What tools to use when trimming an antenna?

[Necer149]

Hey everyone...

I like to listen to the railroad frequencies that run through my town. I just bought a Larsen NMO mount with a Larsen NMOQSPEC VHF antenna. When it comes to cutting the antenna, I know where to cut it, but what tools should I use? It is a stainless steel 1/4 antenna.

Thanks!

Mark

 

[WA0CBW]

Some people use a chisel to "nick" the rod and then "snap" it off. Others use a carbide cutoff grinding wheel.

 

[popnokick]

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I've used bolt cutters or a hacksaw as well. The "nick then snap off" is cleanest method. After nicking, grab short end with Vise Grips or put in vise and snap.

 

[prcguy]

I've found filing a small notch in the whip allows you to snap the whip in two with your fingers in most cases or with pliers for larger diameter whips. A standard fine flat (bastard) file works great for this and when the whip is at the final length I like to file the cut end end smooth. The stainless steel used for whips is very hard and breaks like glass when scored and stressed.

In my early career I installed about a thousand radios/antennas and we also offered free SWR testing and the resulting tuning of antennas, so I've cut a lot of whips and the file method works best for me.
prcguy

 

[mmckenna]

A good pair of vise grips will cut the whips, but the methods mentioned above are easier.

Don't use wire cutters, as they'll usually deform the cutting edge.

 

[Necer149]

Wow! Thank you very much for the tips everyone. I'll use the score then snap method. I just ordered the antenna a few days ago and have not gotten it yet, so once I get it I'll report my results.

Thanks you so much everyone!

Mark

 

[LIScanner101]

I have one of those monster, 3' long boltcutters in the garage that works great for cutting antennas

 

[jaspence]

Tuning antennas

I use a Dremel with a cut off wheel. Quick and leaves a smoother cut than notching and breaking off.

 

[n5ims]

Once I'm satisfied with the tuning, I mark the location and remove the whip for one final task. I use my grinder or sanding wheel (with appropriate sanding material) and gently round off the whip to eliminate sharp edges. This will make it easier to insert into the mounting and if it ever needs to be removed will reduce the chances of it scratching the paint or your skin. Not 100% required, but sure makes it appear to be a more professional job.

 

[Necer149]

So I got the antenna today and have another question. When I cut it, should I cut it so the steel ball on the top comes off or cut it so it stays on?

 

[mmckenna]

Technically, it doesn't matter. The ball on top is a safety item to protect eyeballs. It's a really good idea to keep it in place. Many, many years ago I had a 5/8th's wave VHF antenna on my pickup. 49 inches long, or so. At some point the ball had disappeared. I didn't really care, until I was backing out of an underground parking garage and the sharp point got jammed into a concrete seam and yanked the NMO mount out of the roof.

Cutting it so it stays on is a good idea, but there are those that just trim from the top down. If you are not in a hurry, do it from the bottom up.

 

[jim202]

A point to pay attention to is that there are two types of blades for bolt cutters. One is for soft metals and the other is for hard metals. The normal bolt cutters that you obtain from Home depot and places like that generally have soft metal cutting blades. If you try to cut a stainless steel whip with these, you will generally end up with these real neat half round holes in the blades where you tried to cut the rods.

Back to the comment about an NMO mount being pulled out of the roof of a vehicle. All the antennas I have ever seen using "Larson" coils will break the plastic coils, long before the mounts pull out of the roof. If you use another brand of plastic coil on the NMO mounts, then all bet's are off. That was the reason I first started using the Larson bases. They always fail long before the roof does.

Another reason for taking off the balls at the top of the whips, is that they don't get caught in tree branches and pull the base off the roof. You can talk to many radio shops and get all sorts of answers on the good and bad about removing the balls. I like to keep customers happy and not have them pay for body work on the roof of a vehicle.

Do as you please.