[FedCom] TSA at Portland (Maine) Jetport, et. al.

[HornSmoke]

Folks, I dropped off family at the Portland Jetport (PWM) yesterday morning 
and got a confirmed TSA  on 172.150. There was a split-second drop of 
 encryption, and a DPL of 145 registered. This happened twice, which 
leads me to believe it is accurate. I was sitting 500 meters or less 
away from the terminal, and had it full quieting.

Extensive traffic in Maine on 170.625; Customs/BP? Mostly encrypted; PL 
tone of 151.4 shows up, even WITH the encryption, about 70% of the time 
there is a transmission. One would think that they'd hide the PL in the 
encryption process.

"Foxtrot" units are the primary users on the 170.625. I'm quite sure 
there are multiple repeaters with this output positioned along the 
western Maine border with New Hampshire and Canada. I'd welcome any 
"input as to the input" to this freq. I also suspect that there is a 
linked system, with varying input PL's matched to the standard output PL 
of 151.4, much like our civilian LifeFlight helo ambulatory transport 
here in Maine that utilizes multiple towers on 453.650R with a universal 
pl tone output of 103.5. The +5 MHz input has a different PL for each 
tower. Could any of the Group Gurus enlighten us as to any known federal 
S.O.P.'s along these lines? Or, is it up to each individual radio shop 
how the system is programmed?

To codify my rambling questions, they are as follows:

1) Input to 170.625?
2) Possible linked repeater system on 170.625? New Hampshire monitors 
could especially help here.
3) Programming Standard Operating Procedure in federal radio shops, as 
there is a proliferation of "cross-agency" usage.
4) Group experience on how PL/DPL tones are either suppressed or "in the 
clear" when encryption is used.

Thanks in advance for any help.

Best to the Group from wintery Maine,

Loren