Multi-slicer design discussion

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DaveNF2G

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I'm splitting this conversation from the other thread so it doesn't turn into a giant hijack.

I originally posted this:

I'm in the very early (thinking it through) stages of designing a multi-trunking box based on the various slicer designs that are out there.

The box would have:

1 or more computer ports
2 or more radio ports
a 2-level slicer
a 4-level slicer
low-pass filtering, switchable to the 2-level slicer circuit
other useful features I haven't thought of yet
rfmobile replied with these suggestions:

1. econo-version: leave the 2-level circuit out - since the 4 level will provide this for you.
2. some software can't handle multiple inputs (CTS, DCD, and DSR) simultaneously so provide a switch to disconnect two of those pins (this would become your 2/4 level switch).
3. leave the 2-level circuit in - but only provide low-pass filtered audio to it.
4. your 2 vs. 4 way switch becomes ...
a. four level
b. two-level non-LTR (unfiltered)
c. two-level LTR (filtered)
d. two-level LTR and non-LTR (simultaneous on different pins)
5. use external power - allows the RTS and DTR pins to provide software control in place of a manual switch.

Options 5 and 4d above would allow software to automatically switch from one protocol to the next.
My head hurts. I have some circuit drawing software on either this computer or my Linux box, so I'll have to start roughing out some pseudo-circuits (rather like pseudocode) for discussion and reference.

[edit] Rats!!! It occurs to me that this thread probably belongs in the decoding software forum. Would the Moderator please move it over? Thanks! [/edit]
 
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SCPD

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My head hurts.
Tune your radio to a local control channel. Place head down on table next to speaker. Wait 5 to 10 minutes - you'll feel better. :)
I have some circuit drawing software on either this computer or my Linux box, so I'll have to start roughing out some pseudo-circuits (rather like pseudocode) for discussion and reference.
I'm looking forward to it ...
-rick
 

Audiodave1

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Hmmm....
I like the idea. I'd be happy to build up a beta sample from some rough plans and report back.

Most of my IC's laying around are bipolar so if you could do it with TL072's or similar that would be great, otherwiose I'll adapt it.
Us beggers can't be choosers though.

A thought for the LPF LTR filter, Dallas/Maxim has a MAX7401 chip that provides an 8th order LPF on a dip8.

Dave
 
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SCPD

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Audiodave1 said:
A thought for the LPF LTR filter, Dallas/Maxim has a MAX7401 chip that provides an 8th order LPF on a dip8.
The idea behind Eric's filter is that it doesn't introduce group delay. There might be other issues behind using a switched capacitor bessel but I think that was the main concern.
 

Audiodave1

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Looking at the Phase response that could be a problem.
Just an idea...that I haven't tried, being an audio guy I wasn't think about the effect on a data stream, not damaging data that is,

I've been collecting the parts lately to go on a ltr-data-decoder-slicer building spree so I got some free samples from them.

My main interest was a local MultinetII system but I'm ending up buying a programmed RX only radio for that.
 

SCPD

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PCB layout for Eric's LTR Slicer

I've been messing around with PCB123 ... here's what I've got so far. Some of the parts are wrong ... I'm still learning how to get the software to do what I want.
 

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