Hi all,
last year I was using an IBM Thinkpad A31, and the integrated sound
card for DVK functions. All was fine. Now I have an IBM Thinkpad
T30 (same sound card), and I'm getting strong rhythmic computer
generated background noise like "brrrrrt --- brrrrrt --- brrrrrt".
This noise is exactly corresponding to the serial interface polling the
Yaesu FT-1000MP on COM1. When the "CAT" sign on the MP is
lighting, the noise is on... BTW: the noise was also noticable on the
"old" A31 - but VERY much weaker than my voice, so it didn't hurt.
Interestingly the signal is absolutely clear, when I'm using the notebook
integrated microphone (not an option for contesting ;-). Every time
I plug an external mike in, the noise is starting. And, the noise is
significantly weaker, when operating on the battery instead of the
power supply... I am using the same microphone (Heil headset) and
cables (!). Just to make sure that the problem is directly related to the
notebook, I got my old A31 connected, and the signal was clean.
I have:
* used ferrites
* used a 1:1 transformer
* tried to ground the notebook
Can it still be a Windows setting? I was using Windows 2000 Server
on the "old" A31, now there is Windows XP Professional on the T30.
What else could I do, but get rid of that new T30 ? ?
73 Ben
DL6FBL
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