Using database, I get a (audio option) on more than one convential channel while searching on the database search. It is usually a NAC??? format. I don't see the option on the RR frequency database. Usually it is red in car when it is transmitting then it disappears. I am wondering if I should write it into my sentinel or leave it alone?
From your description, is the frequency in the main database, but without any NAC assignment? If so, submit the updated NAC(s) to the database. One of the neighboring counties near me uses the same fire dispatch frequency for several cities, but with different PL tones for the individual departments. So the example you are seeing could be similar, except that the channels are P25, with individual NACs. If the frequency is listed in the database simply as "FM" or "NFM", with no PL, DCS, or NAC specified, be sure your submission confirms that it is P25.
There is no way to enable NAC on a HP series, first ones to use it are SDS100 and SDS200.
While the SDS100 & -200 are the only ones (at present) that can utilize the NAC on a trunked system, the OP referred to it as being conventional, which the HP-1 & HP-2 series can handle.
