Interference between CAT5E and Sat?

J

John Augustine

Member
My Satellite Setup
Pace 2600CI, Invacom C120 Twin LNB
1.5 m prime focus
Canal Digital on 90cm offset
My Location
South Norway
I have 2 dishes 30 meters from the house connected using WF125 cables which is routed along the outside house wall for 8 meters. I now need to install a CAT5E network cable (computer broadband) and the simplest route is to run along the same route at the sat cables (zero separation).

What is the likelyhood of interference? Would I be better of with a screened CAT5E cable with a poor earth or unscreened one?
 
The rule of thumb here is to avoid it if at all possible. I say keep them separated, shielded if you can ... the nature and type of earthing/ grounding is a different issue.
 
I agree with pedro2000uk to keep them separated and shielded if at all possible, thus avoiding interference.


But


I had to run a cat5 cable to my dreambox and the only way I could get the cable to it was to use the plastic tube that is buried in the plaster of the lounge wall and share the tubing with the satellite cable and the cable from the normal uhf TV antenna. The cat5 cable is not screened or earthed.


I have not noticed any interference problems to the television reception either using satellite or uhf analogue, nor have I experienced any problems on the computer network,


You may just be lucky like me


Regards
 
it's not luck at all - CAT5 is unscreened because it is balanced - the twisted pair carries the signal on one core, and the inverse of the signal on the other. As a result, interferance is negligable...
 
Very good point... mich :)

...and that should limit anything getting on the sat cable if it's accurately inverted enough for that and not just what's required for data transfer,

it's like having a loud noise and matching it with an inverted version of it = no sound .. sort off.

I know some audio equipment is available with that now and it was used on jet engines 20-30 years ago feeding pilot's headsets with the inverted noise of the engines ...

.....but what it leads to is .....could you do it with interference effecting a satellite dish/ cable/ stb......

now there's a thing... hmmm

can/has it been done?

must have…. anyone..?
 
Apart from what's already been mentioned, Network cable is only rated to a couple of hundred MHz, way below the minimum IF frequency used by satellite.
 
I was thinking of inverting noise - local interference & ground noise (near KU) and playing it back into the dish... plus same near the IF for the cable & the stb...

but what you’re saying is ...you couldn't do it fast enough at KU & the IF?

where as audible sound & cat5 tx'ing you can?.
 
I wouldn't worry, you can put many many network cables next to each other and they won't affect each other (a combination of the balancing and the twisting) and also coax screen acts as a reflector at radio frequencies - actually, the outside and the inside become effectively separate conductors when used at high enough frequencies! That's why it's so good at rejecting noise. This combined with gsteigwiler's comment :
I have not noticed any interference problems to the television reception either using satellite or uhf analogue, nor have I experienced any problems on the computer network,
Click to expand...
and I think you should be fine... Both satellite coax and cat5 are designed specifically to avoid interferance... in fact in the same way that satellite coax is 75 ohms impedence, cat5 is actually 100 ohm balanced transmission line... and if you're completely paranoid, you can get shielded cat5 and metal connectors :-)
 
I use a CAT5 cable along the run of my 2 dishes and I have never had any interference so I think you should be fine
 
Thanks everybody - I'll instal as planned.
 
I really wouldn't trust it all implicitly...

Nothing in electronics and especially radio electronics is ever absolute and is only ever measured as acceptable percentages.

Data transfer on cables or within a PC are far more robust & tolerable to noise than trying to pluck tiny feint signals from a satellite signal like 7w H's that have done a 50,000 mile round trip through x,y,z weather conditions and interference and er.. aren't supposed to be here anyway. Any cable run is also an aerial and conductor for induction etc, noise will always get in, it's not limited to what’s on either cable.


If you are in the game of getting weak signals like 7w H's then it's still a good rule to avoid anything and everything that adds up to another variable into the noise equation at that very low level, but if it's strong satellite signals like a multipoint 28e here + network cables then it's far more acceptable at those levels.
 
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