Posted by FlashP on April 23, 2001 at 07:27:52:
In Reply to: 780 errors in CC mode on EPSCA posted by Dennis on April 19, 2001 at 13:28:34:
: Is anyone with a 780 having errors when placed in Control Channel mode on 868.775? I hear the Eastside fire traffic(TGs in the 20,000-range on these SPD tactical TG's, such as ERT and Host. Neg. (TGs in the 4400-range). It's not constant tho and I'm uncertain whether to suspect the 780 in CC mode or ???. It doesn't do it when scanner is in non-CC mode.
: If someone wants to try and duplicate the situation, please e-mail privately and I'll send the Excel spreadsheet for the free 780 programmer.
This is "normal" operation. No receiver can
decode the bit stream perfectly - there's always
some percentage of missed bits, measured as 'bit
error rate' (BER), depending on signal quality etc.
Bit errors can be detected and sometimes corrected
depending on whether error-correction info is
included and the sophistication of the receiver.
The data systems I work with have big $$ algorithms
to keep the uncorrected BER down in the 10E-7 range
(expect your scanner not to fall into this category!)
If the error only shows up in the talkgroup, then
it must decode to a different TG that you also had
programmed - mostly this doesn't happen, so you
rarely see it, regardless of being in CC mode or
not.
If the error causes a decode to a bad channel
number, then it depends on the scanner mode: the
traditional Uniden method won't scan to a freq
that's not programmed, which gives tremendous odds
in your favor (~20 freqs/18 MHz band). In CC mode,
it doesn't do any checking on the frequency, that's
the trade-off for convenience.
I expect the bit error rate of the scanners is
actually quite high, but most errors are
caught by the scanner as obviously bogus, or are
weeded out by not decoding to a programmed TG.
Flash