Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

That's an awfully nice radio to tie up for an audio feed.

Gary


On 12/27/2024 8:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

On 12/27/2024 9:15 PM EST Joe <k1ike_mail@...> wrote:


Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and
18-GND for a broadcastify feed. The diagram says this output is DC
coupled. The feed is going to a computer soundboard input. Any
suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Most computer sound cards include a coupling capacitor, so the radio can be coupled directly to the sound cards input.  If you're going to use a transformer - also install a coupling capacitor so the primary of the transformer doesn't short out the output circuitry of the radio.

I'd look at the sound card to see if it has coupling capacitors on its input channels - if it does, just connect it up.

Kevin


On 12/27/2024 9:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Hi Joe,

My notes say there is a 0.1Mf cap inside the TK8180 in series with the output from pin17. I checked pin 17 on a TK8180 on the bench and no voltage with a digital VM, after the initial discharge. I run pin 17 to a controller with 100K input and the audio is outstandingly straight line flat from 300-2800cps.. Because of the 0.1 in series, if you were to use 600 ohms as an audio load the audio would sound tinny because of loss of lows due to this series cap's greater loss at the lower frequencies.

John

On 12/27/2024 9:15 PM EST Joe <k1ike_mail@...> wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and
18-GND for a broadcastify feed. The diagram says this output is DC
coupled. The feed is going to a computer soundboard input. Any
suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Hi Kevin,

Thanks for the information. I'm concerned with the possibility of a ground loop causing AC hum between the radio and the computer. That was the reasoning for using a transformer.

Joe

Looking at the sound card circuitry would be difficult due to the lack of documentation and gaining access to the internals of the computer.

On 12/28/2024 7:15 AM, Kevin Custer wrote:

Most computer sound cards include a coupling capacitor, so the radio can be coupled directly to the sound cards input.  If you're going to use a transformer - also install a coupling capacitor so the primary of the transformer doesn't short out the output circuitry of the radio.

I'd look at the sound card to see if it has coupling capacitors on its input channels - if it does, just connect it up.

Kevin


On 12/27/2024 9:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Joe,

You could use an ohm meter connected to the sound cards input to check for resistance or reverse the leads to see if you have a capacitive reaction - since the internals are difficult to access.  If you can take a look, the coupling capacitor would be the first thing the audio goes through looking at the traces from the sound cards input jacks.

Someone has mentioned that the radio may actually have a coupling capacitor and its output is not really DC coupled.  That's easily tested with an analog multi-meter and a portable radio capable of going 5kHz above and below the operating frequency.  If the radio's discriminator is truly DC coupled - the voltage at the discriminator will go positive and negative at 5kHz above <>below the operating frequency and stay there.  If it's capacitively coupled - you'll see a brief deflection and the meter re-stabilize at its resting place.  An analog meter has a lower input impedance and will react 'better' to a signal that's AC coupled - as compared to a DMM with an incredibly high impedance that may take minutes to hours to show the existence of a coupling capacitor without additionally adding some load resistance.

As a manufacturer of sound cards made specifically for connection to two-way radios, I can assure you that as long as you supply a good (low impedance) ground connection between the radio and the computer's sound card, hum isn't going to be a problem - even with a stock sound card.  The wire doesn't even need to be shielded because of the level involved, but shielded wire usually has a nice thick braid.

Kevin

On 12/28/2024 7:31 AM, Joe wrote:

Hi Kevin,

Thanks for the information. I'm concerned with the possibility of a ground loop causing AC hum between the radio and the computer. That was the reasoning for using a transformer.

Joe

Looking at the sound card circuitry would be difficult due to the lack of documentation and gaining access to the internals of the computer.

On 12/28/2024 7:15 AM, Kevin Custer wrote:

Most computer sound cards include a coupling capacitor, so the radio can be coupled directly to the sound cards input.  If you're going to use a transformer - also install a coupling capacitor so the primary of the transformer doesn't short out the output circuitry of the radio.

I'd look at the sound card to see if it has coupling capacitors on its input channels - if it does, just connect it up.

Kevin


On 12/27/2024 9:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

Hi Kevin,

I'm doing all this remotely, as neither the 8180 or the computer are at my location.  I'm just trying to do a little homework ahead of time.

Thanks for the idea, if I get the computer here I'll test it.  I'm considering doing a USB sound card that I have here and will give it a test.

And thanks for the test info on testing for DC coupling.  I just picked up a nice Simpson 260 and this will be a good application to try it out.

Joe

On 12/28/2024 7:59 AM, Kevin Custer wrote:

Joe,

You could use an ohm meter connected to the sound cards input to check for resistance or reverse the leads to see if you have a capacitive reaction - since the internals are difficult to access.  If you can take a look, the coupling capacitor would be the first thing the audio goes through looking at the traces from the sound cards input jacks.

Someone has mentioned that the radio may actually have a coupling capacitor and its output is not really DC coupled.  That's easily tested with an analog multi-meter and a portable radio capable of going 5kHz above and below the operating frequency.  If the radio's discriminator is truly DC coupled - the voltage at the discriminator will go positive and negative at 5kHz above <>below the operating frequency and stay there.  If it's capacitively coupled - you'll see a brief deflection and the meter re-stabilize at its resting place.  An analog meter has a lower input impedance and will react 'better' to a signal that's AC coupled - as compared to a DMM with an incredibly high impedance that may take minutes to hours to show the existence of a coupling capacitor without additionally adding some load resistance.

As a manufacturer of sound cards made specifically for connection to two-way radios, I can assure you that as long as you supply a good (low impedance) ground connection between the radio and the computer's sound card, hum isn't going to be a problem - even with a stock sound card.  The wire doesn't even need to be shielded because of the level involved, but shielded wire usually has a nice thick braid.

Kevin

On 12/28/2024 7:31 AM, Joe wrote:

Hi Kevin,

Thanks for the information. I'm concerned with the possibility of a ground loop causing AC hum between the radio and the computer. That was the reasoning for using a transformer.

Joe

Looking at the sound card circuitry would be difficult due to the lack of documentation and gaining access to the internals of the computer.

On 12/28/2024 7:15 AM, Kevin Custer wrote:

Most computer sound cards include a coupling capacitor, so the radio can be coupled directly to the sound cards input.  If you're going to use a transformer - also install a coupling capacitor so the primary of the transformer doesn't short out the output circuitry of the radio.

I'd look at the sound card to see if it has coupling capacitors on its input channels - if it does, just connect it up.

Kevin


On 12/27/2024 9:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike

I agree. Don't waste that radio for something like that. Buy a throw- away Chinese radio and use that instead.
Chuck
WB2EDV
On 12/27/2024 9:22 PM, Gary Cook via groups.io wrote:

That's an awfully nice radio to tie up for an audio feed.

Gary


On 12/27/2024 8:15 PM, Joe wrote:

Hello to All,

I friend wants to source audio from a TK-8180, DB-25, pin 17-AFO and 18-GND for a broadcastify feed.  The diagram says this output is DC coupled.  The feed is going to a computer soundboard input. Any suggestions? I was thinking of 600:600 transformer coupling.

Thanks for any input.

Joe, K1ike