[PVRCNC] -SPAM- (5.6) What! No Voltage?

[mike at bentwire.net]

The cable TV world operates a little differently than what we hams are 
used to. In the cable TV arena, they transmit signals down the cable 
using a signal quantum called Bels. Bels are quite large units of 
signal, and correspondingly very expensive to create and transmit. 
Hence they feed them out very frugally, using only the minimum amount 
necessary. Thus, they measure them in deci-bels, 1/10 of a Bel. To 
avoid wasting these deci-bels, they install hardline coax, and 
adequate, but crappy, F-connectors on their system.

In the ideal world, if they had no losses in the cable, they could 
transmit the signals with zero Bels of signal. This is the ultimate 
goal of the industry. Whoever manages to accomplish this will be given 
the No Bel Prize by the cable TV industry.




"Jim Jordan, K4QPL" <k4qpl at nc.rr.com> wrote:

Cable repairman down at the coast came to investigate on Saturday why 
the 
cable modem kept dropping out causing erratic internet access. Having 
nothing better to do I thought I'd learn something about how the bits 
and 
bytes get to us from the cable.

As he was cleaning up and replacing connectors corroded by the salt 
air, I 
made the innocent comment: "I can see where corrosion on those 
connectors 
could cause voltage drop and loss of signal"

To which he set me straight:  "There is NO voltage on a digital cable-
--only 
decibels".

After replacing some cables, connectors, lightning protector, splitter 
and 
anything else readily to hand and the system was working again, he 
then 
pulled up the analysis software on his laptop and said that everything 
was 
now fine at our end except the "Receiving SNR line".  "Minimum 
decibels on 
the 'Receiving SNR line'  should be >33 and we were only getting 
30db". I 
looked at the screen and while trying to keep a straight face on that 
explanation of the signal to noise ratio analysis being done by the 
software, I asked what was the problem with "the receiving SNR line"? 
Response: "We're having some issues with that in the system". End of 
explanation.

I wanted to ask if they had anyone out looking for those lost decibels 
that 
should have been on the 'Receiving SNR Line' but thought better of it. 
As 
there's no voltage involved, I shouldn't be concerned.

Painting by numbers applied to tech service     ;-)

73,

Jim, K4QPL




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