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Re: [RFI] More cowbell?

To: rfi@contesting.com
Subject: Re: [RFI] More cowbell?
From: "Peter Laws" <plaws0@gmail.com>
Date: Thu, 1 Jan 2009 14:01:15 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Wed, Dec 31, 2008 at 23:36, Roger (K8RI) <k8ri@rogerhalstead.com> wrote:

> ADMS cable?

Sold with/for Yaesu VHF/UHF gear to allow programming from a PC.  It's
just a level converter and works just ducky to control the Icom ...
well, ducky minus RFI.  Mine was from my FT50RD HT.


> The Icoms are good for "pin 1" problems. I'm surprised any thing gets
> into the CI-V though. It uses a standard serial cable to the computer

It's not a real CI-V box.  I actually have a friend that has one of
those and should probably test with it in place of the ADMS cable.

Do you have a link to a description of the Pin 1 problem?


> This sounds like more than just getting into the CI-V. I have one fed by

It is, it is.  My wife actually mentioned that she *doesn't* hear me
in the telephone any more, so I am making some progress.  :-)  I did
test on many band/mode combos at one point and should repeat that.




> Although you may have a pin one problem, I'd bet "good" current chokes
> at the antennas, and grounding the braid at the base of the antenna
> support and where it comes in the house will get rid of most of those
> problems.


Just built the "current balun kit" from Palomar.  It's just 5 or 6
ferrite beads that slip over a length of RG8-style cable (LMR400 in my
case) and shrink tube to secure them.  I think they are probably Mix
43, but the page doesn't actually say.

He actually publishes impedance figures, and having just read W1HIS's
paper at http://yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf,
I see that I could probably use "more cowbell".

http://www.palomar-engineers.com/1_1_Balun_Kits/1_1_balun_kits.html


> Another question that comes to mind based on the wide spread RFI, do any
> of the antennas run close to, or parallel to the telephone wires (in or
> out of the house) or the speaker cables?

It may no longer be as wide-spread as I thought given my wife's
revelation (that I don't get into the phone any more), so I need to do
more testing.  I definitely still interfere with the Radio <-> PC
connection (and the PC speakers).



> Nuther thought, does the ground for the rig also tie into the house
> electrical ground?

Sadly, no.  I need to look into getting my electrician to bond my
ground rod to the house ground.




> Where do you ground the coax shield?

The only point that the shield is grounded, aside from via the radio
chassis, is via the A-D TransiTrap at the feed-through panel.



> Do you have to room to just stick up a plain old fashioned dipole on 40
> as a comparison?

I have the room, but not the trees!!  :-)  Or at least not well-placed
trees.  Next summer, I'm going to look at something wire for 160 and
maybe 80.  I sure love the simplicity of the trap dipole - it's worked
acceptably well, 80-10, for years.  It's 80-15 now, but it sill works
FB on those bands.


> IOW start with the very basic station with only one coax even run into

This is likely the next step.  I can't go too "basic" though, since my
main symptom is the computer control link dying.  It does the same on
'phone, though, so I don't need the RB+ for testing.



> system look like with an analyzer? Are you sure the connections are good
> at both ends.  What about the 9913 and coax connectors?  I've had lots
> of problems with 9913, but never RFI.

The system is OK on the analyzer, with dips to 1.4:1 at 3785 and 2.2:1
at 7275.  Better on 20 and 15.  Over 8:1 across 10.

Connectors on the 9913 were recently redone.



> As long as they are on the same circuit. It might pay to check out the
> polarity of the AC outlets. Finding them reversed is not at all uncommon
> and particularly so in older homes.  Never assume.

New outlets in the radio room and I've checked them!  They're good



> go...wait...got it... <sigh>  What kind and size of power supply do you
> have in the computer? Not all computer supplies are equal and some are
> prone to RFI (in and out) What kind of case does the computer have? All
> computers here have metal cases and none are grounded. Three are full

All phone line is now Cat 5e as is the Ethernet - had that installed
when we moved in (old phone wire was Cat 3 on the outside of the
house!).

Radio PC has an Antec tower case and MoBo is a fairly cheap Soyo with
a Duron on it.  I don't actually know the specs on the PS, but the
system was built with a fast (for the time) Athlon (which I later
killed :-) so I suspect it's a pretty decent PS, but worth checking.
I'm sure the unit can use a good blowing out anyway.


Thanks for all the suggestions, but what I'm really looking for is a
magical silver bullet.  Got any of those??  :-)

Seriously, thanks!


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

No Trillion-dollar blank check for crooks!
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