On Tue, Dec 17, 2013 at 8:50 PM, Jim Brown <jim@audiosystemsgroup.com> wrote:
> Hi Peter,
>
> See comments interspersed.
Likewise. FINALLY got time to do something about this. Meantime, I
bought some ferrite.
> A connection to earth is NOT part of a solution to RFI. Proper bonding of
> equipment IS. That includes short fat copper (#10, or copper braid stripped
> from transmitting coax) from every chassis to every other chassis that is
> interconnected. In your case, that means from the computer to the microHAM
> to the 746. The rig must also be bonded to the power system ground, and to
> all other grounds in your home.
All items mentioned have thick braids to a copper bar at the back of
the desk. DK-II, IC746Pro, Power supply, PC.
Bar is connected to ground rod outside window, though the braid is
suspect, of course. I picked up 25' of 6 ga at the local bigbox but
balked at the price of ring terminals (over a buck a piece?), so
that's not installed quite yet. There are TransiTraps on each of the
feedlines that are also connected to the ground rod you say isn't
important for RFI.
>
> Maybe a Pin One Problem, but also a possible power problem. How are you
> powering your microHAM? The wall wart that came with it, or from the 12V
> bus? Use the wall wart, not 12V.
No wallwart. USB, but not powered that way. Pulls 13.8 V dc from the
ACC1 on the radio.
> Is this problem present on all bands, or only on 17M? Take one of your
> ferrite cores and wind 4-5 turns of the ACC1 cable through it. Do the same
> with the USB cable.
Bought 2.5" OD Fair Rite toroids, 4 ea mix 31 and mix 43. Bought some
snap-ons, too, just for fun.
Got 4 passes through a #31 toroid. Not sure if a 5th is possible.
No change, though, I still hear it through the headphones. I'll find
someone to give me a report after I run some errands, but I already
know the answer - it will go away the instant I unplug ACC1.
As I noted a while back. Same PC, same radio, same antennas, same
ground using a RigBlaster Plus had no audio problems ever. The RB+
has no audio device in it, or USB, and is powered off shack power
supply ... but all audio, coming and going, passes though it. Never a
problem.
Swap in the DK-II and I boom - RF on the audio.
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