1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

3GHz Coxial Cable & HD In-line Filters

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by 1953, Jul 23, 2007.

Thread Status:
Not open for further replies.
  1. 1953

    1953 Icon

    777
    10
    Feb 7, 2006
    Desoto, TX
    I know that this is a really dumb question but what the hell........................

    I learned today that the new DTV coxial cable standard is 3GHz as opposed to 2.5GHz.

    Does this mean our coxial cabling must be rated 3GHz?

    Or are the filers converting the 2.5 signal to 3GHz?

    Or ....?

    Thanks,
    1953
     
  2. Earl Bonovich

    Earl Bonovich Lifetime Achiever

    30,092
    3
    Nov 15, 2005
    Where did you see that?

    The "ghz" rating for a cable, is the relation to the maximum frequencies that can be reliable carried on the cable.
     
  3. 1953

    1953 Icon

    777
    10
    Feb 7, 2006
    Desoto, TX

    Earl, I got my information regarding the 3Ghz from the following post.

    Thanks for your help.
    LP


     
  4. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

    42,683
    348
    Dec 9, 2006
    As I posted in your other thread: the highest D* signal is 2.150 GHz coming from the dish.
    Even when the new SATs come on-line they will be using Ka-lo which will be 250-750 MHz in the coax.
    The only place I've read where signals are "up there" are with MDU units that stack the channels for multiple apartments to use a single coax.
     
  5. 1953

    1953 Icon

    777
    10
    Feb 7, 2006
    Desoto, TX
    To All,

    I posed my question to Directv, here is their response.

    "As long as the cable in your house is RG6 coax cable, then it’s exactly the kind of cable that should connect your DIRECTV System receiver to your satellite dish. If your cable is not RG6 coax, you will need to run new wire. It’s important that you use RG6 cable due to the frequency of the digital signals it must carry. RG6 has the correct impedance (75 ohms) and acceptable signal losses at 950 to 1450 MHz.

    In addition, Filter depends on both model and service. When you get HD, or if you get any channels from the 119, it means you have a 6x8 multi-switch with your 72 or 95 service. The currents from a 6x8 multi-switch could fluctuate. The filter modulates the currents so your programming is always properly transmitted to your receiver."
     
  6. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

    42,683
    348
    Dec 9, 2006
    Seem to have missed it here too. As 119 is still Ku band, but they seem to be referring to the 99 & 103 SATs.
    "Filtering DC"? Wouldn't that be signs of poor output from the receiver that is powering it? The 6x8 multi-switch is the Zinwell WB68 that is passive. Filtering the 22 KHz tone off the control signal would cause the 119/110 not to be selected.
    Sometimes you have to wonder what D* was thinking.
     
  7. harsh

    harsh Beware the Attack Basset

    21,192
    183
    Jun 14, 2003
    Salem, OR
    The biggest motivation for demanding RG6 is the ampacity of the center conductor. RG59 is rated for .729 amps and RG6 is rated for 2.3 amps. An honest 2150MHz RG6 should do just fine. A triple LNBF assembly may consume more power than RG59 can deliver.
     
  8. 1953

    1953 Icon

    777
    10
    Feb 7, 2006
    Desoto, TX
    I saw a powered 6x8 multi-switch yesterday at Best Buy. Is there any advantage in a powered as compared to a passive multi-switch?

    Lp
     
  9. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

    42,683
    348
    Dec 9, 2006
    A powered switch could drive the LNB assembly, but only the Zinwell WB68 [passive] & WB616 [powered] are rated for the new Ka SATs.
     
  10. 1953

    1953 Icon

    777
    10
    Feb 7, 2006
    Desoto, TX
     
  11. hasan

    hasan Well-Known Member

    5,957
    54
    Sep 22, 2006
    Ogden, IA
    You are one step ahead in the equation....the maximum current capability is not likely to to be approached, the issue is resistance per foot, which determines at a given level of current, how much voltage can be delivered to the load. It's not that the terminal device "runs out of current", but that the voltage can't be maintained at the load end because of resistive losses in the wire.

    The "ampacity" (I've never seen that term used before) or current carrying capacity (without excessive resistive losses) of RG59 isn't the limit, it's the resistive losses in the smaller center conductor. It is true, that ultimately, smaller wire will eventually run out of current carrying capacity, but it is most probably going to run out of voltage way, way before the current maximum is reached.

    I've never seen a rating for "ampacity"....it certainly isn't the fusing current of RG59 center conductor.

    I've seen wire rated at its fusing current and in resistance per "x" feet, but never in "ampacity". Did someone just make up a new term, so they could sell something, or it sounded nice?

    There are two problems with RG59:

    1. Frequency response (it doesn't have the bandwidth for even moderate satellite runs (it has too much attenuation per foot at an RF frequency of 2 gigs.

    2. DC losses: the center conductor is too small to meet the voltage requirement at the load end for the current being drawn by the device.

    Both of these can easily be overcome with RG59 if, and ONLY if, the run is very, very short. (hence attenuation is specified in dB/ft and power losses are a result of ohms/ft). Bottom line it shouldn't be used, but "ampacity" is just something I'm not ....shall we say...comfortable with. When it shows up in the IEEE reference manual with a "real" definition, I'll have to look at it. Until then, it sounds like someone just made it up.
     
  12. veryoldschool

    veryoldschool Lifetime Achiever Staff Member Super Moderator DBSTalk Club

    42,683
    348
    Dec 9, 2006
    The powered Zinwell WB616 has six inputs and sixteen outputs.
    The passive Zinwell WB68 has six inputs and eight outputs.
     
Thread Status:
Not open for further replies.

Share This Page