Need some help with RFI guys.

[ke7trp]

I am having a real heck of a time getting my RF signal out of the neighbors TV.  He is a real nice guy and family so I am willing to do what it takes.  Maybe I have overlooked something. 

At anything over 100 watts out of the icom, The TV shows Blue and black Bars on across it. The screen is totaly gone and they cant watch TV.

I had my friend go over to his house with Hi pass TV filters and a bag of snap on 43 and 77 chokes from amidon.  I stayed at the radio and keyed up as he added the filters and chokes one at a time.  We communicated over cell phone. Nothing worked. Some filters helped a little. But it was never solved.  We then added a Brute force filter on the TV's power line, Radio shack model, This helped. But again, Did not solve it.

I opened his cable interface box at the side of the house and found the cable co had added a "wide band RF amplifier and splitter. Its made by scientific atlanta and it has 6 outputs. The ground wire was broken.  Cox never mounted the unit, It was hanging in the elements. I mounted the unit and put an MFJ hi pass filter out of the unit leading to his TV.  Then I ran a ground wire to the service ground and to the lug on the Amp

This seemed to really help. In fact, I can run the big box at legal limit AM on 75 meters and all is well.  I can run the GK 500 on 160 and he never has a problem.

If I try to use 40 meters and above its all over. This morning I keyed up the Icom and Commander 2500E tuned up at 1kw SSB and the phone rang in less then 5 minutes. 

It makes no difference if I am on the vertical or the wire antenna.  It makes no difference what radio or amp. I even used my FT450 and he called right away.  His daughter is in town with a toddler for the hollidays and the toddler was watching Cartoons this morning at 8am.

So, Anything I can do to solve this once and for all?  The cable co added the RF amp becuase the signal strength at his house was low.  Can I filter this thing?  Or is the real solution to pay to have that run of Coax replaced and then bypass the RF amp?  My gut tells me that the issue is the 1985 coax that is stiff as glass that wraps his house.  If you bypass the amp now, The signal is weak at the TV.

What would you do? Please dont get into the fact that its not my issue and he should do this or that... These are good people and I want to just fix this and move on.  He rebuilt my lawn tractor, He watches my dog ect..  I just want to fix it.


C

[WV Hoopie]

C

TV cable systems are by FCC regs a closed system, so 1st step get the cable company involved. If RF is getting into the cable system, their cable is leaking. Big NO-NO.

Should be interesting, lets us know how the world turns. I've been fighting an RFI issue for months with no luck or support from the FEE CEE CEE.

Craig,

[WA3VJB]

Is the house coax also 25 years old ?   When you say "wraps the house" I don't know if you mean just the feed from the street pedestal, which could be older and more deteriorated than what's in a house built much later.

We had some RG-59A/U in our 1975 vintage house, and the center insulation had deteriorated from the heat in the attic, where the builder laid the grid feeding the upstairs rooms.  It was very lossy, so the proportion of desired signal was quite low and vulnerable to my transmitter.

The solution was to replace it all with modern foil/shield RG-6, using the old stuff as a puller to the room boxes and plate-mounted "F" connectors, which I also upgraded.  You could probably test the idea of whole-house replacement, by selecting a run and directly connecting the new stuff to the distribution amp. Even before that, try disconnecting a combination of existing runs to perhaps help you target the culprit for replacement or further remediation.

[WA1GFZ]

Just for the heck of it buy a length of good quality RG6 that will go from the cable box to the TV. Run the cable outside the house and shoot it in a window near the TV. First connect the output of the amplifier to the TV through the new coax. Try your rig.
If there is a problem it is the coax in the house, if not.
2. Disconnect the amplifier and get a barrel connector to connect the cable from the street directly to the new RG6. Try the rig
If problem goes away there is a good chance you are saturating the amplifier causing IMD.
If the problem is still happening then the cable company needs to replace the cable to the street.
You might try to measure the shield resistance to ground to see if there is an open shield termination. This could be the real reason the cable signal is weak.
Sounds like the amplifier was used as a bandaide for the real problem.

[k4kyv]

Maybe with new coax temporarily in place, the signal will be sufficient without the amplifier. In that case the old coax needs replacing. Hopefully that wouldn't be too much a PITA.  The cable co may or may not have installed the in-house cable wiring.

Back in the rooftop antenna/fringe area days, a lot of TVI was due to "booster" amplifiers that mounted right on the outdoor TV antenna.

Maybe the cable co. could be convinced to replace the cable at their own expense, if you told them that signal from your transmitter could get into the system via that defective coax and interfere with other customers as well.

Is he getting a digital signal off cable, using a converter box or does the cable co supply an analogue signal for older TVs? Your description definitely sounds like analogue TVI.

[K5IIA]

my little girl came running back a few weeks ago and said i was messing up the tv. there was no tvi when on the tv antenna, only when she was playing her wii. all it ended up being was the rca connector at the tv for video coming from wii was loose. i pushed it in all the way and problem was solved.

[The Slab Bacon]

Cable TV techs are a bunch of trained monkeys stamping cookie cutters! !! ! ! ! ! ! ! !
Most of those guys dont know their arses from holes in the ground. I have had a similar experience with my own neighborhood. It was driving me nuts, every time I would get on 75M, my telephone would ring!!

the problem was Common Mode interference!! (RF on the coass shield.) The cable jerks would come in and hook their anal izer box to the end of the cable, and if the signal level was acceptable, they would leave and tell my neighbors there was nothing wrong with their stuff and leave. After a while this began to really piss me off more than my neighbors. They swore that nothing could be done about it.

the real problem was that all of the drop lines that fed from the main cable trunk to the houses were right between 60 an 65 feet long!! A perfect 1/4 wave on 75m, go figger.
I tried the little Rat Shack Hypass filterz and they did absolutely nothing. I tried the little snap-on chokes, they helped ever so slightly, but nothing dramatic. Then..............

I experimented with some common mode chokes...............POOF, PROBLEM GONE!!!
I ended up wrapping as much rg-59 coass as I could on 2" red toroids and distributing them to the neighbors closest to me, told them to install them between the incoming line and the splitter and my phone never rang again!! No matter how much power I run!

Now with all of the television and most of the telefonium service gone digital, it's all a moot point! Go figger ! ! ! ! ! ! !    

[WA1GFZ]

Just for the heck of it I measured the inductance of a common mode snap on bead last week. It was only 3uh. So a number of turns on a 2 inch core would be a lot higher.

[ke7trp]

Sounds like I need to pay for the highest quality coax and then ditch the RF amp/booster.  I will call the cable co.


C

[WV Hoopie]

C

Just food for thought, how does anyone know where the leak IS? Could be on the street and not AT the house. Get the cable company involved.

Craig,

PS: My last 2 cents, are you treating a symptom, the leak is still there. The cable company will thank you for spending your money. Or will someone go for the cure? Fix the leak.

[flintstone mop]

no no no
Clark
You can go online ( I hope) and get a common mode filter specifically designed for cable TV coax. cleared up a stubborn problem I had with a neighbor a few years ago.
Googled around and cannot find a source for a common mode choke with the Cable TV terminations

Fred

[Detroit47]

Clark
As I recall you told me to use a counterpoise perhaps that will work. If not try these people they are very helpful www.coilws.com | www.cwsbytemark.com

73 N8QPC

[WA1GFZ]

Why waste good money on a commercial choke when you can wind one yourself.

[flintstone mop]

C

Just food for thought, how does anyone know where the leak IS? Could be on the street and not AT the house. Get the cable company involved.

Craig,

PS: My last 2 cents, are you treating a symptom, the leak is still there. The cable company will thank you for spending your money. Or will someone go for the cure? Fix the leak.

It's not a leak from the cable. It's the Amateur radio TX riding on the ground shield of the coax and getting into the TV. The common mode choke breaks the path of the shield from the TV circuits.
Fred

[WV Hoopie]

C

Just food for thought, how does anyone know where the leak IS? Could be on the street and not AT the house. Get the cable company involved.

Craig,

PS: My last 2 cents, are you treating a symptom, the leak is still there. The cable company will thank you for spending your money. Or will someone go for the cure? Fix the leak.

It's not a leak from the cable. It's the Amateur radio TX riding on the ground shield of the coax and getting into the TV. The common mode choke breaks the path of the shield from the TV circuits.
Fred

No use any of us getting into a p*ssing match. Have the cable company fix the problem or at a minimum check for leaks, cost nothing.

[Mike/W8BAC]

Clark.
If you have a plug in 120 volt service checker I recommend you try it. I'm talking about those yellow plug in checkers that tell you if your 120 and neutral are reversed or if your safety ground is disconnected. I fixed my neighbors bedroom TV when I found the outlet wires reversed and on ground. Some times it's the easy stuff we miss.

Mike

[KB2WIG]

 " No use any of us getting into a p*ssing match "

There were very few takers for Festivus this year. A real disapointment.

klc

[ke7trp]

Thanks for all the help.  

The problem is not my station.  Its clean as tested on the spec AN.  No Issues here or with any other people around that I know of.  

No RF in shack, Shack is cold.  My TV, speakers, coffer maker, ect ect are all fine.

The MFJ "shield breaker" filters have great reviews.  These are hi pass coble tv coax filters. They did help but did not cure the problem. We experimented by placing them at every location possible.  

I think the real issue here is the ancient RG59 coax that is rock solid that wraps his house and runs to his main TV.  They wanted to charge him to replace it and he refused. So the cable company put a booster on the wall  at the interface from the street to his house.  

I am sure that this booster is taking my signal and shoving it into his TV which causes the black screen and bars.

I found a 500 roll of 9275 duoshield coax cable.  This stuff is 100% foil and 40% braid.   Should I use it?  Or should I go down and get some new RG6?  

He needs to call the cable company, Its his house.  I dont want to bother them now because his Daughter and new born are here from Germany (son in law is in military).  They are here until the 3rd.  After that, I will talk to him about us replacing the run or him calling Cox and getting a price to have it done which I will have to pay.

I just want this over with once and for all.

C

[W1RKW]

Clark,
You mentioned that there's an amp/splitter at the entrance.  Are all the output connections on the splitter being used?  If not, are the unused connections on the splitter terminated with 75ohm plugs or are they open?  If they're open terminate them with 75ohm plugs/caps.  Also, make sure all cable connections are crimped tight and screwed on tight, not hand tight but socked down with a pair of pliers.

[Mike/W8BAC]

Before you go to the expense of replacing that cable do like Frank suggested and run out some nice cable (just enough RG-6) on the ground and through a window to see if it works. You wouldn't believe how easy it is during installation to put a staple through the cable. That might explain why they have a distribution amp in the first place.

[WV Hoopie]

I think the real issue here is the ancient RG59 coax that is rock solid that wraps his house and runs to his main TV.  They wanted to charge him to replace it and he refused. So the cable company put a booster on the wall  at the interface from the street to his house.  

C

If your guess is correct the booster/RG59 is leaking: A Cox problem if they installed it! Neighbor's problem if he installed it. That is the reason for asking to check for leaks. Leaks on the street might be causing issues elsewhere and others are just bitting their lips and not saying anything. Last; the system belongs to Cox, don't make changes that make you liable.

[ke7trp]

Ok. After the hollidays, I will run some RG6 on the ground and run a test one saturday.  I will call cox tomorrow but I have a feeling I will get nowhere. I think I will call and say I am having trouble with my cable and pay the fee to get them out here, then when the guy gets here, Show him the shotty install of the booster and let him test it.

ALL ports are used on the splitter as far as I can tell.  However,  Some are no longer used. The kids have all moved out, I would not be suprised if some of those 6 lines are now laying on the floor or just panel jacks in the room open.  I am going to get some terminators and ask to plug up all the unused portions.  He only has two Tv's and one is used for internet.

C

[KA2DZT]

Put the high pass filter ahead of the signal amplifier,  Most of those broad band amps are 5Mhz-1000Mhz amps.  Your signal is getting into the signal amp and overloading it.  The fact that your 40M signal is still giving you a problem is probably due to the fact that 40M is within the bandpass of the amp.

Also make sure the "F" connectors are in good shape, not corroded and are tight (use a wrench).  Check to make sure the shields are making good contact with the "F" connectors.

If the "F" connectors are these newer waterproof type with a rubber "O" ring inside, make sure these connectors are tighten with a small wrench.  I've seen where the "O" ring has isolated the back of the "F" connector from the front part and the ground shield is open inside.  An open shield anywhere in the system will cause all sorts of strange problems.

the real Fred,   not to be confused with "the other Fred"

[WA1GFZ]

Options:
1.Demonstrate to the home owner that the problem is in his house and suggest he get it fixed.
2. If you really like him offer to help him replace the coax.
3. Do the job yourself and take the risk of doing damage that could come back to haunt you.
4. Have the home owner call KB3AHE for spiritial advice

[flintstone mop]

Hi C
Involving the cable company will get complicated. They do not understand what is going on.
That booster amp might be your problem. I know you do not want to disturb the family now but try an experiment to see what happens to his cable TV without the booster. There cannot be that much loss within the house no matter what cable is there now. Unless it's been skunned while pulling it through tight places. And it is damaged now
Cable TV folks only know that you need millivolts to get their trash to your TV.
The other FRED