[Scan-DC] Trunked Radio audio quality

Wed, 19 Mar 2003 12:45:45 -0500

The I.M.B.E. vocoder uses a different algorithm than those
used by the cell carriers. Further, the APCO Project 25 effort,
or at least Motorola's implementation, allows for data to be
combined with the signal as I understood it from Big-M's
training web page (now gone). The cell carriers send data bursts
somehow differently, but it's not the same intent as APCO had.

The reason that you find mixed-mode systems is...TA-DA! MONEY.
It's cheaper to buy analog subscriber units for trash collectors,
building inspectors, dog catchers, and others, so that's what they do.
In many cases these mixed-mode systems are upgrades of existing
analog systems, so they don't need to buy new radios for the
have-not agencies. All new systems like Michigan can start
digital from the ground up.

Bote
F.E.C. milepost 339.3 
Look -> http://pages.prodigy.net/bote/rail
Listen -> http://groups.yahoo.com/group/scanaudio_FLL (DEAD)
Live -> http://www.fecrs.com

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Alan Henney
> Sent: Wednesday, 19 March, 2003 01:27
> To: Scan DC
> Subject: [Scan-DC] Trunked Radio audio quality
> 
> ...  I can understand advantages of building an all-analog
> or all-digital system, but why have several jurisdictions chosen to mix both
> on the same system (Howard, Upper Eastern Shore, Worcester, maybe Charles)?
> Either you intend to conserve bandwidth or not.
> 
> With regard to the note that digital systems are intended to conserve
> bandwidth, I would have to point out that APCO audio sounds significantly
> worse to me than digital audio used by the cell carriers who also have
> spectrum efficiency goals.  It's as if APCO is older technology.  Although
> Nextel sounds pretty awful at times.