Concerns about ruining quality of satellite system

Currently we have a very good signal on a dish with a single output LNB. We are considering using a twin or quad output LNB. Will this affect the quality of the signal, ie will we halve or quarter the quality each device receives.

Thanks in advance for any help with this.

Hi Michael, My Humax box was showing high readings before swapping out the LNB, i changed it on a whim really, i will need the extra outs in the near future, and took your advice about the octagon.. my picture was good before swapping out, and remained the same after,, but with the Humax showing 95/100 on input 1 and 100/100 on input 2. i think i'll settle for that.. I don't have a pro signal to noise meter.. but if it stops the static i get from t.o.h when the picture breaks up.. that's fine and dandy.. now i have a good LNB..maybe we won't have any storms or snow to test it's headroom?..

yeah right,,, no chance.. lol

thanks Mike..

Hi Bob,
I don't know what kind of receiver you have but signal and strength are the same thing and signal at the receiver is not particularly relevant.I would have expected an increase in Q unless it was already high. If "no improvement in picture quality" means that your picture is still breaking up, then have you checked the dish alignment and LNB skew & focus ?
Digital signals suffer from the "cliff effect" whereby, as the signal to noise ratio decreases,picture breakup will suddenly start to occur followed by complete loss of picture. Using this LNB should significantly improve the signal to noise ratio thus taking you further away from the cliff edge and increasing the amount of "headroom" against "rain fade". Using the cardboard sheet technique I previously mentioned is the only way I know of to assess your headroom in the absence of a professional type meter which can directly measure signal to noise ratio..other than waiting for rain and then realigning your dish and LNB skew.

Attached is a pic of such a prof type meter showing signal to noise ratio (C/N or carrier to noise) of 17dB which I obtained with the Octagon LNB last summer. Actual S & Q readings are average and not as relevant as the C/N figure, and picture breakup occurs when C/N falls below 7dB on an HD channel,6dB on an SD channel,as signal level into the LNB is reduced using sheets of cardboard etc...mimicking the effect of rain.

Hi Michael, The Octagon is installed and working fine… i haven’t seen any change in signal or strength, as they were and still are reading 85 strength and 100% signal… yes, i know it’s only a guide… but nothings changed…
there’s no immediate improvement in picture quality… so i’ll have to wait the storms or snow…
and it certainly hasn’t made the jeremy kyle show any more tolerable… no i do not watch it, but it happened to be on to see if HD is changed…

Hi Bob,

look forward to hearing how you get on..I am able to align and measure my system with a professional type meter but presume you have to rely on your receiver's metering so here's a trick you can maybe try..if you insert some material such as cardboard between the LNB and dish face the signal will be attenuated and your dish/LNB adjustments will then be more critical. I found that In the summer I was able to insert about 6 sheets of thick corrugated cardboard before the onset of picture breakup and that equates to 6-7 dB of headroom, equivalent to using a much larger this time of year that has increased by another 2 or 3 dB.... a 70cm dish worked fine for me with less headroom, but I changed to an 80x90 dish which I had previously used for sat. internet.... I've never watched a single episode of Eastenders !!

Hi Mike,

Thanks for the info.. and it's on order and due to arrive thursday.. now it means digging the garden to run in the larger gaine for the cables.. but that's fine, as i needed to re-align the cable routing for the footings of the extension..

and maybe it'll help reduce the pixies in rain.. and yes you're correct it is a narrow 70, but my signals are pretty good at present, and with the new lnb should be as good and as you say, the headroom should help reduce drop out.. hope so, nothing worse than the wailing bashee missing the shouting and sheer bad tv of EastEnders.. makes me cringe to see the way my home territory is portrayed..

update when it arrives and fitted.. ta

My secondhand dish, with quad LNB, was free to take away. Maybe something more technically advanced would make a marginal difference, but not enough to pay for it.
Unlike analog, digital TV is a "go/no go" system. When the signal is of insufficient strength or quality the picture rapidly breaks up or disappears completely. Correct alignment of the dish is probably the most important factor Careful adjustment will amply repay the time spent.
If you get a decent picture, it ain't broke, so don't fix it!

Hi Bob,

The important thing about the Octagon and Best PLL LNBs is that they contain 2 "phase locked loop oscillators" which were previously only used in professional LNBs yet these LNBs are no more expensive than any other LNB and actually cheaper than many..Both Octagon & Best make a range of LNBs so it's important that you see PLL in the description of the Octagon LNB and "quartz crystal control" in the description of the Best LNB. What you gain is more headroom against "rain fade" because the amount of noise in the signal is reduced, so the signal level has to fall more before you start seeing picture breakup during rain etc...It's likely that, if you're getting regular picture breakup, your 80cm dish might actually be 70cm wide as it's the width that determines the effective size but 70cm wide dishes are commonly described as 80 cm ! in any event you would undoubtedly see an improvement with the Octagon PLL.. I was amazed at how good it is compared with several others I have..

If I were buying a quad LNB now, I'd buy this:

Michael, i looked at the spec for the octagon lnb… a ;ittle tooooooo techy for me, but interesting to read, i’m considering moving up to a quad lnb for another humax, but with so many lnb’s on the market with wildly varying prices, it’s difficult to know if cost equals quality and would it be noticable on a normal household install?.. and at present,4k is a step too far until it’s been around a while… specially as i’m about to build a new kitchen, and probably new fosse system… so; i’ll have to suffer t.o.h moaning about pixellating when it rains during Corrie…

Bob, I use an 80cm dish on the Lot/Dordogne border together with the Octagon LNB I wrote about above and no loss of picture a any time of year except during the heaviest of downpours.

UHD (4K) TVs are now readily available at prices no higher than HD sets of a year or 2 ago. UHD test transmissions can already be received from several satellites and I can receive them using a cheap PC sat card...Because of the new HEVC/h265 codec UHD channels don't require as much extra bandwidth as you might think.UHD pics look absolutely stunning even when displayed on my 27inch standard HD PC monitor.

the old perforated mini dish works fine here in Dordogneshire, but 80cm is a great improvement.. HiDef was a load of hype until getting a 47inch LED.. then the switch to HDMI and 1080 made all the difference.. shame the prorgam content of Corrie, etc aren't up to HD.. but Countryfile and Pirates o t Carri are great, etc.. Ah.. good old 405 and vanishing spot CRT.. good entertainment to watch the spot for at least 15seconds.. better than Ena and Co at the rovers.. 3D.. all but forgotten now.. 4K is the next push.. but the cost is mega.. and will need more sats to cope with the data?... here we go again!!!.. up to 32inches, scart is fine..40 inches or larger and HD is much better.. i.m.h.o..

I picked up any old Sky Minidish from the UK and it works fine for me. But I grew up with 405 lines black and white and don't feel the need for HD and the like. So if you think it is worth the money, you may want to go for top of the range kit.


If you are planning to upgrade your LNB then I would highly recommend fitting a "PLL" LNB.There are only 2 manufaturers of such LNBs, that I know of ...Octagon and Best..both German. Here is a link to the Octagon PLL LNB:

"PLL" LNBS are particularly useful in regions of poor signal strength and especially so for HD channels because they add less "phase noise" to the signal than other LNBs. I have compared both the Octagon PLL LNB and the Best "quartz controlled" LNB to others and they are both significantly better than all others I have tested.

Just search ebay for PLL or quartz controlled LNB and you will find suppliers of 2,4 & 8 output versions. The satellite cable you can find in any brico is perfectly suitable...

i'm running a dual lnb on an old 80 dish from 2007 with a Humax recorder and LG 47inch led.. i do see the difference in quality between SD and HD.. SD can be like looking at an old 625 screen.. the difference is quite pronounced.. some friends are saying they can't see the difference either.. but they're connected via scart.. so no wonder..

I agree that it will not make a noticeable difference.
For satellite problems, my first port-of-call is -
They do have stuff to sell, but there is no obligation to buy and they have a large database of useful information.
They will also give a quick personal reply to straightforward questions.

If you are replacing your LNB two main factors (besides dish size & postioning etc) will govern your signal quality :-

1) Use good quality satellite feed cable....DON"T be temped to cut cost on this and buy cheap or use normal TV co-ax cable, it is just NOT good enough especially if distance is involved.

2) Buy the best LNB you can. There is plenty of guidance on the net if you Google LNB's etc. Normally the lower the noise specification the better, but don't rely on this only.......there much more to it......

No, is the simple answer. We have an 8 output LNB feeding HD receivers with no problem. The biggest factor is the dish size (and quality). A 20% increase in dish diameter = approx 100% signal gain. If you are getting pixillation it is either the dish needs tweaking or the dish isn't large enough.

Thanks both for your helpful replies.
David, the link is really useful. Cheers for that.

Ditto, the same although we have a fairly large screen TV. Our French and other TV does not work for some other unknown problem that has totally foxed two technicians, so that does not really count.

It shouldn't do. You may find this link useful

We have a twin LNB which feeds our Humax for UK TV/Radio via Freesat and a separate single output LNB aligned to the satellite for French Digital TV. There's no discernible difference between quality on UK LNB and the French one though I guess the signal strength is probably better on the French sat.

UK reception is fine although the HD broadcasts don't seem so robust. As we don't run a monster TV there is little difference between HD and non HD except that our HD can from time to time pixellate or whatever the appropriate tem is.