Marshall Stewart marsh at ka5m.net
Tue Feb 5 12:25:12 EST 2013

DirecTV RFI -- February 2013

I recently moved to a new QTH and to get back on the air as quickly as
possible I put up an OCF dipole (not a Windom) at 70'.  The antenna is fed
with RG8X into a Balun Designs 4114ocf balun designed specifically for use
with OCF dipoles. At the station end of the transmission line there are 50
Fair-Rite #31 1-1/8"long ferrite beads (Mouser Part # 623-2631540002.)  

The station is located on the second story.

All grounds -- electric power, telephone, satellite, and station ground are
all bonded together and connected to ground rods and to the cold water
plumbing which is all copper tubing.  I also built a ground grid system per
W8JI's website in the attic behind the station.

The DirecTV system in my house is a "whole house" system with 1 HR24-100 HD
DVR receiver and 3 H25-100 HD non-DVR receivers. The DVR receiver has an
internal power supply, and the non-DVR receivers each use a DirecTV AC
Adapter EPS10R0-15.  All new satellite TV coax was installed with the
system.  The satellite dish is not under the antenna and is aimed away from
the antenna.

With only 20 watts of RF power output on 80M all 3 H25-100 HD non-DVR
receivers would crash then start the re-boot process.

In my case, most of the problem was the DirecTV AC Adapter EPS10R0-15 that
DirecTV supplies with the H25-100 HD non-DVR satellite receivers.  With no
RFI suppression, the no-load output voltage would drop from 12VDC to 2VDC
when I transmitted with 1000 watts RF output power.

With a RadioShack Enercell 12VDC AC adapter Cat. No. 2730461 with no RFI
suppression the no-load output voltage stayed constant when I transmitted.

The RadioShack AC adapter uses something called an Adaptaplug Tip.
RadioShack tip "U" looked the most like the plug on the 12VDC end of the
DirecTV AC Adapter.  But no joy, it would not plug in to the DirecTV HD
non-DVR receiver.  So I cut the molded-on plug along with a short length of
cable off the DirecTV AC Adapter and soldered it onto the end of the
RadioShack AC Adapter 12VDC output cable.

My final RFI suppression configuration:
(All ferrite toroids are Fair-Rite 2.4" O.D. #31 Mouser Part #
> RadioShack AC adapter
> 16 turns of the AC adapter 12VDC output wound on 1 toroid
> 7 turns of the RG6 satellite TV cable to the satellite receiver through 5
stacked toroids
> As many turns as possible of the HDMI cable on 2 stacked toroids
> As many turns as possible of the AC power cord to the TV on 2 stacked

This is what worked for me to resolve my DirecTV RFI issue in my individual
circumstances -- location, antenna, station, house, and DirecTV system.
What worked for me may or may not necessarily work for others.  But
hopefully something in there might help.

Jim Brown, K9YC, has an excellent in-depth article about RFI on his website
named RFI-Ham.pdf that was extremely helpful.    

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