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Old 13-Nov-2014, 2:16 AM   #1
ZippyTheChicken
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Join Date: Jun 2014
Posts: 59
Attenuation guide and sensitivity different channels have to signal loss

here is a guide for signal loss due to the length of coax tv cable you install

as you can see there is a
signal number
Long Length 100 meters
Short Length 100 feet

Although most of us will want to stay below 100 feet from our antenna to our tvs it is important to look at this guide for a different reason.

If you are setting up an Antenna and you are selecting between ones with different rated gain this guide can be helpful.

100 feet is the constant here

the difference is the signal frequency.

As you can see lower frequencies have less loss
Higher frequencies react harsher to the same signal loss
THE LOSS HERE IS THE LENGTH OF CABLE

it can also be related to choosing an antenna which is rated at say
5db .. 10db or 15db or better with an amp

The higher stations will perform worse under the same conditions.

for your consideration
VHF is 54 to 216
FM and other signals live between VHF and UHF
UHF is 470 to 800


at 100feet of cable
channel 2 will lose 1.60db of available signal from the antenna
and channel 69 will lose about 6db

I hope this might give reference to those doing research.

Code:
Electrical Performance
Frequency Attenuation (dB/100 m) Attenuation (dB/100 ft)
5 MHz 1.90 0.58
55 MHz 5.25 1.60
83 MHz 6.40 1.95
187 MHz 9.35 2.85
211 MHz 10.00 3.05
250 MHz 10.82 3.30
300 MHz 11.64 3.55
350 MHz 12.63 3.85
400 MHz 13.61 4.15
450 MHz 14.43 4.40
500 MHz 15.29 4.66
550 MHz 16.08 4.90
600 MHz 16.73 5.10
750 MHz 18.54 5.65
865 MHz 20.01 6.10
1000 MHz 21.49 6.55

Last edited by ZippyTheChicken; 13-Nov-2014 at 2:18 AM.
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Old 13-Nov-2014, 11:28 AM   #2
ADTech
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Posts: 2,942
Different manufacturers will have different attenuation factors for their coax and different types of coax will have different attenuation factors, that's just one example of a "typical" coax. It's easier to just use 5.5 or 6 dB/100' or 15-20'/dB as a worst case insertion loss for coax and be done with it when calculating a signal loss budget. Unless you have a very long cable run that will require tilt compensation, it's not worth the effort to use the whole chart.
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Old 14-Nov-2014, 3:44 AM   #3
ZippyTheChicken
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Join Date: Jun 2014
Posts: 59
Quote:
Originally Posted by ADTech View Post
Different manufacturers will have different attenuation factors for their coax and different types of coax will have different attenuation factors, that's just one example of a "typical" coax.

Yes I am not sure which cable manufacturer that was from it was for commercial quality RG6 but it is not just the reference of what loss will be caused by a static 100 foot length of cable... or to calculate any loss due to cable ...

Its that the same 100 foot length of cable
will cause a different reaction of loss depending on the frequency of the station.

It can help people understand if you split a cable -7 to VHF may still get you the signal but -7 to a same powered UHF station may drop it out.

or if you have a 14db antenna vs a 10db
or if you have your antenna inside vs outside

Those things may effect some signals more than others.
It is still relatively small unless you are in my position where fringe means you might only get 6 db of signal from a station to your home..

If you are in the burbs or city and your signals are over 30db to your home it won't matter.

... anyway

IDK just thought it was interesting.
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Old 14-Nov-2014, 3:49 AM   #4
ADTech
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You design the loss budget for the worst case insertion loss and call it a day. It's really not necessary for most people to do even that.
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