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Thread: Extending range of handheld radio on the ground

  1. #1

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    Happy Extending range of handheld radio on the ground

    As many of you not doubt do, we here in Southern California have a group of pilots who do missing man fly-bys at private and national cemeteries. Rather than flying over at a preset time we have a guy on the ground who coordinates the timing of the fly-by with the honor guard so the flight is overhead on the last note of "Taps"...well, that is what we are always shooting for. Communication from ground to air is therefore very important.

    I have a Vertex Standard Pro V handheld radio that I use to communicate with the flight. My job as the "ground guy" is to figure out when to give them the cue such that they fly-over at the end of "Taps". Holding for the flight is about 2nm away but due to the size of the orbit can put the aircraft as far as 3 or 4nm away. Very often I have found they cannot hear me which makes me think I need a more powerful radio, but then it occurred to me: Do I need a different radio or is the range of my handheld radio a function of the small "rubber ducky" antenna that came with it. If I get a bigger antenna, elevate it a few feet, and connect it to the post on the radio where the antenna screws in, would that be all I need?

    I have done a little reading and found the following which talks about placement of a marine VHF radio antenna placement:

    Square Root of Height Above Water (in feet) times 1.42 equals Range in Miles. Example: Highest point of your boat is 6 feet above water. You attach your 3-foot antenna at that point. The antenna is now 9 feet above water. The square root of 9 (which is 3) times 1.42 equals 4.26 miles.

    So it sounds like a suitable antenna and coaxial cable on a pole connected to my handheld radio sounds would do wonders for helping with ground to air communications.

    Have any of you already figured this out? Is there a particular antenna and cable you recommend?

  2. #2
    rwanttaja's Avatar
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    Been a long time since my antenna classes, but my first stab is that you're lacking radiative surface and a ground plane. You need a longer antenna, and a flat piece of metal to act as the ground plane.

    The standard antenna for VHF is one-quarter of the transmission wavelength...this comes to about 22 inches, in the middle of the aviation band (not the 36 inches of the marine radio). Ideally, the ground plane would be about the same distance across, but that's a pretty big disk.

    Then again, you're standing on the biggest darn ground plane in the world: the world.

    I'd try to rig up something with a long spike. Have the spike poke into the ground, connected to the braided part of the coax cable, and have the center conductor go to the bottom of a 22" rod.

    Here's an antenna I built into my Fly Baby. It's probably about 75% of what you'll need. Either supply a flat sheet of metal for a ground plane, or jam the aforementioned spike into the ground.

    http://www.bowersflybaby.com/stories/antenna.htm

    Alternately, they make magnetic mounts for CB antennas. Replace the CB whip with a 22" one, slap it on a car, and you're probably in business.

    Edit: Cable should be good ol' RG-58. Make sure you the the -58, not the -59 used in TV systems. I've got a writeup on installing the BNC connectors at:

    http://www.bowersflybaby.com/tech/bnc.html

    Ron Wanttaja

  3. #3
    Search the KitPlanes archives for an Aero ’lectrics column. Maybe a 2013 issue.
    I have seen several articles on just such portable cheap antenna for a hand held radio. I just don't know which issue.
    Bill

  4. #4

  5. #5
    FlyingRon's Avatar
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    The other Ron gives a description of a simple quarter wave that will work better than the rubber coated dummy load that comes with most handheld transceivers. Actually, I've got a Sporty's rig that has a somewhat longer flexible antenna that works REALLY well.

    If you build Ron's, you don't need a "disc" for the ground plane. You can use four counterpoise radials as shown here: http://www.diylightanimation.com/wik...ve_Antenna.pdf

    The idea of using a CB or HAM antenna mount is a good one. Already has the coax integrated into it (though you may have to find an appropriate adapter to mate it to your radio).

  6. #6

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    Or, if going for simple, cheap, and almost 2x the range of a rubber duckie for a handheld, recycle. I affixed a broken extendable transistor radio (?) antenna into a bnc connector that was missing a couple parts, marked the elements to show when it is extended to the midrange of the aircraft com band. Your mileage may vary.

  7. #7
    At VHF frequencies line of sight is everything. If the aircraft or you could be a little higher, it might make all the difference in the world. More transmit power also helps.

    Bob
    WB8NQW

  8. #8
    Derswede's Avatar
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    Bob has it right. One thing, you may try to use a "Yagi" stype antenna or a "cubical quad". Both are directional antennas that will "shoot" the radio signal in a more concentrated direction, which is basically focusing the power in that direction. Caveats are that you must have the antenna physically pointed towards the aircraft to gain any benefit. If you search "Yagi design" or "Quagi design" on the interwebs, several simple plans can be found. AL tube works great for such antennas. Befriend a couple of Hams and let them build it for you! I use a simple wire and PVC pipe Quagi on 144 mhz (just above airband frequencies) for portable communications and have achieved good communications at extended ranges with such antennas. Think I have $5 in my last one. Use a piece of PPVC pipe as a mast, and an old deck umbrella base to support it upright and you should be good. Don't know of amy (legal) amps for the airband, so you're limited to either an older mounted radio (12V King or similar, 15-20W output) instead of a 3-5W handheld or a better antenna. Hope you get it worked out!

    73 de N4ABA

    Derswede

  9. #9
    Jim Heffelfinger's Avatar
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    Actually as noted ANY antenna is better than a rubber ducky. I have seen way too many light aircraft using the rubber duck antenna attached to the transceiver inches away from lots of metal tubing. Lousy antenna further hampered by installation. In fact, one builder/pilot actually ran coax inside the wing and exited mid span to mount a ….wait for it… rubber ducky. He gained very little in improved propagation. Would have been better to just stick in a piece of welding rod. As noted – no ground plane needed at these frequencies. Here is one off the shelf that will be MUCH better. http://www.ebay.com/itm/AVIATION-AIRCRAFT-BAND-RADIO-TRANSCEIVER-MOBILE-ANTENNA-/252034998347 Here is another that is better served for a base station. http://www.jpole-antenna.com/shop/av...e-antenna/Note costs on these are reasonable. RST engineering Jim Weir has a system using ˝ “copper foil tape and a few ferrite beads to fashion low cost antennas. Something I have on the vertical fin on my wood aircraft. http://www.rst-engr.com/ As noted as well at these frequencies it is all line of sight and buildings, heavy tree cover, your body, etc will influence range. Additionally the orientation of the antenna (horizontal/vertical) will also affect the range. All handhelds operate at nearly the same power output so an antenna is your best range booster. I might also mention that the aircraft radios might have their squelch set too high to hear you.
    Derswede notes two types of antennas that would be impractical for you to walk around with as would a base station radio. hope this helps
    jim
    Last edited by Jim Heffelfinger; 01-18-2016 at 05:26 PM.

  10. #10
    Dana's Avatar
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    On my Kolb I had coax running down to a connector, to the original rubber ducky antenna on the bottom of the aircraft pointing straight down. I could hear people fine from many miles away, and people reported they could hear me fine, too, at least in the traffic pattern. But I did that to eliminate the RF feedback issues when using my Icom radio with a headset, not to improve propagation.

    OTOH, a friend of mine has a longer wire antenna very close to a frame tube on his powered parachute, and you can barely hear him a half mile away.

    BTW, please note that although aircraft radios no longer require an FCC station license, ground based transmitters still do. Not that enforcement is likely, but it's always good to know...
    Last edited by Dana; 01-18-2016 at 06:50 PM.

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