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3/8 thread or NMO ???

Discussion in 'Mobile Radio Systems' started by N4MTB, Jul 3, 2018.

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  1. N4MTB

    N4MTB Premium Subscriber QRZ Page

    I have one of those little "stinger" AM/FM antennas that I'd like to remove and install a VHF/UHF antenna with. I don't mind making the hole larger. What should I get the 3/8 thread or NMO? I haven't decided on an antenna yet so any suggestions are welcome.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    A NMO makes it easy to use different antennas and may be a bit stronger.

    In the center of the roof is the best placement.
  3. W9GB

    W9GB Ham Member QRZ Page

    Wider selection of Antennas with NMO mount.
    3/8” x 24 was popular for mobile HF antennas.

    Larsen / Pulse Electronics Amateur Radio Mobile Antennas (2013)
    PRIMER : Pages 3-9; 16-17; Short Form Catalog Volume 2.pdf

    Pulse / Larsen does make disguise and stealth VHF/UHF mobile antennas for law enforcement, military, intelligence, and business that Land Mobile dealers install.
    SOME are direct replacements (remove OEM, install disguise in its place).
    Land Mobile Radio (LMR) Catalog LMR Catalog 05 09.pdf
    Last edited: Jul 4, 2018
  4. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    Before you redial the hole, look at Larsen's SHF adapter. It replaces the existing mess with a better solution overall.
  5. N7WR

    N7WR Subscriber QRZ Page

    NMO gives you a lot more antenna options and there are adapters that will mate it to other types of antenna using different mounts
  6. ND6M

    ND6M Ham Member QRZ Page

    There is a valid reason for the NMO mount, using just a 3/8 thread mount requires a shunt to ground for proper operation.

    Thats why "most" antenna manufactures don't even offer many VHF/UHF thread mounted antennas.

    They get around it by using a cap in the base, that works for only one antenna, if you change the whip, all bets are off.
  7. W9GB

    W9GB Ham Member QRZ Page

    Glossary : pages 6 and 7 Short Form Catalog Volume 2.pdf

    There are actually four (4) different mobile antenna mounts.

    3/8 inch x 24 tpi NMEF : Originally used with Ball/Spring mount (Antenna Specialists ASP-3) in 1950s and 1960s (LMR, Lo-Band VHF 1/4-wave mobile)
    In 1960s, Hustler / Newtronics introduced their Mobile HF resonators using this thread.
    Widely used with mobile mounts for CB radio (27 MHz).

    NMO (Motorola style) : 1-1/8 inch x 18 tpi
    Common usage by Land Mobile Radio (LMR) as it migrated to Hi-Band VHF, UHF, and 800 MHz in 1970s and 1980s.
    Mounting variations exist for frequency (tab versus pin), vehicle mounting or body/chassis thickness. CABLE ASSEMBLIES/doc_part/ASB14 CABLE ASSEMBLIES.pdf

    PO (UHF connector style, SO-239) : 5/8 inch 24 tpi UNEF
    Using Amphenol UHF connector threads,
    designed in 1930's by Amphenol engineer Edward Clarke Quackenbush

    LM (Larsen Mount) : 5/16 inch x 24 tpi UNEF
    Introduced in 1970s, this mount style never achieved wider acceptance.
    Last edited: Jul 4, 2018
    W0GSQ and KB0MNM like this.
  8. W0GSQ

    W0GSQ Ham Member QRZ Page

    I installed many of the LM mounts on off road company vehicles in the 1980's, had zero issues with them.

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