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Author Topic: Interference from a laptop  (Read 565 times)
G3UCQ
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« on: December 14, 2005, 12:27:19 PM »

Hi
I have a Sony Vaio laptop (only a few months old so it should be up to spec on interference radiation etc.) which I have connected to my Kenwood TS-570, using the ACC2 connector audio output to the mic input on the laptop, in order to use the CW decoder program MRP40.
Only on 40m do I get an increase in background noise which is coming from the laptop.  I have put 2 ferrite filters on the screened connecting cable but they make no difference.
The background noise increase is about 4 S points which makes working weak stations impossible.  Other bands are OK.  Any ideas how to cure this please?
Many thanks
John
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KG4RUL
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« Reply #1 on: December 14, 2005, 05:34:10 PM »

My older IBM laptop has high noise radiation from the display.  I suspect it is originating from the backlight since the noise level changes as the intensity is changed.

That seems to be the only hotspot in this unit.

I have a separate HF antenna input on my TS2000 so I used it to plug in a 'sniffer' antenna. I made it from a short piece of RG-174 with an RCA plug on one end and a 2" dia., 4 turn loop of 22 GA insulated wire on the other end.

Dennis KG4RUL
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G3UCQ
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« Reply #2 on: December 15, 2005, 08:28:10 AM »

Hi Dennis
Thank you for your response but I don't think (but am willing to be corrected) my problem is air borne as the hash level drops when I disconnect the cable connecting laptop to TS-570. The increase in hash noise is only apparent on 7mhz.
Cheers
John
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N3ZKP
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Posts: 2008




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« Reply #3 on: December 15, 2005, 12:59:26 PM »

It could be a ground loop problem, too. Do you have an isolation transformer between the computer and the rig?

73,

Lon - N3ZKP
Baltimore, Maryland
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G3UCQ
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« Reply #4 on: December 16, 2005, 01:27:09 AM »

Hi Lon
No, I don't have an isolation transformer.  I'm going to try connecting the TS-570 to my main PC to see if that helps. I'll post back with the result.
73s
John
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N3ZKP
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Posts: 2008




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« Reply #5 on: December 16, 2005, 07:42:48 AM »

You want an isolation transformer, no matter which computer you use. Ground loops can cause all sorts of problems.

If you don't want to homebrew something, there are numerous interfaces available rather inexpensively that do a nice job.

Hope your solution is something simple.

Lon
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WD8PTB
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« Reply #6 on: March 07, 2006, 06:17:33 AM »

Radio Shack has a 1 :1 audio transformer that I used. You can put connectors on the transformer and insert it between the computer and the radio. Good Luck; Don WD8PTB
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