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jitendra

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#11814 13-Feb-2007 10:05
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I got Sky UHF recently.  However, the technician said that the signal I was getting was the strongest he has seen (we have perfect line of site to the tower )  He said that the Sky box and my TV could get damaged in the long run because of the signal strength.

He also tested the signal with some weird equipment to confirm this.  He recommended connecting rabbit ears with the Sky box in order to reduce the signal strength.

So . . . .has anyone else ever had this problem - ie the signal is just too damm good?  Is it actually a real problem, will my TV (Panasonic Plasma) get damaged?


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cyril7
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  #60631 13-Feb-2007 10:12
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Neither will get damaged, they can electrically withhold a lot more signal than you would imagine. However if the signal is too large it may overload the input stages of either, not such to physically or permanently damage them, but to cause intermodulation that can create some poor pictures and other ill side effects. Rather than use rabbit ears I would recommend an inline attenuator, or more commonly available a terminated line tap used as an attenuator.

If you use rabbit ears especially in a high signal area you just open youself up to worse reflection and ghosting problems.

Cyril

sbiddle
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  #60637 13-Feb-2007 10:23
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You really have to wonder about the knowledge of the particular installer when they recommend rabbits ears. Have they not heard of an attenuator?


 
 
 
 


jitendra

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  #60639 13-Feb-2007 10:29
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Any idea where I can get an attenuator?

As an aside, following the installation of SKY, my regular TV reception is not as good.  TV1 and Prime in particular are not as clear as before.  Any ideas what may have caused this?

Also, I should add that the SKY picture itself is pretty average for what is apparently such a strong signal . . .



grant_k
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  #60640 13-Feb-2007 10:37
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jitendra: Also, I should add that the SKY picture itself is pretty average for what is apparently such a strong signal . . .

In my experience, the Sky UHF picture quality is never very good.  The scrambling/descrambling process adds a lot of noise to the picture, even if you have a strong signal.

Some years ago when we had Sky UHF, we also had to use an attenuator because the strong signal was overloading the input of our Sky Decoder, thus reducing the picture quality.  You should be able to find attenuators at Dick Smith or MasterTrade.

cyril7
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  #60644 13-Feb-2007 10:47
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F connector fixed attenuators and line taps can be got from satellite and TV hardware wholesalers, but not many sell without an account. There is a variable one at Jaycar LT3050 for around $12 which has bellinglee PAL connectors which should do the job although not the most ideal.

Cyril

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  #60671 13-Feb-2007 14:03
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Also, I should add that the SKY picture itself is pretty average for what is apparently such a strong signal . . .


How does the Sky decoder connect to the TV, RF, composite or S-Video?, i.e., do you press the AV button on your remote to select the decoder or simply choose a (RF) channel. RF in to the decoder and RF out to the TV will be quite poor for sure as two tuners are involved.





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richms
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  #60676 13-Feb-2007 14:32
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the problem with using the RF out on sky uhf is that it still has all the other channels mixed in with it. There is already enough in the UHF band to cause problems and trying to mix a much weaker signal in with it just means the RF output is lost among the other stuff. Thats typically what attenuating the input helps solve, the actual tuners can take huge amounts of signal without problems.

I suspect the installer you had was clueless to not fit an attenuator.




Richard rich.ms

 
 
 
 


jitendra

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  #60687 13-Feb-2007 15:53
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To select Sky, I select an AV channel on my TV (AV2)

The sky box plugs in to the TV via the White/Red/Yellow plugs

Hope that helps

I am beginning to suspect the installation guy was not up to scratch . . .

JohnPorter
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  #60827 14-Feb-2007 22:17
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Before I got MySky, the Sky installer (don't remember if it was UHF or digitial at the time - I have had both) connected it with composite (read white yellow) and RF. Having the rf lead plugged into the tv severely degraded the fta signals, even though I could watch Sky quite well through AV (composite).

I suggest you ensure there is not an RF cable running out of the sky box into your tv as well as the composite leads. Your fta antenna should run directly into your tv (or vcr), not into the sky box.

cyril7
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  #60838 15-Feb-2007 07:00
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Dont recall any issues with the RF loop through on the UHF analog boxs, nor any of the current Digital Sky boxs, however some batches of the Zenith digital STBs had unusable loss on the RF loop through. At the time this was an acknowledged fault with certain batches of Zenith STBs, I dont know if it was ever resolved.

Cyril

richms
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  #60884 15-Feb-2007 13:37
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The problem ususally shows as all sorts of nasty inter modulation because of the lousy amplifier in them. Happens even on moderately strong signals, which is why the modulators output gets swamped. I wouldnt call 85dBµV excessive, but thats all it took to completely obliterate the UHF band when looped thru. The solution was some attenuators ahead of the sky box and an amplifier after it, and to not loop the VHF thru it at all, which was a hell of a lot of dicking around just to get a usable picture on all the tvs.




Richard rich.ms

grant_k
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  #60888 15-Feb-2007 13:46
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richms: The problem ususally shows as all sorts of nasty inter modulation because of the lousy amplifier in them.

Yep, we had this exact problem years ago before upgrading to Sky Digital.  Large areas of a single colour showed a crawling bar pattern which changed angle and frequency depending on other picture content.  It was really annoying at times.

As Cyril7 said in another thread, the UHF service provides such a poor selection of channels and such lousy picture quality, it doesn't represent value for money any longer.

richms
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  #60891 15-Feb-2007 13:57
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yeah, thankfully when upgrading to digital you no longer have to run the RF thru the box.

Friend had so many issues when they had UHF that they gave them an external VHF modulator that solved all the problems. An installer told me that the UHF boxes were actually designed to be used on some European cable network, which is why they do not handle high/low signal strength very well at all.




Richard rich.ms

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