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Diplexer Question

Discussion in 'DIRECTV General Discussion' started by SATGATOR, Sep 29, 2007.

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  1. Draconis

    Draconis New Member

    Mar 16, 2007
    Las Vegas, NV
    Before anyone asks, I am not a DIRECTV employee. I just do a lot of reading from sites like SBCA's Educational Programs Website.

    Now, it does not matter where you put the diplexer on the cable. It is an invalid configuration and will only cause problems with the satellite and OTA reception. DIRECTV has always stated, from the first deployment of the H20, that diplexers are no longer compatible with the DIRECTV system and need to be removed.

    The reason the myth exists is because DIRECTV was not using the B Band until the recent launch of the HD national feeds. Because the B Band was not used it did not cause interference with the OTA signals. Now that the B Band is live this is no longer the case.

    Lets explain this a little further…

    OTA signals are in the 30 MHz - 862 MHz range (depending on which station you are watching).

    DIRECTV’s A band is in the 1650MHz - 2150 MHz range. As you can see, the ranges are completely separate and there is no overlap. This is the reason why the Diplexer was able to combine the 2 signals onto one cable and then separate them successfully.

    Now DIRECTV’s B Band is 250 MHz - 750 MHz. That’s right, the B Band is COMPLETELY overlapped by the OTA signals.

    Think of Monty Python’s giant foot descending from the heavens and squashing something.

    Now the H20 / HR20 cannot see the 250 MHz - 750 MHz range without a SWM, that is what the B Band converter is for. To up-convert the signal to a range the receiver can see. If you have OTA stations using this range it will up-convert them as well.

    So lets see what happens, if you have the Diplexer before the BBC on the cable the Diplexer separates the 30 MHz - 862 MHz range, taking the B Band with it. Result, no new HD national feeds and the B Band interferes with the OTA reception.

    If you have the BBC before the Diplexer everything in the 250 MHz – 750 MHz range gets up-converted to the 1650MHz - 2150 MHz range and you just lost any OTA stations that were broadcasting in that range. Not only that, but the OTA signals are now mixed into the satellite signals and will cause interference on the HD national feeds.

    Of course, if you have a SWM the SWM up-converts the signal at the multiswitch and this is not a problem. Remember, a SWM installation does not require a B Band converter and all this is handled internally.

    Now some people MAY LUCK OUT and none of their OTA stations are using the 250 MHz - 750 MHz range. But this is a crapshoot and depends on their market and what range their local stations are using to transmit the OTA signals.

    The best thing to do, and the best way to play it safe is to run the dedicated line until the SWM becomes widely available.
  2. medic4jc7

    medic4jc7 Guest

    May 22, 2007
    Found more Info:
    The SWM will be released very soon and would seem to be the answer to your problem. You take all four cables from the dish to the SWM. It can be mounted outside but the power supply has to be indoors, (connected via one of the cables connecting to the receivers). The SWM comes in two versions at the moment, the SWM5 and the SWM8. There is rumored to be an SWM11 on its way. Each tuner occupies one channel, so a DVR takes two channels. The SWM5 has five-channel capacity and so on. The SWM5, which I have been testing for about six months, has two outputs each of which carries the same five channels, and two "legacy" connections for older receivers that do not work with the SWM. The SWM8 has three legacy connections. The only boxes compatible with the SWM are the HR20 DVR, the H20 receiver (with a new download), the new H21 receiver, and the D12 SD receiver. All new DirecTV receivers and DVRs will be SWM-compatible.
    You can take a single cable from the SWM5 and connect up to five tuners just using splitters (eight with the SWM8). You can also diplex OTA onto the cable since the SWM channels don't overlap the OTA band (even with the new satellites).
  3. jwd45244

    jwd45244 Hall Of Fame

    Aug 18, 2006
    From the information you just provided:

    OTA: 30 - 862 Mhz
    BBC converts to: 1650 - 2150 MHz (Question: what OTA signals are in this range? Answer: there are none.)

    NO OVERLAP as long as you put the BBC upstream of the combining diplexer. Guess what? This is exactly what the SWM does with the B-Band signals. No more no less.
  4. saryon

    saryon Icon

    Aug 12, 2007
    Ratara: The BBC UPCONVERTS the B-Band out of OTA. It works. I do it. I get my local HDs via the sat. I get all my OTA from 2 to 68 via the OTA feed. It's diplexed as stated above. As we said, it's not supported and won't work for everyone, but for those of us who are doing it, IT WORKS JUST FINE. FOR ALL THE CHANNELS IN THE OTA RANGE. We're not talking about diplexing CATV here, but I've even got that working to one of my sets, although it might be clipping the top-top end (due to the frequency limitations of the OTA side of the diplexer). This all being done through the diplexers you continue to tell me aren't working.

    See http://www.dbstalk.com/showthread.php?t=62299 for many more samples of persons who are doing this.

    The original poster, and others, problem is that they don't have a multiswitch inside the house, so they'd have to put the BBC outside in the elements. That's not gonna work for any length of time.
  5. betterdan

    betterdan Icon

    May 22, 2007

    I have my ota antenna diplexed in with one of my sat lines and everything works.
    Just have to put the BBC before the diplexer where the antenna and sat signals are first combined. Pretty simple.
  6. betterdan

    betterdan Icon

    May 22, 2007
    That's exactly what I did. Mine is outside and inside a plastic box on the side of the house that was put there by Cox Cable a long time ago. It stays dry in there, the only thing I have to worry about is the cold and heat. I guess I'll find out how well the BBC holds up to temperature changes but so far so good.
  7. Keeska

    Keeska Legend

    Feb 10, 2007
    Obviously this is wrong if you read many different web sites discussing OTA and BBC's, including this one.

    Perhaps you could spend some more time reading and less time arguing against something which no-one has yet argued in favor of. In all examples it has been stated that the diplexor is placed AFTER the bbc (except for maybe a typing error - please point out the offending thread).

    Diplexor AFTER, not before.
  8. LDLemu4U

    LDLemu4U Legend

    Oct 16, 2006
  9. Draconis

    Draconis New Member

    Mar 16, 2007
    Las Vegas, NV
    I have not read the post by LDLemu4U but felt that I needed to post this.

    I did not want to believe that so many knowledgeable people on this forum were wrong. So I’ve been thinking, thinking a lot.

    Then it hit me, why can a Diplexer be used with a SWM and not with a standard WB multiswitch?

    The reason, the SWM steps up the B band into the A band at the multiswitch, therefore, there is no overlapping once the Diplexer is added.

    I have been fixated with the position of the BBC, it always plugs directly into the receiver. That is where my knowledge failed me.

    Theoretically, it is possible to use a Diplexer if the BBC is plugged directly into the multiswitch, then plugged into the first Diplexer. If the B Band is stepped up into the A band range before the OTA signals are introduced then there is no overlapping.

    So the installation would look like this:

    Dish -> Multiswitch -> BBC -> Diplexer-> [cable run] Diplexer -> Receiver.

    Not an approved installation model but theoretically possible. I sit bemused and corrected.

    Update: I have read the article by Cap'n Preshoot, I have no problems being wrong if I learn something from it.
  10. saryon

    saryon Icon

    Aug 12, 2007
    It's not theoretic. It's being done. In the field. As I and others posted to you hours ago.
  11. gb33

    gb33 Legend

    Sep 8, 2006
    I'm in a similar boat and am having troubles. I am looking to run a dedicated new line for sat (RG6) and leaving interior RG59 for antenna in attic. I tried the bbc before diplexor mess and it didn't cut it.
  12. carl6

    carl6 Moderator Staff Member DBSTalk Club

    Nov 15, 2005
    Seattle, WA
    DirecTV engineering stated that the BBCs were designed to be used "relatively close" to the receiver, and that they may not be reliable when moved a distance away. This was before D10 was even launched, so there was no way to know beyond the "theoretical" level.

    Based on that advice, the people who are "drinking D* kool aid" have advised that moving the BBCs upstream a distance might not work.

    Now that the new channels are up and running, and that a number of people are successfully diplexing OTA by moving the BBCs upstream, it is quite obvious that it can be done. What we do not know is whether or not that type of installation will work reliably over time. I hope it does, but if anyone who is doing that experiences any problems with the new HD channels, the first thing they should try is moving the BBC back to the receiver, and taking out the diplexers.

    And yes, the "official party line" is still to keep the BBC by the receiver and not to diplex. That doesn't mean it can't be done, it means that for the "average joe customer" who does not understand the complexities involved, it shouldn't be done. It is a non-recommended configuration that they (DirecTV) are not going to try and train thousands of CSRs to understand and consider when trying to help a customer with problems on the phone.

    So, for the folks here who know what they are doing, and want to try this, have at it. If it solves your problem for getting OTA in without pulling cable, great. And for the millions of customers who are not part of these forums, and don't have the faintest idea what an "F connector" is, then put the BBCs at the receiver.

  13. Ein

    Ein Mentor

    Sep 3, 2007
    This is kind of funny. For most of the HR20 owners SWM actually eliminates diplexing. We are already running two lines to the receiver. The logical choice would be using the extra line for OTA.

    SWM benefits new installs the most.
  14. Ein

    Ein Mentor

    Sep 3, 2007
    Ok, this is too deep for me. :)
  15. saryon

    saryon Icon

    Aug 12, 2007
    ein: If you use SWM8's OTA insertion you still need a diplexer at the receiver end. One of the benefits of the SWM is to not have 2 lines to the room. If you want to have two cables, great, but as-designed you only need 1 to the back of the TV cabinet.
  16. Draconis

    Draconis New Member

    Mar 16, 2007
    Las Vegas, NV
    At this point everything HD is theoretical to me. I get what I know by reading the forums, manuals, & installer technical sites.

    (I have been slowly upgrading my system to get HD, currently the only thing I am missing is the HD receiver. So I do not have a system to try the model out on.)

    Now I am not a satellite engineer, nor am I an installer, so I leave the specifications of these installations to the people who are. While the other method of diplexing OTA signals may work, I will continue using the model that the experts say works.

    Besides, what is the big deal about running one extra line to the receiver? The more complicated you make something the more likely it’s going to break. It’s not like it’s going to kill me to run the second cable.

    I will say no more on the matter.
  17. sptrout

    sptrout AllStar

    Dec 29, 2006
    Spring, TX
    In my case DTV would not install the second DirecTV cable when they installed my HR20 last year because I have a fire break somewhere in the middle of a 10 foot interior wall. So I had no choice expect to diplex the OTA with one DTV cable (I had two RG cables installed when I built the house 12 years ago). Luckily, the diplexing is working fine and I am receivng the new HD channels. BTW - -My second BBC in installed in the attic, before the diplexer, with about 20 feet of cable between the attic and the HR20 input.
  18. texasbrit

    texasbrit Well-Known Member

    Aug 9, 2006
    This whole thing issue is full of mis-information. Here are a few facts, and a few of my opinions which may or may not be correct.
    FACT: The BBC moves the signals coming from the dish in the b-band, which can't be received by the DirecTV receivers, and also overlaps the OTA band, into the a-band which can be received by the receivers and also does not overlap the OTA band.
    FACT: If you place a BBC before the first diplexer (where the OTA antenna is connected to the sat line), subject to other potential issues (see later) it will convert the signals before the diplexer and therefore leave the OTA band free for OTA signals. This means diplexing will now work OK
    FACT: The BBC is not designed to work outdoors.
    FACT: DirecTV does not recommend this approach to diplexing. They suggest you run an extra line instead.
    OPINION: I think DirecTV's non-recommendation of this approach is based on three issues. First, it's yet another part of the installation that the installer, or the user, can screw up. Second, the BBC was not specified to work at any distance from the receiver and DirecTV has not done any testing to show it will work in all instances. Third, running a separate cable moves the OTA completely away from the DirecTV system and reduces the number of ongoing issues.
    OPINION: There is no obvious reason why the BBC should not work with longer distances, any more than a multiswitch. The BBC presumably has to take power from the receiver, just like an LNB. It also takes signalling which uses the 22KHz tone generator in the receiver, same one as used by the multiswitch/dish to select the correct LNB.
    It converts the signals to a different frequency band and there will be some losses in the conversion but not enough to cause a problem unless your installation is already marginal.

    So my recommendation to anyone with OTA is to try the BBC relocation approach. If it does NOT work we would all like to hear about it, since everyone I know who is using it (including me) finds that it works just as you would expect from the theory.
  19. TreyS

    TreyS Legend

    Aug 22, 2006

    Thank you.

    I will add I finally got my second diplexer yesterday and hooked up everything like this diagram suggests and it worked like a charm the first try. I get 88-97 on 103(b) with both tuners, just like I did before I added the diplexers. I now have my locals via OTA!!

    Thank you dbstalk!!
  20. flipptyfloppity

    flipptyfloppity New Member

    Aug 20, 2007
    Personally, I think DTV doesn't want people to try this for two primary reasons:
    signal loss/reliability issues, as mentioned above.

    They don't want people to have non-standard installations, because at a later date, another installer will have to come in and upgrade the installation (perhaps even with a new homeowner who doesn't understand the layout) and they'll have trouble upgrading the setup. This goes back to the whole point why BB converters aren't just built into the receivers to start with, because if you have a BB in the path, SWM will not work.

    In a normal install, the BB converters are right there by the receiver. It's easy to know they're there, it's easy to remove them when upgrading the setup. In one of these types of installs, the BB converters are in a closet somewhere, and installer might have a bit more difficult finding them.

    Even though all the equipment is in your own house, I think DTV wants to treat the installation like cable companies do as much as possible. Make it all standardized so installers can can work on all of them as if they were the same as much as possible.

    When you get to your opinion below ("no obvious issues"), you're just plain missing "tilt" issues. That is, coax cables suffer increased signal loss per foot of cable at higher frequencies. By keeping the signal down in the low frequencies for as much of the cable run as possible, the issues with this tilt are minimized. This tilt is why you even have two cables to your receiver at all. If coax could carry these higher frequencies well, DTV would just stack all the signals on a single cable instead of having multiple cables.

    Unlike insertion loss (like a splitter or multiswitch), the tilt issue does operate differently in a system with short cable runs than one with long cable runs.
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