K3 CAT noise

[bill4570]

While operating in the PSK-31 data mode, my K3 produces a noisy waterfall any time CAT control is enabled.  This shows up as horizontal lines on the waterfall about 1 mm apart.  As soon as I disable CAT, the lines dissappear.

I can copy right through the noise, so it's not an operating issue, but it's distracting.

Has anyone else come across this?  What was the resolution?

Bill,  W7QQ
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[Julian, G4ILO]

bill4570 wrote

While operating in the PSK-31 data mode, my K3 produces a noisy waterfall any time CAT control is enabled.  This shows up as horizontal lines on the waterfall about 1 mm apart.  As soon as I disable CAT, the lines dissappear.

I can copy right through the noise, so it's not an operating issue, but it's distracting.

Has anyone else come across this?  What was the resolution?

I remember this coming up once before. I believe it was a problem with grounding the shields of the cables between the rig and the computer.

[Paul Fletcher]

bill4570 wrote

While operating in the PSK-31 data mode, my K3 produces a noisy waterfall any time CAT control is enabled.  This shows up as horizontal lines on the waterfall about 1 mm apart.  As soon as I disable CAT, the lines dissappear.

Bill,

I had similar problems and traced this to the shielding of the cable. I found that the shield needed to be connected to the shell of the d-type connector at both ends of the cable (soldered directly to the shell) to get rid of the interference.

Hope this helps.

73 Paul M1PAF

[Jim Brown-10]

On Fri, 22 Aug 2008 09:20:21 -0700 (PDT), Paul Fletcher wrote:

>I had similar problems and traced this to the shielding of the cable. I
>found that the shield needed to be connected to the shell of the d-type
>connector at both ends of the cable (soldered directly to the shell) to get
>rid of the interference.

Not surprising. The ONLY good connection for a cable shield is the shielding
enclosure of the devices being connected. Without that connection there is no
shielding. A connection of the cable shield to wirng inside the box often
excites what is commonly known as "the pin 1 problem," which is a form of
common impedance coupling. In the case of the noise SOURCE, noise is coupled
onto the cable shield and radiated by the cable shield. In the case of a
VICTIM, the noise is received on the cable shield and coupled into the victim
equipment.

Another point. If the noise is being leaked from the differential signal on
that CAT wiring, it can be DRASTICALLY reduced by using good twisted pair
cable (for example, CAT5/6/7).

The Pin 1 problem is discussed in detail in

http://audiosystemsgroup.com/RFI-Ham.pdf 

73,

Jim Brown K9YC


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