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996 Discriminator

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STiMULi

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I want to do it, but I would rather you open it up and be the man whose name goes up in lights.

Just don't let the smoke out :)
 

N9JIG

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Many years ago I experimented with the diode matrix in my Pro2004. After a $200 repair bill they welded the cage containing the diodes shut with 8 spot welds.

I did get a credit in Monitoring Times when I wrote in about the results....
 

N9JIG

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From memory, one of course was the cellular switch, one added 100 channels, another deleted the 30 KHz. step size in the cellular band, another deleted certian bands for the European market. There were a couple thers, but I don't recall right now.
 

N9JIG

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I Found the Discriminator!

OK, I dug around a little and it appears our friends at Uniden made it real easy!

Take off the outer case shell, and then the top inner case. Just about dead center on the board look for the solder pad labled "DISC". Run a single insulated wire to this point to a jack of your choice (I prefer RCA jacks) mounted on the rear of the radio. I also like to use a tantalum capacitor in line with the jack as well.

If you take the bottom inner cover off the radio you will see the best place to installe the jack apears to be the area of the bar code/serial number label. You could also just run an audio cable into the radio thru the threaded rear hole or even one of the holes on either side of the radio's rear.

Hear is a picture of the Discriminator tap.
 

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scannerfreak

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N9JIG said:
OK, I dug around a little and it appears our friends at Uniden made it real easy!

. Just about dead center on the board look for the solder pad labled "DISC".



Hear is a picture of the Discriminator tap.


:lol: thanks..Just got done ordering my RG 174, RCA solder jacks and the capacitor (Radio Shack 272-1436) Hope to have them soon, I'll post pics if I'm succesfull :)
 
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mam1081

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Tap point looks pretty obvious to me...

This is the top-most curcuit board in the 996. It clearly has "DISC" marked on a solder point.

Other points of interest:
+6V (maybe for internal GPS)
+8V (")
232C-RST2 (Front serial RST - is this supposed to be RTS?)
232C-TXD2 (Front serial TXD)
232C_RXD2 (Front serial RXD)
V_CPU (3.3V !! - add internal GPS here?)
232C_STBY2

RTS (real serial RTS)
RXD (real serial RXD)
TXD (real serial TXD)
V_GPS (whoa! is it really?!?!?! - don't get any voltage off that pin - maybe there is a jumper somewhere)


Looks like the designers of this scanner really made it easy for little mods!
 

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scannerfreak

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mam1081 said:
Tap point looks pretty obvious to me...







ya ya i know..Should have known..But I wasnt going to open it up until I got the parts and was ready to go..Thanks for the great pics!
 

mancow

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What's up with the tantalum cap?

Can someone tell me the technical reason why there is always a cap in line somewhere in disc. tap applications? I have never really been sure if I needed it or not.

I don't think I put one in my tapped PRO-83. Could that be part of the problem when trying to interface it to Unitrunker?

Sorry for a thread hijack but it seemed like a good time to ask.

BTW, you guys got some balls tapping the 996 already. I think I would have to cuddle it a while longer before digitally violating it.
 

Go-24

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mancow said:
BTW, you guys got some balls tapping the 996 already. I think I would have to cuddle it a while longer before digitally violating it.
You can say that again - I'd probably melt half the board if I tried to solder that in.
 

STiMULi

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In the category "Discriminator Locator in the UNIDEN BCD996T Scanner"

Envelope please...


















And the Winner is...




















Rich Carlson, N9JIG
 

N9JIG

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mancow said:
What's up with the tantalum cap?

Can someone tell me the technical reason why there is always a cap in line somewhere in disc. tap applications? I have never really been sure if I needed it or not.

I don't think I put one in my tapped PRO-83. Could that be part of the problem when trying to interface it to Unitrunker?
I have discriminator taps in just about all of my scanners using RCA jacks, I use them for both Trunker type applications and PL decoding. I have the caps in most of the radios, as I have read many places that they are needed to prevent bad voodoo if the discriminator is shorted. That said, I don't have them in all my radios and have never had a problem. I also have not seen any difference in performance one way or another...
 

N9JIG

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STiMULi said:
In the category "Discriminator Locator in the UNIDEN BCD996T Scanner"

Envelope please...


And the Winner is...

Rich Carlson, N9JIG[/b]
I would like to take this oppurtunity to thank my agent, my wife, my girlfriend and all the little people who made me possible...
 

dbrown2

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Hello,

I have read the wiki on discriminator output and went to google and looked up. But I don't understand what I would expect to get from this? Thanks to N9JIG I now know how to do it to my 996t, but not sure what I would get from it. Does this give me a way (with software I would guess) to read the text that is sent to the police cars on their screens? What other things would I see? Sorry for the newbie question.
 

SCPD

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No problem on the newbie question. All of us were there at one time (and some of us still are). The discrimination tap for most scanners is used in conjunction with what's called a 2-level data slicer for decoding digital information such as ACARS and other information transmitted in FSK format. Most, if not all trunked systems transmit what's called a control, along with the audio channels, which is basically a series of tones at certain intervals that can be understood with a computer. By using the discriminator (base audio unfiltered) from the scanner and a data slicer you can use a program called trunker. This allows you to see the control channels used for trunked systems.

I'm sure there's a few in here that can (and will) give you a much more detailed description of what it is and how it works. This is more the 60,000 ft view, which is a little fuzzy.
 

SCPD

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One other thing. Here an individual that sells data slicers. I’ve purchased from him the in past and he has a quality product.

http://www.dataslicers.com/

You can also surf the net and find plans to build one on your own; that is if you have the soldering skills and time.
 
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