Jim,
On 2/16/2016 2:04 AM, Jim Brown wrote:
Indeed, it would darn near impossible to do it right without starting
from scratch withunit a properly made cable from the MicroHam unit to
the radio, with each signal path having its own coaxial cable.
Please confine your comments to areas where you are knowledgeable. The
microHAM cables *DO* use a separate coaxial cable (or shielded twisted
pair) for each signal path. The shields are connected to the shell of
the respective connector on each end of the cable. With properly
designed transceivers, this design will minimize RFI issues. When good
engineering practice is used in the station installation - including
antenna systems - there should be no RFI problems with a properly
implemented microKEYER II, MK2R+ or micro2R system.
Schematics for every microHAM cable are available from the support area
at www.microham.com or www.microHAM-USA.com/support.html.
73,
... Joe, W4TV
On 2/16/2016 2:04 AM, Jim Brown wrote:
Bernhard,
It's NOT common mode, it's the simple fact that the audio interface is a
mess. The antenna on the roof transmitting high power is doing its job,
putting a lot of RF in the shack. If it didn't (based on proxmiity), it
would be a lousy antenna. The problem is that the interface (wiring plus
electronics plus termination) does not reject RF because it fails to
conform to fundamental principles that reject RF. That is, every cable
must be a transmission line, every shield must be terminated at the
shielding enclosure of the equipment at both ends, and every equipment
chassis must have a short, fat, bond to every other equipment chassis.
Yes, the signal is audio, but the interference is RF, and it takes
proper transmission line techniques to reject that RF.
I have VERY limited experience with MicroHam, but the jumble of wires
that I encountered with the MicroHam unit at W6OAT violated all
principles of good engineering practice for operation in a high RF
environment. It was nothing more than a multipin connector with a lot of
wires soldered to that connector. Indeed, it would darn near impossible
to do it right without starting from scratch withunit a properly made
cable from the MicroHam unit to the radio, with each signal path having
its own coaxial cable.
I have no idea if that describes ALL MicroHam units, but it does
describe Rusty's. And don't ask the model number -- I was so disgusted
by what I saw that I just rolled my eyes.
73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to arch...@mail-archive.com
