[Motorola] public safety using DCS

[JEFFREY MICHAEL KENYON]

ewer radios would obviously support DCS, but I remember reading a while
back that some older crystalized radios like the Expo will do DCS as well
as encryption.  What did you do about your old old radios like the MT-500s
and older mobile radios?





On Wed, 31 Jul 2002, Eric Lemmon wrote:

> Jeffrey,
> 
> Digital Coded Squelch (DCS) has been around long enough that most radios that
> are retired from commercial  and public safety service have that capability.
> 
> The most common reasons for using DCS instead of PL are that  it is universal
> across radio brands (unlike PL) and it is much more difficult to hack.  DCS
> usually requires direct coupling to the modulator, and this is perhaps too
> difficult for inexperienced techs.
> 
> The downside to using DCS is that the turn-off tone, about 134 Hz, is the
> same for all codes and thus prevents- or seriously impairs- the creation of
> talk groups on one RF channel.  Also, if another user on the same RF channel
> is using PL of 131.8 or 136.5 Hz, it might mute your radio.  Some low-end
> radios from Standard, Uniden, Maxon, and others use a rather crude means to
> generate the DCS codes, and I have almost always had to tweak even brand-new
> radios in order to make them code and decode the DCS signal properly.  That
> is one reason why cheap radios are much more costly over time than good
> radios!
> 
> Because Kenwood and Motorola use different phase shifts and timing for their
> respective reverse-burst squelch-tail elimination schemes, these two brands
> do not mix well in systems that both code and decode CTCSS- public safety
> services, for example.  That is why most police and fire departments (at
> least, those that I know about) will use one brand of radio throughout the
> system.  In the system I maintain, I converted the entire fleet to DCS just
> to avoid the annoying squelch tails that almost always occurred during
> contacts between brands.  It's one of the dirty little secrets that both
> Kenwood and Motorola publicly deny exists, but for which they both have flash
> upgrades to correct.
> 
> 73, Eric Lemmon WB6FLY
> 
> JEFFREY MICHAEL KENYON wrote:
> 
> > Hi everyoen. Last weekend while on vacation in Sanilak County, Michigan I
> > noticed something odd.  The County Law Enforcement frequency is currently
> > using a repeater with a DCS on it rather then a PL tone.  This county
> > doesn't have much in it other then summer homes, and I would not have
> > guessed that the county would have much money to upgrade to anything
> > special, but I don't know how long they have been on VHF and what they
> > switched from, but has anyonworked with this county, and what would a
> > county like this use radio wise if many of the older radios won't support
> > DCS?  Any information would be appreciated, and thanks in advance.
> >
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> 
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