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Thread: Question on communicating on HF from mountainous terrain

  1. #1

    Default Question on communicating on HF from mountainous terrain

    Hello All:
    Not yet a Ham operator, studying for my Technician license. I am interested in HF communication with my sailing buddies. I happen to live in the mountains of Utah! My questions are as follows:
    I have two possible antenna sites. The first is in a mountainous canyon with ridges on both sides approximately 1/2 mile away at least 400 feet above my homes elevation. I have the room and local permission to run an antenna 50-60 feet above my elevation. Will I be able to communicate long range on HF if my lowest angle of transmission is 15 degrees above the horizon?
    My second site is a hilltop at the 9,000 foot level but I still have higher terrain 2-7 miles away (by topo maps) that block the horizon over approximately 3 of 8 octants. In other words, I have wide views of the horizon down three separate canyons.
    At what angle does the HF transmission emit into the ionosphere for a "bounce?" Is it unrealistic from either of these sites to transmit HF long distance?
    Thanks in advance for your info.
    Gene

  2. #2

    Default

    Considering the HF bands (1-30MHz), as you get higher in frequency, less bending occurs for a given amount of F layer ionization and signals start to get lost to space. Shooting DX out 1200 miles will be difficult for you at any frequency when you are in a hole like that because the signals are hitting the ionosphere at high angle of incidence. That means you are sending everything above about 20MHz right into space and everything lower than 20MHz is making short ionospheric hops and will likely peter out before they get more than a hop or two away. Another problem is D-layer absorption on the lower frequencies which eats everything HF under about 10MHz during the day.

    40m is good for daytime because it can get thru the D layer (hoping the F layer is strong enough that day) and 80m is good for at night where there is no D layer as the wavelength is long enough to bend in a weak F layer.

    Look into something called MUF (maximum usable frequency) and a technique called NVIS. If you set up a good ground screen on the ground (rock is a horrible conductor) and a horizontal dipole just high enough not to zap anyone near the antenna (not much higher or it wont work), your signals will go mostly upward and you should be able to work a good 500 mile radius with a shorter hop, and perhaps the east coast on a second hop. As for reaching other countries from that canyon (outside those 3 directions you mentioned), ducting may be your only hope.

    Grab one of the countless free pdf files online on RF Propagation. You'll need to know that stuff if you expect to pass your general and get on HF.
    Last edited by brandon lind; Sat 18th Apr 2020 at 15:05.

  3. #3

    Join Date
    Nov 2019
    Location
    Ash Fork, Arizona
    Posts
    88

    Default

    I live at the 5,300 foot elevation in Northern Arizona. There are lots of hills and ridges around me, but I can get out pretty good. When it's the right time of day, and the propagation is good, I can talk to Europe. Sometimes the local landscape aids in the communications, sometimes not.

    The canyon with high ridges would probably cause communication problems, but the hill top would probably work well. You might start with a vertical antenna, with a good ground plane. That will provide you with the lowest angle radiation and will be a little easier to erect and maintain.

    Ionospheric bounce is a very common mode of communication, but it's difficult to predict. During the day you have a D, E, and two F layers. But during the night, the D and E layers go away and the two F layers combine. The F layer, at night, is useful for long distance communication. During the day, it's not very useful. But, during the day, the D layer can be used for NVIS (Near Vertical Incidence Skywave) operation. That could get you useful communication out to about 350 miles. But the angle is almost vertical. A low dipole can usually be operated NVIS on 80 and 40 Meters.

    If you only get a Technician license, you will be limiting your HF communications. Unless you are going to operate CW, a Technician only has SSB Voice privileges in the 10 Meter HF band. 10 Meters has been open lately, with good DX. But it's not very stable. 10 Meters is mostly a daylight band. As soon at the sun goes down, long distance communication dies out. I use to have a 10 Meter radio in my car. I only had a stubby antenna on the trunk lid, but it allowed me to talk from Arizona to the east coast, with only 5 watts of power. However, that isn't the norm.

    The lower frequency bands, like 40 or 20 Meters, would be better for reliable long distance communication. However, for access to the other HF bands (e.g. 80M, 40M, 20M, etc..), using SSB Voice, you will need a General or Extra Class license.

    And note that this is not a one way deal. To communicate with your friends, your friends will also need a license. It is illegal for a licensed Amateur Radio operator to communicate with a unlicensed station.

    When you go for your test, if you pass the Technician test, you will be able to take the General test. And, if you pass that test, you will be able to take the Extra test. It all depends on your preparation. You could walk in with nothing and walk out with an Extra. It's more common to do that, than it was 20 years ago.
    Martin, K7MEM
    http://www.k7mem.com
    Ash Fork, AZ - 60 miles from the Grand Canyon on Rt-66. Elevation 5,300 ft.

  4. #4

    Default Mountain Propagation

    Thanks for the info guys.
    i have a contact in a local club. Maybe I will study for all three tests.
    Cheers
    Gene

  5. #5

    Default

    technician class license only allows you to operate 10 meters phone - 10 meters isn't open right now, maybe in a couple of years.

    10 meters when it is open, even just a couple of watts, you can work around the world with nothing but a vertical.

    Predictions are that we are in a solar minimum that may last a couple of hundred years - surely longer than I will be alive.

    Your best bet will be to get at least a General Class License, that will allow you to operate all of the HF bands, just not all of the segments of those bands.

    Nothing is 100% sure thing with HF, one day it might go here, another day it goes there, another day it don't go anywhere at at..

    HF - other than having a good take off angle if you can get a mountaintop location, doesn't really matter for HF.

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