Non-conducting antenna masts

[daveleonard]

I recently heard that one should never use a non-conductive material like PVC for an antenna mast. Why is this true? PVC is lite, easy to put up and take down especially if you use a tilting mast. The antenna, say a HF vertical, would be grounded to copper rods in the ground eight feet deep all having copper straps grounded to the antenna and the coax cable. A lightening protection rod would be used being ground in common with all the others. Of course all the station equipment would be grounded to a common plate attached to the copper coated rods. All equipment and antenna would be grounded in common using good grounding practice. So why can't a non-conductive material be used?

[W9WLS]

There really is no reason not to , EXCEPT for the physical limitations of the mast material and / or guying / support arrangement of the mast it's self.
Many antennas by design are "ground independent" meaning they are isolated from the support mast / structure (the Gap Titan comes to mind here) but one way or another they do work against ground .
The military has used "fiberglass" mast section kit's for antenna supports for many years for everything from small UHF antennas to large dipole array's.
PVC, has some draw back's , some is not too tolerant of U/V radiation (Sun Light) for long exposure, wall thickness in the material is another thought relative to build strength.

Bottom line is,,, Plan WELL, chose the material wisely, and expect the "UNEXPECTED" when installing (Murphy's Law).

[TimeToGetGoing]

Plus 1.

The military has used "fiberglass" mast section kit's for antenna supports for many years for everything from small UHF antennas to large dipole array's.
PVC, has some draw back's , some is not too tolerant of U/V radiation (Sun Light) for long exposure, wall thickness in the material is another thought relative to build strength.

73
Bob
KV4MJ

[N3LYT]

+2 The fiberglass ones are very strong for portable operation. If your using a beam or a base antenna on a tower PVC/fiberglass may not be a good ideal for lighting protection as most antennas are DC grounded.

[Radio]

#3 and welcome aboard Dave.

I personally have 2 bags of Army surplus mast sections. Very, very handy for quick and dirty portable antenna solutions.

I think the point of conductive masts is to direct lighting to ground. If a storm comes up, pull the plug and get off the air! :rain:

[N3LYT]

Here is my camper with my home brew 17 meter rotatable dipole and 24' of fiberglass poles. 26' of antenna and 17'10" of camper!

[NN5I]

I recently heard that one should never use a non-conductive material like PVC for an antenna mast. Why is this true?

Why is it true? Well, it isn't true. Remember who told you that, and don't ask his advice any more.

Using a nonconductive mast may mean you need a little more attention to lightning protection. You ought to be paying some attention to that anyway.

Some antennas, when mounted on an insulating mast, will tune differently from the same antenna on a metal mast. Since any antenna should be tuned at its operating position anyway, this effect, if present, won't make any difference in your procedure, because you've got to tune the darned thing anyway.

[wa8yxm]

THe advantage of a conductive mast, properly set in the ground and grounded, is that it is a lightening rod and protects nearby buildings against direct hits. A non conductive mast does not do this.

I am thinking the person making the claim thinks the conductive mast may protect the radio as well as the building.. If that is the case.. He is very very very mistaken... Though that said.. I have seen radios survive a direct hit to the tower.. but those were hardened radios. (Military/Police specifications installed by Police certified Ham/Professional Radio operator/engineers who knew exactly what they were doing).

Though I got to say it was a fun day at work when it happened.

[wa8yxm]

Opps computer sent it twice

[Mr. Ham]

I have seen others in the past that has used the fiberglass poles successfully for a temp antenna situation.. They were not putting beam antenna's up, just using them to hold up their dipole antenna..
A good 80 meter off-center fed dipole antenna will work wonders on most everything except 15, 30 and 60 meters.

A good one with excellent performance is the HY Power OCFD -
http://www.hypowerantenna.com/

http://www.hypowerantenna.com/products/off-center-fed-antenna

This one will work everything from 440 mhz to 80 meters without a antenna tuner... ex 15, 30, 60 meters...

[Radio]

I'll tell you something else about fiberglass mast sections, especially those that have bee exposed to UV light and weather for some time:

WEAR GLOVES!!

And if you do get fiberglass shards in your hands, repeated application and removal of REALLY REALLY sticky tape, like Gorilla Tape, will get most but not all of it out.

[wa8yxm]

There have been articles in QST about using telephone poles (non conductive) and the repeater I sort of founded (Even if they do not give me credit) originally had the receiver site on such a pole.

If you have an antenna mounted on the roof of your house, as most every house did for several years back before Cable TV and many still do today.. It is on an insulated ROOF (As is my own TV antenna)

There is no problem with a non-conducting mast..

Now, here is another consideration....

A conducting mast of the proper length is..... an antenna. and if that antenna happens to be resonate on the 2nd or 3rd HARMONIC of your transmit frequency... I can see big problems.