RFI and Direct tv or Dish network

[Eric Swartz - WA6HHQ]

Great info. :-)

Now that the OPs question is answered, let's close the thread now in the interest of containing email overload for our other readers.
73,
Eric (in the air heading to Dayton..)
Moderator
elecraft.com
_..._



> On May 18, 2016, at 9:56 AM, w9hak <[hidden email]> wrote:
>
> Thanks to all that replied to my question. Great list!

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[Edward R Cole]

First off, the Dish-NET receiver produced no RFI.  It was not digital
satellite so used s-video connections to Home Theater receiver which
was connected to TV via HDMI.  New Direct-TV receiver is high-def
digital receiver so it uses HDMI interconnect to home
theater.  TV/home theater is on other side of wall from ham shack.

The PS is not a wall wart.  It looks more like an overgrown laptop
PS.  But I can try toroids on power cable and HDMI to see if that
quiets it.  Really no problem most of the time as 2m is not in use
when TV is in use.  I have not determined what the dc voltage out of
the satellite PS.

KX3 in AM mode works fine as RFI sniffer.

73, Ed - KL7UW

From: "John K9UWA" <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] RFI and Direct tv or Dish network
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=US-ASCII

Jim is 100% correct. The Direct TV receivers are HORRIBLE for noise
generation. Maybe you can't hear it if your Ham Antenna is far enough away
but it is there for sure. I bought a Sony model ICF-2001 to use looking for
various noises about the house. You don't want the later models as they
have auto noise blankers in them. The radio covers AM/SW/FM and does
AM or SSB.

Jim is exactly correct regarding the Wall Wart type switcher supply on these
Direct TV receivers. They are 12.6 vdc so easy for us Hams to pick up a
nice small linear transformer powered regulated supply. I also hooked up
the Modem and Router to this same linear supply. Yes every one of them
made noise.

Next the HDMI cable from the Direct TV receiver to the TV set also mades
lots of racket. I use TWO of the FT-240 mix 31 cores and managed to get
about 5 turns through both chokes. That killed the HDMI cable noise.

John k9uwa




73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

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[Warren Merkel]

Thanks for the note Jim,

However I've already got multiple passes of the OCF Feedline fed through
a stack of five 2.4"  #31 donuts, per your very own, excellent
RFI-Ham.pdf article.   Picture on my QRZ page.
https://www.qrz.com/db/KD4Z 

The RG6  has a stack of three donuts with a large number (didn't count)
of turns, located at the demark point to the house.  I guess I could add
another set and spread out the Z over frequency a bit more.

I believe I need to look for other entry points to the entertainment
system as a whole, as the DirecTV DVR is network connected and of
course, connected to an AV receiver.  Lots of points of entry to squelch.

Warren, KD4Z

On 5/18/2016 8:29 PM, Jim Brown <[hidden email]> wrote:

Your antenna, an off-center-fed Windom, is notorious for generating

common mode current on the feedline, and there's no way to choke it
effectively to kill that current. So what you're calling a feedline
Mother Nature calls part of the antenna. THAT'S a primary cause of your
problem.

If you're having issues on 80M, you'll need at least 13 turns of the RG6
through a single #31 toroid to make a dent in the common mode current.

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[Jim Brown-10]

On Thu,5/19/2016 6:41 AM, Warren Merkel wrote:
> Thanks for the note Jim,
>
> However I've already got multiple passes of the OCF Feedline fed through
> a stack of five 2.4"  #31 donuts, per your very own, excellent
> RFI-Ham.pdf article.   Picture on my QRZ page.
> https://www.qrz.com/db/KD4Z

But that choke is in the wrong place -- to kill feedline current, it
must be at the FEEDPOINT, up in the air where the feedline connects to
the horizontal part of the antenna. Remember -- this is not DC, it is
RF, and the feedline between the feedpoint and the choke is part of the
antenna. All you have done is make current small at the location of the
choke, but because the feedline is part of the antenna, current will
vary along it following the laws of physics that determine how antennas
work. To understand this, think of an ordinary resonant center-fed
dipole. Current is near zero at the ends (it's an open circuit, with
only capacitive coupling to space), and peaks at the center (because the
center is a quarter wavelength from the end point).  The same thing is
happening with your feedline -- common mode current is near zero at the
choke (you've forced that with the choke) and increases along the line
toward the feedpoint.

The problem with antennas fed with open wire line is that it is simply
not practical to choke them at the feedpoint. OCF antennas have the
additional problem that the off-center feed makes them VERY unbalanced,
which creates a lot of common mode current on the feedline.  This
doesn't prevent them from working as antennas, but it does put a lot of
RF in the shack and the feedline can also receive a lot of noise (if
there is any around it).

> The RG6  has a stack of three donuts with a large number (didn't count)
> of turns, located at the demark point to the house.  I guess I could add
> another set and spread out the Z over frequency a bit more.

Spreading Z over frequency depends on the frequency range where
transmitting causes problems.

> I believe I need to look for other entry points to the entertainment
> system as a whole, as the DirecTV DVR is network connected and of
> course, connected to an AV receiver.  Lots of points of entry to squelch.

I don't remember seeing a description of the symptoms of your problem.  
I would expect that interference to the DirectTV unit would be indicated
by "breakup" -- a failure to decode, or interruptions in the decoding of
the signal.  If that isn't happening, but you're hearing detected audio
or clicks, I'd suspect gear in the entertainment system and work on
choking cables connected to it.

But never rule out the possibility that there can be multiple points of
ingress to that system.

73, Jim K9YC

>
> Warren, KD4Z
>
> On 5/18/2016 8:29 PM, Jim Brown <[hidden email]> wrote:
>
> Your antenna, an off-center-fed Windom, is notorious for generating
>
> common mode current on the feedline, and there's no way to choke it
> effectively to kill that current. So what you're calling a feedline
> Mother Nature calls part of the antenna. THAT'S a primary cause of your
> problem.
>
> If you're having issues on 80M, you'll need at least 13 turns of the RG6
> through a single #31 toroid to make a dent in the common mode current.
>
> ______________________________________________________________
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> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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