Eric,
Thanks for the excellent response. The information in your response was just
what I was looking for. I'm evaluating an MX828 decoder chip for a project
and the reference to TIA-603-B will be especially useful.
Steve
WA6ZFT.
On Sunday 10 October 2004 15:46, Eric Lemmon wrote:
> Steve,
>
> The industry standard for Land Mobile Radio is TIA-603-B. This standard
> states that the maximum response time for CTCSS frequencies 100 Hz and
> above shall be 250 ms. Below 100 Hz, the maximum response time in
> milliseconds is found by dividing 25,000 by the CTCSS frequency in Hz.
> Therefore, a CTCSS frequency of 67 Hz must be decoded within 373 ms.
> Note that this standard is based upon a CTCSS deviation of 500 Hz.
>
> Modern receivers use digital signal processing, which may respond much
> faster than either PLL or reed based schemes. Personally, I like radios
> to unmute for CTCSS in 150 ms or less, but I'm not going to choose a
> brand or a model to achieve the quickest response time. I ignore the
> "specsmanship" game played by some decoder manufacturers; they know what
> TIA-603-B requires, and they might state "better than" or "maximum" or
> "typical" response times. Who knows? Most of them seem to work okay...
>
> It is true that higher CTCSS tones decode quicker, but some some radios-
> Amateur rigs in particular- have little or no high-pass filtering to
> keep the tones out of the speaker audio, and the higher frequency tones
> are more likely to make it through the receive audio chain and cause an
> annoying buzz to be heard. This effect can be minimized by keeping the
> tone deviation within the 500-700 Hz range.
>
> 73, Eric Lemmon WB6FLY
>
> Steve Rodgers wrote:
> > What is considered a high performance number for CTCSS/PL ackquisition
> > time? According to what I see posted on the web (which may or may not be
> > real) The Comspec TS-32 is 250msec, and the TS-64 is 150msec. The actual
> > decode time should get worse as you go lower in frequency, so what would
> > you think are high performance numbers for at say, 67 hz?
> >
> > Steve
> > WA6ZFT
> >
> >
> > Yahoo! Groups Links
>
> Yahoo! Groups Links
>
>
>
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