Hi Skipp, Understood.
I'm coming in at a slightly different angle because our job was to build dial-access base station controllers that could be installed and accessed anywhere in North America regardless of phone line quality. Decoding and notching F1 and F2 sequences from all brands of consoles and tone remotes via lossy, noisy, and prone-to-crosstalk dial-up lines was a genuine challenge. In other words, when it came to tone signalling, it was much more like using radio technology than nice, short, phone-company-certified leased lines. We examined lots of tone remotes and tone remote adaptors from various vendors. Some were crystal controlled and accurate. Some used rather unelegant circuits, from LC oscillators in the encoders to cheap op amps and 5% Rs and Cs in the decoders. Sometimes the frequencies were off by tens of Hz. But our TRA was expected to reliably detect, and deeply notch, the sometimes-inaccurate 2300 Hz and 2175 Hz keying tones -- and detect the function tones. We never found anything better than our switched-cap-based design at doing that. Regarding Dayton, I can't break away due to contract work, but have a brat for me. 73, Bob -----Original Message----- From: [EMAIL PROTECTED] To: [email protected] Sent: Tue, 3 Apr 2007 1:21 PM Subject: [Repeater-Builder] Re: Tone filter Hi back, For a plug and play solution it's great. Don't tell anyone but in my opinion it's just a clone of an earlier Selectone circuit I already use. So I build them when I have time and buy them when I don't. One bad thing about these homebrew and kit-built filters is how they can and do drift with temp and time. The newer Norcomm units are much more stable & smaller using current surface mount parts. If you home brew something... get good stable parts (ie quality caps and resistors) or you'll make un-needed repeat alignment service calls. Yes they are narrow... but they also respond to slightly off frequency signals and in most cases it's enough to get the job done. For a number of smart reasons... one of the large linked repeater systems here on the West Coast use notched ctcss vs a low pass filter. Works well and I/we have never had to realign the notch filters since the system was installed. gonna' see you at Dayton this year Bob? cheers, skipp > [EMAIL PROTECTED] wrote: > Hi Skipp, > > What's your satisfaction level with the Norcom notch? A spec of +/-0.1% > BW means only 3.5 Hz of BW at the -40 dB points at 1750 Hz. And that's > for a tunable product, so you'd have to tune it dead on to get just 40 > dB of notch. The users' generators would also have to be very accurate > to be in the center of the notch. > > 73, > Bob > ________________________________________________________________________ AOL now offers free email to everyone. Find out more about what's free from AOL at AOL.com. =0
