Freeview signal problems

allanp

Active Member
My freeview reports that I am getting 100% signal but that the signal quality is slightly below 50%. I'm using a computer based setup and am picking up from the crystal palace transmitter. Anyone know what I could do to improve this as a lot of the channels are a bit choppy. I'm already using a booster box.
 
R

RB2004

Guest
signal shouldnt be 100%, as analogue signals will be too strong, and swamp the digital reciever leading to bad picture quality, try without the booster box, if you still have problems you may need to attenuate, do you have a post code so we can check your estimated signal strength?
 
R

RB2004

Guest
As mentioned previously, your problem is your signal is too strong, remove the booster and you should see an immediate improovement, if it still has problems check which type of aerial you have,

freeview requires between 55dBuV - 60 dBuV for best results, and your predicted signal strength is 58dBuV.. without the gain from your aerial, and booster.

your predicted signal strength for analogue is 75 dBuV..and the maximum freeview recievers can handle before being swamped by the analogue is 80dBuV.

Your recommended aerial type for christal palace is a group A long periodic

http://tvaerials.com/product.aspx?productid=676
 
R

RB2004

Guest
in your situation i would use a variable attenuator, as you do not have a signal meter availiable to tell you which one you need.

With a variable attenuator, you can start off by attenuating the signal to the lowest level, then slowly increase it until your picture quality improves on all channels.

http://tvaerials.com/product.aspx?productid=554 - if you are using standard coax plugs,

http://tvaerials.com/product.aspx?productid=93 - if you are using "F" type screw connections.

if you need to break the cable to use this, i would advice the use of "F" screw type connectors as they give a better connection, as used by cable and sky.

but definitely do away with the booster. then you should see a noticeable improvement, even if its not much.
 

allanp

Active Member
OK, I went and got a 12 and 18db attenuator, was all I could find on a Saturday afternoon. I'm not really sure they make much difference to be honest, so I'll order one of those in the links you provided and see if things improve.
 
R

RB2004

Guest
they should do, with digital a strong signal does not always mean a good signal, because when the signal is too strong analogue interferes with the digital tuners ability to process digital signals,

you already have a very strong signal which is why i recommended you remove the booster, signal strength should only be around 75% to get a good picture
 
R

RB2004

Guest
i know it sounds strange, weaker signal better picture, even though a weaker signal can still give a bad picture, but it is the analogue signals which cause the problems, which is why when the analogue is switched off the transmitter power will be increased, and people will find their signal is alot stronger. Analogue and digital signals should be kept within a certain range for best results.

analogue should be less than 80dBuV
and digital should be between 53-60 dBuV

your estimated signal already within the digital range, as it is 58 dBuV.. this is without the increase in signal strength which is caused by your aerial and booster. with the combination of them two your signal i imagine is over 60dBuV which is pushing your analogue signal over 80dBuv, as it is already 75 dBuV.

If attenuating the signal still does not work, the next step would be to examine the downlead from the aerial and alignment alignment.

has the removal of the booster and introduction of the attenuators shown any improvement in picture?
 
R

RB2004

Guest
if the picture has improved you are on the right tracks, is your aerial ok for digital and properly aligned?.. also check the download. if all is fine, was the picture better with the18dB attenuator?
 
R

RB2004

Guest
if it was, you may need to attenuate further, as your aerial maybe too big,

a normal aerial has a gain of about, 12dB,

but because of the signal strength in your area an aerial with a 8db gain is recommended, such as this

http://www.tvaerials.com/product.aspx?productid=676

to use your existing aerial the fact the picture improved when you removed your booster, and attenuated indicates that further attenuation is required.
 

clemenzina

Active Member
Excuse me butting in, but I'm having a similar problem and don't think I should start a new thread (will if I'm told to):

I gave my Nokia OnDigital box, which had served me well with no problems for many years, to friends who live closer to Crystal Palace than I do, and higher up. They tell me that they cannot receive ITV/C4 channels, and I've been told that this could be because of too strong a signal.

They've changed from their loft aerial to an indoor one, but the problem persists. I'm looking for an attenuator for them (they're not English and they're even less techie than I am), would this one be worth trying?

Post code is SW16 2QU.

Attenuator_byArcher.jpg


clemenzina
 
R

RB2004

Guest
as they live only 2 miles away from crystal palace, according to wolfbane, their estimated signal is 96 dBuV without the gain of an aerial..this is far too strong, which would explain bad signal pictures, it should be around 55-60 dBuV for a good picture, normally i wouldnt recommend set top aerials, or loft aerials as they give bad performance, but according to wolfbane, a set top aerial is recommended so there is no reason why it shouldnt work..

i recommend you use one of these,

http://www.tvaerials.com/product.aspx?productid=92

that will reduce it from 96, to 78 dBuV

then use a variable attenuator as below,

http://www.tvaerials.com/product.aspx?productid=93 - this requires F type screw connectors

http://www.tvaerials.com/product.aspx?productid=554 - normal tv type connector.

on maximum that will reduce it down by up to another 20-25 dBuV depending on which one you purchase, if you purchase the 20 dBuV one it will reduce it down to 58 on maximum attenuation which should provide an ideal signal.

but if you still have problems, a better solution would be to get an external aerial installed if possible, and point it to Reigate at 195 degrees.

for this you would need a wideband extra high gain aerial with masthead amp, but it would certainly make things easy, as the signal is alot lower, as it is estimated to be 34dBuV.. and with a variable masthead amp, you can easily amplify this by 7 and 22 dBuV which would bring your signal strength up to between 41 and 56 dBuV which is fine.
 

JayCee

Distinguished Member
Excuse me butting in, but I'm having a similar problem and don't think I should start a new thread (will if I'm told to):

I gave my Nokia OnDigital box, which had served me well with no problems for many years, to friends who live closer to Crystal Palace than I do, and higher up. They tell me that they cannot receive ITV/C4 channels, and I've been told that this could be because of too strong a signal.

When your friends received the box from you and connected it to their aerial did they do a "Store New Channels"? as "Add new Channels" wouldn't.
 
R

RB2004

Guest
When your friends received the box from you and connected it to their aerial did they do a "Store New Channels"? as "Add new Channels" wouldn't.

Should it matter because they are on the same transmitter? always worth checking suppose anyway lol, just wouldnt of thought it would of mattered being its coming from the same transmitter, and if that was the case. i would of imagined that other channels would be missing as well
 

JayCee

Distinguished Member
Should it matter because they are on the same transmitter? always worth checking suppose anyway lol, just wouldnt of thought it would of mattered being its coming from the same transmitter, and if that was the case. i would of imagined that other channels would be missing as well

It matters a great deal especially with the old on-digital boxes.
It's always a good idea to wipe the memory of any Freeview box and retune whenever there is any change of signal be it transmitter, aerial, downlead etc.
 
R

RB2004

Guest
ok, i stand corrected then lol.
I always do it anyway, just didnt know it mattered. Thanks
 

clemenzina

Active Member
did they do a "Store New Channels"? as "Add new Channels" wouldn't.
As far as I know they did - I gave them the manual and gave them instructions over the phone.

It's awkward, I'm not allowed to go there and help because my friend thinks her house isn't good enough (you'd think she hadn't seen my clutter :D ). Perhaps I shall tell them to speak to a close neighbour who has Freeview.

Thanks for the detailed advice, RB, I'll try to explain it to them.

clemenzina
 

johntheexpat

Distinguished Member
they should do, with digital a strong signal does not always mean a good signal, because when the signal is too strong analogue interferes with the digital tuners ability to process digital signals,

you already have a very strong signal which is why i recommended you remove the booster, signal strength should only be around 75% to get a good picture

Does this mean that when the analogue is switched off, a strong digital signal will be OK? I ask because my niavety was taken advantage of :eek: and I have ended up with, by the looks of it, way more signal strength than is good for a bloke and his STB. My sad story, in a nutshell goes like this.
We moved to France and wanted French TV for language skills, but the signal was poor-ish, so I bought a booster, not initially realising it was a masthead amp. But it seemed to improve the signal a bit so I lived with it. Then Digital TV arrived (TNT in french, but basically the same system as the UK) so we bought a cheap STB. Which worked for about 2 hrs, one Saturday afternoon, then stopped. So, we called in the engineer who after careful consideration, told me we needed a new aerial. So we got a new aerial, with masthead amplifier correctly installed (18 elements?-I have pictures if you want) which made no difference. He then 'tweaked' a junction in the bedroom and the picture was fine. (If he had done this first I think I may not have needed a new aerial).
So everything was good, but a nut 'sheared' on the mast (I think it may have been installed like that, so he could come back and make more money from 'the rich ex-pats' (ha ha if only he knew)). Well the aerial started to point away from the transmitter. The cheap STB started to object and soon the picture was B&W only. So we bought a better one, which worked fine. The aerial continued its merry turn and eventually, when it was maybe 65-70 degrees away from the transmitter, (again, I have photos if they would help) we had lost maybe 1/3 of the channels and decided enough was enough. So we called in a different engineer to fix the problem. He pointed the aerial in the right direction, secured it and went on his way. So now we have a good STB, big aerial pointing in the right direction and a masthead amplifier. The box now crashes with monotonous regularity, the only way to un-crash it seems to be to unplug it for a second and then it comes back to life when switched on. But the signal strength is right up there. And from the previous comments, too far up there.
So, these are my questions.
1 Is there a way to 'turn off' the mast head amp, other than unplugging it which gives no signal at all, or getting some in which costs?
2 Is it the over-strong digital signal that crashes the box, or the analogue interference, or something else? It did crash occassionally before, but nowhere near as often (ie will this problem go away with digital switch-over?)
3 Would an attenuator reduce things to acceptable levels and if so where should I put it relative to the amp power pack and TV
4 Could I cheat and just add a 50m run of co-ax, which I can hide discreetly, to reduce the signal strength?

Technical info:
Masthead amp Johansson Kit 7403/2430A (max output level 105 dBuV)
Cheap STB: Metronic Zapbox 441505 (which works in colour again, now)
Better STB: Philips DTR 320/00
Aerial unknown, 18 elements? (ie 18 lateral bars along the length of it)

Thanks for any help!!
 
R

RB2004

Guest
Hi, what was the junction in the bedroom he tweaked? which caused the picture to be ok?

if you have a french equivalent of a post code, i can try to check your estimated signal strength.

i have never heard of an instance where a strong signal crashes the box, but i could be wrong.

masthead amps can be switched off by removing its power supply, but then the chances are you wont get a picture due to the way they work, it is the same with boosters. power off = no picture, only way to remove it from the system is to join the 2 halves of the downlead together on the mast with a suitible connector, and properly tape up to prevent entry of water and dampness. masthead amps are always better than boosters as it is a always better to amplify the signal nearer to the aerial, because then you arent amplifying a signal which may have picked up interference from within the house.

a 50m run of coax wouldnt reduce the signal, unless STB was actually connected to it, but this wouldnt be a recommended solution as you run the risk of interference and signal degradation.

a strong signal causes problems, because at present there is also an analogue signal, which is at a higher level than digital, so it swamps the digital reciever and prevents it from identifying, and displaying the digital signals properly. Also each reciever has tolerances as to how much signal it can handle, analogue tuners are the same but it is less noticeable when your signal is too strong.

it would appear you are not the only person to have a problem with the box crashing, it might be a common fault.

read this buyer review,

http://www.pricegrabber.co.uk/rating_getprodrev.php/masterid=16616899/form_keyword=
 

johntheexpat

Distinguished Member
The box just seems to crashing more at the moment and as it comes just after the aerial was re-aligned I wondered if the two were connected. Perhaps its the warm weather:thumbsup:
My 'Postcode' is 49150 and we use the Le Mans transmitter, but the 49150 area is not very specific to me, but if you can, great, ta.
As for by-passing the masthead amp, its way up on the roof and too high for me! I am trying to avoid costs, so calling someone out to do it is a no-no.
Thanks for the feedback, the problem is irritating rather than anything else. I fitted a switch just by where I sit so if it crashes I can kick the switch on and off and get narked for about 15 secs as it sorts itself out and then we get back to normal. (That actually sounds much worse than it is- I do move away from the TV occassionally)
 

SamRadford

Well-known Member
3 Would an attenuator reduce things to acceptable levels and if so where should I put it relative to the amp power pack and TV

The attenuator should be close to the aerial input of the receiver. Without knowing your signal strength it's impossible to suggest a value for the attenuator but they come in (typically) 3dB steps so you could start with, say, a couple of 12dB attenuators - try one, then 2 in series. If that makes no difference try more. If you need finer adjustment try a 6dB or a 3db attenuator. Or buy a 20dB variable one.
 

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