Samuel,
As luck has it, I just spent a week in Cheboygan with my PSR-500. If you would like I can send you my file.
Where about in Cheboygan are you staying?
With the PSR-500 and the stock antenna I was able to hear 4 tower sites from Cheboygan:
T401 - CHEBOYGAN 868.4500C, 867.9500A
T402 - WOLVERINE 868.8625C, 868.3625A
T404 - CORDWOOD 868.9375C, 868.4375A
T435 - BLISS 868.3875C, 867.7750A
If you are traveling up I-75 I even have the file setup for each county you will go thru starting in Livingston Co.
Most of the State Police units have the Sheriff/County radio's in their cars and use them. But, they also have the Statewide Digital system in their cars (MPSCS).
You will find some of the counties are still on VHF and others are on the digital system. Some of the counties are simulcasted on both.
Cheboygan County is still VHF but they do have a patch onto MPSCS.
Let me know if you need the file.