RFI MODS for ATT U-Verse TV system date: may 2008
Hams involved: KC9DSI-Mike & his neighbor, (at-t U-Verse TV Interference)
KC9KZM- Bob & W9IH- Chuck
Problem: When KC9DSI transmits on 80meter band frequencies; his next-door
neighbor's AT&T U-Verse system locks up.
(TV Screens freeze and no pix updates are received.)
TEST:
ON Air checks:
1..Checks on 80-40-20 meters CW & SSB at 100, 250, 500 watts
-80 meters had the worst effect on the U-VERSE system, so
most of the test
and rf choke design was done on 3810khz.
Equipment; kc9kzm, brought a Pico spectrum analyzer
and laptop.
Measurements: spectrum analyzer showed AT&T signal at 4-5mhz and
KC9DSI transmissions were developing peaks on the incoming line of better
than 90 volts peak.(spikes following the SSB peaks) [excerpts from KC9DSI-mikes help request]
Observations:
1..Grounding on the next-door neighbor's Power pole, AT& T equipment
and the main house Telco box was poor to fair (very suspicious!!)
2..AT&T has a very good (long ) antenna, next to a ham
operator… Possibly
exceeding the specifications for
transmission of Ethernet capabilities?
VDSL INFO link
3…KC9DSI equipment was well grounded and functioning properly!!!.
4…AT&T wasn’t to receptive to making changes or providing better cabling.?!!!!
5…Neighbor didn’t have HAM RFI problems from KC9DSI with Comcast TV system .
6…. Other HAM (k5af)notes INFO link….HF frequencies affected but VHF & UHF ok!
Waveforms -U-Verse:
Left pic…ATT U-Verse TV system 25khz-8.5Mhz spectrum.
Right pic…3800khz mod sig on the 25khz-8.5Mhz spectrum.
| 
Modification:
1.. Several RF chokes were tried…at the neighbor's Telco house box; outside wall.
2.. Best results were achieved with installation of TWO.. toroids on each side of the
incoming TELCO line (inside their box mounted on the House outside wall).
Two turns using the existing Telco blue wires on the toroids complete the choke mods..
(note: Ferrite beads may do as well? Need further testing).
3…Check & repair all grounds, add if needed….(yours & RFI location)!!!
4…No Changes were needed to KC9DSI's ham station!!!!!!
Results:
1.. Final checks were made on 80-40-20 meters….SSB/CW at
100 - 250 - 500 & 600 watts.
2...RF chokes eliminated all U-Verse interference, in all
modes up to 500 watts .
Above 550 watts some Pixalating or loss of the TV signal
began to appear…
| 
Conclusion:
-The RF chokes are acceptable at lower power levels when
ham antennas
are located (within 200 feet) of the neighbor's U-Verse
system.
Some further design for Higher ham power situations is
needed.!
-AT& T didn't do their homework on who the FCC
assigns (Ham) freqs.
below 30 MHZ
and how much power they can run.
-KC9DSI & neighbor have worked together to solve this
interference problem,
outstanding
Amateur radio public relations…
- ATT plans to sell this TV system nation wide, perhaps
this article will help the
next Amateur
radio operator experiencing same or similar RFI problems.
article by Chuck -W9IH