[aprssig] APRS on all Radios!!!!

Mark Miller kramrellim at tx.rr.com
Sun Aug 17 13:44:32 EDT 2008

FM receivers that use CTCSS typically have a low pass filter (~250 
Hz) that directs the CTCSS to the CTCSS deocder, and a high pass 
filter that blocks the CTCSS from the normal audio chain.  FM squelch 
circuits use another high pass filter (4K or so) that is used to 
determine the quieting on a channel.

Mark N5RFX

At 11:47 AM 8/17/2008, Scott Miller wrote:
>I'm afraid I don't even know how the radio
>suppresses the PL tone - 100 hz is most certainly within the audible
>range.  Is everything filtered below a certain cutoff frequency, and if
>so, what's the cutoff?

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