Joe - how do you know you have "next to none!" RF in the shack?
If you have an OCFD that's not got a REAL current choke (no voltage baluns
or single core 4:1 baluns need apply here) then you have RF in the shack.
If you are using a "Carolina windom" with a radiating vertical feedline
with a balun at the bottom, you have RF in the shack.
There's only one way to quantify it and that's with a meter. If you have a
conventional OCFD, add a substantial-CMI current choke to the feedpoint and
it'll probably end what common mode current is coming down into the shack.
You can build those for a few dollars. Check out K9YC's publications on the
matter:
*audiosystemsgroup.com/RFI-Ham.pdf
<http://audiosystemsgroup.com/RFI-Ham.pdf>*
*audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf
<http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf>*
*audiosystemsgroup.com/CoaxChokesPPT.pdf
<http://audiosystemsgroup.com/CoaxChokesPPT.pdf>*
You can check out Steve's chart and other information at:
*http://www.karinya.net/g3txq/chokes/
<http://www.karinya.net/g3txq/chokes/>*
If you have a "carolina windom" with a purposely radiating feedline (that's
got common mode current all over the outside of the coax by definition)
then you MIGHT be able to add a choke wherever the 4:1 balun is and choke
of the current going past the balun. You may have to move the radiating
vertical element further away from your shack somehow to eliminate it
completely.
If you want to learn MUCH more about the OCFD antennas and their
requirement for substantial choking, check out:
*http://www.dj0ip.de/off-center-fed-dipole/
<http://www.dj0ip.de/off-center-fed-dipole/>*
Ethernet, even CAT6, is quite susceptible to RF ingress. Are your CAT6
cables properly terminated, with the shield correctly installed into the
connectors? If not, they're not really shielded. Decent factory cables
should be OK, but homemade cables are frequently lacking in this regard.
Heck, even some of the Motorola "shielded" cables that we got straight from
Mama-M in Schaumburg, IL when I worked at the nearby Motorola Service
Center weren't properly terminated, having the shield snipped off right at
the connector, rather than having the shield properly inserted and crimped
into the connector. The use of CAT5 connectors on CAT6 cable will do the
same thing.
I encourage you to do some reading at the above links.
Good luck with it!
73
Matt
AK4MK
On Sat, Dec 2, 2017 at 1:30 PM, Joe <w7rkn.7@gmail.com> wrote:
> I think I forgot to mention...I have **no** audio issues with the L7, only
> the Henry. Go figger!
>
> OH, and I have very little (read: next to none!) RF in the shack. That is
> what is puzzling me! How in the heck is the RF getting into my network and
> only affecting the printer?
>
> Joe - W7RKN
>
> -----Original Message-----
> From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Dave Cole
> (NK7Z)
> Subject: Re: [RFI] RFI In My Shack
>
> Hi again,
>
> Given the old amp caused issues with your audio, and your new amp causes
> issues with your network, we can assume you have some level of Common Mode,
> (CM).
>
> My first step would be to buy or build a common mode sniffer. MFJ makes
> one
> for around $100.00, or you can build one for around 10 bucks:
>
> https://ham.stackexchange.com/questions/1271/how-to-detect-
> common-mode-curre
> nts-or-rf-in-the-shack
>
> If after testing with that you discover lots of CM, then start choking it
> on
> the booth ends of the feed-line.
>
> That may solve both your RFI issues; audio, and Networking.
>
> If that does not solve things report back here with results. The AC would
> be the next thing I would look at...
>
> 73s and thanks,
> Dave
> NK7Z
> http://www.nk7z.net
>
> On 12/02/2017 10:07 AM, Joe wrote:
> > Yes, A Windom, that is coax fed into a 4:1 balun. Remember, I did
> > *NOT* have this issue with my Henry amplifier, even at over 2000 watts
> > out. [Euro version of the amp!]
> >
> > Joe - W7RKN
> >
> > -----Original Message-----
> > From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of Dave Cole
> > (NK7Z)
> > Subject: Re: [RFI] RFI In My Shack
> >
> > Let me guess, you are using an Off Center fed dipole, or some sort of
> > asymmetrical antenna If not what is your transmit setup.
> >
> >
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> >
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