I've never looked at Bob's filter, but some generic things to look at... 1. Filters are lossy devices typically. Did levels drop off behind it to the point where your DTMF detector is now unhappy? 2. Twist now wrong? (In other words, does Bob's filter leave the audio passband from 300-3000 Hz generally "alone" and not have a steep "slope" through it. Having seen Bob's work here, I would assume it does. But if one tone of the two-tone set is now a lot higher in level than the other, at some point the DTMF detector will give up.
Those are be the two places I'd start... grab a scope, take a look. Or if no scope and desperate, a high-impedance amplified speaker and listen at each stage (prior to Bob's filter, and after it) and it might SOUND real obvious why it's not working... I would think that would already show up on how the repeater sounds though -- just bypass the filter, then put it back in, WITHOUT changing any levels on anything, and listen... you'll probably hear it. (If the human voice sounds different behind the filter, so will the DTMF! Not rocket-science, right?) Nate -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Doug Hutchison Sent: Thursday, March 19, 2009 6:32 AM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] PL (CTCSS) Filter Hi, Have built the filter circuit by Bob Dengler NO6B from the site. The unit works a treat but for some reason, DTMF detection fails on my 210 controller with the filter in use. DTMF is present on the output. Any suggestions re what might be causing this would be appreciated. Thank you, Doug - GM7SVK
