Pro-163 - Discriminator tap?

[ETMegabyte]

I have a couple Pro-163 scanners here, which I use for all of my non-digital stuff (FRS, Ham Repeaters, etc)...

One of the things I want to do is hook my scanner to my computer to decode things like PSK on VHF/UHF. I want to be able to turn the volume knob up and down depending on whether I want to actually listen to it or not, but I want the audio to always go to the computer. So I basically need to add a constant-level-audio-output that won't disable the internal speaker when it's connected.

My understanding is that a discriminator tap will do this quite nicely. A 10k resistor to TP4, and back to a mono jack, in theory, should give me a constant level audio output regardless of where the volume knob is set. Also, this will allow, in theory, the ability to leave the scanner connected to the computer all the time without disabling the internal speaker (again, for when I'm listening to regular scanner traffic).

And, as a final thought, this would also give me the ability to run a software decoder to translate the local DSTAR and DMR repeaters as well.

Is this correct? Or am I barking up the wrong tree here?

 

[DickH]

I have a couple Pro-163 scanners here, which I use for all of my non-digital stuff (FRS, Ham Repeaters, etc)...

One of the things I want to do is hook my scanner to my computer to decode things like PSK on VHF/UHF. I want to be able to turn the volume knob up and down depending on whether I want to actually listen to it or not, but I want the audio to always go to the computer. So I basically need to add a constant-level-audio-output that won't disable the internal speaker when it's connected.

My understanding is that a discriminator tap will do this quite nicely. A 10k resistor to TP4, and back to a mono jack, in theory, should give me a constant level audio output regardless of where the volume knob is set. Also, this will allow, in theory, the ability to leave the scanner connected to the computer all the time without disabling the internal speaker (again, for when I'm listening to regular scanner traffic).

And, as a final thought, this would also give me the ability to run a software decoder to translate the local DSTAR and DMR repeaters as well.

Is this correct? Or am I barking up the wrong tree here?

Sounds right on all counts.

 

[ETMegabyte]

Sanity question.

I'm ready to put in the discriminator tap, but the only 10k resistor I have is a MONSTER size-wise. Does it matter if it's too large? How small can I go? eBay has a pack of 10 for like $1.50 but they're 1/4 watt resistors... There are also 1/8 watt and 1/2 watt... How big would I need for a discriminator tap?

This is a pic of the one that I have...

ps. Why do I need a resistor at all? What purpose does it serve? Yes, I plan on putting it in, I just want to understand why it needs to be there. Thanks