Alpha Moto Mobile antenna

Discussion in 'Mobile Radio Systems' started by ZL1MHS, Sep 22, 2014.

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  1. ZL1MHS

    ZL1MHS XML Subscriber QRZ Page

    Have read good things about this antenna and have sent two or three messages to the ARS store asking the following question but as of yet have had no reply, so was wondering if anybody here could answer my questions re this antenna.
    Obviously from reading the reviews the Alpha Moto mobile antenna system works very well mobile and I am considering buying one.. however I was wondering if it would be possible to use it also in a portable configuration possibly onto of a portable mast or tripod and also possible to enhance this by running ground radials from the base of the mobile antenna itself just below the coil where the antenna mount is?
    Anybody tried this or has any thoughts please?
    Many thanks
    Kevin
    ZL1MHS
     
  2. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    I wouldn't buy one on a bet!

    There have been other mobile antennas with basically the same "supposed" attributes, and all have fallen short. Where the base contains a 4:1 or 6:1 balun, 50Ω resistor, or some other "magic" circuitry, it all boils down to snake oil.

    Length matters. Radiation resistance, hence efficiency (all else being equal), is a square function. In other words, a 9 foot antenna will have twice the efficiency of a 6 foot one. All mobile antennas need to be installed with as much metal mass under them as possible. When they say they don't need that, then common mode is a real issue. If they don't have common mode, it just means they're a dummy load on a stick!

    Suit yourself, but I wouldn't even think twice.
     
  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Oh my, loads of snake oil weasel words....


     
  4. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Snake oil indeed. The answer you received on eham.net is typical, and so are the reviews.

    A few years back, there was a company called Maxx-Com. Their antenna was nothing more than a 50 ohm resistor with elements tied to each end. They even made a mobile version. Adding insult to injury, was the fact they imbedded used circuit boards into the potting mixture, just in case someone x-rayed the unit. The ARRL did just that, and then unpotted one replete with photos. The reviews for that antenna, incidentally, were 4.5 out of 5. Go figure!

    Today, both Diamond and Comet make similar antennas. One uses a 50 ohms resistor, the other a 6:1 transformer. Depending on the frequency in question, they average about 30 dB down, to over 50 dB down. Yet both models garner rave reviews. This sure puts credence in the old adage, Caveat Emptor!
     
  5. WA9WVX

    WA9WVX Ham Member QRZ Page

    Or as P.T. Barnum once said, "There's a sucker born every minute." This is why the newer ham operators need our honest help as Elmers. Can you take care of the next op in line as I'm busy screwing a Bird Dummy Load on to my transceiver to improve the signal to noise ratio. WOW! No noise ... Hmmm, no signals either. lol
     
  6. ZL1MHS

    ZL1MHS XML Subscriber QRZ Page

    Oh my i seemed to have triggered some cynicism on this matter. Cant understand why there hasn't been one negative remark written or posted about this antenna either here or on eham or elsewhere on the net apart from the above.... ???? Have to wonder why really???
     
  7. N0TES

    N0TES Ham Member QRZ Page

    Reply that was provided on eHam

    Reply that was provided on eHam
    image.jpg
     
  8. KD6RF

    KD6RF XML Subscriber QRZ Page

    Generally Kevin, those who are antenna theory wonks, or those with more experience. are not going to buy such an antenna in the first place - so there's a whole chunk of the ham radio community that isn't going to give negative reviews to an inefficient antenna (especially on the lower bands), simply because with so many better choices out there (including home-brew) we would never own one in the first place.

    Why on earth would I spend $$$ on an antenna I know is going to be inefficient? Hence, there is no negative review from KD6RF...

    Customer testimonials and reviews are generally unreliable for the reason above, and because those who do buy such products usually don't have the time, inclination, or equipment to do the real-time co-located a/b on-air testing (or have access to the facilities and equipment to do absolute calibrated field strength measurements) that would reveal the flaws and inefficiencies of the resistively loaded and/or lossy magnetics type of antennas that we are talking about here.


    So we are left with reviews by those who make a few contacts and are happy.

    Which is just fine.

    But anecdotal "evidence" about wet-noodle radiators shouldn't be confused with real data, which will show gross inefficiency, especially on the lower frequencies.
     
    Last edited: Sep 24, 2014
  9. KH6AQ

    KH6AQ Ham Member QRZ Page

    http://alphaantenna.com/images/moto/Alpha MOTO All Bands ref to antenna.png

    The graph at this link above shows the VSWR (red line). The link below is the user manual. The antenna has no provisions for tuning and presents a VSWR of roughly 5:1 from 40 to 15 meter bands. The information at the two links tell us that the antenna uses a lossy "matching" circuit and the antenna will exhibit low efficiency compared to even Hamstick-like antennas. http://alphaantenna.com/pdf/Alpha_Antenna_MOTO_User_Guide.pdf


    This antenna, like all small antennas, follows Dave's law of small antennas.

    Small
    Efficient
    Wideband

    Pick any two
     
  10. N0TES

    N0TES Ham Member QRZ Page

    Antenna tuners hide the issues associated with using an inefficient shortened whip on mobile HF installations. The Tuning Coils on many mobile HF antennas are simply a tuning mechanism for an inefficient shortened whip. All mobile HF antennas are hiding the same issue (an inefficient shortened whip). Remember to do as K0BG says, and keep as much metal mass directly under the antenna as possible!
    The attached image shows the lengths of just a few MULTI-BAND MOBILE HF ANTENNAS.
    image.jpg
     
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