K2, PSK31 & microphone

[Matt Osborn]

I'm using Ham Radio Deluxe/PSK31 Deluxe software which handles the
PTT, but I still need to connect from the sound card to the K2's
microphone jack.

I have the Proset-K2 headset that has an 8 pin adapter that accepts
the monophonic Proset-K2 microphone plug.  I would like to use an
audio ground loop isolator to connect the sound card audio out to the
Proset-K2 adapter microphone plug.

However, when I installed the Proset-K2, I had to install a 5.6K
resister between 5V (pin 6) to the AF (pin 1)  on the back of 8 pin
microphone adapter on the K2.

I don't know the purpose of this resister; I assumed it was just a
pull up.  Is it safe to leave this resister in place?
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[Don Wilhelm-3]

I would suggest leaving the resistor in place because your microphone needs
it -- it provides power to the electret element in the mic.

You could put a capacitor in series with the audio to the K2 to provide DC
isolation.  Somewhere between 0.1 uf and 1 uf would seem like the proper
range for the value.  The use of a capacitor will allow you to use
transformer isolation between the computer and the K2 - transformers from
defunct computer modems work well in that application.  Put the transformer
directly on the line from the computer (be certain to isolate any grounds
coming from the computer from the ground in your isolation box and the K2),
and the voltage divider and capacitor on the K2 side of the transformer.  It
should work FB.

You may be able to use an optoisolator instead of the transformer, but
beware of paths created by the grounding of the computer input jack, the
isolator power return line and the K2 ground - the grounds must be properly
isolated as well as the signals if you are to avoid computer noise.

73,
Don W3FPR

> -----Original Message-----
>
> I'm using Ham Radio Deluxe/PSK31 Deluxe software which handles the
> PTT, but I still need to connect from the sound card to the K2's
> microphone jack.
>
> I have the Proset-K2 headset that has an 8 pin adapter that accepts
> the monophonic Proset-K2 microphone plug.  I would like to use an
> audio ground loop isolator to connect the sound card audio out to the
> Proset-K2 adapter microphone plug.
>
> However, when I installed the Proset-K2, I had to install a 5.6K
> resister between 5V (pin 6) to the AF (pin 1)  on the back of 8 pin
> microphone adapter on the K2.
>
> I don't know the purpose of this resister; I assumed it was just a
> pull up.  Is it safe to leave this resister in place?
>

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[Matt Osborn]

High Mark,

The 5.6k resister came with the microphone and instructions to install
it and how to set the jumpers.

You provided the key word here, 'electret'.  I'd seen the word before,
but had thought it was a branding term rather than a functional term.
I just did a google search and now I know why the 5.6K resister is
needed.

This reminds me of 25 years ago when every software package had to
develop special code to support each of the various graphics cards
then available.  There were few standards at the time and most were
honored only in the breach.

I was surprised to find that the standard 8 pin microphone connector
is but a physical standard, not an electrical one.  It seems that
switching microphones isn't as easy as switching light bulbs.  Not
only do we have to configure differently for electret vs dynamic
microphones, but we also have to worry about PTT switches, Up Down
buttons and the like.

Choices, choices, choices...

On Fri, 29 Jul 2005 20:51:41 -0400, [hidden email] wrote:

>Hi Matt,
>
>I had used my K2 with PSK31 for a while as well, lots of fun.  I had my
>K2 microphone wired for a standard Kenwood configuration as my "big
>radio" was a Kenwood TS-940S.  I also used two different Heil headsets
>with the K2.  Both used the standard Kenwood plug adapter (actually I
>built one of these rather than paying for the "official" one from
>Heil).  One of the headsets is the ProSet Plus and the other is the HM5
>(I think, it is a single earpiece headset with the HC5 mic element).  I
>did not need to use a 5.6k ohm resistor to pin 6 and 5V to get these to
>work.  I did however change one resistor on the KSB2 SSB module, R14
>from 1k ohm to 10k ohm and I use the mic gain setting of 2.  Using PSK31
>you apparently don't want to have any compression, so make sure you set
>it to 1:1, although I sometimes forgot to switch over from my voice
>setting of 3:1 and I think things still worked okay.
>
>I'm not sure why you had to use a 5.6k ohm resistor.  Did it not work
>unless you used it?  From what I know about the Heil microphones, if it
>is the HC5 or HC4 element it doesn't need any bias and could actually
>harm them if there is bias.  However some mic elements (like for Icom)
>do need the bias.  I forget if they are electret or dynamic microhones.  
>Would it hurt to leave it there?  First I'd figure you why you really
>need it in the first place and then decide.  If you don't really need it
>maybe now would be a good time to take it out.  I think I remember
>somebody else on here had the voltage on pin 6 but put the resistor from
>pin 6 to pin 1 in the microphone plug itself for the microphone that
>needed it.  That way if you use a different mic the extra resistor is
>not there and the K2 should still work like normal.  Actually, that
>might be a better solution for you as well (if you decide that you do
>need it for you Proset-K2).
>
>73,
>
>Mark, NK8Q
>
>Matt Osborn wrote:
>
>>I'm using Ham Radio Deluxe/PSK31 Deluxe software which handles the
>>PTT, but I still need to connect from the sound card to the K2's
>>microphone jack.
>>
>>I have the Proset-K2 headset that has an 8 pin adapter that accepts
>>the monophonic Proset-K2 microphone plug.  I would like to use an
>>audio ground loop isolator to connect the sound card audio out to the
>>Proset-K2 adapter microphone plug.
>>
>>However, when I installed the Proset-K2, I had to install a 5.6K
>>resister between 5V (pin 6) to the AF (pin 1)  on the back of 8 pin
>>microphone adapter on the K2.
>>
>>I don't know the purpose of this resister; I assumed it was just a
>>pull up.  Is it safe to leave this resister in place?
>>_______________________________________________
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>>  
>>
>

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[Matt Osborn]

Thanks, Don.

I picked up two audio ground loop isolators from Radio Shack last week
when I wanted to recalibrate my filters using Spectrogram. I figured
if I needed one for audio to the computer, I'd probably need on for
audio out as well.

The isolator worked very well with Spectrogram; it removed all the
spikes and the 'noise' that made up the first 20db or so of the
Spectrogram signal display and made the roll off at high end of the
filters much easier to see.

On Fri, 29 Jul 2005 20:43:24 -0400, "W3FPR - Don Wilhelm"
<[hidden email]> wrote:

>I would suggest leaving the resistor in place because your microphone needs
>it -- it provides power to the electret element in the mic.
>
>You could put a capacitor in series with the audio to the K2 to provide DC
>isolation.  Somewhere between 0.1 uf and 1 uf would seem like the proper
>range for the value.  The use of a capacitor will allow you to use
>transformer isolation between the computer and the K2 - transformers from
>defunct computer modems work well in that application.  Put the transformer
>directly on the line from the computer (be certain to isolate any grounds
>coming from the computer from the ground in your isolation box and the K2),
>and the voltage divider and capacitor on the K2 side of the transformer.  It
>should work FB.
>
>You may be able to use an optoisolator instead of the transformer, but
>beware of paths created by the grounding of the computer input jack, the
>isolator power return line and the K2 ground - the grounds must be properly
>isolated as well as the signals if you are to avoid computer noise.
>
>73,
>Don W3FPR
>
>> -----Original Message-----
>>
>> I'm using Ham Radio Deluxe/PSK31 Deluxe software which handles the
>> PTT, but I still need to connect from the sound card to the K2's
>> microphone jack.
>>
>> I have the Proset-K2 headset that has an 8 pin adapter that accepts
>> the monophonic Proset-K2 microphone plug.  I would like to use an
>> audio ground loop isolator to connect the sound card audio out to the
>> Proset-K2 adapter microphone plug.
>>
>> However, when I installed the Proset-K2, I had to install a 5.6K
>> resister between 5V (pin 6) to the AF (pin 1)  on the back of 8 pin
>> microphone adapter on the K2.
>>
>> I don't know the purpose of this resister; I assumed it was just a
>> pull up.  Is it safe to leave this resister in place?
>>

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[k7nhb]

The posts on this topic mention an isolation transformer to
"separate" the computer from the PSK audio line. So I might have
missed the boat a little when I decided to ground the computer
chassis/case to the common equipment ground. That is, I have a ground
rod with a wire coming up to a copper tube/pipe behind the operating
desk. I've attached all available ground connections - on rigs, power
supplies and antenna tuners to that common copper.

Is that a mistake? Should I disconnect the computer or any other
equipment from that common ground? What about the wing nut on the
tuners - note that they are for unbalanced (coax), not twin lead or
random wire. That is, I think it is supposed to be an electrical
ground, not and RF ground.

Sort of related is the LCD screen - it came with its own power
supply, but I run it off an small amp. accessories power supply that
is also connected to the common ground.

I'm wondering if in my enthusiasm to minimize noise I have actually
created more. I could and will experiment. But if someone sees a
clear, "do it this way instead of that" to the setup, I'd appreciate
knowing.

Thanks and 73,
Paul
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[Jim Price-3]

Conventional wisdom seems to be always use an isolation transformer in the
PSK-31 output to your mike input.  I think most also agree it best to use
one in your PSK-31 input from your rigs audio out.  Several of the
commercial kits/units do not do the latter.  I have tried it with and
without and not seen a 60-Hz line (or harmonic thereof) in my audio.  YMMV.

73, Jim - N4ST


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[Don Wilhelm-3]

Paul,

Connecting all your equipment to a common ground is NOT a mistake.  Whether
you still have to use isolation transformers in the computer audio lines or
not depends on your particular computer - the audio return path is to the
motherboard instead of the computer chassis, so whether or not it is
required in your case depends on the internal construction of your
computer - the transformers will not hurt.

The grounding connection to your tuner is most certainly for an RF Ground
when that is required, but it can also be connected to your common shack
ground and should create no problem - in fact safety concerns dictate that
any exposed metallic surfaces of any equipment should be grounded.

73,
Don W3FPR

> -----Original Message-----
>
> The posts on this topic mention an isolation transformer to
> "separate" the computer from the PSK audio line. So I might have
> missed the boat a little when I decided to ground the computer
> chassis/case to the common equipment ground. That is, I have a ground
> rod with a wire coming up to a copper tube/pipe behind the operating
> desk. I've attached all available ground connections - on rigs, power
> supplies and antenna tuners to that common copper.
>
> Is that a mistake? Should I disconnect the computer or any other
> equipment from that common ground? What about the wing nut on the
> tuners - note that they are for unbalanced (coax), not twin lead or
> random wire. That is, I think it is supposed to be an electrical
> ground, not and RF ground.
>
> Sort of related is the LCD screen - it came with its own power
> supply, but I run it off an small amp. accessories power supply that
> is also connected to the common ground.
>
> I'm wondering if in my enthusiasm to minimize noise I have actually
> created more. I could and will experiment. But if someone sees a
> clear, "do it this way instead of that" to the setup, I'd appreciate
> knowing.
>
> Thanks and 73,
> Paul

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[Stuart Rohre]

The transformer is to break the ground loop of having the computer ground
connected to the RF chassis ground of the radio and producing possible
ground loop currents.  In that case, you defeat the transformer if you
connect the computer case to radio case.

The computer case ground should be the 3rd pin on AC plug, and use that one
alone for computer.  That will correct any voltage difference due to a line
filter in computer.

Some audio lines are floating, and the transformer gives them a reference
known load.  The transformer is the way its done in commercial broadcasting
to avoid hum problems.

Stuart
K5KVH



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