discriminator taps...

[SCPD]

Using a sampling rate of 44100, I get absolutely no deflection on the oscilloscope. The only rate that shows anything is 22500.

Bizarro. Try 48000 and / or 96000. Also - what options do you have besides "default input" for the signal source? You should have at least two others. Try selecting those and repeating the steps earlier to verify the connection.

This is first I've heard of a non-telephony recording input that didn't accept the "standard" CD audio quality 44100 sample rate. I would have to modifiy UniTrunker to accept 22050. It wouldn't perform well for EDACS 9600.

 

[DaveNF2G]

I have two choices, default and Audigy SB00. Here are tests at all sampling rates using the Audigy input (I have to post a second message showing the other 4 tests because of forum limitations):

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[DaveNF2G]

Here are the default input tests:

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[SCPD]

Thanks Dave.

You mentioned microphone and line inputs on this computer. I'm suprised you don't have one more choice for line input.

The Audigy 1 and 2 are high end sound systems. A small amount of digging online reveals that the Audigy 1 likes 48k samples per second at 24 bit as it's native format. If you're running Windows XP - the built-in drivers will transcode to whatever sample rate / sample size is requested (with a corresponding cost in CPU load and fidelity loss).

I'll experiment with supporting larger sample sizes (24 and 32 bit). These are overkill for our purposes but if the hardware doesn't like 16 bit samples ... that may be what's needed.

Oh ... here's a tip. I noticed your screenshots are cropped - probably by hand. You can take a screenshot of the active window by using the Alt key in combination with the PrtSc key. Paste the image to MS-paint and you're done.

-rick

 

[DaveNF2G]

Keep me posted. If you want to create a limited beta for that purpose, I'd be happy to test drive it for you.

My screenshots aren't cropped. They are "area" captures using Paint Shop Pro 8. I need to figure out how to keep it from capturing its own announcement of the window size.

 

[SCPD]

Keep me posted. If you want to create a limited beta for that purpose, I'd be happy to test drive it for you.

Cool. I'll send an updated Uniscope you're way - probably this weekend (oh, wait ... maybe later next week).

My screenshots aren't cropped. They are "area" captures using Paint Shop Pro 8. I need to figure out how to keep it from capturing its own announcement of the window size.

If PS Pro 8 can accept pasting an image from the Windows clipboard ... try using the [Alt] + [PrtSc] key combination to copy/paste the currently active application window into PS Pro 8.

-rick

 

[DaveNF2G]

By all means, enjoy your holiday first! I can wait.

Thanks to you and all the other forum users for the mutual assistance. I've been watching the beta threads with great interest and I look forward to giving UniTrunker a good workout with the various Motorola and EDACS and LTR systems in my neck of the woods.

 

[Dewey]

By all means, enjoy your holiday first! I can wait.

{SNIP}

Maybe you can wait, but I'd love to have a new version of UniTrunker under my tree for Christmas :lol: :lol: :lol: . Seriously though, I would like to THANK Rick and the rest of the UniTrunker development team for such a great product this year!!!

Dewey

 

[mtindor]

I'm awaiting a 2-level slicer from dataslicers.com. I know, I should have/could have built one - but I was lazy and likely couldn't have built one of the same quality.

My 996 is less than a month old but I'm going to tap the discriminator - Given how easy it is to get to the tap point for the discriminator, a monkey ought to be able to do this and so I'm counting on the fact that I am at least on par with a monkey (this has been disproven before though).

if I'm going to be hooking that slicer up to the 996, is the recommended procedure still to use the 10k resistor / 10uF tantalum combo at the tap point? Dave seems to be having problems with his setup that way. I want to do it whatever way is thought to be best. I've seen various opinions on what works and is safe in this thread - I'd just like some clarification because I've seen mention of different values for the tantalum cap.

The audio will be fed into an Audigy 2 card.

Incidentally, I've been monitoring the type II motorola systems in my area without a discriminator tap - I get 50% copy in Unitrunker. I want to be able to monitor EDACS too though so I gotta take the plunge.

Mike

 

[slicerwizard]

You can connect the discriminator directly to your sound card's mic input, or add the recommended resistor and cap - your decoding results will be the same either way. Of course, without the resistor, every time you plug the cable in to the sound card's jack, you'll short the discriminator to ground as the plug goes in. And if you ever build a data slicer and accidentally connect the discriminator to the +/-12V present on some of the serial port's pins, the DC blocking cap might save your scanner from an untimely death.

 

[Dewey]

You can connect the discriminator directly to your sound card's mic input, or add the recommended resistor and cap - your decoding results will be the same either way. Of course, without the resistor, every time you plug the cable in to the sound card's jack, you'll short the discriminator to ground as the plug goes in. And if you ever build a data slicer and accidentally connect the discriminator to the +/-12V present on some of the serial port's pins, the DC blocking cap might save your scanner from an untimely death.

I've been watching this thread also. Slicerwizzard, your reply has me a little confused. You start off saying "Of course, without the resistor...", but finish saying "the DC blocking cap might save your scanner...". Sorry for the confusion, but maybe I'm not understanding something. Which will could possibly "save" the scanner, the resistor or the cap?

Thanks,
Dewey

 

[slicerwizard]

They both provide protection. The resistor limits current flow if the tap point is grounded or connected to a voltage source and the capacitor will quickly stop that current completely. Only small AC currents (e.g. audio) will get through, which is what you want.

 

[mtindor]

You can connect the discriminator directly to your sound card's mic input, or add the recommended resistor and cap - your decoding results will be the same either way. Of course, without the resistor, every time you plug the cable in to the sound card's jack, you'll short the discriminator to ground as the plug goes in. And if you ever build a data slicer and accidentally connect the discriminator to the +/-12V present on some of the serial port's pins, the DC blocking cap might save your scanner from an untimely death.

Well, that's good news if you're somebody who likes quick results and usually tempts fate like a fool. Went to get the goods at Radio Shack (because our local electronics store, hosfelt.com was closed til after the holidays). The small nearby radio shack didn't have any tantalum capacitors of any size near 10uF. I've got the resistor. So I'm thinking I'm still going to bite the bullet, and then just take a chance until I can get all the components next week. I'll just hold off connecting the slicer until I have the proper resistor/cap combo in place.

Thanks for the explanation.

Mike

 

[DaveNF2G]

I plan to re-tap my 996. For one thing, I put the tantalum cap in "backwards" - meaning that the plus leg is toward the computer rather than toward the discriminator. Also, I put the resistor in series with the capacitor, but I've been reviewing circuit diagrams for another project and it seems the resistor should go from the negative leg of the capacitor to ground.

Any comments before I open up the scanner again?

Also, does anyplace carry a 1/8" jack with a long barrel? The one I got from Radio Shack doesn't leave enough threading outside the scanner to catch the hardware to hold it in place. The scanner has a very thick back panel.

 

[slicerwizard]

I plan to re-tap my 996. For one thing, I put the tantalum cap in "backwards" - meaning that the plus leg is toward the computer rather than toward the discriminator. Also, I put the resistor in series with the capacitor, but I've been reviewing circuit diagrams for another project and it seems the resistor should go from the negative leg of the capacitor to ground.

No, they go in series to a sound card or data slicer. The only thing you might run to ground in the scanner would be a very small cap (like 47pF) to eliminate any RF that came in on the audio cable. It's not necessary and you don't want to be complicating your setup until you get it working.

 

[BurbsGuy]

Tap question from a newbie.

Asking for a little help and tolerence from you guys...
Let me describe what I am trying to do and get some (not to techinical) advice...

Using PDW 2.14 to decode Alphanumeric pages in the 154.025 freq. for Fire Dept use. Will be a standalone monitor for certain cap codes. Using standard ext. speaker and earphone jacks out of my BCT15 into my soundcard I am getting a lot of jibberish. I see a great improvement using a friends BC560xlt with what appears to be just a simple line from a tap to an added on 3.5mm jack.

So now that I am kicking myself for throwing out old "outdated" scanners, I am going to find a used one or two and attempt to mod them for this use.

Do i need to be adding any capicitors or resistors to this project for what I am going to be using them for? Any other recommandations for scanners or parts?

Learning as i go here so appreciate your help....

 

[mtindor]

No, they go in series to a sound card or data slicer. The only thing you might run to ground in the scanner would be a very small cap (like 47pF) to eliminate any RF that came in on the audio cable. It's not necessary and you don't want to be complicating your setup until you get it working.

Can you diagram that?

Is it:

<tap point> --> resistor --> (+)capacitor(-)- --> audio jack

<tap point> --> (+)capacitor(-) --> resistor --> audio jack

Specifically, is the + of the capacitor going toward the tap point or toward the audio jack? And does it matter if the restistor is next in line from the tap point or does it need to be the cap?

Thanks

Mike

 

[slicerwizard]

Specifically, is the + of the capacitor going toward the tap point or toward the audio jack?

Tap point. It very likely has a positive DC voltage. The negative side of the cap points towards ground (through the audio cable and data slicer / sound card; those devices which shouldn't be putting any voltage on the audio cable)

And does it matter if the restistor is next in line from the tap point or does it need to be the cap?

As far as the electrons are concerned there is no difference, so do what you find most convenient and/or most likely to stay put.

 

[mtindor]

Ok tried it.

tap point --> 10k resistor --> 10uF tant cap (not sure of polarity - didnt appear to be marked)

grounded by wrapping ground around screw on chassis.

Results look similar to Dave's, except mine are even weaker on the one screenshot where his shows results - enough deflection for me to see it, but not enough to adequately capture it with a screenshot.

Will a capacitor installed in reverse cause it to not function? Do you think it is more like bad grounding?

Mike

 

[slicerwizard]

I doubt the polarity will have much effect. You can always short the cap while testing - you still have the resistor in there.

If you're attached to a screw that's in to the frame/chassis, it should do the job just fine.

Try the volume control and recorder tests.