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6m mobile omni options

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by K3RW, Jun 19, 2020.

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  1. K3RW

    K3RW Ham Member QRZ Page

    Please don't ding me for posting an antenna question in the VHF forum. I never get any answers on VHF+ antennas there.

    I worked as a rover this latest VHF contest. I was stuck through numerous issues having to work 6m on my 2m 5/8s whip. It worked but only on 6m FM and FT8. SWR was sky-high on the SSB portion.

    A PAR OA-50 would have been far better, given omni pattern and horizontal polarity.

    A 6m 'big wheel' would be even better, but I only know of WiMo out of Europe that sells it. And almost 11ft in diameter, probably not /mobile legal on the road without flags (?). If thete is a North America seller, I don't know of one.

    But its partly because the OA-50 is a single dipole and the Big Wheel is 3 dipoles folded and phased. Its way bigger.

    Is there a 2 dipole design that is still omni and horizontal? For 6m, or any VHF+ band, that could be used /mobile?

    The PAR omni angles from 2m on up are just fine if I have the vertical space for stacking. Even 432 'big wheels' and other bands from places like The Olde Antenna Lab would work, stacked, phased, etc.

    Anything I can do for 6m? I don't know if a 6m two-dipole antenna (maybe a figure-8, Saturn ring type, back to back triangle, something else?) is out there. Mostly it would be great to have a bit of gain on 6m over the OA-50 while mobile. Its really not feasible to use the PAR stressed Moxon while mobile. Maybe there isn't something, but if there is a bent 2 dipole 6m omni (not crossed dipoles) it may actually be what I am looking for.
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't know of any. A 6m turnstile (nearly omni, horizontal) has no gain but they work quite well; however, one would be 9' across in both directions so not a very attractive solution for 6m.

    The OA-50 is a good antenna. No gain, but then anything with even a modest 3 dB gain would be bigger in some dimension. For 6m "roving," I've used the M2 1/2-wave horizontal loop (square halo) and it's worked fine. Not so many extra contacts would be made if it had 3 dB gain (which it doesn't).

    When roving, location and timing are more important. I haven't "roved" in a while, but when we did (I say "we" because I was usually part of a group of rovers who went in various directions) the team leader (N6NB) had already checked out dozens of viable locations to "park" and work well, and had them all mapped out with GPS coordinates for us. Making contacts in motion adds a bit to the score, but most of our scores (very high ones) resulted from driving to a grid, parking in a really good location, and making contacts for 1-2-3 hours and then driving to the next one, parking in another really good location, and doing the same until the whole contest period was used up.

    Another 3 dB gain on six would have likely netted almost zero "more" contacts. We all used gain antennas on the higher bands (144 MHz through 10.3 GHz), on rotators mounted on platforms strapped to our roofs via roof racks.
    K3RW likes this.
  3. K3RW

    K3RW Ham Member QRZ Page

    Great points. An omni would definitely not be my choice antenna, but in-motion I was surprised how many QSOs I made in-motion. Probably more a factor of local geography than maybe much else.

    If our grid corners weren't in wilderness areas, oceans, etc., I'd be curcling up high near them and doing much better. The Seattle crowd has it much easier because of it. Roving in SW Washington and anywhere in Oregon vs Puget Sound makes being competitive extremely difficult

    A 6m Big Wheel might be road legal. I just don't know of any US sellers of it, and the hub and tricky (for me) phasing are a bit beyond my homebrew ability I think. I don't know anyone who has one, but then again there are few rovers here who use omnis.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I've never even seen a 6m Big Wheel. 2m Big Wheels were quite popular and Cushcraft sold a lot of them. Now Wimo in Germany makes and sells them (for 2m), but I haven't seen a 6m model. It would be pretty huge.

    Re the roving, I don't know your area very well but would "think" I'd try to map out every hilltop anywhere in the various grids and try to find ways to access them by road. If it's like California (and probably is), many mountaintops will not be road accessible, anyway. Common to find communications towers, cell sites, Doppler weather RADAR radomes, water towers and all sorts of stuff on "visible" hilltops that either have gated private roads, or rocky and terrible "roads" that are best for llamas or mountain goats but not vehicles, and sometimes no road of any kind and they did all the work by landing helicopters in clearings and such. No joke. We have scores of hilltops in the 8500 to 14500' high range that are only "hike-in" and have no motor vehicle access purposely -- something CA has favored since John Muir's time.

    But, there are still good sites! You may have to research and experiment to find them.

    I know here, if not for Wayne Overbeck N6NB ("King of the Rovers"), a whole lot of very good "rover stops" would have gone completely undiscovered -- he's spent probably thousands of hours finding them, mapping them, figuring out ways to get to them.

    Good luck and have fun!
    K3RW likes this.
  5. K3RW

    K3RW Ham Member QRZ Page

    WiMo also sells the 6m Big Wheel. Its almost 11ft diameter. I asked and they said just the shipping to USA was $279!
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That actually seems about right.

    I ship stuff via FedEx International Economy and also DHL (DHL is based in Germany, and most there use it for international shipments) and shipping almost anything we manufacture, including fairly small stuff that weighs ten pounds, usually does cost in the $200-300 range to ship to most EU destinations.

    A 6m BW seems awfully large for a mobile setup.
  7. WA4SIX

    WA4SIX Ham Member QRZ Page

    What are you driving?
    In the late 90s, as a No-Code tech, I needed a ladder rack on the fiberglass topper of my Dakota pickup. Found some 1 1/2" aluminum handrail with T fittings. Had it set up in the driveway & ready to install. Measured the perimeter & did the math. Cut the width a bit & had a full wave loop as a ladder rack. Used a Q section of RG^. Worked all of Europe, back then on it. Of course, there were great conditions.

    K3RW likes this.

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