ENG News Live Truck, Ham conversion w/35 foot mast

Discussion in 'Mobile Radio Systems' started by KG7LSD, Jun 7, 2019.

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  1. KG7LSD

    KG7LSD Ham Member QRZ Page

    so i have a few questions, before i get to far into this and then find out...?

    i'm needing some advice for my newest project.
    i've 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, and controller) but in any case i will have the mast that is deploy-able.

    I'm not looking to spend much right now ( have a budget of about $100 or so maybe 200. )

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

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

    antennas:
    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. (its 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, truckn has mounted genset, and i have probable Honda inverter gen,that will run everything but the truck a/c, and i have the 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. I would like to have a future plan in mind as i'll like to do all my cabling now, wile the racks are empty and accessible.

    first off feed line. the way the mast is set now the feeds lines and cabling all coil around the mast and raise like a spring being stretched, inside a large pvc type coil jacket, i'm unsure if i can pull the old cabling out of it, to reuse pvc jacket.

    for temp use i can always just run cable on each deploy. but for future and for the Finnish install, can i coil the cable around the mast spring like it is now? do i need to install in a protective pvc hose/tube?
    the mast and mounting are all aluminium, pan and tilt are the only ferrous metal on mount.

    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. pulse i'm thinking that in the horizontal position it would be simpler to make a stowed mount, then installing the antenna every time before use. this is the same idea i have with the Jpole.

    the screwdriver antenna i was thinking as a future bumper install for a hf rig with a head that i can use from the dash or the back of the van.

    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, and putting the mast in to power lines, (look up and live) is there
    anything else i need to take in consideration, plan for, eliminating stray rf and noise?

    Im hoping to have two radios running to start, one main off the mast installed antenna, and the other some other random antenna through the outside patch panel antenna in .

    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.

    any help and pointers would be very helpful.
     
  2. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    You really shouldn't use the chassis for a ground return for the power. Grounding them otherwise is perhaps okay, but do them one (piece of gear) at a time. Doing it this way, will help you reduce the chance for a ground loop.
     
  3. AA5CT

    AA5CT Ham Member QRZ Page

    If the rig can display output power *and* SWR than you can forgo an antenna analyzer - I made do without one and did multiple tune-up tests on a number of different loops for six years before buying an AA.
     
  4. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Remember. The built-in SWR bridge, measures the impedance at the RADIO end of the coax. Done correctly, an antenna analyzer measures it at the ANTENNA end, where it should be measured.
     
  5. AA5CT

    AA5CT Ham Member QRZ Page

    Do you know what a "constant SWR circle" is?

    They are found on Smith charts. Extra points if you know what this means.

    Extra point question: Is there an "SWR circle" associated with a 50+j0 Ohm load at the antenna end of the coaxial cable?
     
  6. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    In all due respect Jim... You should know exactly what I was implying, rather than implying I don't!
     
  7. AA5CT

    AA5CT Ham Member QRZ Page

    Well, we should all known that if an antenna is "matched", it matters not the length of the coax with respect to SWR.

    And we should all know that if an antenna is mismatched, the same SWR will measured at the antenna end of the coaxial cable as at the radio end of the cable, but the impedance, of course, the x+-jy value, will change according to the length of the cable.

    But, unless you're doing numerical computations to design specific matching networks, the average ham (as do I for the most part) only concerns themselves with the SWR value and, of course, it matters not where the SWR measurement is made.

    .

    * Neglecting line loss and assuming Z0 of coax=50 Ohms.
     
  8. W9GB

    W9GB Ham Member QRZ Page

    Highly likely the telescoping mast requires routine maintenance,
    since service may not have been performed before sale.


    The Will-Burt Company, headquartered in Orrville, Ohio, USA, is the world’s premier manufacturer of mobile telescoping masts, towers and pan-tilt positioners.

    [​IMG]

    The Will-Burt company has been the number one provider of elevation solutions (mobile TV van masts) for the broadcast industry for several years.
    https://www.willburt.com/products/telescopic-masts/

    Will Burt Service Centers across North America
    https://www.willburt.com/contact-will-burt/us-service-center/

    The Will-Burt Company
    401 Collins Blvd
    Orrville, OH 44667
    United States
     
    Last edited: Jun 8, 2019
    WA7PRC likes this.
  9. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, but who says the antenna's matched? The truth is, almost all 2 meter/70 cm antennas are a compromise, even a Larsen. Three and four band ones are even worse. Adding insult, internal SWR bridges are notoriously inaccurate, and seldom linear in response.
     
    AI3V likes this.
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    For starters. I would replace the O-rings on the mast.

    Then worry about what antennas to put on it.

    Bad O-Rings let water in.
     
    WA7PRC and AD5HR like this.

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