Simpler Data Dicer

[pro92b]

There are new Passport systems being installed but I think MultiNet is a dead issue.

Here's the tap point link: http://myweb.accessus.net/~090/bc-780xlt.html#disctap

 

[letarotor]

Thanks pro92b. Just completed the tap on point "A". Used a 1.0uF Tantalum capacitor, then hooked to my 741 op amp design slicer, LTRTrunk will not run. However, LTRDumper will it seems occasionally decode something. Here is a short file from about 3 minutes of monitoring a Passport channel:

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Sat May 7 01:02:04 2005 Dumper Version 10-Nov-2004
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1c04f82828c28ae Passport DCC:0 450MHz N:0 S:31 I Nbr-> 450MHz N:0 463.30000
========================
Sat May 7 01:02:42 2005 Dumper Version 10-Nov-2004
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7b1fffff *revcrc Area:1 (Unknown) C:29 H:17 G:255 F:31
========================
Sat May 7 01:03:22 2005 Dumper Version 10-Nov-2004
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1c04f8282880003 Passport DCC:0 450MHz N:0 S:31 I Nbr-> 450MHz N:0 None
========================
Sat May 7 01:03:58 2005 Dumper Version 10-Nov-2004
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000007000001000 Passport DCC:0 (Unknown LCN 0) T:0 S:0 G:57344 F: 16
========================
Sat May 7 01:04:01 2005 Dumper Version 10-Nov-2004
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7f800003 Area:1 (Unknown) C:31 H:24 G: 0 F: 0
========================
Sat May 7 01:04:11 2005 Dumper Version 10-Nov-2004
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3fffffa40000ab0 Passport DCC:1 (Unknown Type 0) C:2047 S:127 G:62592 F: 10
========================
Sat May 7 01:04:34 2005 Dumper Version 10-Nov-2004
========================
1c04f82828c28ae Passport DCC:0 450MHz N:0 S:31 I Nbr-> 450MHz N:0 463.30000
========================
Sat May 7 01:05:04 2005 Dumper Version 10-Nov-2004
========================
000005a2 *revcrc Area:0 (Unknown) C: 0 H:0 G: 0 F:11
========================
Sat May 7 01:05:12 2005 Dumper Version 10-Nov-2004
========================
0e70fffff847694 Passport DCC:0 LCN 1142 Free LCN 924 Active(00) -> 31-65535
========================
Sat May 7 01:05:13 2005 Dumper Version 10-Nov-2004
========================
0e70fffff847694 Passport DCC:0 LCN 1142 Free LCN 924 Active(00) -> 31-65535
========================
Sat May 7 01:05:14 2005 Dumper Version 10-Nov-2004
========================
0e70fffff847694 Passport DCC:0 LCN 1142 Free LCN 924 Active(00) -> 31-65535
========================
Sat May 7 01:05:15 2005 Dumper Version 10-Nov-2004
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0e30fffff847694 Passport *badpar (00c2)
========================
Sat May 7 01:05:16 2005 Dumper Version 10-Nov-2004
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000007000001000 Passport DCC:0 (Unknown LCN 0) T:0 S:0 G:57344 F: 16
========================
Sat May 7 01:05:28 2005 Dumper Version 10-Nov-2004
========================
7f800003 Area:1 (Unknown) C:31 H:24 G: 0 F: 0
========================
Sat May 7 01:05:45 2005 Dumper Version 10-Nov-2004
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6fffffe0 *revcrc Area:1 (Unknown) C:23 H:31 G:255 F:31
========================
Sat May 7 01:05:48 2005 Dumper Version 10-Nov-2004
========================
00006800 *revcrc Area:0 (Unknown) C: 0 H:0 G: 6 F:16

I'm getting there, but something is missing. Am I going to have to build the filtered slicer? :?

Mark

 

[cg]

For me, the filtered slicer works at least as well as the LTR tap point in the 780 all the time. For looking for new signals, the huge advantage is that the scanner does not have to be in "TRUNK" mode when using the external decoder.

chris

 

[letarotor]

Thanks CG, guess my next question is, when you use point "A" in your BC780 as the slicer how do you connect it to your computer for decoding. I've got an OptoLink, can I use that? Thanks

Mark

 

[cg]

The signal that is in the LTR tap does not go through a slicer. The discriminator tap goes through the filtered slicer. I use a homemade cable to go directly into the computer for the LTR tap. The discriminator tap goes through a 1/8" jack into the slicer.

cg

 

[letarotor]

Thanks CG for clearing that up for me. I'm about to order all the parts necessary to build the filtered slicer Eric recommends. Wish me luck. In the meantime, if anyone has a nice digital photos of their completed circuit boards, both top and bottom, that would be insurmountedly appreciated. Yea, I know, I don't ask for much do I. :wink:

 

[EricCottrell]

Hello,

I noticed my circuit diagram did not make it through the upgrade. Here it is

73 Eric

 

[Comint]

Eric

Back in August 2004 you said that you were "ready to go from the breadboard to a soldered version . . . for field test", but I haven't seen any reports on the test.

Also, I haven't seen any comments from you about pro96b's proposal to have a lower cutoff frequency on the filter. I'm interested in your views on the matter.

Comint.

 

[EricCottrell]

Hello,

So far it has worked fine. I need to put it in a box. I added a resistor in the input to prevent loading when connected to my AOR. There are a few other tweaks I need to look at as well.

I need to go back and correct the drawing but this will take a few weeks with my schedule.

73 Eric

 

[WayneH]

I've got the circuit built but I bought the wrong cap so it's not working for LTR yet. Maybe it's my imagination but my old WB5NBQ Hamcomm slicer seems to work better for Motorola (a slight bit better on 'accuracy'). But I didn't build it for that so...

I originally tried the more complicated LTR circuit out there and had too many problems (had to restart LTRDump/Trunker repeatedly, reattach the battery, all sorts). I'd like the reliability of my WB5NBQ circuits I've had for a decade in an LTR circuit.

-Wayne

 

[EricCottrell]

I've got the circuit built but I bought the wrong cap so it's not working for LTR yet. Maybe it's my imagination but my old WB5NBQ Hamcomm slicer seems to work better for Motorola (a slight bit better on 'accuracy'). But I didn't build it for that so...

I originally tried the more complicated LTR circuit out there and had too many problems (had to restart LTRDump/Trunker repeatedly, reattach the battery, all sorts). I'd like the reliability of my WB5NBQ circuits I've had for a decade in an LTR circuit.

-Wayne

Hello,

The difference could be due to filtering. My circuit does not have any filtering of the Motorola/EDACS signal. So if the receiver has a "noisy" discriminator chip (like the one used in the VR5000) then accuracy for Motorola will be lower.

It might be possible to put in some filtering for Motorola/EDACS but I do not like to add another IC chip or make the circuit more complex. I may be able to put in a DPDT switch for Mot/LTR to also switch a value on the first stage of the Low Pass filter to turn it into a simple 2 pole Low Pass.

73 Eric

 

[WayneH]

I think if there really is any difference it's very minor. It seems to be working well enough for me.

Eric, or anyone else, what do you use to design low-pass filters for circuits such as these?

-Wayne

 

[hkrharry]

Hi Eric and Gregg

The site in question your seeing there is the KCwireless Passprt site at the KMBC TV Tower
that one is site 10.


058857ef3039041 <<<< ESN info
Passport DCC:0 <<<< is the Digtal color code, KCWireless is DCC 0
LCN 912 <<<<<is most likly the Pass Port Home Ch
Free LCN 354 <<<<<<Free Ch
Active(00) -> 10 <<<< Home Site
64998 <<<<< Home Talk Group

058857ef3016070 Passport DCC:0 LCN 352 Free LCN 354 Active(00) -> 10-64998
058857ef301476b Passport DCC:0 LCN 327 Free LCN 354 Active(00) -> 10-64998
058857ef301454e Passport DCC:0 LCN 325 Free LCN 354 Active(00) -> 10-64998
"
Now i may have some of this mixed up but i will look up some of my notes and share
what i know if the system. (i have extensive notes for this system in particluar)
there is no Commenco site at 25 & Booth(I know I maintain that sites radio gear)

73
Sm0ke

Hello,

That is great. You need to set the time and date on your computer 8->.

Sometimes the serial port on a newer computer does not have enough drive to power a slicer. Mainly a problem with some laptops.

You are getting good decodes. Site number is 10. There are at least 2 other sites. See if you can receive the sites using 452.01250 and 462.37500. I did a quick search of the FCC DB and WPMU736 Commenco, Inc Kansas City MO located at 25th and Booth uses 452.0125. I could not seem to figure out the licensees for the other sites.

73 Eric

 

[ksmoscanner]

Im getting ready to convert one of my LTR slicers built from Erics plans to run off external power (9v battery) for use with my laptop. Do I just need to unhook the DTR & RTS pins from the DB-9 and hook power to them instead or do they still need to be connected to the DB-9 and power fed to the V+ & V- on the chip itself.


Thanks

Gregg in KC

 

[rickey456]

Would someone be willing to build [and sell] a filtered slicer for LTR

Rickey

 

[DaveNF2G]

While we're at it, I'd be willing to buy a box with at least dual inputs and dual outputs that contains a "normal" slicer for Mot/EDACS trunking and a filtered slicer for LTR. Being able to switch the non-filtered slicer from 2-level to 4-level operation would be great, too.

 

[inigo88]

As embarrassed as I am to admit it, I'm a total novice when it comes to building circuit boards. I know rat shack would never carry all the parts, and even my local electronics supply store lacks the necessary variety of ICs to build this, but I'd really like to try! Can anyone recommend a good electronics supply website to buy all these parts from? Also, I'd like to second the previous request for a photograph of someone's completed board so I can get an idea of what my finished product should look like.

Thanks guys - I really appreciate all the help you've contributed so far with all this great info!

-Inigo

 

[n8yid]

Group,

Has anyone updated the schematic for the circuit (per message #29). I know Eric is prolly very busy, but since I am about ready to order parts for this, I was wanting to get the latest and greatest info on the circuit. Also, anyone have any info/suggestions about material/parts/list for this beast? I have one made, I am jes wanting to get the correct parts so i can get this thing made correctly the first time around......

Thanks for everyones patience....

Dave T.

 

[inigo88]

Sorry to resurrect an old thread, but I'm again ready to try and attempt to start this slicer. I'd like to build it on breadboard, and I'd like to second the request for a parts list if possible (since I'm not exactly sure of all the dimensions needed for a breadboard on mouser.com, or what they all mean). Does anyone know offhand what dimensions I'm looking for for a component that will fit on the breadboard? (I keep stumbling upon chip resistors and caps by accident.) If not, this isn't a big deal and I'll figure it out.

I did just want to clarify one thing on the above circuit diagram, because I am relatively new to reading them. Following the discriminator tap audio in thru the buffer 1/4 of the IC, past where it branches off to go down to the (Mot/EDACS) / (LTR) switch, and past the 4.42k resistor in the 4 Pole 300 Hz Linear Phase LP Filter section, there is a four way intersection of the wires. (There are three more prior to the wire leaving the filter to the switch.) Now I understand that the previous T-shaped 3 way intersections are in fact areas where the wires branch off in different directions, however I've read about circuit diagrams that unless otherwise indicated, the four-way perpundicular crossing wires are simply two different sections of wire that cross / overlap eachother in that place on the diagram (but do not actually join together). In other words, it wouldn't be sending the current 3 ways each time it reached one.

Is this a correct assessment? If so, I think I have a solid enough understanding of the circuit, the IC pin locations and the op-amp symbology to get started.

 

[EricCottrell]

Hello,

All four wires are connected together. If the wire crosses and is not connected then a half circle is used to indicate no connection.

I am working on an update and a parts list.

73 Eric