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boosting signal for a long cable?

newbie1

Distinguished Member
Hi

One of the cables for TV distribution in my place is around 50m long and from time to time the signal strength falls below the minimum needed resulting in frozen picture.

The setup is as follows, local cable TV and satellite feed is combined in a multiswitch and distributed from there to all the TV points. For all but one feed this works fine with no problems. However for the long cable run we have an annoying intermittent problem.

I have tried both inline amplifier (with control voltage set to on from the receiver) and regular tv signal amplifier and neither work, the signal is lost completely.

Any ideas please?
 

newbie1

Distinguished Member
Hi Trollslayer

This is one that I tried and it did not work, and yes I did connect it the right way around ;) Maybe it is because the cable is between the multiswitch and the receiver rather than a direct connection to an LNB?

What to try next?
 

pedro2000uk

Distinguished Member
Hi

...........

The setup is as follows, local cable TV and satellite feed is combined in a multiswitch and distributed from there to all the TV points. ...


What is on the local cable TV ?

By satellite feed does that mean Sky/ freesat & are all channels there on the other outputs
and where does that come from... your own dish or a remote dish somewhere.

Do you have access to the multiswitch- is it yours/ did you fit it?...if yes what make / model is it

what are the wall sockets like
 

newbie1

Distinguished Member
Hi Pedro, thanks for taking a look!

What is on the local cable TV ?

The local cable service had digital and analogue broadcasts, TV, radio, and Internet.

By satellite feed does that mean Sky/ freesat & are all channels there on the other outputs
and where does that come from... your own dish or a remote dish somewhere.

The satellite feed are the four cables from a quatro LNB on my dish to the multiswitch. I am using it for FTA broadcasts including freesat. This and the cable feed are the only inputs to the multiswitch.

Do you have access to the multiswitch- is it yours/ did you fit it?...if yes what make / model is it

All the kit is mine. The multiswitch is an Elcon SNL 904T (see here for spec http://www.mpsat.com.cy/mpsat/elcon/snl_904t.htm). I used this to combine the sat with the cable as although I thought I had specified two cable feeds to each faceplate only one was run.

what are the wall sockets like
These are all triplex faceplates.

As I said earlier the setup works fine for all but one cable run where I think the problem is signal loss due to length. I had the same problem before the multiswitch when it was the local cable feed only.
 
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pedro2000uk

Distinguished Member
What size dish is the quattro on & where are you.

Are there any gain adjusters on the multiswitch.

Have you tested the long run with a seperate cable.

What is the cable make or made of etc.. (copper or ali .. sheilding type etc)

Is there any mains cables it runs along side for any of its distance.

That multiswitch is I think for 2 satellites (2 x quattro LNBs = 8 inputs) & 1 TV input with diseqc A/B to switch the 2 sats- not 100% sure because the spec is limited on their site & others are in German etc..

But the way you have used it has worked so that's OK. Which input have you used for the local cable.
 
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newbie1

Distinguished Member
Hi Pedro

I am in Switzerland, the dish is 1m, there is no gain adjustment on the multiswitch, and i dont have the equipment to test the long run.

The cable spec is here http://www.cavel.it/schpdf2.php?id=DG113 (75ohm class A+ shielding - copper with foam dielectric and aluminium tape / tinned copper braid) and runs though separate tubes in the concrete from the power supply. The spec indicates about a 30db drop off for 50m at the sat frequencies if I have read it correctly.

You are right about the multiswitch it can take 2 sats, at the moment I just have one. I connected the cable feed to the "Terr" input.

Hope this all makes sense! I was hoping there would be a simple 15-20db amplifier that I could attach to the multiswitch output for the problem cable to give it a boost (but still let the control voltage and 22khz signal back through).
 
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newbie1

Distinguished Member
How about one of these?

http://www.spaun.de/files/e86ab_de_nvf 115 f.pdf

"For terrestrial and SAT-IF.
• Splitband technology
• Wideband in- and output
• DC through path to LNB is 22 kHz tone and DiSEqC capable"

Has anyone got experience using this type of amplifier?
 

pedro2000uk

Distinguished Member
Here is the English PDF of that wideband post amp. It looks exactly right if you were using the multiswitch as standard, but you have to check the way you are using it and the frequency of that local cable- try to ask both manufacturers & the cable Co.

In the UK when we install multiswitches to distribute satellite etc. usually to several properties or residents (hotels etc). The rule is to use a bigger dish to help compensate for any insertion loss & added noise of the multiswitch.

In an area where a 45cm dish would normally be used for 28e/Sky-Freesat UK, an 80cm+ is usually used instead. (quite a bit bigger on surface area/ gain).
As you are near the edge of the published 2D beam footprint carrying the main Freesat channels then the 1m you are using is similar to a 45cm used here, but the noise level (noise floor) then becomes far more critical- and amplifiers usually add more noise (it could still work to a level that does what you want- but in bad weather there could be a % of picture loss sooner).
As you are at 1m already, it might not be an option to go much bigger.

That cable certainly can be improved as it is part Aluminium. The loss can be improved on as can the noise pickup of the cable by going to all (near) pure copper cable & going up to 125- here we use Webro WF100 or WF125.

The 125 not only has a better loss factor but also the larger dielectric increases the shielding factor.

You could also change the cable to all copper from the quattro to multiswitch too and look for any improvements at the dish sight- fine tune alignment/ focus/ skew/ LNB make & any local noise issues that can be dealt with.

With it being 2D on the fringe - it's one I'd have avoided using a multiswitch on unless the numbers were already giving quite a big margin to begin with (a 1.8m or 2.4m there) & used a good quad LNB instead. So I think you have done very well mixing the cable Co.'s output etc.. with only this one long run being a problem.

So the wideband post amp might work as a quick solution- but I do prefer the basics of good clean cabling, good connections, shielding, dish fine tune etc.. but it's a lot of work & only gives what looks like small improvements (until you get bad weather).

We use Invacom quattros btw ...
 
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newbie1

Distinguished Member
Pedro, many thanks for the very helpful reply.

I think you are right about the quality basics. As the 50m run was a complete pain to pull in the first place so I am loathe to disturb and replace (and I think I read the spec wrong its 28.10 db drop over 100m vs 30.3 for WF100 at 2150 mhz) plus I had the problem with local cable only before adding in the multiswitch so I think I will try a wideband post amp, but I think it will need to be a powered one.

Will let you know how I get on.
 

pedro2000uk

Distinguished Member
Well spotted on that loss factor-

That figure is better than you'd expect here for ali foil xx100 cable- the reason is it's not 100 (not 1mm core & not copper alloy core either) it's 1.13mm & it's pure copper core so a lot nearer 1.25mm reducing the loss nearer to WF125 cable & compensating for the loss due to the ali foil etc...

So the loss is a lot less than expected & the gain changing to 125 a bit less at about 3dB x 50m... not 4dB- still worth looking at for the 50m if it were an easy pull through.

I am not sure what noise pickup effect & return loss that ali foil & tinned copper braid shielding has compared to pure copper foil/ copper braid of WF100 or WF125 because we don't use it here. But on loss alone it actually looks quite good.
 

MartinPickering

Prominent Member
I've read this discussion twice and I still can't figure out if your "signal loss" relates to satellite or UHF (or both).

If UHF, you need a powered masthead amp between aerial and multiswitch and possibly UHF attenuators connected to TVs with short cable runs.

If satellite, you need a bigger dish, although it is worth trying an equalised slope LNB amplifier after 30 - 40m of the offending cable.
 

pedro2000uk

Distinguished Member
I've read this discussion twice and I still can't figure out if your "signal loss" relates to satellite or UHF (or both).

If UHF, you need a powered masthead amp between aerial and multiswitch and possibly UHF attenuators connected to TVs with short cable runs.

If satellite, you need a bigger dish, although it is worth trying an equalised slope LNB amplifier after 30 - 40m of the offending cable.

He's in Switzerland with a 1m so on the edge of the published footprint for 2D, so that 1m is more like a z1 sky dish there but much higher noise floor, low loss 1.13mm core cable, a quattro LNB to a multiswitch in the normal way, but the UHF is from a local cable company not his own aerial and it carries digital & analogue TV & internet & radio services, at UHF by the look of it, so he's used the UHF 'in' on the multiswitch for that cable feed (& it works), there are 4 outputs on the multiswitch with that combined feed to faceplates that split it all OK except for the long 50m run. He's tried RF amps & sat amps and they don't work, he can't increase the dish size easily as he might need a 1.8m to compensate for the MS there & the xx113 cabling is quite good (better than WF100 on loss anyway), so he's found a wideband post amp made for that job that should do the trick unless there is a problem with that non standard cable feed (instead of RF from an aerial).

I think making sure the quattro LNB & dish are at 100% is also another one to aim for.

-----------------------------------------------------------------------

By the way... the multiswitch has 2 LNB (quattro) inputs, however, if another LNB is added (for say Hotbird or Astra1) that will probably add a bit more noise to deal with on 2D.
 
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MartinPickering

Prominent Member
By the way... the multiswitch has 2 LNB (quattro) inputs

All multiswitches have 4 LNB inputs. :confused:

I'm still non the wiser about whether it's the satellite or the UHF signal that he's trying to boost.
An equalising LNB amp has enough gain low down so it won't degrade UHF.
 
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pedro2000uk

Distinguished Member
All multiswitches have 4 LNB inputs. :confused:.


I would have thought you'd do them at Satcure.

Can't remember the max number of satellites that some multiswitches will do - probably 4 atm= 4 x 4 = 16 in + UHF/FM.

He's got 2 quattros in (2 x 4= 8 in... & using just one of them) & 1 UHF & the 2 sats switched by diseqc from each receiver. (I'd expect FM/DAB in too).

I'm still non the wiser about whether it's the satellite or the UHF signal that he's trying to boost.
An equalising LNB amp has enough gain low down so it won't degrade UHF.

I'd expect a good amp of either to use a cut off as a filter.

And it's got to be 2D, where he is, dish size, going through a multswitch, 50m cable run...
 
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MartinPickering

Prominent Member
I'm using an LNB Amp for UHF, powered by the RF2 Digibox output (9 volts). It just happened to be convenient and available.

So it's satellite he's trying to boost? Try an equalising Amp to prove the point. It doesn't matter whether it passes UHF for the purpose of testing.
 

newbie1

Distinguished Member
Hi Martin

Just to clarify; the problem really seems to be the 50m cable run for both UHF and Sat signals. Most of the time it is OK, but now and again the picture freezes because the signal falls below the threshold level. This means switching off and starting again and quite annoying for the family. This happened when we had only the cable feed and no Satellite. Now the Satellite is added in to the mix probably the picture freezes a bit more often. For all the other rooms the system combining sat and cable is working fine with no problems.

So I am thinking of ordering the following amplifier to sit between the mutliswitch output and the offending cablerun.

AXING SAT-BROADBAND AMPLIFIER 47-2200MHz: Amazon.co.uk: DIY & Tools

Do you think this would help?
 
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MartinPickering

Prominent Member
On that Amazon page "Damping controller" should read "Attenuation Control". I have my doubts that any amplifier will help. The correct solution is to place the Multiswitch so that no cable run exceeds 30 metres. An amplifier adds noise and, if the signal is already weak, that may raise the base noise level as much as it raises the signal level, resulting in no net gain. Also, if the problem is caused by interference, an amp will exacerbate it. Let's hope it really is a threshold problem. Please let us know your results.
 

newbie1

Distinguished Member
Thanks Martin

Unfortunately due to the layout I just cant see a way to adjust the cable lengths - the house is concrete construction so I should have planned the 30m limit from the start, but was unaware...

I will get the amp and let you know what happens. Fingers crossed.
 

pedro2000uk

Distinguished Member
Is there no way you can just run a cable down the hall & bypass the 50m cable run just to check there isn't a fault on that 50m run.... and have you tried swapping outputs on the multiswitch or the stbs you are using in each room.
 
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newbie1

Distinguished Member
Hi Pedro I have a test report for all the cables from when construction finished as this was satisfactory. I did try swapping the outputs on the multiswitch but no noticeable difference. The TV has built-in DVB-S so I could try using a standalone stb if the amp doesnt work when it arrives in the next few days.
 

newbie1

Distinguished Member
Update:

So the amp arrived today and the TV has been running for several hours with no interruptions. The kids are enjoying being chief testers and watching closely ready to report first failure....so seems to be working and family happy! :thumbsup:

Many thanks for the feedback
 

pedro2000uk

Distinguished Member
Update:

So the amp arrived today and the TV has been running for several hours with no interruptions. The kids are enjoying being chief testers and watching closely ready to report first failure....so seems to be working and family happy! :thumbsup:

Many thanks for the feedback

A result... well done and nice to know it worked..well so far but it sounds like it's doing it's job..... and that's both right? (same as Martin).. both?
 

newbie1

Distinguished Member
Martin, Pedro this device is amplifying both UHF and LNB signals output by the multiswitch for one cable run, the long one.

I have set the attenuation control at about 1/4, at higher levels too much noise is introduced as you suspected making the situation worse, but at this level does seem to be enough improvement to make the difference. The signal level at the TV has increased a few dB and the C/N and BER readings improved by small amounts too.

Thanks again
 

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