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.
    Mike/N4MTB
     
  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;
    https://www.pulseelectronics.com/docs/library/Amateur 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.
    https://pulselarsenantennas.com/
    SOME are direct replacements (remove OEM, install disguise in its place).
    Land Mobile Radio (LMR) Catalog
    https://www.pulseelectronics.com/docs/library/Larsen 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
    https://www.pulseelectronics.com/docs/library/Amateur 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.
    https://productfinder.pulseeng.com/doc_type/WEB301/doc_num/ASB14 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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