500c strange weak signal problem

[pcs333]

Hi
i`ve got two boxes, both have been tried seperately on the same connection.

The first box works perfect with no booster, getting 94-96% snr levels on all channels.

Now the second box gets most channels (remember on the same physical connection as the first), at about 90-94% snr , but doesn`t pick up setanta 1 or rangers at all, snr about 80%.
If i stick a variable booster inline, all channels drop to 62% snr and i get nothing, no matter what boost level i try. This happens on both boxes with the booster.
There is also an attenuator on the wall that vm installed, this also makes no difference if taken out, from there it is a 2 meter cable straight to the box.

Can anyone give me any ideas on how to get the secong box working ?
I guess its got a weaker tuner than the first one, but the booster making the signal worse is baffling me.
Another thing to add is that at a different house both boxes work fine although the second one is about 1-2 % lower on snr.

One more thing, i`m using the Pli jade image, but does anyone know what the other level under the snr means? On box one its 36% but on box two its 51%.

 

[Donnie Darko]

Welcome to the world of head scratching dreamboxs,try an attenuator they screw onto the feed come in 3/6/9db just play about with them.

 

[pcs333]

thanks i`ll try that, any idea where i can get some?

 

[nozzer]

Looks like you have a noisy incoming signal. When you amplify a signal that has a relatively small signal level above a high noise threshold then you can effectively swamp the tuner with noise at which point it is unable to recover anything usable.

Your amplifier also may not be suitable for this particular task. As a minimum you need a fairly wideband UHF amp that can handle between 100Mhz-850Mhz.

It might be worth checking or even re-doing your cable connections. Small things like corrosion or even pitting/scarring on the end of the conductor can cause noise.

As you've spotted, some tuners are better than others. You'll probably find that both those tuners are still in-spec for the signal conditions they were designed for (which was not UK). Dreamboxes tend to work in the UK only where the signal level is realtively high and the signal is also clean with good snr levels.

For attenuators etc, a certain auction site is usually the place or alternatively you can usually get them at a good sat shop.

 

[pcs333]

thanks for the info nozzer
i`m learning all the time thanks

 

[señor ding dong]

You can get a variable attenuator here...
Coaxial Cable Accessories for satellite and cable TV
(I should get a commission, considering how often I plug these guys )

With one of those, you can gradually try and find the best level of attenuation by monitoring the signal levels as you turn the little dial.

Another thing to consider is that the signal may be unbalanced, which means it's stronger at one end of the spectrum than the other, in which case a Forward Path Equalizer would be the way to go.

EDIT:
Forward Path Equalizer link
http://www.in-home-network.co.uk/cable-tv-signal-conditioning-12-c.asp

 

[alexh]

You'll probably find that both those tuners are still in-spec for the signal conditions they were designed for (which was not UK).

Eh?? Surely that is not true? The UK cable networks use industry standard DVB-C frequencies and modulations.

 

[nozzer]

Eh?? Surely that is not true? The UK cable networks use industry standard DVB-C frequencies and modulations.

Signal Power levels vary widely for cable systems (as do the snr margins). The majority of the UK uses a relatively low signal level in comparison to the rest of Europe. There's also various problems caused by the carriage of analog TV that requires signal levels to be even lower around certain frequencies.

The modulation is reasonably standard. There is no real standards for cable frequencies, the providers are effectively free to use whatever they want.

The actual DVB-C streams are a mixture of standard and decidely non standard features.

 

[pcs333]

thanks for the links señor ding dong
nice one


edit: that beststuff site has some great stuff on there, a p.c toolkit with cd storage, just what i`ve been looking for for ages...thanks alot !!