antenna splint

[dotnmarty]

My roof mounted antenna cracked in half. I had it laying flat under the full winter cover and it cracked at the end of the roof. Can I just splint it with a 3"piece of 1/2" dia galvanized pipe or will that interfer with reception somehow? Thanks

[Sea Wolf]

Marty-

The antenna is really a metal wire or ribbon inside the fiberglass sheath that holds it up and in position. The radio "pumps' an eletric charge on the metal part, sending out signal waves. A metal sheath around it to splint it would greatly interfere with the broadcasting of the waves, depending on how long it was. A three inch plastic or wooden splint shouldn't hurt your antenna too much, however.The metal part inside the antenna should be intact for good performance, as the length is "tuned" to the range of frequencies that the radio typically broadcasts.

However, in an emergency where there is no other alternative, a shortened antenna will work over limited distances, just keep the metal part that's left from being grounded out to anything.

Be careful with the fiberglass rod. The glass fibers are sometimes exposed and can be inserted into a person's fingers and skin quite easily, causing nasty itching and pain. I have clear coated with urethane and even wrapped with tape, a fiberglass antenna that was worn to keep it from displacing it's glass shards into someone .

If you have one that frequently abrades when trailering, a section of clear plastic tube (Tygon at the hardware store) can be placed where it usually rubs to stop the abrasion and problem exposure.

Joe.

[dotnmarty]

Thanks for the good advice Joe.

[tpbrady]

Joe,

You're a one man help desk.

[thataway]

Don't use the metal pipe. Often 1/2" CPVC pipe is the correct size to fit over the antenna--check it out. If the antenna is too big for the CPVC then the PVC will work. Slide the pipe over the antenna and pump in some sealant (silicone will work fine).

I would not use a shortened antenna or broken wire. The radio output transisters will shut down when there is a SWR mismatch--and the output may be very low. You can either carry an "emergency antenna" or make one--but it has to be a specific length of wire to have the proper SWR.

[mikeporterinmd]

[dotnmarty]

Thanks Dr. Bob, I will do that.

[Captains Cat]

While the connecting cable has some to do with the Standing Wave Ratio (SWR), it's not much. If the radio works (transmits/receives) on high and low power, it's not "damaged". The shutdown mentioned is a temporary thing the output circuits do to protect themselves. When the high SWR condition goes away, they're back up and running.

Charlie

[dotnmarty]

Well, thanks to your help, she's up and running. But I am worried about 'next time'. Is there a recommended 'shorter' VHF antenna that won't overhang the roof when folded down? My mount is simple and on the hand rail. I don't want to move the whole thing down and have to drill holes. Thanks again.

[journey on]

One can buy all lengths of VHF antennae, down to the short 3 ft. sailboat antennae. The tradeoff is gain (the taller put out twice as much electrical power: 6 dB vs 3 dB,) and height. I have a 8' plastic antenna and of course need to lay it down when we're trailering. To do it neatly, I have to remove the antenna from the mount, and then tie it to the handrails. I left enough of a service loop in the cable to be able to do this. Pain in the rear, but it works.

Boris

[dotnmarty]

Boris-I only trailer the boat and since it is a 16 footer I'm gonna have overhang. I really don't want the extra nusiance of doing that disconnect every time. Also and probably more importantly, I don't want to poke a hole in my winter cover to avoid the stress on the fiberglass pole. I wonder how much practical difference 3db vs. 6 db gain really would make in my Puget Sound boating? Thanks

[Alasgun]

We have an 8 ft digital antenna , rail mounted on Huda Thunkits roof. When folded about 4 inches hangs off the back of the cabin. When trailering and when in winter storage we just slip a 6 inch piece of 3/4 pipe insulation over the antenna end. Using one of those smallest bungee cords, the one with a ball on the end, we can hold everything securely to the rail.
We are into our 2nd winter with this arrangement and it has endured numerous snow removals with out incident.
Mike on Huda Thunkit

[dotnmarty]

Mike-Your response couldnt have come at a better time I just bought 8 feet of PVC pipe to get the 3 inches I need for a sleeve/splint. You know, between the help I get on this site and the guy at ACE hardware, I might actually build a bird house before I die. Thanks

[thataway]

Agree that trimming down the coax to the antenna will make little if any difference in the SWR. Most antenna manufactures will say not to make the coax shorter than 3 feet. There is a little loss in Coax, but it is so little that not negiable.

For a short antenna, I used a 3 foot Metz SS whip base loaded on top of a 2 foot SS extension. This prevented the broken whips which overhung the cockpit or top.

I like the digital over the Shakespheare. I take my antenna analyzer to the store when I buy an new antenna, and find that the SWR seems slighter better on the Digital.

Bob Austin

[dotnmarty]