THP Question???

[kc402002]

Hi group, I live in District 4 and I noticed while listening to the THP on 42.56 that when Memphis Dispatch transmitted, that their PL tone was 131.8 but when the cars answered on the same frequency that their PL tone was 151.4. Can someone tell me why it is set up this way???

Thanks.........

 

[Airdorn]

Just be lucky you even hear any cars at all.... I never hear any troopers in their cars, unless one just so happens to be within a few miles of my antenna.

Do a search for 'THP' and your question will probably be answered by previous posts.

 

[EZlistener]

THP is a multi-site system and the sites are what is know as "PL steered." Mobiles select one of several sites for their district based on location and send a unique PL for that site.
The tone on which the dispatch centre sends and the mobile receives is the same throughout the district. Each district uses one and only one PL decode tone. This eliminates expense and nuances of automatic voting.
131.8 hz is the decode (mobiles) tone for District 4. 151.4 is tone "6" , indicates the Millsfield site in Dyer County.

 

[kc402002]

Thanks Thad, you really seem to know your stuff.

 

[firemedic2150]

When I originally entered all of the sites in to the database I wanted to include an explanation of the PL usage, but I was advised against it that it would be confusing to people and since this is a monitoring forum then the single district tone was more advisable.

Mark Mc.