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[RFI] More cowbell?

To: rfi@contesting.com
Subject: [RFI] More cowbell?
From: "Peter Laws" <plaws0@gmail.com>
Date: Wed, 31 Dec 2008 20:32:53 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Or ferrite, as the case may be ...

Background:  I have a Spi-Ro D-56 80-10 trap dipole at about 26'.
There is a Spi-Ro D-314 (30-12) at about 34' some 30' away.  D-56 is
fed with about 63' of 9913.  Note that prior to the Fall, it was fed
with about 110' of RG8X.

There is an 8' ground rod in the soil outside the shack window and all
coax feedlines have TransiTraps connected to the ground.  There are
also braids from the rig, power supply, and (recently) PC to the same
ground.  Rig is an IC746Pro with a RT Systems "ADMS" cable for CI-V
control.  There is also a Rig Blaster plus connected to one of the ACC

I've had issues with RF getting into the CI-V port all along, not to
mention the PC speakers and the telephone, but lately it's so bad that
I couldn't use the CI-V at all on the low bands (40, 80) during SS
SSB.  RTTY Roundup is this coming weekend, and the 'puter becomes a
little more important for that.

Recent updates below. Any and all suggestions welcome!  Help!

---------- Forwarded message ----------
From: Peter Laws <plaws0@gmail.com>
Date: Tue, Dec 30, 2008 at 18:31
Subject: Re: [RTTY] Looking for resources: log analysis, RFI solutions
To: RTTY Contesting <rtty@contesting.com>

Man RFI is still eating my lunch.  One of the traps is bad on my
Spi-Ro D-56, so it isn't even close to resonant on 10.  15-80 is fine
(well, fine as it ever was - it's a trap dipole).  The RFI happens on
40 and 80 and not on 20 or 15.  The sweet spot on 80 has an SWR of
1.4:1 or so and on 40, it's 2.2:1.  Worse further from the sweet spot
as you'd expect.  And the busted trap has not changed the RFI
situation - it was there before the trap failed.

I bought a Spi-Ro D-52 to replace it (longer, only 2 traps) but
contrary to how Spi-Ro markets it, it's only an 80-40 dipole (fine
antenna - make me an offer).  So, I put the D-56 back up and have
another homebrew dipole for 10.

Bought a current balun kit from Palomar Engineers as someone here
suggested and installed it just now - no better.  The CI-V connection
STILL resets when transmitting.

In N1MM, this shows up as a dialog box inviting me to "reset my
radios".  In DXLab Suite's Commander, it's not as obvious that you've
lost the connection until you do something like change freqs.

Commander's debug capture window, however, shows that after getting
RFIed, it just sends a continuous stream of 0xFD.  As an aside, I can
also hear myself though my cheap PC speakers and in the telephone, but
I don't care so much about those - I figure when I get the CI-V issue
fixed, the rest will magically go away. :-)

And yes, I've got ferrite on both ends of the serial cable (and a
toroid on the speaker leads).

Some other stuff I tried:

Connected the PC chassis to the same ground as the radio.  No change.

Connected the PC chassis to the ground braid from the radio only (no
connection to earth ground).  No change.

I disconnected the ground entirely (as suggested below).  No change.

Other suggestions?  RTTY RU is only days away!!!


On Mon, Nov 17, 2008 at 12:33, Bill, W6WRT <dezrat1242@yahoo.com> wrote:
> There is no downside that I know of, in fact in my shack I have to
> bond them together or 160 meter RF gets into the computer and wipes
> out the soundcard.  If possible, have the radio and the PC right next
> to each other so the ground wire is as short as possible.
> Also, you mentioned having a separate ground rod for the rig. This
> might be a source of trouble too, since you can't really 'ground' RF
> in the sense of making it 'go away'. Your ground rod+wire is no doubt
> acting as an antenna, although an inefficient one. Try removing the
> ground and see if things improve.
> 73, Bill W6WRT
> ------------ ORIGINAL MESSAGE ------------
> On Mon, 17 Nov 2008 11:26:08 -0600, "Peter Laws" <plaws@plaws.net>
> wrote:
>>What would the downside be to running a braid from the PC to the radio
>>ground bus, I wonder?

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

No Trillion-dollar blank check for crooks!

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

No Trillion-dollar blank check for crooks!
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