2m/440 Dual Band Mobile Antenna

Discussion in 'Mobile Radio' started by KG4YBJ, Jan 30, 2014.

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  1. KG4YBJ

    KG4YBJ Ham Member QRZ Page

    I am in the process of purchasing a Dual Band mobile radio and I am looking for suggestions on a low profile antenna that I can attach to the fender of my truck. Does anyone have any suggestions?
     
  2. KS2G

    KS2G Subscriber QRZ Page

    Dustin,

    I assume that by "low profile" you mean as short as possible.
    That, of course, will mean that the antenna has less gain, and you'll have less range than with a longer antenna.

    Also, you don't say what kind of truck you have, and I'm not sure what you mean by "attach to the fender".
    Do you mean by drilling a hole in the sheet-metal to install an antenna mount?
    Or using some sort of "trunk lip" style mount to clip on without damaging the sheet metal?

    All that said, take a look at:

    Diamond NR72BNMO (13.8" -- NMO mount)
    http://www.diamondantenna.net/nr72bnmo.html

    Diamond SG7000A (18" -- UHF mount)
    http://www.diamondantenna.net/sg7000a.html

    I have had very good results for many years with a trunk-lip mounted Diamond NR770HB
    http://www.diamondantenna.net/nr770hb.html
    But that's a much longer (38") but also 50% higher gain.

    Good luck.

    73,
    Mel - KS2G
     
  3. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    We all have to be very careful about advertised gain figures without those sources citing what the gain is referenced to. Publishing gain figures which do not contain suffixes indicating whether the reference (common one) is either a dipole, or isotropic source, should be highly questioned. Even then, we need to be extra careful in reading the fine print there in. This is especially true when dealing with Pacific Rim antenna suppliers.
     
  4. KS2G

    KS2G Subscriber QRZ Page

    Yes, for sure.
    Always compare only isotropic-to-isotropic (dBi) or dipole-to-dipole (dBd) gain figures.
    And even then, be skeptical of comparing one manufacturer to another.
    But it's fairly safe to use whatever gain figures are provided to assess the relative performance of different antennas within a manufacturer's line.

    And, as I said, generally speaking for VHF/UHF dual-band mobile antennas ... longer antennas provide more gain than shorter antennas.

    73,
    Mel - KS2G
     
  5. AG6JU

    AG6JU Ham Member QRZ Page

  6. KS2G

    KS2G Subscriber QRZ Page

    Looks like their "knockoff" of the Diamond NR770.
     
  7. AG6JU

    AG6JU Ham Member QRZ Page

    yes, it is. Diamond NR770 is good antenna, it first came out in 1986 or so. it sold very well in Japan at that time.
    however, MFJ-1412 is $30, NR770 is $50. I used to use NR770 / MFJ-1412 for indoor antenna for long time, it hang from ceiling with push pin and string. because, it did not need good ground, I can just connect directly to coax to radio with RF choke between them. since, I lived on 2nd floor , it worked well.

     
  8. KG4YBJ

    KG4YBJ Ham Member QRZ Page

    Sorry it took so long to respond. I purchased a vehicle specific fender mount from Pro-Fit. My question is I purchased a Comet B-10 NMO in 12" to keep with a stealth look of my truck and I can receive channels well but it doesnt seem like I am getting out on my repeater channels. I am new to my area so I dont really know anyone that I can test with. Even with the antenna attached to a metal fender mount and attached to the factory fender of my truck do I still need to have it grounded?

    Here is the antenna I purchased. http://www.gigaparts.com/Product-Lines/VHF-UHF-Dualband-Antennas/Comet-Antennas-B-10NMO.html
     
  9. KS2G

    KS2G Subscriber QRZ Page

    Doesn't sound like an antenna problem.

    1) Have you checked to see if your radio is transmitting (e.g. putting a watt meter on it)?

    2) If you're getting rf out of the rig, have you properly set the transmit/receive offset and/or subaudible tone ("PL") for the repeaters?

    3) How far are you from the repeater sites and how much power are your running? That is, are you "within range" or the machines for what you're running? Since most repeaters are transmitting through antennas in high places (on mountain tops, on tall buildings, on big towers) it's not unusual to be able to "hear" a repeater that you can't "reach" because you're not running sufficient power (for example, a 5-watt handie-talkie).
     
  10. KG4YBJ

    KG4YBJ Ham Member QRZ Page

    Thanks for the reply. I am running full power (I believe 50w). I actually did make contact with a few folks the other night so I do know that I am transmitting. Our repeater is having some static issues but that is being fixed so the audio is clear most times but at points it starts to static during transmission. I may have to get a taller antenna tho.
     
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