I have a Larsen NMO50B (link here) mounted on my truck. I lost the whip and I'm looking for a replacement. Since I"m not super smart I'm not sure what whip to use, ideally I'd get something of the same length or a little shorter. Can anyone recommend one?
Thanks

something shorter would screw up your SWR

 I’d reach out to LARSON

Comet SBB2-NMO. SWR is perfect, not a great performer on 2M but adequate for most. Only 18" tall.

Thanks!

Here is one source for the whip


Whip for Larson NMO 150


Black whip:

Replacement black whip 49 inches

By the way, the replacement 49 inch black whip is an excellent replacement for a Little Tarheel II screwdriver whip over the stock 32 inch SS whip. It gives a slight amount of gain (well, less loss, because we are dealing with negative gain in the whole antenna here, with the possible exception of 6 meters)  But the big advantage is that it is a tapered whip and is not as stiff as the 32 inch whip so it is more "whippy" when you hit objects and less likely to tear up the coil. The slight amount of "gain" is just a bonus. It resonates on 6 meters with the coil all the way down perfectly. I did lose the plastic "corona ball" or eye protector fairly quickly from hitting the overhead obstruction at Wendy's but I soldered on a solder one and it has stayed on now for years.  

I made a depression in a brick with a 1/4 inch masonry bit  Then took a torch and melted solder in the depression forming a molten ball of solder.

The whip was prepared by scraping off the black coating until you see the copper plating over the SS whip. Put a tiny bend in end of the whip.

Tin the copper whip, and then dunk the end into the molten ball of solder in the brick.  This will solidify into a nice round ball at the end of your whip. Then hit the end with some black spray paint to restore its beauty. Now you have a nice sturdy corona ball on your whip that will stand up to Wendy's or any other overhead obstruction you encounter. Looks good, lasts a long time, what more can you ask of a whip?

Larsen whips are made with a plating process that's different from typical whips, but they are the standard .100 diameter that is common to most LMR antennas so any 49" .100 whip will work fine. It will need to be the correct tuned length for whatever frequency you are using, the stock NMO150 with full length whip tunes at 144 typically, usually take about 1/2 inch off for typical 2 meter FM use.

If you call a local two-way radio shop and tell them you need a 49 inch whip for a replacement they probably have a dozen sitting around. Don't take a used one as it will probably be cut for 155ish LMR frequencies. If they have a Larsen that's great, but if it's a Maxrad or whatever it will work fine as long as it's the typical .100 size. There are some .125, much less common but out there so they won't work unless you also get a Larsen .125 whip adapter.

If you have a black whip and want another, there aren't many other than Larsen.

And just to be sure, you lost just the whip, or did you lose the little whip adapter? Make sure the little hex tapered thing is on top of the plastic base, and not just a threaded post. Also, check to make sure the little set screw is there in the whip adapter, that's what holds the whip in. If it's gone you will have to get a replacement set screw at the hardware store if they have stainless, or get a whole replacement whip adapter with the whip.


Yes the length is critical to the tuning of the antenna. Here's the Larsen cutting charts:
https://www.repeater-builder.com/antenna/pdf/larsencuttingcharts.pdf
The chart says 48 inches for 146, seems like I only took off about 1/2 an inch, it's somewhere in there.

If you need something shorter I really like the Larsen NMO150BHW or NMOWB150, they're about 40 inches when cut for 2 meters.  A 1/4 wave is about 19 1/2 inches.

When you see an LMR type antenna that says "144-174" or "136-174", that DOES NOT mean the antenna covers that entire range out of the box. That means it's tunable within that range, there will be a specified bandwidth. The Larsen "WB" antennas have a wider usable bandwidth than the standard ones. Ham market antennas like comet/diamond types are just preset for the amateur bands.