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Can a beam overcome terrain like this?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K2HNL, Nov 13, 2017 at 12:16 PM.

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  1. K2HNL

    K2HNL Ham Member QRZ Page

    I moved back in May and can no longer access my favorite repeater and stay in touch with old friends. I just put up a 2m ground plane that I built, and though it seems to work well it isn't good enough. Using 5W I can access the repeater which is about 55 miles away, but what I hear is largely static. If someone is talking I can make out a few words here and there. The ground plane is at about 20-25ft, and I could probably get it about 10ft higher, but is that really going to make a difference? How bout a beam?

    I'm guessing I know the answer to both of those questions but I ask those with more knowledge than me. Will either of these solutions give any significant chance of hearing the repeater better? I am providing the cross section of the distance so you can see what is in the way. Screenshot_20171112-221013.jpg

    Also I know that from the location shown in the plot below I can get into the repeater with a rubber duck and a couple watts. Just for reference.
    Screenshot_20171112-221255.jpg
    Thank you.
     
  2. AF7TS

    AF7TS Ham Member QRZ Page

    It is clear from your plots that a 'direct line of sight' is not possible. Yet the fact is that you can hear something from this repeater and can hit the repeater with poor signal quality.

    This suggests that there is some sort of path between you and the repeater, eg because of diffraction or reflection.

    Based on a hunch, not direct experience:
    In this case, using a beam may actually work; not necessarily pointed directly at the repeater but instead pointed in the direction of maximum signal strength.

    This may change depending on season and things like foliage cover.

    73
    Jon
    AF7TS
     
    KR4IS, NH7RO and N0TZU like this.
  3. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    55 miles isn't very far even for an obstructed path.

    VHF propagates waaaaaay beyond line of sight all the time.

    I'm at 850' asl and to my north is a hill that's 3650' high and four miles away; to my south is a hill that's 2200' high and four miles away; to my west is a hill that's 2300' high and three miles away; and to my east are hills well over 6000' high and about 15 miles away. Actually, the entire San Gabriel range, which runs from about 2500' to just over 10,000 feet asl runs to my NE through to E so that entire direction should be badly obstructed for VHF.

    Yet, I work stations on 2m who are 50-100 miles away to the NE on 2m all the time, on 146.52 MHz simplex, so no repeaters are involved.

    And working simplex stations in San Diego, 120 miles to my SE, is pretty easy if they're set up about the same as I am.

    Takes a reasonably good antenna. I'm using a 2-element vertical omni colinear (homebrew) that's 10' tall base to tip, with radials at the base, and it's up about 30 feet above ground at the base. However, when I had the same antenna at the top of my tower so it was up 68 feet above ground at its base, that was a lot better. Key words: A LOT. When it was up there, I could work mobiles on simplex up in Santa Barbara, ~75 miles to my WNW, over a very obstructed path with Chatsworth Peak (2300' and quite close) exactly in the way.

    I'm "line of sight" to very little from here, but using 100W output power and a decent antenna elevated above the local clutter (other houses and such) makes my "simplex" 2m working range on FM about a 50-75 mile radius circle. My colinear probably has 3 dBd gain.

    Terrain around here is "rugged."

    If you want to work mostly just "one" repeater, a beam is a good idea and as already suggested, aim the beam for best received signal, which may not necessarily be in the actual direction of the repeater.
     
    NH7RO likes this.
  4. KL1T

    KL1T Ham Member QRZ Page

    I'll be "That Guy" - If you just want to keep in contact with friends, is Echolink an option? It's not "real radio" but neither is a repeater.
     
  5. NH7RO

    NH7RO Ham Member QRZ Page

    I'd check out Kent Brittain's (WA5VJB) Cheap Yagi site; you could easily build a six element wood-and-wire Yagi for a few bucks and see how well it works out for you before spending $$$ on a tall collinear or commercial Yagi.

    I bet that would make a big difference and even better if you can go up another 10 feet or more, too.

    73,

    Jeff
     
  6. K2HNL

    K2HNL Ham Member QRZ Page

    Unfortunately the repeater no longer has Echolink.


    As far as yagi's go, I have an arrow handheld dual band I need for satellite work. I failed to mentioned I climbed up on a step ladder about 16ft high and had about the same results as the ground plane. I'm not sure that model has enough gain to be a good test subject. Does this in itself disprove a yagi being the solution?

    What are the chances another 5-10ft higher on the ground plane is going to make any difference?

    Thank you for all the replies!
     
  7. NH7RO

    NH7RO Ham Member QRZ Page

    I suspect that 5-10 more on the GP will make little difference---especially if you can barely make out a word her or there most of the time---I'd stack a pair of cheap Yagis and go for broke...
     
  8. K8JD

    K8JD Ham Member QRZ Page

    If there is any signal at all, the gain of a long Yagi may bring it up to a decent level. Yes ! aim it at the best signal, even if it is a reflection from an object not directly toward the source.
     
  9. N2SUB

    N2SUB XML Subscriber QRZ Page

    Get a beam and work the repeater long-path
     
  10. AI3V

    AI3V Ham Member QRZ Page

    So you get mostly static.

    That's good, we have a baseline to work with re your ground plane.

    You are going to want at least 10 more db of antenna gain.

    So pick a beam.

    Rege
     

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