Thread Tools Display Modes
  #1  
Old 2010-07-08 , 00:40
Geoff D Geoff D is offline
Technical Myriad
 
Join Date: Nov 2008
Location: PTA
Posts: 16,413
Quote:
Originally Posted by Nealsch View Post
I wonder if someone can explain the difference between Signal Strength and Signal Quality. My strength is 98% but my quality varies between 20% and 40% . Needless to say some of my channels quality is VERY poor. What affects the Quality? Why is the quality bad when the strength is good?
(1) Signal strength percentage is reprenst the power level received at the input to the decoder.
(2) Signal quality is a representation of the Bit Error Rate after decoding, which in turn is proportional to the signal to noise ratio.

If the signal strenght is less than 100%, then it normally means thtat the antenna has not been aligned properly to receive maximum signal from the satellite ( Note in the case of the HD PVRs, this measurement is hardly ever better than 98%)

If the signal quality is bad ( as yours is), its almost always because the skew angle adjustment in the LNB is not optimum. A varying level indicates that an interfering signal is being picked up by the LNB.

Antennas alignment and especially skew angle adjustments must be done to get this value to 100% to ensure proper performance of the decoder.

Each frequency on the satellite is used twice, once Vertically polarised and once Horizontally polarised. A unviseral LNB has two receivers inside, one designed to pick up a VER signal, and the other a HOR signal. Once the signals have been detected, they are COMBINED and the combined vaule is then detected and measured as a signal strength.

The decoder on the other hand is looking for a very specific frequency and polarisation, so it detects the "interfering signal" and assumes it is a noise signal = why the Signal to noise ratio will be bad and why the signal quality will be less than 100%.

So it is possible to have a maximum signal level and a very poor signal quality.

You have two choices: Get an installer in to verify the alignemnt and the skew angle of the LNB,

OR do a DIY job.

Check the to make sure that when looking into the antenna ( DISH), that the lnb is approximately at the 4 o clock position with the cables pointeing downwards to the right hand side.

If you wish, I will send you a DIY recipe to get the position almost perfectly corect without using a Field Strength Meter Send me a PM
  #2  
Old 2011-01-11 , 10:25
AndrewD AndrewD is offline
Has mastered the i-Plate and DStv guide
 
Join Date: Nov 2008
Location: Johannesburg
Posts: 374
Hi Geoff

What is the minimum that the signal strength can drop to before you start having a problem ??

I have a small caravan dish which I tune in using a cheap digital signal strength monitor from Ellies.

The best I can generally do for strength is about 65% but the quality is normally 98-100%.

Please post your simple recipe for getting the skew angle right. I always try to put it at 45 deg.

Thanks
  #3  
Old 2011-01-11 , 11:40
AndrewD AndrewD is offline
Has mastered the i-Plate and DStv guide
 
Join Date: Nov 2008
Location: Johannesburg
Posts: 374
OK don't worry - found the previous post.

I would like to know how you set up your skew angle though ??
  #4  
Old 2011-01-11 , 11:50
Tulani's Avatar
Tulani Tulani is offline
Changes remote batteries daily
 
Join Date: Feb 2010
Posts: 2,837
these levels can also vary linearly with weather and coax cable conditions
__________________
8Way Universal LNB; (UEC 4tuner HDPVR primary;digital coax to hometheater, HDMI to HDTV +1110 secondary;SDTV)

silent witness
  #5  
Old 2011-01-11 , 13:39
Geoff D Geoff D is offline
Technical Myriad
 
Join Date: Nov 2008
Location: PTA
Posts: 16,413
Quote:
Originally Posted by AndrewD View Post
Hi Geoff

What is the minimum that the signal strength can drop to before you start having a problem ??

I have a small caravan dish which I tune in using a cheap digital signal strength monitor from Ellies.

The best I can generally do for strength is about 65% but the quality is normally 98-100%.

Please post your simple recipe for getting the skew angle right. I always try to put it at 45 deg.

Thanks
Send me a PM message and I will atch the method in reply

Decoders all have a threshold level below which they will not "lock" onto the satellite signal.

This is typically about 60% of the maximum signal level. Unfortunately as MC has stated previously, the values we "see" on the decoders do not actually reflect the true signal measurements accurately, so it is still the best to get the best possible signal possible.

The skew angle needs to be optimised for every site - the 45 degree is just a rough guide that works "okay"

For single tuner decoders, with single LNBs it is not as critical as it is for decoders with more than one tuner that require more than one LNB.

I am pretty sure that you would be able to boost the signal level after doing some skew angle adjustments --- it would be interesting to see wht you get as an improvement.

Caravaners are generally very adept at finding satellite signals as they have plenty of practice!
__________________
Easyview, UEC 4T HD PVR, SD PVR, XV
Spare decoders: SD PVR(2), PACE HD PVR 4T, DSD 660, 1110, 1131, Explora 1
2 unmentionable FTA decoders
Win 10 Pro (64-bit) version 1703, build 15063.138
1.2m antenna, 8-way universal LNB, 2x6 MS, FSM permanently connected.
MS Edge 40 with MSEdge HTML 15
  #6  
Old 2011-01-11 , 14:23
Theo's Avatar
Theo Theo is offline
Changes remote batteries daily
 
Join Date: Nov 2008
Location: in front of a Pace 4T.
Posts: 2,159
Quote:
Originally Posted by Geoff D View Post
Caravaners are generally very adept at finding satellite signals as they have plenty of practice!
Yip, to watch "Sewende Laan".
__________________
I hate people who take drugs......Customs men for example.
« Previous Thread | Next Thread »
Thread Tools
Display Modes
Posting Rules
You may not post new threads  | You may not post replies  | You may not post attachments  | You may not edit your posts
BB code is On  | Smilies are On  | [IMG] code is On  | HTML code is Off