2m/70cm antenna for my RV with a rubber roof (no ground plane)

Discussion in 'On the Road' started by KC9OO, Jul 18, 2017.

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  1. VE3DDL

    VE3DDL Ham Member QRZ Page

    do not foget 13ft 6in to top must brigdes
     
    AI7PM likes this.
  2. KD4NFS

    KD4NFS Ham Member QRZ Page

    i hace a class c, about 30 ft long, and about 11 feet high. the standard size i guess. i have 3 antennas mounted on the ladder. a tarheel screwdriver, and two (2) jetstream jt-82b. ive tore off all 3 antennas. had the best luck using a tarheel 2. tunes up good, it seems to work. now the jt-82b...high swr, and i cant seem to get them down. tried a old cb whip cut down to about 78 inches. fine on 2 meters but not on 70cm. the jt-82b is about 17 inches long. any longer and its a battle with the trees. the trees usually win. i cant say for sure what will work. ive even tried to mounting antennas to the front fenders. no joy. high swr. the ladder is grounded well also. im open to suggestions. thanks
     
  3. KN7S

    KN7S Swapmeet Moderator Emeritus Volunteer Moderator Platinum Subscriber QRZ Page

    I don't know if this would work on your RV or not, but for decades I have used Diamond X-50's and X-30's with very good luck on several fiberglass boats. Since they use counterpoises there is no pressing need for a ground. Boats are pretty much all fiberglass so being able to ground you antenna is kinda hard. These antennas also hold up very well in the salt air marine environment.
     
    Last edited: Jun 12, 2018
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    When I installed 2-way radios (mostly CB) into cars/trucks/RVs in the 1980s, I used 2" wide aluminum tape w/ adhesive on the back. I laid it down in the form of an "X" under the antenna mount. I bought it from the local hardware/lumber emporium. I see it's still available from the big box stores for cheep.

    Another technique I saw a friend use on his Corvette was to "wallpaper" the (inside) surface w/ aluminum foil. He secured it using spray adhesive. On the outside, you'd probably want to use thicker foil (or thin sheet), and coat the surface to protect it from oxidation/damage.
     
  5. DL4NO

    DL4NO Ham Member QRZ Page

    Is a 1 m long antenna acceptable? Then try a "radial-less" antenna like the Diamond NR-760 or NR-770 series. They contain a matching network and feed the radiator at the current knot - on 2m and on 70cm.

    One problem is how you get the antenna cable into the vehicle. But no problem is the antenna mount: If nothing helps glue a magmount to the roof. The magnet itself is dead weight for you. But you need the rest of the magmount to distribute the torque on the roof.

    Such an antenna is far from a compromise: It is a stacked design and therefore radiates at a quite low elevation angle. I have compared my NR-770 to quarter-length radiators on a metal roof. The difference is quite a bit higher that the 2 dB on paper.
     
  6. KC3JEQ

    KC3JEQ Ham Member QRZ Page

    Thin piece of magnetic metal glued to the roof will work 2'X2'
     
  7. N8VIL

    N8VIL Premium Subscriber QRZ Page

    They make a NMO ground plane kit to use an NMO antenna as a base antenna. Possibly adapt that for use on your motorhome.
     
  8. NE6PG

    NE6PG Ham Member QRZ Page

    John build a dual band J-pole and attach it to the ladder side using a couple of saddle clamps, the J-pole needs no ground plane and you can get the plans off of American Radio's website. I have a telescoping aluminum pole, (came off of a McCloud float) that can extend above when parked. Cost is less than $25 to build. I use the sat jack to bring in the lead in so I didn't have to punch a hole. I made the saddle claps from home depot chain link fence clamps covered them in heat shrink, but you could use tool dip instead.
    Just use 70 ohm feed line.

    Pat NE6PG
     
  9. K6SAL

    K6SAL Premium Subscriber QRZ Page

    Dimond Antenna has a mobile antenna that is a half wave dipole stacked witch needs no ground has good gains i have one on my RV NR770HB
     
  10. AI7PM

    AI7PM Ham Member QRZ Page

    Eh,...no. It's a single element 1/2 wave on VHF, and collinear 5/8 over 5/8 on UHF. And yes, a good aplication for an RV or plane compromised installation.
    I re-learned a lot about antenna theory from this antenna.
     

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