[RFI] Keyboard

[Roger (K8RI)]

Fix RF getting into the kbd, BUT this is only a problem in the one 
configuration!
If so, then the problem should not be the kbd, nor should there be a 
need to go through RF chokes and any other cure at, to, or on the kbd.
As this happens in only one configuration the problem HAS to be from 
something different in this one configuration.  Your later work has 
pretty much proven this to be the case with the reconfiguration of the 
cabling using the SB220 hookup.

Therefore, look carefully at what is different.  Remember, all coax 
lines to the amp provide grounds. Not earth grounds, but ground paths 
between equipment units. network grounds, keying lines, coax shield 
lengths, common ground lengths between driver and final, different 
lengths to "earth (CPG)" compared to grounding between equipment grounds 
while being careful to differentiate between grounds between equipment 
and earth grounds (CPG) connections.  Changing comparable lengths can 
and often does create different voltages between pieces of equipment.  
With the kbd we are looking at small voltages that can be created by 
changes of only a few inches, let alone, feet.

So the key question becomes, what is, or was different in the equipment 
intersections that could have caused this. For me, the problem going 
away would not be enough.  I'd be forced to find the answer as to what 
had been causing the problem.  Trying to fix the symptoms is like 
treating a cold. You never cure it, you just make yourself feel better 
while you have it.  In the case of the kbd interference, you should be 
able to discover what was causing the problem.

As I've mentioned a number of times, I have never needed to go through 
adding chokes in the equipment lines, or wiring.  I did need to add a 
second common mode choke in the feedline to the center fed 75 meter, 
half wave sloping dipole as a single choke wasn't enough, but I was 
fixing the source, not treating the symptoms.

73, Roger (K8RI )

On 3/3/2018 Saturday 10:47 AM, GaryK9GS wrote:
> A better idea would be to fix the RF getting into the keyboard in the first place.  That's not normal.
> What kind of antenna are you using?  Does this happen on only some bands?  At any power level.
>
>
> 73,
> Gary K9GS
> -------- Original message --------From: dalej <dj2001x at comcast.net> Date: 3/3/18  9:32 AM  (GMT-06:00) To: Joe <nss at mwt.net> Cc: rfi at contesting.com Subject: Re: [RFI] Keyboard
> I’d use a #31 mix snap-on and wrap several turns though it.  I purchase mine from Mouser.  I don’t have the PN handy but if you need it let me know.
>
> Those from RS I don’t count on to do a good enough job.
>
> 73
> Dale, K9VUJ
>
>
>
> On 03, Mar 2018, at 9:24, Joe <nss at mwt.net> wrote:
>
> Is RF getting into a keyboard issue OK here, it is RFI in a way..
>
> OK, Say you get RF into a USB keyboard. It just stops working and the only way to get it working again is a total re-boot.
>
> I'm assuming the best option is ferrite beads on the cable.
>
> Now question, where is the best placement of the beads. Keyboard end? Computer end?  BOTH?
>
> I have two here, a small one where I could get one or two passes through the hole. ( it is a Radio Shack split thing )
>
> and then a much larger one, also split,, but the hole is close to a inch ID. so I could do many turns.
>
> What would be best to put where?
>
> Joe WB9SBD


-- 
Roger (K8RI)


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