Antenna Springs

There are really only two reasons for putting on a spring:
1) If your antenna is too short. as evidenced by a lower SWR on Ch 40 than 20 or 1; or
2) If you're constantly running afoul of overhead obstructions.

The spring has an internal "shorting braid" so that the electrical length doesn't change as you sail merrily down the road, flexing the spring hither and yon. Putting a spring onto a properly-tuned antenna will make it longer overall, and you may end up having to shorten the antenna's whip (or windings, if it's fiberglass) to compensate.

Otherwise, I wouldn't run with a spring, especially if you have a stack or some similar body of metal behind the antenna, as the antenna will interact somewhat with the metal as it flexes rearward. And as it flexes, the radiation pattern will be affected. If your antenna leans back at, say, 30 degrees from vertical as you drive, your pattern will be up into space at 30 degrees in front of your truck, rotated 30 degrees towards the horizons to your left and right, and firing into the ground at a point around your rear bumper. But an antenna has to be pretty long and/or wide to present enough drag to bend it that far.

On my service van, my base-loaded Maxrad antenna has a spring when I'm using it for CB. When I'm going to run on 10 Meters, I remove the spring to make the antenna 3 inches shorter. My antenna is somewhat more sensitive to length changes than a longer one, because so much of the electrical length is in the coil, and the whip is only 42 inches long. A CB antenna that's longer overall will show less change in SWR for the same length change made by a spring.

If you were to use one of the big "pot belly" springs, that are usually used with 102-inch whips, on a 3-ft or 4-ft antenna, you may find that the spring is so stiff that it doesn't really let a shorter whip bend down enough quickly enough to save it when it hits overhead stuff.

The spring typically goes between the whip and the mount. Some springs already have one male and one female thread on them, so the positioning is easy to see once you remove the whip from the mount. If you get a spring that just has two female threads, buy a short stud to go between the mount and the bottom of the spring.

Hope that helps,
-- Handlebar --

 

I would just go to one of the whip style antennas such as the wilson 2000. They can take alot more abuse then any fiberglass antenna and you can get replacment shafts and whips at most any truckstop, if the need should arise.

 

You got that wrong Rat .....

He needs hardend fiberglass stuff so tough that it snaps those pesky branches off and dumps them on the car behind


All kidding aside I have lost several 5db gain 2 meter fiberglass antennas to low branchs ...... no fun and costly ....

 

Springs and quick disconnects are gimmicks
Nothing good comes from their purchase,not to mention some ungodly high SWR's.

 

AGAIN .....

Springs is corectly used will not detune a antenna and disconnects are fine too..... SWR on the 10 meter cut down 102 wip I used for years was under 1.2:1 spring or no spring as long as you knew what ftequency the antenna would be at when you removed the spring.

At 50 mhz or above springs are not needed .....so you just dont see them used much.

I run NMO mounts at HF -UHF

 

You're passing incorrect information. Depending on the situation, a spring is absolutely the best solution and lowers SWR. For example, a standard 102" stainless whip mounted normally works best with a spring. The added length of braided wire in the spring brings the SWR downs to where it needs to be. Obvsiously, there are mounting advantages to using a spring as well.

 

you are right this is one reason the wips are a bit short so the spring will tune it

 

I don't where you got your info? But you are incorrect on both items. If you have a high SWR (It's SWR not SWR's). It's because of some of factor. Not the spring or quick disconnect.