Diplexer distorting sky RF output-DTT Fine

mossym

Hi all
due to a limit of 1 coax cable in a certain room(bad planning by me, i put multiples on every other room), i'm using a diplexer to combine an lnb feed and the rf2 output from my sky box down the cable. the rf2 feed from my sky box carries both the sky box output and the dtt signal which is being input to the sky box on the rf input from my aerial in the attic

my issue is, in the room with the single cable, both the feed from the LNB, and the dtt signal are working fine. however, the sky box signal(i.e. the analog signal carrying the sky box decoded channel), although watchable, is very poor, has wavy lines all across the image, and has ghosting.

i have tried changing the sky box rf channel out, but it didn't seem to do a lot

also, if i disconnect the cable connecting the downstream diplexer to the sat box, the picture is perfect again.

any ideas on other things to try? the diplexers were a relatively cheap pair, is there a big variation in diplexer quality?

Tony

If you disconnect the "aerial in" to the sky box does that make any difference?

mossym

Tony wrote: »

If you disconnect the "aerial in" to the sky box does that make any difference?

haven't tried, but i should mention, the rf2 output is fine on other tv's in the house, it is only on the tv through the diplexer there is issues

i have two sets of diplexers tony, one i got from you, and the ones feeding this room, i'm going to try swapping them tonight to see if the ones i got from you make any difference...

Tony

ok, try disconnecting the aerial too this may be an overload problem. I know its working on other tv's but tv tuners can vary in how they handle incoming signal.

mossym

if it was an aerial overload problem, i didn't think disconnecting the cable from the sat connector on the diplexer to the STB would fix it? i'll give it a go but not sure on that one

Tony

mossym wrote: »

if it was an aerial overload problem, i didn't think disconnecting the cable from the sat connector on the diplexer to the STB would fix it? i'll give it a go but not sure on that one

Thats not what I asked you to do, dont do anything to the diplexer just disconnect the aerial in on the sky box, the output from the sky box will still be present.

mossym

Tony wrote: »

Thats not what I asked you to do, dont do anything to the diplexer just disconnect the aerial in on the sky box, the output from the sky box will still be present.

yeah i know, i meant if it was the aerial overloading the tuner on the tv, then previously when i tried disconnecting the lnb feed(which fixed the problem), the aerial would still have been overloading the tuner so shouldn't have fixed the problem, which it did.

i'll try disconnecting the aerial though

Tony

mossym wrote: »

yeah i know, i meant if it was the aerial overloading the tuner on the tv, then previously when i tried disconnecting the lnb feed(which fixed the problem), the aerial would still have been overloading the tuner so shouldn't have fixed the problem, which it did.

i'll try disconnecting the aerial though

Not necessarily as there may be other things like intermodulation going on

mossym

well tried both things, disconnected the aerial feed to the sky box, and tried swapping around the diplexers, neither made any difference

one thing that does work is pulling the power cable on the freesat box. problem goes away straight away, unfortunately powering down the freesat box via the remote only switches off the video ouptut of the box, i.e. it powers down the HDMI Tx, rather than switching off the box. confirmed this by pulling up the network settings page in the menu, starting to enter some manual settings, then switched off the box via the remote, when i powered back on was at the same screen with the same entered numbers

so, if i want a decent picture i'll need to pull the plug on the freesat box, and power back up for freesat..hardly ideal, by any stretch of the imagination..

putting windows 7 media center on my htpc in another room and using the xbox as a media extender in this room seems to be getting more and more attractive

Tony

where does the freesat box fit in in your set up? Can you do a block diagram?

mossym

Tony wrote: »

where does the freesat box fit in in your set up? Can you do a block diagram?

the rf2 output from the skybox, (which has the dtt signal plus the sky box output) goes to the attic, where it goes through a distribution amp. one of the outputs from there goes to a diplexer, where it is merged with a feed from my quad lnb down a single cable and sent down to the room in question. in that room, another diplexer is used to split the signal again, the sat feed goes to the freesat box, the uhf feed goes to the mpeg4 capabale which is giving me perfect dtt, but problematic sky, as described. powering off that freesat box fixes the problem(much the same as disconnecting the cable from the diplexer to the freesat box fixed it).


both sky and dtt are perfect in every other room in the house

Rippy

Do you have perfect reception on the freesat box or are some channels missing/ pixilating?
I have seen problems diplexing some freesat boxes.
What brand is it? HD or SD?

darth_maul

find some of the freesat boxes very noisy (interference wise), you could try decoupling the cable coming from the UHF side of the diplexer, or try a different fta box, also had similar issues with freesat causing a humming noise on TV, fixed by earthing the box. Also a decent diplexer wouldn't hurt

mossym

Rippy wrote: »

Do you have perfect reception on the freesat box or are some channels missing/ pixilating?
I have seen problems diplexing some freesat boxes.
What brand is it? HD or SD?

perfect reception on the freesat box, it's a grundig HD box

darth_maul wrote: »

find some of the freesat boxes very noisy (interference wise), you could try decoupling the cable coming from the UHF side of the diplexer, or try a different fta box, also had similar issues with freesat causing a humming noise on TV, fixed by earthing the box. Also a decent diplexer wouldn't hurt

have tried couple of different diplexers, but i can try the decoupling trick for the cable easy enough. cheers for that, really should have thought of it!!


if this doesn't work, rather than get another box i reckon i'll go the xbox extender route as a first step.

Tony

I did not think of it either

mossym wrote: »

, really should have thought of it!!
.

Does it make any difference if you just disconnect the HDMI cable rather than powering down the box?

mossym

Tony wrote: »

I did not think of it either


Does it make any difference if you just disconnect the HDMI cable rather than powering down the box?

haven't tried that, can try, wouldn't expect it to, but will give it a shot. if it did the only thing i can think of is a ground loop that removing the hdmi cable is eliminating?

glineli

I had the expect same problem with 2 sky boxes, one a sky+ and the other a HD. They were conencted into an SPC4 and then into 4 way distribution amp. I had the waves on the sky + box only. I never managed to get it resolved with those boxes. I had to get another HD box and the interference went then.

mossym

glineli wrote: »

I had the expect same problem with 2 sky boxes, one a sky+ and the other a HD. They were conencted into an SPC4 and then into 4 way distribution amp. I had the waves on the sky + box only. I never managed to get it resolved with those boxes. I had to get another HD box and the interference went then.

the output from the sky box is fine on 2 other tvs though, only the one through the diplexer is having a problem, and when the diplexer is out of the picture, the problem goes away, so i don't think it is sky box

glineli

did you ever get this sorted out?