[Tekkytyke]

Hi, I hope someone can help. Im having trouble receiving Freeview in the 2 bedrooms. Ive hooked up from my roof aerial a Philex SLx 6B 6 Way Aerial Amplifier which sends the signal to TV 1, HDD, and to TV2 and TV3
However TV2 isnt too bad but the third room i cant get much signal at all and when i do its extremely blocky

Does anyone have any advice? Should I try better quality coax cable or would a sender be a better option

Any help much appreicated

[chrisjr]

Sounds like you have either really poor cable or it is damaged or incorrectly terminated.

With decent quality coax and properly terminated plugs you should not be having issues in the average house. If your home is the size of Wembley Stadium and you were running from one end to the other then that might be a different matter.

So I would look at what type of cable you are using, how well it is run and how well the plugs on each end are connected. There are all sorts of things you can do running cables to affect reception. Badly kinking the cable, putting the nail of a cable clip through the cable are just a couple of examples.

If you put the plugs on the ends of the cable yourself check the screen braid is neatly made off. It only takes a single stray strand of screen braid to touch the inner conductor and things can be seriously upset.

And what sort of sender were you thinking of? There is no legal way to take the raw aerial feed and re-broadcast it wirelessly to another location without getting Ofcom involved and paying shed loads for a licence. Not likely to happen.

The common types of video sender would require a Freeview box somewhere to tune into whatever channel you want then send that to the TV. They can often be very flakey and a lot more hassle and expense than a bit of wire.

[SnrDev]

To add to the above; don't use the thin white cable that comes in handy 15m extension kits for a fiver in supermarkets. It's tat. Invest in a long enough decent length of quality 75 ohm co-ax from either Wickes or some other similar outlet. Maplins will sell it but they add a premium on and it adds up.

[Winston_1]

Do you actually need an amplifier, or would a passive splitter do? That distribution amplifier has an 8dB gain per port which is wrong. A distribution amplifier should have zero gain per port.
What I'm saying is you could have an overloading problem which ofter appears the same as poor signal on digital.

[Nigel Goodwin]

Quote:

Originally Posted by Winston_1

That distribution amplifier has an 8dB gain per port which is wrong. A distribution amplifier should have zero gain per port.

It certainly shouldn't, it should have enough gain to make up the loses in the extra long wires (and a bit more 'in reserve' - 8dB sounds pretty reasonable).

There's a MASSIVE signal strength range where a distribution amplifier works perfectly well, and a MUCH smaller range where a passive one works well - you really need an exceptionally strong signal to overload a distribution amplifier.

[Chris Frost]

Pulling together much of what's been said above, and then giving you some stuff to try so you can troubleshoot your system, here's my take...

First off, aerial distribution amps are pretty straightforward devices. The only real problems generally revolve around (#1) bad connections; (#2) putting the wires in the wrong holes; (#3) a poor aerial signal i.e. garbage in - garbage out; and (#4) over-amplified outputs.

The output gain of a distribution amp should be sufficient to compensate for the losses cause by introducing something in-between the aerial (the noise figure) and the losses in the signal cable from the amp to the TVs. Good coax (Webro WF100) loses about 1.5dB of signal strength per 10m. All those who said avoid cheap cable were bang on. The thin white extension cable kits use really poor coax which is much lossier.

In total then you've got the gain from the amp and the combined losses from the amp's presence and the cable losses. These could tip the balance either way: You could either have started with only just enough signal from the amp and it loses a bit too much which then equals blocky pictures; or you have almost too much signal from the aerial and that's combined with a nett gain from the amp and cables which then pushes some of the tuners over the top and you get blocky pictures again

Let's now start breaking down your system in to chucks to help you troubleshoot in easy stages...

First off, you haven't got a professional signal meter to use to look at the signal strength and quality, but you do have something almost as useful. Most Freeview TVs have some kind of display showing Strength (S) and Quality (Q). They can measure a bit on the optimistic side, so factor in about 10% for that when looking at the readings. If you have a portable-ish TV then take that over to the amp to help with testing. Signal Quality is by far the single most important of the two readings. If the signal is over-amplified then signal Quality will take a nose dive.

If possible, start by unplugging the aerial lead going in to UHF IN on the SLx and plug it direct in to the small TV instead. Have a look at the signal Q and S. Ideally you're looking for around 80%+ on Q and somewhere in the 50-70% range for S. If you can't measure next to the amp then make a direct connection using a barrel connector so that the aerial feeds directly to a known good TV. When taking your measurement if you find that Q is very low (<50%) then you might have an issue with the aerial that needs to be addressed. Check first that the aerial coax plug is fitted correctly. You're looking to make sure none of the fine filaments of braid from the shielding are touching the centre core of the cable or plug. If you have done that and there's no other issue apparent on the coax cable such as water dripping out of it or gashes in the outer sheath then depending where the aerial is then this might be time to call in the cavalry.

Presuming that Q is good and S is sufficient without being OTT, reintroduce the SLx and then see what that does to those readings. At this stage all you want is just the aerial connected and one connection to that same TV. Unplug the rest of the coax leads.

Look at the signal levels again. Q should be about the same or maybe marginally lower. I'd expect S to be increased. If S gets to 90%+ then there's too much signal coming from the amp. You can fix this with a Variable Attenuator which goes on the end of the aerial lead going in to the affected TVs. (Look up 'MA1620' on this page). An attenuator is a kind of volume control for signal. It can reduce the power (S) which is responsible for over-saturating the TVs tuner. Fit the attenuator, put the TV on and fire up the signal meter. Turn the adjuster until S starts to reduce and Q goes up. Get Q to the highest measurement.

Now it's time to reintroduce the other TVs, but do one TV at a time. What you're checking for is the one TV or coax cable that when introduced it breaks the rest of the system. Look for bad coax plugs and over-saturating tuners again.

You might get to a point where you find some TVs respond better than others. That's probably because TV tuners can be more or less sensitive to signal. That's just the way it is.

This isn't everything. I haven't touched on masthead amps or signal interference from poorly shielded coax, but it's a good basic start so give the above a whirl and let us know how you get on.