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Subject Author Date
Is HDTV and RG59 coax cable compatible Walter R. 07-17-2005
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Posted by Pop on July 18, 2005, 2:32 pm



> Joseph Meehan wrote:
>
>> Walter R. wrote:
>>
>>>My house is 22 years old and was wired with RG 59
>>>coax in the walls.
>>>
>>>I ran into a problem with my RG 59 cables because
>>>they had too much
>>>signal-loss for my cable modem.
>>>
>>>I will have to replace the RG 59 with RG 6 for the
>>>cable modem. Do I
>>>need RG 6 for HDTV or will HDTV work with RG 59
>>>coax? (Hate to run
>>>more wires through walls than absolutely necessary.)
>>
>>
>> I have RG 59 and no problems with my cable
>> modem. I guess it depends. I do suggest top quality
>> splitters. The ones usually available to the
>> general public are junk. My RG 59 carries HD just
>> fine.
>>
> Hi,
> I think your cable provider was sending weak signal.
> Don't blame the coax cable.
> Tony

What everyone's forgotten, or doesn't know, is that
coax has a specific impedance, which must be matched at
any connection to it. Regardless of the RG number, if
you don't match the impedances there will be signal
loss. The TV will have an antenna input impedance.
Coax has its own impedance. If it's not the same as
the equipment it's connected to, an impedance matching
device (often called a splitter, not always) must be
used. Typical impedances are 45, 75, 90 ohms and so
on. It's NOT something you can measure with a standard
multimeter - go by each product's specs.

HTH,

Pop




Posted by Rick on July 18, 2005, 12:18 pm


Both RG-59 and RG-6 are 75 ohms impedance, the same as TV coaxial
inputs, so impedance differences are not relevent to this discussion.

RG-6 was originally designed as a lower loss 75-ohm alternative. These
days RG-59 is of highly variable quality, so there is even more
incentive to go with RG-6.

Rick



Posted by Wes Stewart on July 18, 2005, 9:34 pm


wrote:

>My house is 22 years old and was wired with RG 59 coax in the walls.
>
>I ran into a problem with my RG 59 cables because they had too much
>signal-loss for my cable modem.
>
>I will have to replace the RG 59 with RG 6 for the cable modem. Do I need
>RG 6 for HDTV or will HDTV work with RG 59 coax? (Hate to run more wires
>through walls than absolutely necessary.)

The "RG" (radio guide) numbers used to mean something when they were
mil-spec (MIL-C-17) cables.

Now every Tom, Dick and Wong build "RG" cables, so the specs are,
shall we say, open to interpretation. In fact cables built to
MIL-C-17 aren't labeled with an RG number anymore, since it's become
so meaningless.

That said, RG-59 and RG-6 are both nominally 75-ohm impedance cables
and the loss (attenuation) characteristics are similar. RG-59 is
slightly smaller in diameter, thus its attenuation is -slightly-
higher than RG-6, but nothing you should notice in the typical
application.

RG-59 should work fine in either application. If you are experiencing
signal loss then you should check for damage or bad connectors
(connections) before condemning the cable.

Also, you likely have splitters in your system. There are so many of
these on the market it's hard to say whether you have good ones or bad
ones. They're all similar in design, so the way they're slapped
together determines more than any design differences. Without
electrical measurement (difficult to do without a lab) or physical
examination, the best alternative is to substitute another one and try
to note any difference(s). Also, these are directional; a splitter
with the input signal connected to an output port will pass something
but it will be highly attenuated.

It's also possible that your cable provider needs to deliver some more
signal to you.



Posted by David Efflandt on July 18, 2005, 11:59 pm


> My house is 22 years old and was wired with RG 59 coax in the walls.
>
> I ran into a problem with my RG 59 cables because they had too much
> signal-loss for my cable modem.
>
> I will have to replace the RG 59 with RG 6 for the cable modem. Do I need
> RG 6 for HDTV or will HDTV work with RG 59 coax? (Hate to run more wires
> through walls than absolutely necessary.)

Make sure that the connectors are good and well attached to the cables.
Replace the connectors if not (I had to replace one and install some on
ends of scrounged cable). I used existing RG-59 cable (from former
owner's cable TV) to connect my OTA HDTV STB to indoor antenna (Silver
Sensor) on 2nd floor. Without an amp some channels from 36 miles are
weak, but with a 30db Radio Shack amp (maybe technically a pre-amp) they
usually all come in strong (except analog 2/digital 3 due to lack of VHF
antenna).


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