[WriteLog] RFI and Keyers
Joe Subich, W4TV
w4tv at subich.com
Mon Nov 12 13:12:48 EST 2007
To follow up on this one time ...
> I've also seen a number of posts on the NCCC list from good
> engineers who have fixed stability problems with Microham
> products using ferrite chokes on interconnect wiring. That
> fix would not work (or be necessary) if he was right.
Others may have fixed alleged problems with "microHAM products"
by adding ferrite chokes on the interconnect wiring but they
are masking a problem that lies elsewhere much like an "antenna
tuner" masks problems at the antenna by applying matching at the
The "Pin 1" issue is in the computer - specifically the USB
port - and not the microHAM product. If you check most of
the consumer computers these days you will find several red
flags for Pin 1 problems. First, the USB connector shield is
often not connected to the motherboard ground plane and not
connected to the metal case of the computer (if the case is
metal). In addition, the USB Power return (circuit ground)
is not connected to the power supply "ground"/chassis. Finally,
most amateurs do not ground their computers other than any
chance grounds through common leads to their radio and/or
the line "safety ground."
The issues with both "radiated noise" related to USB and
data loss in the presence of RF can be related directly
to Pin 1 problems in the computer - laptops are more of a
problem that old style metal case "tower" systems.
The solution is multi-fold ... proper design of the computer
motherboard AND chassis, proper grounding of the computer
(a short strap to the station "common point ground") and
eliminating common mode currents on cables coming into the
shack (e.g., proper grounding of all cables to the common
point ground at the entry window with common mode chokes
between the entry window and equipment).
... Joe Subich, W4TV
support at microham.com
> -----Original Message-----
> From: writelog-bounces at contesting.com
> [mailto:writelog-bounces at contesting.com] On Behalf Of Jim Brown
> Sent: Thursday, November 08, 2007 11:08 AM
> To: WriteLog Reflector
> Subject: Re: [WriteLog] RFI and Keyers
> On Tue, 6 Nov 2007 20:49:42 -0500, Joe Subich, W4TV wrote:
> >With respect, the microHAM products were done correctly with
> >regard to any "pin 1 problem."
> While I respect Joe and his business, I believe that Joe is mistaken
> about this. He and I are corresponding privately, and I've pointed
> out some components of the RFI problem that others are seeing. I've
> also seen a number of posts on the NCCC list from good engineers who
> have fixed stability problems with Microham products using ferrite
> chokes on interconnect wiring. That fix would not work (or be
> necessary) if he was right.
> Jim K9YC
> WriteLog mailing list
> WriteLog at contesting.com
> WriteLog on the web: http://www.writelog.com/
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