Extending coax cable

How far can I extend my coax cable in order to add another tv, (via receiver box supplied by Spectrum) without losing signal strength?  Can I go as far as 200 feet?


Re: Extending coax cable

Any length of coax will decrease the signal somewhat, plus the loss introduced by adding a splitter, but cable boxes are far less sensitive to lower signal levels than are data modems.


Another option may be to extend 200' of ethernet out to the location and use a hard wired Roku to run the Spectrum TV app.

Spectrum Employee

Re: Extending coax cable

You will always loose signal power over distance (this is called attenuation), and it'll vary by what frequency (higher frequencies lose more than lower frequencies) , temperature, and what type of coax. That's normal. Figuring out how much attenuation is nicknamed "cable math".


in order of most attenuation to least attenuation of the common types found:
RG500 (aka. Feeder hardline)

RG750 (aka. Trunk hardline)
RG1000 (aka. Trunk hardline)


Note, while RG11 is preferred for aerial or underground drops (from utility tap to home's groundblock), and RG59 is typically the cheap stuff found in apartments and older homes; there's also RG59 headend which is quintuple shielded and silver clad instead of copper clad. The attenuation is almost identical, but what is gain with more shielding is better resistance to ingress and egress.


Here's a rough approximation table of what you can expect for most coax brands at
20 degrees Celcius:
Cable Size Return 57MHz 591MHz 645MHz 747MHz
RG6 per 100' : 0.8 1.6 5.1 5.3 5.65
RG11 per 100' : 0.5 0.96 3.18 3.3 3.65
500, Feeder per 100' : 0.4 0.54 1.91 2 2.16
750, Trunk per 100' : 0.13 0.37 1.31 1.38 1.48
1000, Trunk per 100' : 0.11 0.32 1.1 1.17 1.24


stupid Lithium forum software broke the table formatting, I'll have to fix it later.



As for what signal levels start with, it depends on the brand/make of taps & actives used on the outside tap and the local FCC standards. I'm only familiar with the Motorola/NextLevel/GI ones that were bought up by Arris (who also makes a lot of good quality cable boxes & modems).


For those (Arris brand squarish-rectangular looking taps) ...
Rx/Forward Levels at Tap:
57 MHz


Outage-severe low at < 0 dBmV
Maintenance needed low at < 5 dBmV
Maintenance needed high at >15 dBmV

747 MHz

  • Outage-severe low at < 4 dBmV
  • Maintenance needed low at <9 dBmV
  • Maintenance needed high at >25 dBmV

Tx/Return Levels at Tap
Tx/Return levels for first tap with no DC splits, usually a 23value labeled tap:

  • 43.3 dBmV Tx is perfect
  • No more than 45 dBmV allowed
  • Too low is below 30 dBmV


What's most important for Forward is that it's even (no power dips, nice & even tilt throughout all frequencies), a strong signal (higher dBmV is almost always better), and a clean signal (modulaton error ratio, MER)


What's most important for Tx/Return is limiting the ingress noise from bad fittings/connectors, cable theft, and physical damage to shielding. Also important (but a bit less so) that Return is fairly even and not too much tilt across the multille frequencies.




Typically there should be enough Rx/Forward power for 200 ft plus the 3.5 to 4 dBmV loss from a 2-way splitter.  But you'll have to estimate it using your current levels at that splitter location and then do the rough-estimate cable math.  Or just buy some RG6-quad & try it out.

My postings on this site are my own, off-the-clock, and don’t necessarily represent TWC’s/Charter's strategies or opinions.