[aprssig] APRStt lives! (DCS=NOT)

[Wes Johnston, AI4PX]

Ahh, but many many radios have the min-din connector for packet and that
would be perfect for this applicaton.
Wes

On Tue, May 18, 2010 at 13:45, Stephen H. Smith <wa8lmf2 at aol.com> wrote:

>  Robert Bruninga wrote:
>
> OK, PL.  Should be easy to decode in a pic... Just count the
> frequency...
>
> Bob, WB4aPR
>
>
>
>
>
> If you are envisioning this as some sort of external add-on gadget
> (otherwise I assume you wouldn't be talking about programming PIC
> processors), this may not be as simple an undertaking as you assume.    "PL"
> ("Private Line") is the Motorola trademark for the signaling system known
> generically as "continuous tone-coded subaudible squelch" (CTCSS).    The
> key is *SUBAUDIBLE*, more or less -- in the frequency range from about 60 Hz
> to around 180 Hz.
>
> Trying to take these tones off the speaker output (or inject them into the
> mic jack) of most radios will not work very well since the audio amps on
> both RX and TX intentionally roll off the low frequency response to keep
> these low tones out of the speaker.  [The RX audio channel typically starts
> with a 200-250 Hz audio high-pass filter.]
>
> You will need a direct connection to the receiver discriminator, with it's
> "down-to-DC" frequency response for these add-ons to work reliably.   [The
> connection point for OEM internal PL options is normally a separate audio
> channel with a 200-Hz cutoff audio low-pass filter tapped directly off the
> RX discriminator.]    If the radio has one of the 6-pin mini-DIN "data" or
> "packet" jacks, then no problem -- one can get at the raw discriminator
> audio easily.
>
>
> Otherwise you will encounter the same issue that prevented 9600 baud packet
> from being widely accepted by the average ham "end-user" -- the need to cut
> into the radio to tap the RX discriminator and TX modulator.  [And when was
> the last time you saw a hand-held with a 6-pin miniDIN data jack?]
>
> ------------------------------
>
> --
>
> Stephen H. Smith    wa8lmf (at) aol.com
> EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
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>
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>
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>
> "APRS 101"  Explanation of APRS Path Selection & Digipeating
>   http://wa8lmf.net/DigiPaths
>
>
>
>
>
>
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-- 
Wes
---
God help those who do not help themselves.
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