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Larsen NMO27 reviews? Pictures?

mmckenna

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I have used the PCTEL/Maxrad MLBDC2700 with spring on front fender mount to good effect. The spring increases VSWR bandwidth for some reason.
Increasing the diameter of the radiating element will increase bandwidth. The wider diameter of the spring at the base is helping.
Not sure how the coil design compares to the larsen, but that may be a part of it, too.


I used to buy the Larsen but I continuously ran into issues of the whip (no spring is available, to my knowledge) breaking off right at the cone.
Chrome spring: https://www.theantennafarm.com/catalog/larsen-spring-3877
Black spring: https://www.theantennafarm.com/catalog/larsen-springb-3878

But 30 years, never broke a whip. If you do, it's easy and inexpensive to replace a whip.
 

mmckenna

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Also: I use an NMO mount that is relatively weatherproof, such as the Larsen NMOKHF and put a piece of adhesive-lined heatshrink at the coax crimp ferrule for best weatherproofing, for fender mounting. The 'regular' NMO mounts usually have a soldered connection to the mount, with a plastic cover which is in no way weather resistant. Especially here on the Oregon coast, with salt air, the regular NMO's go bad in months due to corrosion and moisture intrusion. I have had very little problems with the NMO's as I described above.
Amen.

Been preaching this for years with non-through roof mounts, but it usually falls on deaf ears. Adhesive lined/marine grade heat shrink on the HF model mounts is the way to go.
 

k7ng

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I admit I probably didn't try hard enough to find the spring version. I will flog myself. Maybe tomorrow. :)
 

78k10

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Don't put us through all these questions about good antennas and then bring "Browning" into the conversation.

Yes, a Browning will work, but they are a Chinese knock off brand. They are not on the same level of the Larsen, Laird, Antenex, etc. You might save a few dollars, but you'll likely not get the longevity out of it.
Haha I knew they weren’t a very good option, but it was one of the few options I knew of. The 3/8x24 cb antenna market is flooded with options, NMO mounts seem to be few and far between for some reason. I guess because of the hole drilling issue.
 

mmckenna

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Haha I knew they weren’t a very good option, but it was one of the few options I knew of. The 3/8x24 cb antenna market is flooded with options, NMO mounts seem to be few and far between for some reason. I guess because of the hole drilling issue.
Yeah, good natured ribbing on the Tram/Browning, but seriously, you can do better.

That's the issue with the hobby/CB crowd, often they are looking for the "easy" solution and will cut every corner they can. I've had good luck with CB by doing the same level install I'd do on any other appliction:
-Power direct from the battery.
-Proper grounding.
-Proper antenna install.
-Test everything.

Unfortunately consumers want the easy solution. Cigarette lighter plugs, mag mount antennas, etc. Doesn't work out well.
 

mmckenna

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I admit I probably didn't try hard enough to find the spring version. I will flog myself. Maybe tomorrow. :)
Ah, no biggie.
I've never heard of anyone snapping a whip before. Probably just buying a new whip is cheaper than the spring. With the taller NMO-27 coils, adding a spring to that height probably isn't the ideal solution. I've found the whips bend over pretty well. They can take a permanent kink, though. I've got a Laird 1/2 wave VHF antenna on UTV that hit a few low branches at high speed. The top 4 inches of whip have a 10º tilt to it.
 

KANE4109

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Just reading along.....wanted to express thanks for this thread.
I never knew there WAS an NMO mount CB antenna.... never thought to look for one.....
And that can solve a problem or two!
 
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Haha I knew they weren’t a very good option, but it was one of the few options I knew of. The 3/8x24 cb antenna market is flooded with options, NMO mounts seem to be few and far between for some reason. I guess because of the hole drilling issue.
I think it's more that they don't have the mystical voodoo magic that makes all of the Wilson, Firestik and Road Pro antennas perform better. Who would want a 0 dBd gain antenna that is only rated for 200W when the competition sells antennas with 6 dB of gain and can handle 1 kW of power? Plus, how can I sell a $24 NMO antenna when my customers want the voodoo for $90?
Just reading along.....wanted to express thanks for this thread.
I never knew there WAS an NMO mount CB antenna.... never thought to look for one.....
And that can solve a problem or two!
Not necessarily a CB antenna. They are all generic low band antennas. With most of them you will have to trim the whips down.
 

prcguy

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The Larsen NMO27 and the Laird/Antenex CW27 are specifically made for CB and not a VHF low antenna cut down. They are also not $24, the Larsen is about $50 average price and the Laird is probably twice that.


QUOTE="Project25_MASTR, post: 3272834, member: 1208252"]
I think it's more that they don't have the mystical voodoo magic that makes all of the Wilson, Firestik and Road Pro antennas perform better. Who would want a 0 dBd gain antenna that is only rated for 200W when the competition sells antennas with 6 dB of gain and can handle 1 kW of power? Plus, how can I sell a $24 NMO antenna when my customers want the voodoo for $90?

Not necessarily a CB antenna. They are all generic low band antennas. With most of them you will have to trim the whips down.
[/QUOTE]
 
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The Larsen NMO27 and the Laird/Antenex CW27 are specifically made for CB and not a VHF low antenna cut down. They are also not $24, the Larsen is about $50 average price and the Laird is probably twice that.


QUOTE="Project25_MASTR, post: 3272834, member: 1208252"]
I think it's more that they don't have the mystical voodoo magic that makes all of the Wilson, Firestik and Road Pro antennas perform better. Who would want a 0 dBd gain antenna that is only rated for 200W when the competition sells antennas with 6 dB of gain and can handle 1 kW of power? Plus, how can I sell a $24 NMO antenna when my customers want the voodoo for $90?

Not necessarily a CB antenna. They are all generic low band antennas. With most of them you will have to trim the whips down.
[/QUOTE]
The Larsen't cut chart covers 27-30 MHz.

The FCC band allocation tables have 27.41 MHz to 28 MHz and 29.7 MHz to 29.8 MHz slotted for LMR Part 90 use.
 

k7ng

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I maintain a radio system and the radios in a fleet of vehicles. I started out using the Larsen NMO27's because I had never broken one of the whips either. I think the customers are having a contest to see who can break the most antennas, and I got 2 or 3 broken Larsen whips a month, after about a year of use. Maybe metal fatigue? Always snapped off flush with the mounting cone. One of my counterparts elsewhere suggested the PCTEL antennas - he's probably smarter than I am. Older at least. Most of the Larsen antenna whips broke off on rigs where the driver/customer is pushing thru brushy trails about 20 MPH faster than most people would go. Anyway, I already put in my $.02 regarding antenna brands so I'll stop.

I know that fender mounting will probably produce an asymmetrical pattern but that seems to be a non-issue in actual use here. I also install a VHF radio on customer vehicles, antenna on roof center... and boy do I replace a lot of broken-or-ripped-out VHF antennas. Imagining what kind of mayhem might relate to a roof mounted CB whip on the same vehicle caused me to discount that idea.
I began to use vehicle-specific mounting brackets if available because the metal seems to be beefier than many 'generic' brackets, and by their design the brackets attach to a reinforced point. Nobody as yet has managed to damage one of those brackets even if the antenna on it is toast.
 

FiveFilter

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Quote: "...Unfortunately consumers want the easy solution. Cigarette lighter plugs, mag mount antennas, etc. Doesn't work out well."

Well, I guess you can say that I've taken the easy solution, and they have worked out very well for me over many years.

In fact, I have found that mag-mount antennas are exactly what I need:. I run a 62-inch Wilson 1000 on the roof of my F250 RV trailer-puller, a 55-inch Wilson 500 on the hood of my Jeep Wrangler woods-and-field vehicle with the removable plastic roof, and a 36-inch K30 on the roof of my Mazda commute car.

I like the ability to place the mag-mounts in the position where they will perform the best, and the ability to quickly remove them when entering low-ceiling parking garages and then replacing them when leaving.

I have never experienced any lack of performance via the mag mount antennas, which I know is a subjective opinion. But tests I've seen indicate that mag-mount antennas perform as well as any other vehicle antennas of comparative lengths, and if they suffer from lack of performance, it is difficult or impossible to show it on field-strength equipment.

And about those cigarette plugs: I've had no problems through the years using them. I'm always ready to string 12vdc lines to the battery if I ever suffer interference etc, but so far I'm batting 100% using them.

So, if anyone doesn't want to punch that hole in the roof or string that wire through the firewall to the battery, don't fear trying those less invasive easy solutions first, if you're so inclined. :)






I
 

mmckenna

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Well, I guess you can say that I've taken the easy solution, and they have worked out very well for me over many years.
If it works, it works, that's all that matters.


I like the ability to place the mag-mounts in the position where they will perform the best, and the ability to quickly remove them when entering low-ceiling parking garages and then replacing them when leaving.
Just for the record, you can do that with any NMO mount. Unscrew the antenna, toss it in the car or trunk and go on your way.

I have never experienced any lack of performance via the mag mount antennas, which I know is a subjective opinion. But tests I've seen indicate that mag-mount antennas perform as well as any other vehicle antennas of comparative lengths, and if they suffer from lack of performance, it is difficult or impossible to show it on field-strength equipment.
Yep, testing will show a 0.1dB difference between a permanent NMO mount and a mag mount in the same space, however that can vary depending on frequency. No one is going to be able to hear that ~0.1dB deficit for a mag mount.
Also, without a true DC ground at the antenna base, and a mismatched antenna, you can get some unwanted RF on the coax shield that can create issues in some installations.

On the flip side, paint damage is a concern for some. And then there's the getting the coaxial cable inside the vehicle. That can require running coaxial cable through doors or windows. That can, in some cases, damage cable. Pinching in doors/windows can change the characteristic impedance or damage the jacket and let water in. As a long term solution, it can be problematic for those that live in rainy/snowy environments.

And about those cigarette plugs: I've had no problems through the years using them. I'm always ready to string 12vdc lines to the battery if I ever suffer interference etc, but so far I'm batting 100% using them.
Seems to vary. For a 4 watt CB radio, there shouldn't be an issue with the connection if you are using good cigarette lighter plugs. Cheap ones can have contact issues over time. That can lead to arcing, damaged contacts, etc.
But, if it's working for you, that's great.
Some vehicles are worse for RFI than others. Since cigarette lighter socket wiring can route along with other vehicle wiring, it can be a common way for RFI to get into the CB. On an CB using AM/SSB, that can be an issue.

So, if anyone doesn't want to punch that hole in the roof or string that wire through the firewall to the battery, don't fear trying those less invasive easy solutions first, if you're so inclined. :)
Yeah, as always, each should do what they are most comfortable with. No one should be attacking their vehicle with a hole saw if they are not comfortable with it.
 

78k10

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Just wanted to thank everyone for the input. In the end, I SECU to take the easy route as well. I decided that I didn’t want a 4-5’ antenna on top of the truck permanently. In the end the cb will be used maybe a grand total of 10 hours a year for 2-3 hunting trips. I decided to just go with the magnet mount antenna and cigarette lighter setup so the radio can be easily put in or taken out. I’ll save the space in the truck and on the roof for some more useful. I can deal with a 6-20” antenna on the roof, but not something as tall as cb requires.
 

K6EEN

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I have a Larsen NMO27 installed on the trunk lip of a small car with the Diamond K400 series NMO mount. With the MFJ-259B analyzer, I trimmed the base of the whip via metal file & pliers snap-off method to 1.8:1 SWR at 27.150 MHz. The 2:1 SWR bandwidth is roughly 26.8 to 27.4 MHz. Being a base-loaded quarter wave vertical design, it really wants to have a full ground plane under it to achieve resonance and a low SWR, which the trunk of a small car does not provide. I'm using the CB only for road/highway conditions on Channel 19, and maybe emergency Channel 9. For comparison, small mag mount CB antennas like the Wilson "Little Wil" and K40 Antennas "K30" achieve a lower SWR in the center of the trunk, and nearly 1:1 on the center of the roof. My guess is the Larsen NMO27 would benefit similarly from center of trunk or center of roof placement, but I'm not going to punch a hole in the car for occasional CB use. I use the K400 NMO mount for other land-mobile band antennas which don't require a good ground plane, half wave 2m and co-linear 70cm for amateur & GMRS bands.
 
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