ARRL

Secure Site Login

Forum Home - Rules - Help - Login - Forgot Password
Members can access, post and reply to the forums below. Before you do, please first read the RULES.

cable one digital box for cable tv

Oct 29th 2014, 18:51

KD0NMZ

Joined: Feb 10th 2011, 04:28
Total Topics: 0
Total Posts: 0
ok I have thee new digital boxes for my cable tv and I am having trouble with the box every time I key my Hf radio any band any power from 5w-500w I turn the box off for the cable tv. the people of the cable station working with me to fix this problem so far we have tried high pass filters. on all in coming lines low pass filters on all my coax lines for the Hf radio. we have even tried hooking a cable digital box up a block away and I still turn it off I am waiting for a younger friend of my to help me get some ferrit bead's put on my coax to see if that will help. now the Highpass filter cableone gave me I was told starts at 54mhz--------- no idea. Now I have looked on line at the ham radio stores and they sell filters that filter from 0-52MHz so would it be worth trying the High pass filters from the ham stores?? now the only other ham in town that has the new cable box is having the same problems he is just running 5-100w
Nov 2nd 2014, 22:52

WD3D

Joined: Mar 1st 2011, 09:28
Total Topics: 0
Total Posts: 0
The Key is you said Cable T.V. Box - please note the term Cable.
Cable television is designed to operate anywhere from about 40 mhz to 900 Mhz - inside of the coaxial cable supplied from the cable service. Usually the cable company will not use any frequency mainly used by amateur radio.
I myself have my HF antenna tied to their aluminum hardline and my UHF / VHF antenna is only 75 feet from the telephone pole.
HF frequencies do not usually cause any interference.
If you have interference, it is usually caused by something in the cable companies system being loose or something being out of tolerance - ex a bad piece of cable.
Rule of thumb - amplifiers should only be used when you cannot make your contact via normal communications - 100 watts or less.
The rules says that you should always use the minimum amount of power necessary to make your contact.
Unfortunately some people feels that it is necessary to hardwire their amplifier to the light switch and they automatically turn on their amplifier when they turn on their HF radio.
This is technically illegal.
The part that is missing is that you have not told us what other components are a part of your broadcasting apparatus.
Things like non resonant antenna's, antenna tuners, ladder line - all plays an important part of the diagnosis.
If someone loads up their rain gutter and then wonders why they have RF problems - it would be self explanatory.
Call the cable company, they have equipment that they can use to sweep test the lines and find the issue.
Nov 2nd 2014, 22:59

WD3D

Joined: Mar 1st 2011, 09:28
Total Topics: 0
Total Posts: 0
The Key is you said Cable T.V. Box - please note the term Cable.
Cable television is designed to operate anywhere from about 40 mhz to 900 Mhz - inside of the coaxial cable supplied from the cable service. Usually the cable company will not use any frequency mainly used by amateur radio.
I myself have my HF antenna tied to their aluminum hardline and my UHF / VHF antenna is only 75 feet from the telephone pole.
HF frequencies do not usually cause any interference.
If you have interference, it is usually caused by something in the cable companies system being loose or something being out of tolerance - ex a bad piece of cable.
Rule of thumb - amplifiers should only be used when you cannot make your contact via normal communications - 100 watts or less.
The rules says that you should always use the minimum amount of power necessary to make your contact.
Unfortunately some people feels that it is necessary to hard wire their amplifier to the light switch and they automatically turn on their amplifier when they turn on their HF radio.
This is technically illegal.
The part that is missing is that you have not told us what other components are a part of your broadcasting apparatus.
Things like non resonant antenna's, antenna tuners, ladder line - all plays an important part of the diagnosis.
If someone loads up their rain gutter and then wonders why they have RF problems - it would be self explanatory.
Call the cable company, they have equipment that they can use to sweep test the lines and find the issue.
Nov 3rd 2014, 10:16

KM3F

Joined: Mar 6th 2008, 13:50
Total Topics: 0
Total Posts: 0
Your not being quite clear about the boxes.
Are there 3 boxes? Is only one affected? etc.
Has another box been tried?
What bands is the box responding to?
The cable boxes are not supposed to respond the your amateur signals especially at such low powers.
Until the interference mechanism is found no filter will help on a wild guess and a hope basis.
More questions; Is the box remote controllable with a hand unit?
If yes, what is the OFF command from the hand unit, as a start to analyze the possible similarity of command signal to your HF signal or harmonics.
Is the box a plastic type cover without any shielding?
This kind of analysis is needed to find a direction to go in; even then it may not be your responsibly for a box that has design issues you cannot overcome with any amount of effort.
Good luck.
Nov 3rd 2014, 18:54

KD0NMZ

Joined: Feb 10th 2011, 04:28
Total Topics: 0
Total Posts: 0
the boxes are the DMT 200 HD box we have found what was giving me the troubles it was the power plug it was a switching adapter plug we took that out of line and put a dif brand/ kind inline and every thing went back to normal. I know about the use a low as power as needed but seeing I have an amp and we was having troubles may as well trouble shoot with it all so for curing the problem as meny hams will use power. so if its fixed on 5 watts who know if it fixed on 500 so best to test it and find out. then have some other people/non hams having troubles of a ham driving by and knocking them off. as for the boxes I have 5 tv so I have 5 boxes all having the same troubles but its all fixed now it was on cableone the providers side with the bad switching adapters.
Nov 5th 2014, 03:14

KM3F

Joined: Mar 6th 2008, 13:50
Total Topics: 0
Total Posts: 0
That's good to hear.
This is why it's best not to launch into all kinds of filters and other things before knowing what the source is.
Good luck.

Back to Top