Estimating distance for VHF

Discussion in 'General Technical Questions and Answers' started by K0HBL, Apr 14, 2020.

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  1. K0HBL

    K0HBL Ham Member QRZ Page

    I am working on a project and looking for a bit of advise as I am not an expert on this. I have two stations I am trying to communicate that are 76 miles between each other with no repeater between them. One site is several hundred feet in elevation higher with not much terrain in between. I did a line of sight calculation based on elevation and the antenna heights I am looking at and found I can get a direct line of sight. With a directional style antenna, thoughts on communicating between the two sights on 2M or even 6M?

    Thank you
     
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    If the path is truly LOS, then no problems. I routinely talk 200mi while hamming on 2m from my Cessna. I run ~25W with just an omni 19inch whip on the belly of the aircraft. Ditto leaving an APRS track from the airplane in my Avatar; that transmitter is a 1W HT with just a 19" whip.
     
  3. W9AFB

    W9AFB Ham Member QRZ Page

    If both stations have yagi antennas mounted outside above other structures, it may be possible. Especially using 6M SSB. You might try some of the modeling programs out there to help out. I haven't used this in a while, but try https://www.ve2dbe.com/rmonline_s.asp
     
    M6TZR likes this.
  4. KD4UPL

    KD4UPL Ham Member QRZ Page

    76 miles shouldn't be any problem if there's nothing in between. A good base antenna and rig at a good location can usually be heard over 100 miles away.
     
    WQ4G likes this.
  5. F5VHZ

    F5VHZ Ham Member QRZ Page

    Definatly go vhf, you can either go for a high gain omni directional design giving added coverage area, or use a simple small beam. You say two stations, im thinking you mean you and one other station. If you are new to ham then its likley you will soon discover others you want to communicate with and this might even include mobiles.
    An easy and cheap startup that would be very effective would be to get a cheap tv rotor (channel master) type and mount a 9el vhf antenna. You can either buy one from tonna or knock up one from any number of designs, hb9cv for example.
    If you do decide to mount a beam on a pole with no rotor, you could make it so that you can loosen a clamp and rotate by hand, just to get you started. I did exactly that, and it worked fine but i soon added a cheap tv rotor that i modded to give a true direction indicator.
     
  6. AI3V

    AI3V Ham Member QRZ Page

    Considering most amateur satellites transmit less than a watt to a quarter wavelength whip and can be received on a handheld with a quarter wavelength whip at dustances greater than a thousand miles,

    If you really have a los path you will have zero issues.

    Search "link budget calculator" for precise numbers.

    Rege
     
  7. AD4U

    AD4U Ham Member QRZ Page

    If everything is the same, usually SSB will cover more distance than FM. FM is not a weak signal mode.

    Dick AD4U
     
  8. W0KDT

    W0KDT XML Subscriber QRZ Page

  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd agree 76 miles is a cinch on VHF if it's a LOS path.

    But a 76 mile LOS path means one or both stations must be seriously high!

    From my most local VHF-UHF "contesting" perch at Saddle Peak here (el. 2830' asl), just parked in my van with a 5/8 2m whip atop the van I work stations 100 miles away who are using practically nothing for an antenna on 2m, and low power (25W) on both ends, if they're in a very clear direction that is LOS or close to it. And that's FM simplex. SSB would provide an advantage, but for that distance and an LOS path shouldn't be necessary at all.
     
    WQ4G likes this.
  10. W1VT

    W1VT Ham Member QRZ Page

    It is 83 miles LOS between Mt Burke and Mt Ascutney. No problem making the path on 2M with an old Icom 2AT and the stock rubber duck antenna!
     

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