LTR Data slicer

[Saint]

I received this email from Optoelectronics, I asked if they made any slicers with extra filtering that would work with LTRTrunk/LTRDump software, does LTRTrunk/LTRDump need a 2 or 4 level slicer.

Steve,
The Optolinx has a 2 level data slicer inside. Need to know whether
your program requires a 2 level or 4 level slicer. A lot of programs
require a 4 level slicer which we don't have.

Steve

[ka3jjz]

Our wiki has the schematic - I think it was from Eric Cottrell - of a 2 level device with what I think is additional filtering in front.
Here's the link for the schematic...

http://wiki.radioreference.com/image.../LTRDicer1.png

I might be wrong here, but didn't I hear somewhere that this was being redesigned?

73s Mike

[Saint]

Originally Posted by ka3jjz

Our wiki has the schematic - I think it was from Eric Cottrell - of a 2 level device with what I think is additional filtering in front.
Here's the link for the schematic...

http://wiki.radioreference.com/image.../LTRDicer1.png

I might be wrong here, but didn't I hear somewhere that this was being redesigned?

73s Mike

Thanks Mike I went to the wiki before posting and was not sure if I should send this picture to optoelectronics or not, I think your right it may have been changed since this picture was submitted.
Steve

[slicerwizard]

Originally Posted by ka3jjz

I might be wrong here, but didn't I hear somewhere that this was being redesigned?

That one has a 300 Hz cutoff, but it should be 150 Hz. So all the resistor and capacitor values in the top half of the schematic get changed.

Also, the input line (marked "Discriminator") should have a resistor+cap running to the actual discriminator tap point, plus a high value resistor to ground.

------radio------   ----slicer----

disc----R----C---------+----opamp
       10k             |
       to              |
       20k             R  100k to 1M
                       |
                     ground

[DaveNF2G]

The most important slicer specification when dealing with LTR is that it have a low-pass filter in front of it. Normal 2-level slicers do not have this feature and cannot be used on LTR signals.

[ka3jjz]

Originally Posted by slicerwizard

That one has a 300 Hz cutoff, but it should be 150 Hz. So all the resistor and capacitor values in the top half of the schematic get changed.

Also, the input line (marked "Discriminator") should have a resistor+cap running to the actual discriminator tap point, plus a high value resistor to ground.

------radio------   ----slicer----

disc----R----C---------+----opamp
       10k             |
       to              |
       20k             R  100k to 1M
                       |
                     ground

OK, if someone would be so kind as to redo the schematic, I can arrange to have it uploaded into the wiki for safekeeping. Thanx es 73s Mike

[Saint]

Just talked to Optoelectronics and they can't help with this kind of slicer, tried several other companies to see if they either made these or were interested in going down this road and make one for comercial sale but all said at this time they were not interested, I'll keep trying to find someone or some electronics company that will make these and if I do I will post infomation on this web site, I see that from other post that other people are interested in a filter that we could use to decode LTR Sytems so maybe sooner or later someone will start making these.
Steve

[wayne_h]

An alternative is to wait for the GRE 500/600 model radios coming out next month which will support outputing all trunking formats in plaintext through the PC/IF port.

If they would only support PassPort too we wouldn't have to dick with these circuits.

[Saint]

Originally Posted by wayne_h

An alternative is to wait for the GRE 500/600 model radios coming out next month which will support outputing all trunking formats in plaintext through the PC/IF port.

If they would only support PassPort too we wouldn't have to dick with these circuits.

Hi Wayne, thanks for the info, When It comes to these decoder programs I far from an expert, I just started to use Unitrunker decoder and have that up and running.

Are you saying that the new GRE scanners will allow me to decode LTR Standard systems with the LTRTrunk/LTRDump DECODER program without the filter, or will there be another way to do this with the new Gre scanners. I really would like to be able to decode LTR Systems, I have over 20 standard ltr systems I collect information on and submit the information to this web site.

With the new gre scanner how would I go about setting the scanner up to decode standard ltr systems. Thanks for any information you can give me on this isue.
Steve

[inigo88]

Read all 7 pages of THIS thread and you should be in business.

[Saint]

Originally Posted by inigo88

Read all 7 pages of THIS thread and you should be in business.

Ah, I'm sorry if I'm missing something but how do all of these threads help me with what I asked about the new GRE Scanner.????
Steve

[loumaag]

Originally Posted by Saint

...Are you saying that the new GRE scanners will allow me to decode LTR Standard systems with the LTRTrunk/LTRDump DECODER program without the filter, or will there be another way to do this with the new Gre scanners. ...

I will try and give this a shot.

No, LTRTrunk/LTRDump are specifically designed to be used with signals pulled from base band audio through a slicer. The GRE scanners are *supposed* to provide already decoded data at the PC/IF port, translating that data will be up to the user.

Now I don't mean you have to write the program, when GRE did this on the Pro-96/2096 for Project 25 trunking systems, it was not long before a program appeared and through back and forth and a lot of time on Mike's part we have Pro96Com. Mike has expressed an interest on expanding that project, but of course one has to wait for the radios to appear for testing purposes.

[Saint]

Originally Posted by loumaag

I will try and give this a shot.

No, LTRTrunk/LTRDump are specifically designed to be used with signals pulled from base band audio through a slicer. The GRE scanners are *supposed* to provide already decoded data at the PC/IF port, translating that data will be up to the user.

Now I don't mean you have to write the program, when GRE did this on the Pro-96/2096 for Project 25 trunking systems, it was not long before a program appeared and through back and forth and a lot of time on Mike's part we have Pro96Com. Mike has expressed an interest on expanding that project, but of course one has to wait for the radios to appear for testing purposes.

Thanks loumaag, I think what I will do is I will be buying one of the new GRE Scanners, so I think after awhile when people have a chance to use these scanners they, as you say will start to try and make some of these decoder program compatable with these new scanners and this may start a new line of decoder programs that use this type of Tap in the back of the scanner. It looks interesting.
Steve

[DaveH]

Originally Posted by DaveNF2G

The most important slicer specification when dealing with LTR is that it have a low-pass filter in front of it. Normal 2-level slicers do not have this feature and cannot be used on LTR signals.

Not quite true, you can use a regular slicer but it will be prone to falsing
and talk-off, due to voice interfering with data decoding. It can provide some
system information, although far from ideal.

Dave

[LauDauns]

hehehe~~!I support your point of view