Need advice for multiple antenna placement on suv

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KG9ZTX, Jan 18, 2019.

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  1. KG9ZTX

    KG9ZTX Ham Member QRZ Page

    I have a 4x4 off road SUV and overland with various groups in areas where cell phones are of little to no value.
    Thus the need for radio communication such as HAM and GMRS & CB. Why GMRS & CB, because there are many in several groups who don’t wish to take the time to take a test for ham, or pay the license fee for GMRS.
    I do have a HaM, and GMRS license

    Sometimes our outings involve aircraft. This the need for aviation radios as well. Aviation is VHF.

    And of course we know GMRS is UHF.

    I also wish to have two Kenwood dual banded vhf/uhf ham mobile radios. (710ga, 71)

    While I have made use of the mod capability to use GMRS Channels 15-22 462mhz on the Kenwood 71 and 710 radios. All these radios create the need for 4 antenna.

    1 CB antenna,
    1 VHF Antenna for aviation radio
    2 vhf/uhf antennas for the Kenwood 710 and 71 radios

    So my mounting options are front steel bumper, or engine hood, somewhere on my 4’x7’ metal roof, or my back bumper/tire carrier. One other note, is that my vehicle is Kevlar coated. So hood mounts and roof mount magnetic mount antennas don’t provide an adequate ground plane. I do have a steel roof rack which is NOT coated and has provided a decent ground plane for my CB antenna. Roof rack is 3’x5’

    Recommendations on where to mount each of the antennas? As well which antennas you would consider for the uhf aviation, and the 2 for Kenwood radios? CB using a single timetable fiberglass “fire stick”

    Your advice is greatly appreciated.
  2. NH7RO

    NH7RO Ham Member QRZ Page

    GMRS and CB are acronyms. Ham is not.

    For mobile placement of antennas I suggest (Alan also moderates the Mobile Radio Forum here on the Zed, too)---your one-stop for all mobile questions, answers and info.
    W6KCS likes this.
  3. N7WR

    N7WR Subscriber QRZ Page

    The short answer to your antenna question--I have had very good results mounting multiple antennas (HF, VHF and UHF) on the roof rack on my SUV but ran a couple of ground straps from that roof rack to the frame to make that happen. However, there are a couple of issues. #1 Modifying your amateur radio transceivers to operate on GMRS frequencies is NOT legal. #2. Getting licensed to operate an aviation band radio except in an aircraft or FBO is not likely to happen.

    I would add that over the years I have built multiple Mobile Communications Units for public safety agencies with a dark to daylight assortment of radios on various services to include both aviation and marine band. Marine band--no problem. To get licensed for the aviation radio was not easy. It can be done but unless your vehicle is "sponsored" by a public safety agency which uses aircraft (for SAR missions for example) don't hold your breath.

    As far as placement of antennas I agree with looking at K0BG's site. Putting antennas for like bands as far from each other is a good idea. If multiple radios on the same band are in use at the same time you may have some receiver overload issues.
    Last edited: Jan 18, 2019
  4. W6KCS

    W6KCS Ham Member QRZ Page

    A few months ago I tested antenna placement on a vehicle with two VHF high band 1/4 waves (just above 2m). I noticed deep pattern notches of 10 dB or more in-line with the antennas when they were mounted 1/4 wave apart (18 inches), so I'd avoid installing two antennas 1/4 wave apart. In that case, the patterns weren't a problem at 15 or 25 inches, so that amount of deviation from 1/4 wave seemed like enough. More is obviously better for the coupling issues mentioned.
    NH7RO likes this.
  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Of course you will comply with FCC regs by never transitting on the GMRS band with non-certified equipment. Right? (it's a matter of honor, and an example you set for your friends).
    NH7RO likes this.
  6. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Changed Plans. Will post as separate topic for better visibility and discussion.

    Last edited: Jan 19, 2019
  7. AI3V

    AI3V Ham Member QRZ Page

    Up on the roof, as far apart as possible, and connected directly to the biggest chunk of metal you can.

    NH7RO likes this.
  8. AA7QQ

    AA7QQ Ham Member QRZ Page

    May I ask what vehicle you are using? I have not heard of a Kevlar constructed SUV.
    VHF & UHF antennas on the roof. CB antenna where ever you can, except for the spare tire carrier, as it will present proper ground plane issues.

    NH7RO and KA0HCP like this.
  9. NH7RO

    NH7RO Ham Member QRZ Page

    Bullet-proof, whatever it is.:D

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