RG 59 is no longer used by a majority of the franchises. The signal loss is just to great. it was ok for the old analogue system but due to the digital signals being transmitted 20 db down on the analogue. this type of cable was only used externally from the omni box to the internal isolator and from the isolator to the CM/STB.
Signal loss 3dB per 100m at 10MHz
RG 6 this size cable is now the norm for internal and external cabling and on a majority of installations is used as the drop cable up to 130 metres.
Signal loss 2.3dB/100m at 10MHz
RG 7 used for runs between 130m to 180m
Signal loss 1.9dB/100m at 10MHz
RG 11, used for runs of 180m and upwards
Signal loss 1.2dB/100m at 10MHz
Higher frequencies will attenuate greater than lower frequencies so we usually take signal readings in the higher bandwidth area where the analogue and digital signals are being transmitted so lets say at 643MHz on a RG 6 you will get a 1.5 db drop for every 10 metres of cable on a RG 11 cable at the same frequency you will get a 0.95 db drop in every 10 metres of cable.
But it doesnââ‚ƚ¬Ã¢â€žÂ¢t stop there we aim for a signal level of 0 db at the omni box if you have one stb and one cable modem youââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢ll have a two way splitter in the omni box which will cause a signal loss of -3.5db per port on the splitter and a three way splitter youââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢ll lose -6.5 db per port. With the advent of digital and the digital signal levels being transmitted 20 db down on the analogue this has presented us with quiet a few problems and is one of the reasons why some customers will have experienced service call after service call, but we now have a fix for this problem by using a HDU ( home distribution unit ) which in all tense and purposes is a no loss 4 way signal splitter.
Your optimum signal level for a cable modem is -4 db at 402.75mhz some areas may vary. donââ‚Âà ‚¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢t worry if itââ‚ ¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s a few db up on this lets say -1 db , but if your getting lets say + 3 db this may start to cause a problem with noise and packet loss. On the other side of -4 db your Signal can drop down to -12 db without any significant problems. you can check this by looking at your diagnostic screen
http://192.168.100.1/ username: root password: root if you have a Surfboard or an Ambit.
Your optimum levels for your stb at 643 Mhz -5 db we usually take two different readings one on a low frequency and one on a high, we like to see all the signals between 419Mhz to 747Mhz as flat or linear for a bit of perfection, but it is not a problem if we see a bit of a positive slope between these two figures and as long as itâ₠¬ÃƒÂ¢Ã¢â‚¬Å¾Ã‚¢s not greater than 7b.
As for connectors ( F type connector) please do not use the sky type twist on they are absolutely rubbish for use with cable. We used to use a crimp type of connector ( Gilbert connector ) but we found this to be a inferior type of connector and prone to let in ingress. We now use a f type connector called a snap and seal that is air tight, the tools you need for a snap and seal are quiet expensive and q
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