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Author Topic: RV-Digipan-laptop Lines on waterfall from AC  (Read 331 times)
KB9OPW
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Posts: 14




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« on: October 18, 2005, 03:00:04 PM »

I have a problem with some type of interference when using PSK31 and my laptop in my RV. There are many lines running very close together on the waterfall display. I have tried running the laptop on battery power only and still the same thing. Could it be coming from the power inverter? If so how can I eliminate it. Would a high quality surpressor stop the interference or could it be coming down the AC lines? I'm using a Kenwood TS 440SAT and a IBM Thinkpad T22.
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VA7CPC
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Posts: 2355




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« Reply #1 on: October 18, 2005, 03:14:20 PM »

The inverter is a good bet as an RFI source.  They generally use high-power switching circuits and generate lots of hash.

To test, _disconnect_ (or switch off, if you believe the "on/off" switch really stops all electrical activity inside the box) the inverter and see if the lines on the Digipan display disappear.

If that's the problem, the fix involves _at least_ lots of clip-on ferrite chokes on the leads into, and out of, the inverter.  Note that the battery leads carry high currents, and those currents may saturate the ferrite chokes.  Special high-current RFI filters would be the answer, then.

If the RF noise is coming from the inverter box itself (as opposed to being radiated from the leads), your only cure is to shut off the inverter when working PSK31.   That's the situation on my sailboat.



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WA6BFH
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« Reply #2 on: October 18, 2005, 03:15:34 PM »


An inverter would be a likely source. What else do you have running that would be in the few to several 10's of cycles per second (say from 10 to 200 Hz)?
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AA4PB
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« Reply #3 on: October 18, 2005, 04:19:07 PM »

In addition to determining what is generating the RFI you need to break it down and determine how it is getting into the system. One at a time try disconnecting the interface from the radio, turning the radio off, disconnecting the antenna, powering the radio from a separate battery, etc. Is the RFI coming in via the antenna, the power leads on the radio, or do you perhaps have a grounding issue in the interface? Once you determine the path then you will be able to start thinking about possible solutions.
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K4SAV
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« Reply #4 on: October 18, 2005, 04:31:51 PM »

Sounds like ground noise pick-up on the line from your radio to your computer.  Do you have an audio isolation transformer in this line or did you run it direct?  You need a transformer and shielded wire.

Jerry, K4SAV
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VE3TMT
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Posts: 370




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« Reply #5 on: October 19, 2005, 04:12:09 AM »

I agree with Jerry. I was running audio lines from the rig straight into the computer. My waterfall was showing the signs you speak of. My TX signal was also unstable. I now use a RigBlaster Plus and the problems have disappeared.
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KL0S
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Posts: 132




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« Reply #6 on: October 19, 2005, 05:17:29 AM »

Depending on how old your RV is it MAY be coming from the ballast(s) in any overhead flourescent lights you may have.  The company that make those (the name escapes me) acknowledged that was a problem and used ot send out a free kit of capacitors you could install to reduce/eliminate the interference.  I believe they changed the design at some point to address that issue and thus my comment on how old your rig might be.

We had a similar problem and the once I installed the caps the interference disappeared.

Former Winnebago/Itasca owner.

Dino KL0S/4
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KC0KBH
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« Reply #7 on: October 20, 2005, 08:25:54 PM »

My old computer did that.  So did my new one until I switched over to an LCD monitor.  Could it be the LCD inverter on your laptop?  Things still cause RFI, though, like the vacuum.  It causes my whole waterfall to go yellow with interference.  Can't see a thing.
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