MFJ-1786 Super Hi-Q Loop for mobile van with mast

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG7LSD, Jun 7, 2019.

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  1. KG7LSD

    KG7LSD Ham Member QRZ Page

    so i have a few question, before i get to far into this and then find out...?
    and i'm needing some advice for my newest project.
    ive acquired a old tv station live truck. it has a raise-able 35' mast and it has a 360 deg azimuth and a 90 elevation pan/ tilt. (if i get it rebuilt with current steppers and electronics, no controller) but in any case i will have the mast that is deploy-able.

    Im not looking to spend much right now ( have a budget of about $100 or so mabe 200. )

    to get a better idea this is the gear i have available to use/ install as of now.

    kenwood hf transceiver
    yaesu hf +6 transceiver only temp install, to be replaced by ts-850sat when (repaired, after field day)
    moblie 2m/70cm'

    unknown screwdriver antenna (from ham swap)
    mfj superloop and tuner
    MFJ 1622 Apartment Antenna and tuner
    I also have buddy pole/ stick with all the bells
    J pole (if time allows to make)
    homebrew cobweb
    homebrew loop with 8-1400 pf 3kw vac cap (on list for stepper drive of vac cap)\
    **I do not have any antenna analyzers. (on the list to get but it's all money)**

    i also have on hand at lest 500' of rg8-x and various so-239's and pl-259's
    power is not an issue, have truck mounted genset, and probable Honda inverter gen, and shore power cabling.

    im looking to have a good solution for now / field day, and have something for future planing. as overtime, i'm sure this will keep get money sunk in to it.

    first off feed line. the way the mast is set now the feeds lines all coil around the mast and raise like a spring being stretched, inside a large pvc type coil jacket that im usure if i can pull the old cabling out of.
    for temp use i can always just run cable on each deploy. but for future would coiling it around the mast cause issues?

    next is the actual antenna's
    the mounts and mast are aluminium.

    i was thinking the loop as it is smaller, multi banded, and if the pan and tilt are up then i can rotate it and change the polarization from horizontal to vertical.

    the screwdriver antenna i was thinking as a future bumper install for a hf rig located/ or head located in the front in dash console.

    with what i have is this the best solution for now?
    what should i plan to do later down the road?
    issues, concerns, ideas, do's/ dont's....?

    my next question is grounding.
    more of a rf, and nosie question im thinking.
    i am going to run a copper ground that ties all equipment to a single common chassis ground.
    I am aware of the dangers of lighting, putting the mast in to power lines, is there anything else i need to take in consideration, plan for, eliminating stray rf and noise?

    also kinda falling inline with the last one.
    Im planning to make a few patch panels, and now, i'm not sure about termination. I was going to do panel mount soldered so-239's, but wondering if bulkheads or panel mount so-239 to so-239 would be better and worth the investment. again this question is based on noise and stray RF.

    sorry ill come back and proof read and fix, but for now off to work
  2. AK5B

    AK5B Ham Member QRZ Page

    Congratulations on your van acquisition; it would be the ideal rover vehicle if there ever was one! Built-in generator and 35-foot mast; cool.

    I like your idea of tilting your MFJ STL to take advantage of nulling and polarization shifts, but a vertical STL can perform quite well at minimal heights above ground (1 to 2 loop diameters is the rule of thumb). Horizontal or diagonal is where the height advantage will come into play, and the added height while vertical won't hurt, either.

    You might also want to consider a simple inverted V or fan dipole (perhaps 40/20/m as the higher bands are pretty dead nowadays) that would also be fine fed with RG8X looped around the mast in the spiral fashion your arrangement sort of calls for (it would be fine to suspend the coax straight down, too unless I'm missing something here) and this type of wire antenna would be simple to make and use once you're parked. The skies the limit when it comes to all the antenna possibilities but simple and resonant is often best, in my opinion.

    As for the screwdriver of unknown origin I'd suggest checking the Mobile Radio Forum here for great grounding and bonding advice from Alan, K0BG---he's the go-to guru on all that---HF mobile is not for sissies or mediocre installations (common mode abounds and RFI/QRN can be a substantial problem if not properly attended to. has the entire lowdown and do spend a lot of time reading that valuable information posted there---it's worth it.

    More to say but must go now, too.



    Do have fun with your mobile station---consider VHF/UHF roving in fine style once you are fully set up!:)

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