[ct-user] 7 Mhz RF getting into keyboard.

PITMANZ.W9 PITMANZ@westel900.hu
05 Aug 96 08:56:35 +0200

We had the same problem with the keyboards on HG1S/HG73DX. The problem occured 
only when we were operating on 40m. Without any scientific investigation we 
did the following: 
1, Replace the keyboard cable 
Normally these cables are low quality 5wire/mutual-shielded  cables. I went to 
a local HiFi Audio Store and bought a 5wire cable with seperate shielding for 
each wire. 
2, Put small ferrite rings on the wires  
Inside the keyboard we put small ferrite rings on the end of the wires and in 
the PC socket. 
Now there's no RFI in the keyboards. 
I should note that the PCs are connected to a superb grounding system and the 
PC houses are the old "desktop"-style ones. We found them the best, since 
there is enough room to put everything you want into to case and it makes a 
good shielding. Since the hinge which holds the cover is not a good conducter, 
the cover has been connected to the desktop house with thick copper wires (cut 
a piece of RG213 or something similar, remove the shielding and on the edge of 
your desk make it flat. You get a 1/2" wide, 0.1" thick flexible conductor.) 
on both ends.   
If you or anybody still interested I can write about the other modifications I 
did on the monitor,  PC power supply and other accessories to keep the 
spectrum clean.  
Best regards 
Zoli HA1AG 
Ps: The antenna tuners are major sources of RFI. If you have any, check the 
grounding and shielding first.

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