A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

"Al Dykes" wrote in message
...



A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

Depends on the PVC you use. Some of it is pretty bad. Put a sample in a
microwave oven with a cup of water and turn it on for a couple of minutes.
If the plastic gets hot it is bad for antenna use.. Probably OK for supports
but I wouldnt use it to house an antenna element

Jimmie D wrote:

Depends on the PVC you use. Some of it is pretty bad. Put a sample in a
microwave oven with a cup of water and turn it on for a couple of minutes.
If the plastic gets hot it is bad for antenna use.. Probably OK for supports
but I wouldnt use it to house an antenna element

That tells you the loss when in an intense field at microwave
frequencies. It doesn't tell you a thing about the loss near a typical
HF or VHF antenna, except that if it passes the microwave test it's
probably ok. Many materials which fail the oven test are fine for other
applications.

PVC insulation on wire won't hurt an antenna noticeably, nor will PVC at
low-electric field points like a dipole feedpoint. I'd avoid using it
for an insulator at high field points like the end of a wire antenna or
the base of an electrically short dipole.

Roy Lewallen, W7EL

The main problem PVC will probably cause is to detune(*) the antenna
because of its dielectric constant. If you can adjust the element
lengths to compensate, it probably won't be a problem.

(*) By detune I don't mean that it just changes the resonant frequency.
It'll affect the pattern as well.

Roy Lewallen, W7EL

Al Dykes wrote:
A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

"Al Dykes" wrote in message
...



A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore. A Proud signature since 2001

Hi Al

I am using 1/2 inside diameter PVC pipe ( white stuff from Home Depot) to
enclose three foot lengths of TV 300 ohm twin lead folded dipoles at 137
MHz. I have done the microwave oven test and couldnt detect any
temperature increase. I measured the antenna's input impedance with and
without the PVC cover. I detected very litle change when the PVC is
included. The antenna seems to have the same sensitivity with and without
the PVC.

I'd expect my experience to convince you that PVC is an OK covering for 2
meter dipoles. How much change do you see when you Grid Dip a dipole with
and without the PVC??

Jerry

On 18 Jun 2006 12:29:52 -0400, (Al Dykes) wrote:




A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

Should I switch to something else ?

Your brain, not his.

Some PVC is better than others, but I use it often. I use cpvc or the
white pvc for antennas. The velocity factor is changed so the lengths
are a bit shorter, but once trimmed, the antennas do well. I either
use the PVC for insulators or for holding the wire rigid. I built
many a dipole inside PVC for vertical or horizontal use. I also use
it for insulators or spacers on open wire. Never had a problem with
it.

Good luck

i hope this helps
Buck
--
73 for now
Buck
N4PGW

Al Dykes wrote:




A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?



Yes, use thin walled glass fibre pipes!

PVC is not a coherent type/class of material. The producers use all kind of
cheap crap as filler material or as pigment. The common rule is to use
white PVC as most other coloured PVC contains graphite or oxide based
pigments.
However, some white PVC's have chalk as a whitener and as a filler to make
the PVC being formed better in the production gear. It's less sticky that
way.

Some PVC materials are even "soldered" with 70MHz RF!

No, the Microwave oven test doesn't tell you the whole truth - just a hint.

I use very thin walled glassfibre pipes but with a foam filled inside. I use
the expanding "gluey" insulation foam. When dried, the strength of the
pipes have increased dramatically and they bend less in the wind.

Cheers

Dan / M0DFI

"Al Dykes" wrote in message
...



A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

Two possibilities, if you think the PVC is detrimental.

1. Try hollow fiberglass blank arrows. (if the available length is long
enough) They used to be available at certain sporting goods stores, or you
could buy an arrow and cut the ends off. I made a super 2m quad with this
technique. I just used a 1x1 wood boom with two snug fitting holes drilled
at right angles, and slipped/centered the arrows used for spreaders.

2. Wrap the entire PVC in aluminum foil, and tape in place. From
experience, I know this works at 10 and 15 meters when wrapped around bamboo
poles.

--Wayne

Hello,

That's true at UHF but it should be OK at least for the 2m band depending on
the PVC type.
The better choice is PTFE but it's not really cheap!
Another alternative is glass fiber (or wood).

73 de F8BOE Olivier ...-.-


Al Dykes wrote:




A friend is telling me that PVC has crappy electrical characteristics
and having my wire against it for the entire antenna not good.

I've been making simple VHF antennas with small diameter PVC pipe cut
and glued to make the rigid structure and then taping 12ga copper wire
to the PVC to make the elements.

Should I switch to something else ?

"Wayne" wrote in message
news:j4zlg.6911$nS5.3987@trnddc07...
1. Try hollow fiberglass blank arrows. (if the available length is long
enough) They used to be available at certain sporting goods stores, or
you could buy an arrow and cut the ends off.

I spoke to a friend of mine who works in the archery business (Parker Bows),
and he says that hollow fiberglass is almost non-existant now. Everything
has switched over to carbon fiber tubes. He says the blanks are about 32"
long before being made into arrows, so that might limit their uses.
--
Gerry KG4NBB