scanning only trunked input frequencies

[de19805]

Would it work, if I only programmed the input frequencies from a local digital trunked radio system (into a digital trunking scanner of course) as conventional frequencies and only get transmittions from nearby units???

I do realize that I won't be able to hear the dispatcher, just the unit near me. Thanks.

 

[gewecke]

In some cases it works better. On a local analog LTR system here, when I listen to the outputs I get data clicks every 10 seconds which I don't get when listening direct so to answer your question. Yes in some cases the input is better! However on a digital system, maybe.

73,
n9zas

 

[UPMan]

Theoretically, you could adjust the band plan in the scanner so that, instead of going to the output frequency on a channel grant, the scanner will instead go to the input frequency. If it is an 800 MHz system, you would subtract 45 MHz from the base frequency(ies) in the band plan. You would then simply scan the normal control channels output frequencies.

Of course, if it is a P25 system it won't work, as the band plan will be updated with "correct" settings as soon as the control channel is received.

 

[gmclam]

Would that be true with ALL P25 systems and all scanners? What if someone is using an older scanner (PRO-96 or PSR-300) and changes the band plan?

 

[UPMan]

1) No. There are a few (mostly federal or military) that do not transmit the band plan. These you must explicitly program, and you could use this trick.

2) PRO-96: Good question. Don't know that answer. PSR-300: Isn't it analog only?

 

[gmclam]

trunk tacking input frequencies

Yes the PRO-164 / PSR-300 are analog only scanners, but that does not stop them from trunk tracking analog TGs on a P25 system. My point was that it seems like there are scenarios where one could alter the band plan on a scanner and not have it auto-updated from the system they are monitoring. As long as the TGs being monitored are analog, this scanner could (in theory) be used to monitor input frequencies.

My thinking on the PRO-96 was/is that it could be used to monitor P25 TGs the same way, as I don't think the firmware is updated to perform band plan update from over-the-air data. But I don't know for sure.

 

[KB7MIB]

Wirelessly posted (Mozilla/5.0 (X11; Linux i686; U; en-US) Gecko/20081217 Vision-Browser/8.1 301x200 LG VN530)

What's the mobile offset for the 700MHz band and the 900MHz band? 800MHz is -45MHz. UHF is +5MHz. UHF-T is +3MHz.

 

[UPMan]

Yes the PRO-164 / PSR-300 are analog only scanners, but that does not stop them from trunk tracking analog TGs on a P25 system.

P25 systems do not have analog TGs. It is possible for Motorola 3600 systems to have P25 channels (probably what you are thinking about, but unrelated to the systems under discussion). P25 systems use a different control channel and are exclusively digital.

 

[UPMan]

Wirelessly posted (Mozilla/5.0 (X11; Linux i686; U; en-US) Gecko/20081217 Vision-Browser/8.1 301x200 LG VN530)

What's the mobile offset for the 700MHz band and the 900MHz band? 800MHz is -45MHz. UHF is +5MHz. UHF-T is +3MHz.

Offset - The RadioReference Wiki

 

[KB7MIB]

Wirelessly posted (Mozilla/5.0 (X11; Linux i686; U; en-US) Gecko/20081217 Vision-Browser/8.1 301x200 LG VN530)

+30MHz for 700MHz and -39MHz for 935-940MHz. Thank you.

 

[de19805]

Thank you all for your replies....