[RFI] DigiKeyer II

Peter Laws plaws at plaws.net
Sun Dec 15 17:15:43 EST 2013

IC746Pro, microHAM Digi Keyer II.

One USB cable from the radio to the interface.  One squid from the
interface to the radio with 1/4" plug for CW, a 1/8" plug for CI-V and
a howevermanypin DIN for ACC1.  There are snap-on chokes on the ACC1
cable and the USB cable from the factory.  The interface is connected
to the ground bus and the bus is connected to a ground rod buried
outside the window.  Radio is also connected.  To make sure
(hopefully) there was nothing coming down the coax, there is one of
those Palomar buildityourself chokes on a foot long piece of LMR400 in
the shack.

Interface works OK and I played a little in CQ WW RTTY and November
Sweeps CW.  I use FSK not AFSK so that's hard keyed as is the CW (I
think I set it to use the internal K1EL chip).  All of that works

But when I went to play in SS SSB, I had horrible horrible RF getting
into my audio.

I finally had time today to troubleshoot.  SWR (on three wire antennas
coming through an Ameritron remote switch) was acceptable but best on
the WARC band trap dipole (in fact, I'd forgotten just how well that
antenna works even without the tuner.  I went to 17 where I knew the
SWR was good and did some tests. I can hear the distortion through the
headphones with the monitor on.  Unplugged CI-V, no change.  CW, no
change.  Unplugged ACC1 .... no more distortion.  Got on 17 and
chatted with a feller up in Indiana and he heard no distortion either
(though I gather the HC4 in my Heil boomset wasn't doing me any
fidelity favors :)).  Plug ACC1 back in, back to interference.

Interestingly, this unit doesn't power itself off the 5 V available on
the USB connection but off the 8 V available off the ACC1.

I've added two more snap-ons of unknown mix to the big cable from the
interface and this has made no difference.

Ideas?  More ferrite, I assume?

I used a RigBlaster Plus for nearly a decade that pulled audio and
keyed FSK and CW via ACC1 and never had this issue.  I don't even
think it had ferrite on the cable.

Peter Laws | N5UWY | plaws plaws net | Travel by Train!

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