Nac decoding ?

[JASII]

Okay, I finally got back to the project of making the cable to go from the FT-8800s 6-pin mini-DIN to the computer and BOTH cables I scavenged from either a mouse or a keyboard did not have a wire going to each pin of the mini-DIN and in neither case did it have the right combination of what I needed to make this work. I guess the next step is to have a cable made for me. Can anybody recommend the best place to get a cable made?

Here is the schematic to add additional filtering for LTR Dump. If I had a patch built with this additional filtering, will iit still work with kNACk or should I get two different cables made? http://wiki.radioreference.com/images/c/cd/LTRDicer1.png

 

[EricCottrell]

Hello,

You need to get a 1/8 plug. Solder the tip terminal to the wire going to pin 4 of the 6 pin mini-din and shield terminal to the wire going to pin 2. The manual shows the pinout. Use the 9600 baud packet output.

If you put a 1/8 jack on the input of the data slicer you can use the same cable. The data slicer will not work with the nac decoder. The nac decoder uses the sound card input. The data slicer uses the serial port.

73 Eric

 

[wa8pyr]

You get anything on TSA? I get "001" or "000" on them. When I program an ASTRO radio for RX-only with those NACs, I don't get anything. That almost makes me think they are running talkgroups.

Update on TSA....

They are apparently using conventional talkgroups. I've got Unitrunker working quite nicely, as well as the CTCSS and MDC decoding utilities. kNACk decodes the NAC from Ohio MARCS voice channels quite nicely as well.

But, when monitoring the TSA... nada. I know they are using a different channel at each checkpoint so they do not have to listen to each other, so it must be different conventional talkgroups instead of different NAC.

Tom WA8PYR

 

[W4UVV]

Knack still won't work

Hi Matt;
As mentioned earlier, extas will have to come later.
-rick

I have been trying different computer/receiver/scanner interface combinations literally for the past several months off and on trying to get the latest Knack version to work. Could somebody please tell me what, if anything I am doing wrong? I have modified all of my receiver/scanners for baseband (unfiltered) audio except one. My desktop and laptop are Pentiums usng XP OS and work fine.. Two receivers/scanners I have been using for testing are a R7000 and BC796D. They work fine interfaced with a standalone CTCSS tone decoder and for software application processes requiring baseband audio input. and addtionally Trunktracker 3.8.3 in the MS DOS mode. I have tried both line and mic sound card inputs to the desktop and mic input to the laptop. Additionally I have tried a level 2 dataslicer as input to both computers with no success. So far ZERO results on everything I have tried. As previously stated I have NO problem using both these radio baseband audio outputs to Trunktracker 3.8.3 in MS DOS so I know my input signal level is fine. I have adjusted the computer sound card settings with no success with incoming P25 signals transmitting during the adjustments. I have no problem running the MDC ANI program for conventional analog signals with filtered audio output using mic input to the two computers.

Knack executes fine and greys to "000" and "Running" displays and then just sits there displaying "000" no matter computer/scanner/receiver signal audio interface I try or whichever P25 signal is transmitting. I have tried every knack setting combination with no success. The 796D is programmed for approximately 10 stand alone P25 conventional signals I monitor with noise free plus reception. I find it difficult to believe that none of them have a NAC. My understanding is all P25 systems contain both a WACN and NAC. I have exhausted everything I know to try. I have not yet modified my 996T digital scanner for baseband audio output but I suspect the end result will be the same..no NAC decoding. Please don't advise me to build a buffer amp. As previously stated, if Trunktracker works fine with the audio input, knack should work. If the Trunktracker signal works fine the signal quality then that should be good enough for knack.

If anyone can tell me what I am doing wrong I would appreciate any response or recommendations of what else I can try because for now I give up. Tnx.

 

[SCPD]

Please don't advise me to build a buffer amp.

Okay, I won't.

As previously stated, if Trunktracker works fine with the audio input, knack should work.

What I will do is describe my person experience.

BC780XLT tapped with 10uF capacitor.
Compaq Presario laptop with external microphone input.
Direct 1/8th shielded audio patch cable.

Results - EDACS, Motorola and MPT1327 decode fine (100% with good signal). P25 decoding is single digit (0 to 9%).

Insert buffer amp between radio and microphone input.

With a good clean signal, I get 100%. With a fair signal I get 60 to 70%.

You mileage may vary.

Please understand that the waveform is very different than these other trunking protocols.

-rick

 

[W4UVV]

Okay, I won't.

What I will do is describe my person experience.

BC780XLT tapped with 10uF capacitor.
Compaq Presario laptop with external microphone input.
Direct 1/8th shielded audio patch cable.

Results - EDACS, Motorola and MPT1327 decode fine (100% with good signal). P25 decoding is single digit (0 to 9%).

Insert buffer amp between radio and microphone input.

With a good clean signal, I get 100%. With a fair signal I get 60 to 70%.

You mileage may vary.

Please understand that the waveform is very different than these other trunking protocols.

-rick

I don't have the test equipment to troubleshoot nor the technical expertise for this type of DIY build project. Too bad. I give up. Maybe Uniden will add this as a feature option in a future 396T/996T firmware release. Tnx.

 

[wa8pyr]

I don't have the test equipment to troubleshoot nor the technical expertise for this type of DIY build project.

If you were able to put discriminator taps in your scanners, you shouldn't have any trouble building a simple buffer amp. You're an Extra... give it a try.

Too bad. I give up. Maybe Uniden will add this as a feature option in a future 396T/996T firmware release. Tnx.

Don't hold your breath....

 

[Nikko]

Not having any luck either.....

Ok, have knack1 and knack2, tried it on Win98se, win2000, winXP desktop, winXP laptop.
Built the op-amp unity gain buffer. And an in-line attenuator, just to try that too.
Tried mic in, line in. Volume up/down.

Tried discriminator tap, (works great with 4FSK with trunker and pager decoders).
Tried tape out as well.
I am using a PRO-2006. Has anyone tried this as a receiver?
Has anyone tried a maxtrac?


Looked at signals using scope program. I always see clipped inputs independant of attenuation attempts.

Does it matter left channel or right channel?
Are there minimiums expectations of my sound card?

 

[W4UVV]

Welcome to the club

I didn't try everything you did but did some of them and no luck. I am hoping the new GRE scanners will have that decoding capability but I can't find any post who can confirm it either way. The webpage listing the GRE scanner specs are vague regarding NAC.

I used a number of receivers trying to decode the P25 NAC with no luck. They included a R7000, R7100, R796D. All had baseband unfiltered audio output. I haven't tried my 996T yet but I doubt it will work. I received the "000" ready to go display and it just sits there never changing.

I don't have "knack2". I cannot find it on a RR or google search. Can you PM me as to how I can obtain a copy?

 

[mancow]

The new receivers will have it.

 

[Nikko]

Get the kNACk

kNACk1 and kNACk2 as I called them, both are linked as kNACk.zip within this thread
see: 06/07/2006 @ 9:37PM page 1, post 18.
see: 06/11/2006 @ 4:25PM page 3, post 43.

 

[SCPD]

The Unitrunker installer includes the latest kNACk program.

Looked at signals using scope program. I always see clipped inputs independent of attenuation attempts.

Not good. You'll need a way to adjust the level so it does not clip.

 

[Nikko]

The op-amp circuit shown is the mfg's typical use or test circuit and includes a x10 sample circuit too.
So I built both.

As previously stated by me, my scope program sees only clipped inputs (through mic jack), and these are not usable.

So I was thinking, if the output of my discrim tap goes to a 10k variable R on the top leg, bottom leg grounded, and the variable feeds the x10 op-amp circuit though the 1k R, which is part of that circuit, impedances should be maintained with negative to positive gain obtainable.

I haven't tried it cause ... just too busy.

All the op-amp cook books I've looked through either show circuits for: 0db and up, or 0db and down but not -20 to +20 db gain, or anything that passes through unity.
Isn't there a better approach to variable gain?
Looking for a better circuit...

 

[DaveNF2G]

All the op-amp cook books I've looked through either show circuits for: 0db and up, or 0db and down but not -20 to +20 db gain, or anything that passes through unity.

It's not clear from the above whether you know this, but 0 dB is unity gain. Are you in need of a circuit that is capable of operating on both sides of unity gain, meaning that it can provide either gain or loss?

 

[Nikko]

It's not clear from the above whether you know this, but 0 dB is unity gain. Are you in need of a circuit that is capable of operating on both sides of unity gain, meaning that it can provide either gain or loss?

yes, loss to gain.

3 db gain or loss does not seem enough, but more than 20 db is too much.
so 10 db loss to 10 db gain would be nice, 20 db total.

Is this do-able?

 

[n1das]

kNACk1 and kNACk2 as I called them, both are linked as kNACk.zip within this thread
see: 06/07/2006 @ 9:37PM page 1, post 18.
see: 06/11/2006 @ 4:25PM page 3, post 43.

"kNACk1" in Post #18
"kNACk2" in Post #43

I'm also calling them kNACk1 and kNACk2 to describe the two versions.

I recently got "the kNACk" and love it! However, I think I also found a bug in kNACk2. kNACk1 works fine for me but kNACk2 only decodes ONCE and then has to be restarted to decode the same or a different NAC again. My workaround is to use kNACk1.

Radio: Uniden BC895xlt w/discriminator tap. Discriminator audio connected to PC's microphone input. No buffer amp circuit needed.
PC: HP Pavilion laptop (don't remember exact model #), running Win XP home edition. I found I had to invert signal polarity for it to work.

I tested both kNACk versions by talking to my scanner with an ICOM IC-F70DT P25 portable on a 2m ham simplex freq. Then I listened to NHSP and other P25 conventional channels in my area and logged a bunch of NACs.

I also demo'd kNACk1 to a friend of mine using his BC895xlt and a Dell laptop provided by him. kNACk1 worked fine there too but I didn't get to test kNACk2. On his PC it wasn't necessary to invert signal polarity for it to work. We then decoded and logged a bunch of NACs on P25 conventional channels in his area.

kNACk1 works perfectly fine with my setup. kNACk2 consistently doesn't.

EDIT: I haven't tried the latest kNACk program that came with the UniTrunker installer other than it appears to be the same as kNACk2. It may have been updated since I first got "the kNACk".

 

[n1das]

For people having trouble getting kNACk to work, make sure you've got noise-free reception on P25 conventional channels.

I found kNACk won't decode/display on weak/noisy P25 signals. Maybe I need to add a buffer amp to my discriminator tap to improve my setup and make it more tolerant of noise. I was trying to read the NAC on a few NHSP freqs and I had to put a better antenna on the scanner to get better signal strength for it to work. I was also listening to the blast of raw P25 data from the scanner while experimenting with antennas and some stations were initially heard at strength less than full-quieting. Decoding was always reliable with strong/local signals (heard "dead full quieting") but was unreliable or just plain wouldn't decode at all on weak/distant/noisy signals. Getting better received signal strength on the weak stations that previously wouldn't decode now decode like the strong/local stations.

Noise-free reception is important for reliable NAC decoding. Bottom line is the program works as advertised (except for the weird bug I think I found with the second version).

Good luck.

 

[N_Jay]

yes, loss to gain.

3 db gain or loss does not seem enough, but more than 20 db is too much.
so 10 db loss to 10 db gain would be nice, 20 db total.

Is this do-able?

So use a 0 to 20 dB amp, and a 10 dB pad. :roll:

 

[slicerwizard]

As previously stated by me, my scope program sees only clipped inputs (through mic jack), and these are not usable.

So I was thinking, if the output of my discrim tap goes to a 10k variable R on the top leg, bottom leg grounded, and the variable feeds the x10 op-amp circuit though the 1k R, which is part of that circuit, impedances should be maintained with negative to positive gain obtainable.

I haven't tried it cause ... just too busy.

All the op-amp cook books I've looked through either show circuits for: 0db and up, or 0db and down but not -20 to +20 db gain, or anything that passes through unity.
Isn't there a better approach to variable gain?
Looking for a better circuit...

First, loading down the discriminator circuit with a 10k resistor to ground doesn't sound like a good idea. Some might not mind, but some might.

Second, if you're feeding a mic input, you sure don't need any gain.

I would just go with discriminator out to top of 100k pot; bottom of pot to ground; pot wiper to mic in, possibly through some resistance (try zero to 10k)

 

[KC1UA]

FWIW, this is also happening to me. I am using an Icom IC-PCR2500's discriminator tap. Exact same results. I'm going to have to go back and see if I still have "kNACk 1" around.