Larsen 2/70 Mobile Antenna Kicks Butt

A few months ago I had a Larsen 2/70 mobile antenna installed on my truck, (well I had someone put the NMO mount in, and I did the hard...

A few months ago I had a Larsen 2/70 mobile antenna installed on my truck, (well I had someone put the NMO mount in, and I did the hard part of screwing the antenna on, lol). No, but seriously, my truck has some serious side curtain airbags that I didn’t want to mess with. The professional installer even had issues routing the coax through the headliner & down to my radio because of the airbag setup. The bags, and canisters & lines used to inflate the bags took up almost all of the space under the headliner, not to mention the crummy 4″ speakers that Toyota puts up in the headliner (they’re disconnected, but still remain). So the technician had to route the coax towards the front of the truck & bring it down  one of the front quarter panel beams, which worked out fine because the NMO mount I bought came with 17 feet of RG58A/U coax. I bought the cheap browning one on Amazon, I think I paid around $14 for it, still priced accordingly online:

browning

This mount had pretty good reviews, and upon arrival, it seemed of decent quality, gave a slight tug on the ends to make sure a crummy crimp job wasn’t done (as I’ve had on MPD digital cables’ from Amazon in the past!). It took the technician a good hour to do this, and these guys were experienced police/ems/fire radio installers, they said it was one of the more difficult installs they had done because of the airbags. But alas, they did an outstanding job,  so if your ever looking for a good install, give RZ communications a call (they’re located in East Austin).

After installed I placed the Diamond NR770HNMO antenna I already had been using on a previous Diamond mag mount. I wasn’t planning one using the Diamond long though because when I took it off of the mag mount, I noticed that there was quite a bit of moisture underneath where the center contact made connection with the antenna, this was no bueno, I could try an o-ring, maybe some dielectric grease? Well, after using the antenna for a few days, I started to notice quite a bit of flex in the antenna. I just wasn’t comfortable with how the Diamond made contact with the sheet metal, the base was so narrow, and the sheet metal used on most vehicles isn’t exactly super thick, so there was a slight wobble due to this. With the Larsen this was completely eliminated due to the wide base.

nmomount

I used the Diamond for a few weeks, but we started having some really hard rains in Texas over the past several months and moisture just kept getting in there, and I would occasionally have to tighten it just ever so slightly, maybe from the little branches it smacks occasionally? It’s also chrome plated, blah, I hate chrome. So 1980’s, lol. I like matte black, stays clean, hides dirt, hides scratches, I just knew I had to replace this thing with a Larsen. I’d seen so many good reviews on Larsen’s, I just bit the bullet and spent $50 on the 2/70 version, sometimes you can find them cheaper at hamfests or online elsewhere. I’m so glad I replaced it too, because not only did I ‘feel’ like I had a slight increase in performance, but the antenna was so much more stable up on top of the truck! Check out the difference in width of the bases:

larsen

I really like how the Larsen almost cinches down on top of this little black seal that fits perfectly under the base and forms a nice tight seal. I haven’t had any water seep in, you should still occasionally check underneath to clean the contacts, and remove any debris/moisture that might sneak in there. Being exposed to the elements constantly is harsh on these little guys. The Larsen is just a tad lower profile too, which decreases flex. The antenna element is also more flexible, the only downside is it bends back a bit when your doing 65+mph, the Diamond is more rigid in that regards. If the element ever gets bent, you can just bend it back very carefully.

There are all kinds of mobile antennas on the market today, but after using the ones that I’ve used, and viewing others hams setups, I like the Larsen. Hands down, wins every time. The only case where I would use the Diamond over the Larsen, would be if I was using a lip mount, as I occasionally do when I go on a long trip, or to a hamfest and have as many radios hooked up as possible!

lip

I’ve found that the Diamond seats better on the lip mounts, the Larsen hangs over a bit on the edges, so I’m not sure if that would affect the ‘seal’ on the bottom, although I have seen hams use them on the K400 lip mount, there are also other lip mounts available that have a wider base that fit the Larsen more appropriately, so there are certainly plenty of flavors to suite anyones taste 🙂

I like having options. It seems we have plenty to pick from still with amateur radio, which is a good thing. Larsen hit the nail on the head with this product, maybe that’s why the design hasn’t changed in ages? After 3 months of being on my truck, the antenna has shown absolutely no signs of wear, tear, bends in the antenna, etc. The Diamond was also just a tad bit taller than the Larsen, I think Larsen puts one more coil in the center. I will miss the ability to fold the antenna over, but the times I’ve needed to park in the garage, I just pull out a crescent wrench & remove the whip. Takes just as much time as it does for me to get out & fold the Diamond over 🙂

Not to mention when I met up with a large portion of our local club, I’d say about 75% of the hams had one of these on their vehicle! Some were almost 20 years old! The plastic had faded a bit, some guys had even replaced their whips after some pretty nasty run ins with branches, but the base had remained. A little bit of black matte paint, and you could fix that right up!

Just a short little write up to hopefully help someone decide on their next mobile antenna 🙂

73

K5ACL

Categories
Mobile
No Comment
  • ve3ips
    2 October 2016 at 12:51 AM

    Thanks for the write up. I went digging around my antenna box and found three of these antennas. All 25 plus years old and a quick wipe with some steel wool are like new. They will be the antenna of choice for my 3 go boxes I am building

  • Ron
    20 August 2016 at 6:44 PM

    I still have an NMO 2/70 from about 1990. The base, originally gray is slightly discolored. The center loading coil is enclosed, not open as on the current model. After 25+ years off the air I’m resurrecting a dual band HT and thought I might occasionally go mobile. How much magnet mount do you think I’d need? the 3 1/4 in diameter Larsen mount says 90 lbs of holding strength- there is also a bigger rectangular mount for nearly twice as much. Just curious if you have any thoughts. Thanks / 73 de WB3X

    • Johnny
      24 August 2016 at 6:50 PM

      Ron, first & foremost, welcome back to the hobby! Magnet mounts are an ok compromise if that’s what you’ve got to work with, or until you find a more permanent solution. I used a Diamond magnet mount on the Diamond NR770HNMO antenna (which I have since sold). It was smacked loose a few times by some low hanging branches in my neighborhood, and left a few scratches on my roof. Here’s a link to the one I used: Mag Mount. Now that I’m looking at it, the Larsen base may sit nicely on top of that mount!

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