<div>Ahh, but many many radios have the min-din connector for packet and that would be perfect for this applicaton.</div>
<div>Wes<br><br></div>
<div class="gmail_quote">On Tue, May 18, 2010 at 13:45, Stephen H. Smith <span dir="ltr"><<a href="mailto:wa8lmf2@aol.com">wa8lmf2@aol.com</a>></span> wrote:<br>
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<div class="im">Robert Bruninga wrote:
<blockquote type="cite"><pre>OK, PL. Should be easy to decode in a pic... Just count the
frequency...
Bob, WB4aPR
</pre></blockquote><br></div>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. <br>
<br>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.]<br>
<br>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. <br>
<br><br>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?]<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Wes<br>---<br>God help those who do not help themselves.<br>