"Frequency Assignment" .. UHF .. and 180 degree opposites.

Discussion in 'DirecTV TiVo Powered PVRs & Receivers' started by sloan, Jul 14, 2006.

  1. sloan

    sloan New Member

    Feb 13, 2003
    Raleigh, NC


    I just used
    (a great link I found here by searching).

    I'm trying to make sure I've got the concept correct, before going out and getting more equipment (antennas).

    In my area, I have a channel 5 .. VHF .. for analog.
    Using the web site above, I find
    the frequency assignment for 5.1 is 53.
    Does that mean I should buy equipment to try and reach
    UHF 53... if I'm trying to get 5.1 digital station?
    (I just want to make sure of my basics...)

    If non of my digital stations are listed as vhf ... I guess I can get an uhf only antenna.

    SECOND Question:
    I am lucky, in that most of the stations are in the same direction.
    (Around 115 degrees)

    I have one "lone wolf" out there, pbs. Here is my data.

    pbs .. 4.1 ... 300° .... 59 frequency

    cbs .. 5.1 ... 115° .... 53 freq
    fox .. 50.1 ... 115° .... 49 freq
    nbc .. 17.1 ... 115° .... 55 freq
    wb .. 22.1 ... 115° .... 57 freq
    upn .. 28.1 ... 115° .... 27 freq

    abc .. 11.1 ... 118° .... 52 freq

    Can I get two directional UHF'ers ... and point them in opposite directions?
    I'm thinking that since they're so far apart (almost a perfect 180degrees), that I should be ok.

    Thanks for any info.

    Right now I have one of these antennas, in case that matters.
  2. Jason T

    Jason T New Member

    Dec 21, 2001
    1)All the frequencies you listed are in the UHF band, so all you need are UHF capable antennas to get your digital channels. And yes, you tune to 53 to get your 5-1 channel.

    2)From what I've read, you can not just take two antennas and point them in different directions. Your two antennas will be picking up some of the same signals at slightly different times, and that will cause problems. I had a similar problem to yours, and I solved it with a Join-Tenna (bought it here). This device gives you two inputs - one that accepts everything but a single frequency, and another that only accepts the single frequency. The two signals are then combined into one output. So in your case, you would purchase a Join-Tenna for channel 59.

    One warning - as I understand it is that you still can have problems with frequencies that are real close to each other. From what I've read, you can't just block or allow a specific frequency, but instead there is a rolloff, a curve, as to what frequency is allowed or blocked. In my case the channel I needed was pretty much by itself. In your case, your PBS is close to your WB, so this device may or may not work well for you. I didn't look at your distances, but I would first try the single antenna and see if you can find a comprimise that will get all your channels. If not, then I would get a second antenna and try a solution like the Join-Tenna.
  3. lynesjc

    lynesjc New Member

    Feb 10, 2005
    The CM 4221 (4-bay, bow-tie design) isn't very directional. You didn't list your distances, but if the PBS isn't too far away, you might be able to pick it up regardless.
  4. sloan

    sloan New Member

    Feb 13, 2003
    Raleigh, NC
    Ok.. Now it makes sense.

    I found this tutorial:


    Less than 15 miles for the non PBS stations.
    PBS is about 35 miles. But there is not a compromise location (where I point the antenna).
    (Even with my analog stuff, pbs for me likes special directional treatment).

    Thanks for the tip about the "rollover", and the WB/PBS closeness.

    I'll also check the CM 4221 ....

    But a Join-Tenna for channel 59 looks like the ticket.

    THANKS for the info! (My confidence in the project just shot up 200%)
  5. mdh333

    mdh333 New Member

    Dec 9, 2002
    St Pete, FL


    OK - I will admit that I don't know anything about all this frequency stuff...but....

    Here is what antennaweb.org told me about my house (sorry if its hard to read)

    DTV Antenna
    Type Call Sign Channel Network City State Live
    Date Compass
    Orientation Miles
    From Frequency
    * yellow - uhf WTOG-DT 44.1 UPN ST. PETERSBURG FL 81° 23.2 59
    * yellow - uhf WTTA-DT 38.1 WB ST. PETERSBURG FL 82° 23.1 57
    * yellow - uhf WMOR-DT 32.1 IND LAKELAND FL 86° 23.0 19
    * yellow - uhf WFTS-DT 28.1 ABC TAMPA FL 82° 23.2 29
    * yellow - uhf WEDU-DT 3.1 PBS TAMPA FL 81° 23.2 54
    * yellow - uhf WTSP-DT 10.1 CBS ST. PETERSBURG FL 348° 29.1 24
    * yellow - uhf WFTT-DT 50.1 TFA TAMPA FL 82° 23.1 47
    * green - vhf WFLA-DT 8.1 NBC TAMPA FL 82° 23.1 7
    * green - uhf WCLF-DT 22.1 CTN CLEARWATER FL 86° 23.0 21
    * green - uhf WXPX-DT 66.1 i BRADENTON FL 86° 23.0 42
    * red - vhf WTVT-DT 13.1 FOX TAMPA FL 87° 24.2 12
    * red - uhf WUSF-DT 16.1 PBS TAMPA FL 81° 23.2 34
    * blue - uhf WVEA-DT 25.1 UNI VENICE FL 86° 23.0 25

    My frequencies required are all over the map, and I need mostly UHF channels, but some VHF.

    I just got the DTV free installed antenna, the one that connects to the pole on the dish. I don't have a picture, but the model # is DTV2BUHF

    I can now get every station on that list except CBS (which is coming from a totally different direction)

    Before you invest in multiple antennas, join them together, and whatever else....you might want to try something simple and see what you get.

    Also - before I had this install, I just had some 15 year old rabbit ears connected to my Tivo, and I got a few stations just by moving things around a bit. This might be another good test for you (since you're only 16 miles away) to see how complicated a setup you might need.
  6. brott

    brott at redh dot com

    Feb 23, 2001
    Pleasanton, CA
    Oh, to be in Florida without the hills :). I had to give up my antenna altogether as I could not get a reliable signal. I'm only 35 miles from the tower, but the big hulking mountain about 3 miles from my house blocks a lot of the signal. The changing weather also plays a factor in the signal quality. It works just enough to make you want to try some more, but after a year of toying with it, I've officially given up. I'll swith over to the new MPEG4 DVR when it becomes available.
  7. mdh333

    mdh333 New Member

    Dec 9, 2002
    St Pete, FL
    Yeah - the 23 mile distance for me is pretty much just across water...I can't complain.

    But you have a lot better beers out in Pleasanton that we do (says an ex-PSFT employee)
  8. Lee L

    Lee L Got Basenji?

    Oct 1, 2003
    Morrisville, NC
    Sloan, you might just try an omnidirectional antenna. I am in Morrisville and I can pick up everything fine with a crappy Terk TV-50 that is close to 10 years old, mounted in the attic. PBS comes in fine.
  9. mw1597

    mw1597 New Member

    Oct 8, 2004
    The CM-4221 antenna would likely work since your PBS is about 180 from the other stations. The CM-4221 picks up stations from both the front and back sides. I have the CM-4221 on a rotator and when I rotate it 180 from the tower the signal strength only drops about 3%. I think this is your most cost effective solution. Every antenna installation is unique so there is no guarantee.
  10. reh523

    reh523 New Member

    Feb 27, 2006
    Phoenix, AZ
    Ditto great antenna.............
  11. TyroneShoes

    TyroneShoes HD evangelist

    Sep 6, 2004
    If you check hdtvprimer.com, which shows the polar plot of many antennae, you can see graphically that the 4221 rejects signal from the backside very significantly. In fact, one of the reasons that this antenna is good for ATSC reception is its ability to do this. Antennae for difficult situational reception of ATSC should have a good front-to-back ratio, meaning that they should not receive off the back side very well at all, which the 4228 and 4221 do not do well specificaly because of their significant f-t-b ratio.

    You may only see a 3% difference in your anecdotal situation, but that does not at all mean a difference of 3% in ability to pick up the signal or reject interference. For instance, in a good antenna system non-fringe stations can go to 1/4 power for maintenance, and the signal quality reading will not drop at all, due to the nature of how digital signals are measured, which is based not on carrier power, but on successful decoding of aggregate bits. IOW, if you are decoding enough bits properly, more signal level will not show any improvement in the reading, and a 3% drop in SQR can reflect as much as an 80% drop in received carrier power in certain situations, even though reception itself may not appear to be affected. There is no linear relationship between those readings and fade margin, signal level, signal to noise, signal to interference, or picture quality that can be inferred.

    While the CM antennae are the best choice for a situation where multipath interference is high, that does not make them the best choice or the only choice for every situation. A simple dipole or even a omni can work in certain applications. In sloan's situation, I would recommend a yagi instead, because many of them do indeed pick up off the back side, which is only a problem if interference comes from that direction. I would get a yagi with high gain and high directionality, and point the back side directly at the off-axis channel, with the front beam then falling approximately in line with the cluster of remaining channels. That would give a tight figure-8 pickup pattern, and all relevant vectors would then fall within either beam.
  12. sloan

    sloan New Member

    Feb 13, 2003
    Raleigh, NC

    I think what I'm going to do is get a CM-4221.

    I'll put it up. And if it works 180, then I'll stick with it.

    If not, then I have a good "<all>" (all except pbs) antenna, and I can wire in the join-tenna for the PBS, and use my element antenna I already have for that.

    Lee, thanks for the omni tip. I borrowed one and tried that, I seem to be in some weird hole or something over here N of Lake Wheeler.
    To get PBS (analog), I've got to point my vhf antenna (decent sized one) right at chapelhill (or s durham?) to get it. It may be a huge electric line about 2 miles down the road, or I'm "sunken" a little bit, I don't know. PBS is a needy child, when it comes to antenna resources for me.

    Thanks for all the advice, I'm definately more educated now.

    Hopefully, I'll remember to post the final solution on this one.


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