Signal And Quality Explained.

[whitefish]

A Copied Document.

Dispelling some of the misconceptions about Signal strength and Quality.
Signal strength “S”

This is not the signal from the satellite, it is the level of the signal from your LNB to the receiver, adjusting the dish to improve the “S” will do nothing to improve this, using a bigger dish also will do nothing, some of the things you can do to raise the “S” is to use better coax (RG-6 quad with a pure copper center conductor) or shorten the distance from the LNB to the receiver, one solid run of coax from the LNB directly to the receive is the best way to get the highest “S” you can, when you put ground blocks (needed) switches or splices inline you can drop the “S” 10% to 40% however this will not affect the signals “Q” that much.

Things that can affect “S”.

Bad or poor quality coax, this is the pipe that delivers the signal from the LNB to your receiver, a poor quality coax is like a leaky hose, the more leaks the less water, the same with coax, the more connections, poor shielding, connections to other devices or a copper plated center conductor can lower the signal to the receiver.

Poor quality or wrong type of coax.

The cheaper the coax the more loss it has, this is because they cut back on the amount of shielding or thickness of the center conductor, coax made for CATV (cable) is not recommended for satellite systems, the signal used in CATV is from 40 to 900 MHz, the coax used for this is only rated for that range, the signal from the LNB is from 950 MHz to 2.5 GHz, the coax for CATV has a higher attenuation at the satellite frequency range and you get less “S” to the receiver.

Water.

This is not a good thing to get into the coax, switches or connectors, if you have a coax with a copper plated steel center conductor the water will cause it to rust, this will cause the signal to drop or go away all together, water in the coax can cause all sorts of problems.

Kinked coax.

If the coax was kinked during installation it can cause a loss of “S”, the distance between the center conductor and shield is very critical, kinking the coax will change this distance and change the impedance (75 ohms) of the coax or even short it out (no “S”) altogether.

PVC jacket of coax damaged.

If the PVC jacket is damaged or cracked it can let in water (not good) a nail in a coax staple can pierce the jacket and cause problems, the jacket is to protect the shield from corrosion due to water.



Signal Quality “Q”

The signal used in DSS satellites is digitally encoded and uses what is call Forward Error Correction, (FEC) this is a digital data program that is sent along with the digital video/audio programming to insure the final signal is error free (as possible) when the two signals are compared the FEC will correct any errors in the digital programming to insure it is error free. (bit substitution)

The level of error correction is measured as Bit Error Rate, (BER) to correctly measure the true BER you need some very special equipment, however the receiver has a special circuit in it to do almost the same thing, this circuit is what gives you your “Q” signal at the receiver, the higher the “Q” the lower the BER is, a “Q” signal in the 40 to 60 % range is still useable but will give you problems during rain and snow storms, a “Q” signal of 60 to 80 % is a good signal and if that is all you can get with your setup, its not worth the effort to get a 99% “Q” as you probably wont notice the difference, it will not improve your picture quality.

So if your have an “S” of 60 to 80% and a “Q” of 60 to 80% with your current setup and you have spent countless hours trying to get more it’s not worth the effort to keep trying.

Ways to improve “Q”.

Follow some of the guide lines in the section about “S”.

“Q” is low or fluctuating. Use a bigger dish, most satellite signals can be received on the standard 18” dish found on many homes today, how ever the further you go North or South from the center of the North American Continent the further outside you get from the prime footprint from the satellite your trying to receive, 95% of DN satellites are pointing at the US, BEV satellites are pointing at Canada, so if your in central or northern Canada you may need a bigger dish to receive DN satellites, if your in the US and trying to receive BEV satellites you may need a bigger dish.

Terrestrial interference.

This can affect “Q” and can come from anywhere, the signal from the LNB to the receiver is in the 950 MHz to 2.5 GHz range, anything transmitting close buy to your dish in this frequency range can affect the “Q”, this can be cell phones, cordless phones, routers, local WIFI signals and other things close buy or inline with your satellite dish.

Obstacle interference.

“Q” was good during the winter, now its dropped, the trees/bushes have their leaves back, this can reduce the signal to the dish, moving the dish to an unobstructed view of the satellite is one way to fixe this, the other is to trim the trees.

Building in the way.

No way around this if you can’t move the dish to a better position.

One other thing that can affect “Q” is if the dish is pointing to a satellite that is low to the horizon, (under 20 degrees elevation) you have more atmosphere to go thru, excessive atmospheric attenuation can drop the signal to the dish by about 30%, so a satellite at 45 degrees elevation that has a “Q” of 80% in one area, could have “Q” problems if the elevation was 20 degrees at another location.

note: when pointing at 119 make sure you choose transponder 12239 for quality to show up. once your happy put it back to transponder 12224