Unitrunker & EDACS

[tyytor]

i have used unitrunker for a long time with good results with MOT systems,
however when i try to do an edacs with the same tapped scanners and same computers
it acts like it loades down the mic, at certain points it will start decoding at 1-5% and intermintently and only with EDACS 9600 systems TIA,

 

[SCPD]

i try to do an edacs with the same tapped scanners and same computers
it acts like it loades down the mic, when i pull it out to a certain point it will start decoding at 1-5% and intermintently and only with EDACS 9600 systems.

Run a 'scope program like Uniscope - compare your Motorola waveform to your EDACS wide waveform. Since the EDACS signal is almost 3 times faster - it may suffer some distortion from the circuit dynamics of your particular system (capacitive coupling and impedance mismatch).

In short, run a 'scope program to get a picture of the signal and go from there.

 

[tyytor]

Run a 'scope program like Uniscope - compare your Motorola waveform to your EDACS wide waveform. Since the EDACS signal is almost 3 times faster - it may suffer some distortion from the circuit dynamics of your particular system (capacitive coupling and impedance mismatch).

In short, run a 'scope program to get a picture of the signal and go from there.

i tryied that a while ago and did not find anything to over come it,
filtering, ect....or what would be a good way to over come this?? caps, resistors
how do you have yours setup for this ??
or do you have problem with EDACS systems also?? TIA

 

[SCPD]

i tryied that a while ago and did not find anything to over come it,
filtering, ect....or what would be a good way to over come this?? caps, resistors
how do you have yours setup for this ??
or do you have problem with EDACS systems also?? TIA

Here's a screenshot I made on a trip to San Antonio (for ESK testing). It works well but I have noticed some computer's sound inputs are worse than others. Combine with the fact that signal from some radio models are weaker than others - and you've got a hit-and-miss recipe.

The problem is probably the input capacitor that is internal to your computer's sound input. It is acting as a low-pass filter and smoothing out the sharp edges of the EDACS squarish waveform. That's just a guess.

Does your radio's tap use a capacitor or a resistor to provide isolation? You may want to use a resistor instead. You may also want to place a buffer amplifier between the radio and computer.

-rick

 

[tyytor]

here is what i got as far as signals, any ideas on a buffer amp,
no caps or resistors any values recomended??
first pic is of a moto 3600 decode 99%
second is 9600 EDACS decode 5%
third is 9600 EDACS no decode
all have good signal,i could only get uniscope to work at sampleing rate of 48000, TIA

 

[SCPD]

Sorry, I know this must be a pain. Please change the symbol type to "Oscilloscope" and make some fresh screenshots.

There's something going on here ...

Oh, and what radio do you have tapped?

-rick

 

[tyytor]

all my uniscope has is
C4FM
FFSK
Pulse
Qpsk
for symbol type,
i am running unitrunker beta-3 with a Pro-2052 tapped,
i have also tryied the pro-2026
TIA

 

[SCPD]

Here's an updated version of the 'scope program - this adds a simple oscilloscope display to go along with the eye patterns.

 

[tyytor]

thank you the file, here are the screen shots
first one is the EDACS ,the second one is the Moto both are 800mhz systems TIA

 

[SCPD]

thank you the file, here are the screen shots
first one is the EDACS ,the second one is the Moto both are 800mhz systems TIA

Bingo.

Yeah, it looks like there's a lot of filtering. The Motorola waveform is severely rounded. I'm amazed that the Motorola signal is usable. The EDACS waveform is unrecognizable.

Okay ... can you describe your exact set-up?

On the radio side ...

Where is the signal tap point inside each radio?

Where is the ground tap point inside each radio?

Did you use a resistor or capacitor?

What component value did you choose ?

On the computer side ...

Is this microphone or line input ?

What make / model is the computer?

What chipset is used for the sound (a Yamaha I think) ?

-rick

 

[tyytor]

i will get you the info as soon as i get home,
the messed up thing is that the moto is 99-100% decode all the time,
on all of the moto sysytems i have tried and on all of the radios i have tried,
but the EDACS is the one that i have problems with :-},

 

[tyytor]

computer is a gateway solo 3200 with win98 2nd addition i am running things thought the mic input
w/yamaha chipset
Radios;
pro-2052 tapped at Mc3361cdr2 pin-9
pro-2026 tapped at mj3359D pin-10
no restrors,or caps

 

[SCPD]

computer is a gateway solo 3200 with win98 2nd addition i am running things thought the mic input w/yamaha chipset

Noted - I wasn't able to find the exact Yamaha chipset online.

pro-2052 tapped at Mc3361cdr2 pin-9
pro-2026 tapped at mj3359D pin-10
no restrors,or caps

Good info. Here's the next steps ...

Tune the radio to a control channel. Turn the radio's volume up so that you can hear the sound. Mute the sound of the computer's speakers.

Plug the audio cable into the computer and listen. Unplug the audio cable from the computer and listen. Does they sound about the same? Does the volume drop with the cable plugged in?

With the cable plugged into the computer - is the radio able to scan or does it seem to stick to any channel - even one with little or no signal?

-rick

 

[tyytor]

Noted - I wasn't able to find the exact Yamaha chipset online.

yamaha opl-3 sax??

Good info. Here's the next steps ...

Tune the radio to a control channel. Turn the radio's volume up so that you can hear the sound. Mute the sound of the computer's speakers.

Plug the audio cable into the computer and listen. Unplug the audio cable from the computer and listen. Does they sound about the same? Does the volume drop with the cable plugged in?

yes sound drops,the moto will still decode at 95-100%,the EDACS will not

With the cable plugged into the computer - is the radio able to scan or does it seem to stick to any channel - even one with little or no signal?
-rick

it will stay stuck and squelch will not close,

 

[SCPD]

yes sound drops

it will stay stuck and squelch will not close,

That's a definite sign the sound input is loading the discriminator audio signal. Judging by the waveform - there's no DC offset in the 'scope display so the computer's microphone input probably includes a DC blocking capacitor. In summary, here's what you have now.

radio                                     mic-in
tap >------------------------------------> tip
gnd >------------------------------------> ring

(Pardon the ASCII art)

I thing you've got two options ...

1. insert a resistor in series. A 10 kilo ohm resistor should work. Your setup in schematic form becomes this ...

radio                 10k                  mic-in
tap >---------------/\/\/\/--------------> tip
gnd >------------------------------------> ring

This will increase the electrical resistance of the discriminator audio as at leaves the radio - creating a smaller more manageable load on the radio's internal circuitry. The downside to this is the signal seen by the computer is also much weaker. If your computer's microphone input supports some sort of gain (usually a volume control, a +20 db checkbox or both) - you'll need to experiment. Use the 'scope program to see the effect of this setting on the signal.

It is possibly that you'll end up with a too weak signal (but the radio's scan, volume level, and squelch will work just fine). The good news is that resistors are cheap - pennies a piece in bulk. At Radio Shack - you can get 5 for $1 (or something in that range). I think the RS part # for 10k resistor is 271-1721. Either of the quarter-watt and eighth-watt resistor sizes work fine. Since they're cheap - it's no major loss if this doesn't work out.

2. Get a buffer amp. Place that in between the computer and radio.

radio                                     mic-in
tap >---------------> buffer >---------------------> tip
gnd >--------------->  amp   >---------------------> ring

The buffer amp (perhaps a microphone pre-amp) will provide isolation while presenting a useful signal level to the microphone input of the computer. Run the 'scope program to watch the signal levels. Set the gain control of this amp to its lowest volume and gradually increase until you see a waveform that fits within the scope window - not a flat line or something that is clipped because it's too strong.

 

[tyytor]

i tried to do the 10k resistor and still no edacs,
do you have any name for a good buffer amp,
or should i get plans off internet??

how do you have yours set up to get P-25, Moto, EDACS,

with out changing any thing EDACS will come on for a few seconds give me a 1-8% decode and them goes way.TIA

 

[SCPD]

i tried to do the 10k resistor and still no edacs,
do you have any name for a good buffer amp,
or should i get plans off internet??

Easy thing is to get one of those bubble-packaged hobby kits. You're looking for a generic hi-Z microphone preamp w/ volume control. You'll need to figure out how you want to power the buffer amp. If you can steal 12 volts from inside the radio - find one that will run off of 12 volts. Or get one that's external and pulls power from a wall-wart.

A low impedance pre-amp will probably work. The preassembled ones seem to be low-Z versions. They fairly cheap - like $10 to $15 - maybe less. Most of the fuss and labor is in wiring and mounting.

-rick

 

[tyytor]

i will have to try that is there one that has a volume, the ones i have seen just have the amp,can you just add one to the amp;

http://www.hobbytron.com/UK008.html ,TIA

 

[tyytor]

adding the above item that i ordered and a little patience i got it to do EDACS, MOTO and P-25 trunking, i still get a low decode rate 25-75% but it is better than nothing
thanks rfmobile