSA at Portland International Airport (KPDX) seemed to have moved their primary radio operations to 4 talk groups on the federal Integrated Wireless Network or IWN. I was able to confirm the TSA was using this system by scanning the IWN site at the airport in conjunction with some Close Call captures of transmissions at the same time.

Sometime over the last month of so, they seemed to have moved off of the IWN for their main operations and have gone back to 172.1500 MHz, N001 and 172.9000 MHz, N001, (The Icom analog radios have always been on 169.3000 and 172.1500 with voice inversion). 172.9000 is set up as a wide area repeater that covers the Portland metro area. I have heard some encrypted traffic on this repeater, as well as clear traffic that seems to be supervisors at PDX airport.

Why this move has taken place is unknown. Perhaps the TSA was being billed for the use of the system and it was eating up more system capacity than they expect.

More information as it becomes available.