Discriminator Tap Verification

[rngr2000]

How do I confirm that my discriminator tap is working properly. I installed a tap on my Bearcat BC80XLY by using the instructions found here( Discriminator Output BC80XLT / COM213). Should I hear some sorta garbled audio coming from the tap if I connect a pair of headphones to the tap? I have pictures of my soldering iron magic, but for some reason the site wont let me upload them. Ill keep trying though.

 

[kma371]

Try running a program like Trunker. If you get data on the screen, it's working. It's a quick and easy test.

Just make sure you select the correct data Input when you start the program (microphone input, line input etc)

 

[rngr2000]

Here are the pics. Sorry They are mega huge.

 

[pro92b]

What is the value of the black capacitor? If it is 2.2uF, it is 1000 times too big.

This tap point will not drive headphones.

Will you use the tap with a data slicer or a sound card input?

 

[SCPD]

The cap is soldered to ground. I'd expect it to be wired in series with the 10 k resistor.

 

[rngr2000]

None of this matters now. I was just looking over things and double checking my connections and ended up breaking off pin 9 that i was tapped into. I guess I moved things around too much. Not sure if I can re-solder it or not. What scanners have a built in discriminator output?

 

[pro92b]

The cap is soldered to ground. I'd expect it to be wired in series with the 10 k resistor.

Rick, the web page he referenced uses a direct coupled circuit with an R-C filter to remove the IF frequency present in the 3361 output. There is no series coupling cap in the circuit. There may be some circumstances where a cap is beneficial though. The filter is designed for a 7 kHz roll-off, too aggressive in my view. That's before adding in cable capacitance and any capacitance at a sound card input which will drive the roll-off frequency even lower..

 

[SCPD]

ended up breaking off pin 9 that i was tapped into. I guess I moved things around too much.

Ouch.

You might be able to scrape a small amount of plastic to better expose the remaining stub; solder a short wire fragment to reattach. Delicate work.

Replacing the whole chip might be easier. To remove, solder bridge all pins on one side, heat these pins at once and lift. Allow time to cool. Repeat on other side. After chip is removed, heat and vacuum excess solder.

With a new part from Mouser or DigiKey, carefully solder into place. Avoid cross soldering pins.

 

[SCPD]

What scanners have a built in discriminator output?

PSR800, Icom PC/R series; older WinRadios.

 

[ampulman]

Rick, the web page he referenced uses a direct coupled circuit with an R-C filter to remove the IF frequency present in the 3361 output. There is no series coupling cap in the circuit. There may be some circumstances where a cap is beneficial though. The filter is designed for a 7 kHz roll-off, too aggressive in my view. That's before adding in cable capacitance and any capacitance at a sound card input which will drive the roll-off frequency even lower..[/QUOT

I apologize if this would be considered off-topic, but I wonder: re: the PC/IF output (PRO-106/PSR-500), would a 'plug in' R-C filter yield the desired output?

Amp

 

[SCPD]

I apologize if this would be considered off-topic, but I wonder: re: the PC/IF output (PRO-106/PSR-500), would a 'plug in' R-C filter yield the desired output?

The PC/IF port is not discriminator audio. The control channel data passed over the PC/IF cable has already been decoded by the radio.

 

[scanningisfun]

Trying to decode Lawrenceburg's Mototrbo? This is the exact reason I'm tapping my Pro 79.

Jacob