MYSTERY FREQUENCY 172.4000 MHz

Reports of activity on172.4000 MHz, N088 in the Long Island, NY region. No other information was provided. 

For what it's worth, the frequency of 172.4000 MHz is assigned to mostly US Department of Agriculture and Department of the Interior agencies;
Animal/Plant Health Inspection Service
US Forest Service,
Bureau of Reclamation
International Boundary and Water Commission,
National Park Service
Soil Conservation Service

There are a few allocations to the US Army in New Mexico.

I have logged the N088 NAC a few times in Pennsylvania, and around the DC area out by Dulles airport, but not on this frequency.