[RFI] DigiKeyer II

Dale svetanoff at earthlink.net
Sun Dec 15 18:02:30 EST 2013


Interesting issue.

1.  First, I assume that you are NOT using an amp after the IC746 Pro.  Is that correct?

2.  If you have not tried this yet, REDUCE output power to a level at which the RFI stops.  The difference (in dB) between the lower power and your normal power output (assumed to be 100 watts) is the "threshold of pain" for this problem.

3.  What TYPE of ferrites are you using?  Since you are on HF, common Mix 43 is not optimum - Mix 31 would be a better choice.  Try multiple turns of the cable thru the ferrite choke(s) to increase the insertion impedance.  

Since you say that you had years of OK operation with a RigBlaster on that same ACC1 port of the radio, it would appear that the DigiKeyerII causes a problem to the port.  Besides a different ferrite mix, try improving the cable shielding or termination of the shielding (it IS a shielded cable - right?).  

I'd say that it is important to determine that "pain threshold".  If you are only a few dB away form getting rid of the RFI, then better ferrites and/or shielding should fix it.  If you are 10 dB, or more, away from the threshold, you need to revisit the RigBlaster setup and compare to see what is wrong.  Somewhere, you are picking up too much RF and that ingress route needs to be suppressed.  Good luck.

73, Dale

-----Original Message-----
>From: Peter Laws <plaws at plaws.net>
>Sent: Dec 15, 2013 4:15 PM
>To: "rfi at contesting.com" <rfi at contesting.com>
>Subject: [RFI] DigiKeyer II
>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!
>RFI mailing list
>RFI at contesting.com

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