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Re: KIO3B Audio Spec

Don Wilhelm-4
Zero potential is not necessarily the criteria that is to be achieved.

The important point is that adjacent pieces of equipment be at the
*same* potential, whether that be at zero or 100 volts potential.
OK, that is an extreme example, but the point is that there should be a
low resistance connection between devices sharing an unbalanced
connection between the two, and that low resistance connection should be
something other than the shield of the audio or RF unbalanced cables.
The easiest way to accomplish that condition is to bond the equipment
from point to point by good heavy wire or braid.

Since we commonly use computers in our ham stations, that is one source
of hum, buzz and other noise.  Bonding the computer straight to the
transceiver will cure many ills.

We did not have those problem in older gear where the connectors were
mounted to the enclosure of the equipment, but modern construction where
the input and output jacks are mounted to the PC board causes stray hum,
buzz and noise and RF currents to be coupled to the PC board rather than
being routed to the outside of the equipment enclosure is one of the
primary causes of the problem - that is the "pin 1 problem" that Jim
Brown K9YC refers to.

73,
Don W3FPR

On 12/31/2015 7:44 PM, Bob McGraw - K4TAX wrote:

> Don et al:
>
> Well Jim and I are at 100% opposite positions on this point.
>
> Bonding from equipment to equipment is a series circuit in which the
> voltage divides across each value of R.  Thus none of the equipment
> will be at zero potential.
>
> By using a bond conductor from each piece of equipment to a common
> point, this provides a star system which is endorsed by most audio and
> system design specialists.   It provides the lowest resistance as all
> conductive paths are parallel.
>
> 73
> Bob, K4TAX
>
> On 12/31/2015 6:32 PM, Don Wilhelm wrote:
>> Bonding to a common point may not cure hum and buzz.
>> Follow the advice of Jim Brown K9YC and bond from equipment to
>> equipment - following the path of the shields on unbalanced audio
>> cables and RF coax.
>
>
>

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Re: KIO3B Audio Spec

Raymond Sills
In reply to this post by Elecraft mailing list
I’m not so sure about that.  The various devices are only connected to one other object.  Think of this picture:

A is connect to B, and B is connected to C.  So, you want to bond A to B.. and don’t care about the connection to C, since it needs only be connected to B and not C.  And the same for B to C.   The “star” approach means that the connection from A goes to a common point, and then from the common point to B, creating two additional connection points, for a total of 4, whereas, the A to B connection is just 2 points.

The “star” is fine for safety, but does nothing to assist with the common mode between devices A and B or B and C.  And, we are talking about audio, not safety commons.

73 de Ray
K2ULR
KX3 #211



> On Dec 31, 2015, at 9:11 PM, Doug Person via Elecraft <[hidden email]> wrote:
>
> I've always believed in the star approach and completely agree with the series circuit issue.
>
> 73, Doug -- K0DXV
>

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KIO3B Install

Robert Nobis - N7RJN
In reply to this post by Don Wilhelm-4
I received the KIO3B upgrade kit for my K3 yesterday. Installation and setup was straightforward.

This was nearly a “plug-and-play” setup. I was up and running WSJT-X (v1.6) on OS-X (Mac) after minor adjustments to the audio levels, and had my first JT65 QSO within 35 minutes of starting the installation.

Decode performance appears to be just as good, if not better than my external TASCAM US-366.  I will have to run this for a few days to see how well it decodes low level signals (-23 to -25dB) on JT65.

Also the sure helped to reduce my rat’s nest of cables.

Happy New Year.

73,

Bob Nobis - N7RJN
[hidden email]


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Re: KIO3B Audio Spec

Dan AE9K
In reply to this post by ab2tc
After staring at Knut's KIO3B spectrum with an XG3 signal source, I am wondering how much of that spectrum can be attributed to the KIO3B and how much is due to the K3S RF chain and XG3 phase noise and harmonics.

I tried a different approach with my K3 and DigiKeyer keeping everything at AF and avoiding the RF and XG3 related variables - I think.

I sent the K3 a 1 kHz test tone to LINE IN while the K3 was keyed in TX TEST mode.  At the same time an instance of Spectrum Lab analyzed the return audio (i.e. the monitor audio returned over LINE OUT).

The resulting spectrum lacks the significant harmonics Knut observed although I show some AC spectra (fundamental + 3rd, 5th and 7th harmonics) which might be attributable to my DigiKeyer sitting directly above the KPA500's transformer.



Is analaysis of recovered transmit audio while in TX TEST a viable way to eliminate the RF and XG3 related variables or have I missed something?  If it is viable, I would be interested in the same being done with a KIO3B for comparison purposes.

73,

Dan
AE9K
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Re: KIO3B Audio Spec

ab2tc
Hi,

There is little doubt that most of the noise/blips in that spectrogram is not related to the KIO3B, but rather the K3 RF chain and possibly the KX3 phase noise. I was just trying to show that the audio produced by the USB codec is darned good from an HF radio (and in  my case demonstrably better than what I got from the line out on my old K3). I have never tried to see what the port can do with the transmit audio.

AB2TC - Knut

Dan AE9K wrote
After staring at Knut's KIO3B spectrum with an XG3 signal source, I am wondering how much of that spectrum can be attributed to the KIO3B and how much is due to the K3S RF chain and XG3 phase noise and harmonics.

I tried a different approach with my K3 and DigiKeyer keeping everything at AF and avoiding the RF and XG3 related variables - I think.

I sent the K3 a 1 kHz test tone to LINE IN while the K3 was keyed in TX TEST mode.  At the same time an instance of Spectrum Lab analyzed the return audio (i.e. the monitor audio returned over LINE OUT).

The resulting spectrum lacks the significant harmonics Knut observed although I show some AC spectra (fundamental + 3rd, 5th and 7th harmonics) which might be attributable to my DigiKeyer sitting directly above the KPA500's transformer.



Is analaysis of recovered transmit audio while in TX TEST a viable way to eliminate the RF and XG3 related variables or have I missed something?  If it is viable, I would be interested in the same being done with a KIO3B for comparison purposes.

73,

Dan
AE9K
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Re: KIO3B Audio Spec

Dan AE9K
Sorry, I didn't word my reply correctly.  I didn't mean to suggest the KIO3B was responsible for the spikes of spectra.  I realize those are the XG3 fundamental and harmonics. The XG3 phase noise just makes it impossible to see the audio noise floor of the KIO3B.  My intention was just to advance your "darned good" comment to something measurable for comparison purposes.  But, for all I know my pursuit of measuring USB audio spectrum quality may be moot if we're always RF noise-limited.

Stepping back a bit, my original intent was to determine whether the KIO3B was a suitable drop-in replacement for my DigiKeyer (to eliminate a box and associated connections to the K3).  Part of that is audio-related the other part is interfacing-related (KEY, PTT, etc.).  Someone pointed out off-forum that there is no FSK interface with the KIO3B so that is one disparity with the interfacing aspect.

As for the audio aspect, I'm sure Joe's right in that they're essentially the same unless there was an implementation short-cut taken with the KIO3B - which isn't likely.  That said, I am still curious if the proposed test setup of passing audio in and analyzing the monitor audio is a valid means of measuring the performance of the USB audio path - whether with the KIO3B or other USB audio interface.  Can I, for example, conclude from my test that my DigiKeyer/K3 path has a -110 dB noise floor?

73,

Dan
AE9K
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