K2 KIO2 Polling Noise in PC Speakers w/ HRD

[Brian - N5BCN]

(K2 #6800 w/ KSB2 KIO2 KAT2 KNB2)

Hi,

My first post to the reflector. :-)

I recently completed the KIO2 module (without KPA100) and have been controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT SPKR connection to the PC Mic In and finally out to PC Speakers.  All is well EXCEPT for an annoying buzzing noise coming through the PC Speakers that is caused by HRD polling the K2.  I know this because when I change the polling interval, the noise changes accordingly.  Also, when I disconnect HRD from the K2, the noise goes away.  Even holding down a mouse button, which pauses the HRD/K2 polling, causes the noise to cease.  Of course it starts up as soon as I release the mouse button.

I believe the noise is being picked up by the PC Sound Card.  When I connect the PC Speakers directly to the K2 EXT SPKR port (bypassing the PC sound card), there is no polling noise.  I've also tried the following to no avail:

1)  Tried both Line In and Mic In on the PC.  No difference.
2)  Connected the KIO2 Serial Cable to both a USB/Serial adapter and a PCI Card with a DB9 Serial connector.  No difference.
3)  Tried connecting the KIO2 Serial Cable Pin 1 to the bare shield wire on the PC side vs no connection to Pin 1.  No difference.
4) Tried "dressing" the cables inside the K2 so the KIO2 wires were far from the RF Board.  No difference, despite holding the KIO2 and cabling as physically far away as possible from the RF Board.
5) Tried routing the audio patch cable from the K2 to the PC as far away as possible from the KIO2 Serial Cable.  No difference.

Has anyone else experienced this, and if so, have you found a solution?  Any suggestions would be most appreciated.

73

Brian N5BCN

[Don Wilhelm-4]

Brian,

There may be a potential difference (voltage) between your PC chassis
and the K2.  Try bonding them together (with a wire) to see if that
helps.  No guarantees, but it is worth a try.

73,
Don W3FPR

N5BCN wrote:

> (K2 #6800 w/ KSB2 KIO2 KAT2 KNB2)
>
> Hi,
>
> My first post to the reflector. :-)
>
> I recently completed the KIO2 module (without KPA100) and have been
> controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT
> SPKR connection to the the PC Mic In and out to PC Speakers.  All is well
> EXCEPT for an annoying buzzing noise coming through the PC Speakers that is
> caused by HRD polling the K2.  I know this because when I change the polling
> interval, the noise changes accordingly.  Also, when I disconnect HRD from
> the K2, the noise goes away.  Even holding down a button, which pauses the
> HRD/K2 polling, causes the noise to cease.  Of course it starts up as soon
> as I release the mouse button.
>  
>

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[Julian, G4ILO]

N5BCN wrote

I recently completed the KIO2 module (without KPA100) and have been controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT SPKR connection to the PC Mic In and finally out to PC Speakers.

It's curious that you're getting this using both a real serial port and a USB adapter.  I wonder if you're hearing PC bus noise that is being picked up by the computer? Most of us would be blissfully unaware of this since we don't listen to our radios through the computer. But it could explain why many people claim they get better decoding after switching to an external sound card box like a RigExpert or MicroHam.

Is the noise present when listening to a different audio source (e.g. internet radio) while HRD is polling the K2?

[Brian - N5BCN]

Hi Julian,

Yes, the noise is present at all times as long as HRD is connected to (and talking to) the K2, despite other audio sources. The noise, although less noticeable when some audio is being played through the speaker, becomes annoyingly apparent as soon as things are quiet.

At first, I thought it was a problem with the fact the soundcard is right next to the PCI card with the DB9 connector.  But after connecting the KIO2 cable to a USB/Serial adapter that isn't anywhere near the soundcard, it suggested something internal to the computer is being picked up by the soundcard.

I'll try Don's suggestion of connecting the K2 and computer chassis together and see if that makes a difference.

Brian N5BCN

 

Julian, G4ILO wrote

N5BCN wrote

I recently completed the KIO2 module (without KPA100) and have been controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT SPKR connection to the PC Mic In and finally out to PC Speakers.

It's curious that you're getting this using both a real serial port and a USB adapter.  I wonder if you're hearing PC bus noise that is being picked up by the computer? Most of us would be blissfully unaware of this since we don't listen to our radios through the computer. But it could explain why many people claim they get better decoding after switching to an external sound card box like a RigExpert or MicroHam.

Is the noise present when listening to a different audio source (e.g. internet radio) while HRD is polling the K2?

[Brian - N5BCN]

Hi Don,

Thanks for the tip (why didn't I think of that?!?).  I tied a wire between the PC and K2 chassis and the polling noise dropped dramatically.  Although it is still audible, it is diminished to the point where I can "live with it."  Hopefully the wire will not introduce any ground loops........

THANKS!

73

Brian N5BCN

Don Wilhelm-4 wrote

Brian,

There may be a potential difference (voltage) between your PC chassis
and the K2.  Try bonding them together (with a wire) to see if that
helps.  No guarantees, but it is worth a try.

73,
Don W3FPR

N5BCN wrote:
> (K2 #6800 w/ KSB2 KIO2 KAT2 KNB2)
>
> Hi,
>
> My first post to the reflector. :-)
>
> I recently completed the KIO2 module (without KPA100) and have been
> controlling the K2 via HRD v5.0.  I'm passing the K2 audio via the K2 EXT
> SPKR connection to the the PC Mic In and out to PC Speakers.  All is well
> EXCEPT for an annoying buzzing noise coming through the PC Speakers that is
> caused by HRD polling the K2.  I know this because when I change the polling
> interval, the noise changes accordingly.  Also, when I disconnect HRD from
> the K2, the noise goes away.  Even holding down a button, which pauses the
> HRD/K2 polling, causes the noise to cease.  Of course it starts up as soon
> as I release the mouse button.
>  
>
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[Don Wilhelm-4]

Brian,

The wire actually diminished ground loops.
A ground loop forms between two chassis at different potentials, and
that potential difference causes current to flow on conductors that
normally carry signals.  There may still be a slight potential
difference between the two chassis - it depends on the
resistance/impedance of the connecting wire.  You might reduce the noise
even further with a larger wire or a strap, but one quickly reaches a
point of diminishing returns.

Other similar noise can occur because of what audio pros call a "pin 1
problem".  It does not always relate to an actual pin 1 (except for
audio XLR cables).  The shield of a cable *should* connect to the
outside enclosure of a device, so any noise carried on the shield will
be conducted on the outside of the enclosure.  With the advent of PC
boards and the ease of making shield connections to the ground plane of
those PC boards (mounting the jack on the PC board rather than the
enclosure, the shield connection often goes to the PC board ground plane
first, and then afterward it may (or may not) be connected to the
enclosure case.  That situation is common, and does create the "pin 1
problem" which can induce noise onto the PC board ground plane and will
modulate all signals on that board.

Many (most) amateur transceivers and computer sound cards have this "pin
1 problem".  Extraordinary steps must be taken to eliminate such "sneak
paths".

73,
Don W3FPR

Brian N5BCN wrote:

> Hi Don,
>
> Thanks for the tip (why didn't I think of that?!?).  I tied a wire between
> the PC and K2 chassis and the polling noise dropped dramatically.  Although
> it is still audible, it is diminished to the point where I can "live with
> it."  Hopefully the wire wouldn't introduce any ground loops........
>
> THANKS!
>
> 73
>
> Brian N5BCN
>  
>

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