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I am looking to use a piece of PVC as the center insulator of a vertical
dipole I'm planning to put up. Anyone know the insulating
characteristics of this stuff? It's not going to conduct significantly
@ hf when wet?? Thanks for the help.

gary

"Angela & Gary" wrote in message
...
I am looking to use a piece of PVC as the center insulator of a vertical
dipole I'm planning to put up. Anyone know the insulating
characteristics of this stuff? It's not going to conduct significantly
@ hf when wet?? Thanks for the help.

gary

It works fine.
I used a short piece of pvc to connect 2 pieces of aluminum conduit.
I fed the coax thru one end of the alum conduit to have a vertical dipole
fed from inside where the 3 pieces come together

On Sat, 19 Feb 2005 13:14:55 -0800, Angela & Gary
wrote:

I am looking to use a piece of PVC as the center insulator of a vertical
dipole I'm planning to put up. Anyone know the insulating
characteristics of this stuff? It's not going to conduct significantly
@ hf when wet?? Thanks for the help.

gary


It will work great. If you want to test it, microwave a piece of the
material for 1 minute. IF it gets very warm, you may want a different
material. The white pvc should work as well as you need and then
some.


--
73 for now
Buck
N4PGW

I'd also add a glass of water in the microwave when you do
that...I'm not sure if they are still that way, but it used
to be bad for them to run with no load...IE: food...MK

It's not clear to me how you correlate how warm something gets in the
microwave oven with how much loss it'll incur at the end of an HF
antenna. Maybe someone can explain this.

Roy Lewallen, W7EL

wrote:
I'd also add a glass of water in the microwave when you do
that...I'm not sure if they are still that way, but it used
to be bad for them to run with no load...IE: food...MK

On Mon, 21 Feb 2005 03:55:43 -0800, Roy Lewallen
wrote:

It's not clear to me how you correlate how warm something gets in the
microwave oven with how much loss it'll incur at the end of an HF
antenna. Maybe someone can explain this.

Roy Lewallen, W7EL

The microwave works with RF to heat the 'food'. If an object absorbs
RF, it does so as heat, therefore, if you subject it to intense RF by
using a microwave oven, it will heat up. If it heats up, it is
affecting the antenna's radiation.

Depending on how it is connected to the antenna and type of antenna,
it may not make a noticeable difference on the signal, but in many
cases, especially where the wire is running along with or inside of a
material such as PVC, the material may have a detrimental impact on
the signal or SWR.

Not being aware of this a long time ago, I built a two meter half-wave
vertical dipole by dropping a line of wire into a piece of CPVC and
capping it off. My mobile 5/8 wave whip on the car, twelve feet below
it, using the same rig has much much better reception and signal than
the dipole. I plan to replace that antenna with a similar dipole using
1/2 inch copper tubing.

When I nuke the cpvc for one minute, it gets warm to the touch. I
don't expect to melt it using my 706, but I do have a couple of
repeaters I can't hear from that antenna that I would like to reach.

73 for now
Buck
N4PGW

--
73 for now
Buck
N4PGW

On Mon, 21 Feb 2005 03:55:43 -0800, Roy Lewallen
wrote:

It's not clear to me how you correlate how warm something gets in the
microwave oven with how much loss it'll incur at the end of an HF
antenna. Maybe someone can explain this.


Dear Roy,
Perhaps that is not the objective, Roy - maybe the rationale' is
simply to decide whether or not a particular sample of material is a
"high loss" dielectric or not.

Regards,

Bob, W9DMK, Dahlgren, VA
Replace "nobody" with my callsign for e-mail
http://www.qsl.net/w9dmk
http://zaffora/f2o.org/W9DMK/W9dmk.html

Bob, W9DMK wrote:
"-maybe the rationale is simply to decide whether or not a particular
sample of material is a "high loss" or not."

I think that`s it. The properties of dielectrics are functions of
temperature and frequency. My CRC Handbook of Chemistry and Physics
shows PVC`s dielectric constant is definitely a function of frequency,
unlike polystyrene and some other pastics.

I`ve seen PVC used as a base insulator for vertical elements of a HF
antenna array, and it worked OK.

I think low power factor and dissipation=A0are desirable for an
insulator. My 1987 edition of the ARRL Handbook has a table 47 on pages
35-36 and 35-37 titled "Properties of Common Thermoplastics. Maybe later
editions have expanded tables.

Best regards, Richard Harrison, KB5WZI

Buck wrote:
On Mon, 21 Feb 2005 03:55:43 -0800, Roy Lewallen
wrote:


It's not clear to me how you correlate how warm something gets in the
microwave oven with how much loss it'll incur at the end of an HF
antenna. Maybe someone can explain this.

Roy Lewallen, W7EL


The microwave works with RF to heat the 'food'. If an object absorbs
RF, it does so as heat, therefore, if you subject it to intense RF by
using a microwave oven, it will heat up. If it heats up, it is
affecting the antenna's radiation.

No, that's not correct. If you heat up an object in the microwave oven,
it indicates that an object of that material, size, and shape absorbs
some fraction (how large a fraction, you have no idea) of energy when an
intense microwave field is applied. It says nothing about what that
object will do when put at the end of an HF antenna, where it isn't
exposed to an intense microwave field.

Depending on how it is connected to the antenna and type of antenna,
it may not make a noticeable difference on the signal, but in many
cases, especially where the wire is running along with or inside of a
material such as PVC, the material may have a detrimental impact on
the signal or SWR.

Why yes, it might, or it might not. This can be said of any material.

Not being aware of this a long time ago, I built a two meter half-wave
vertical dipole by dropping a line of wire into a piece of CPVC and
capping it off. My mobile 5/8 wave whip on the car, twelve feet below
it, using the same rig has much much better reception and signal than
the dipole. I plan to replace that antenna with a similar dipole using
1/2 inch copper tubing.

When I nuke the cpvc for one minute, it gets warm to the touch. I
don't expect to melt it using my 706, but I do have a couple of
repeaters I can't hear from that antenna that I would like to reach.

That's an interesting anecdode, but it hardly supports the contention
that there's a direct correlation between heating in a microwave oven
and detraction of performance of an HF antenna when used as an end
insulator.

Roy Lewallen, W7EL

W9DMK (Robert Lay) wrote:
On Mon, 21 Feb 2005 03:55:43 -0800, Roy Lewallen
wrote:


It's not clear to me how you correlate how warm something gets in the
microwave oven with how much loss it'll incur at the end of an HF
antenna. Maybe someone can explain this.



Dear Roy,
Perhaps that is not the objective, Roy - maybe the rationale' is
simply to decide whether or not a particular sample of material is a
"high loss" dielectric or not.

Is a material that is "high loss" at microwave frequencies always "high
loss" at HF? How "high" does the loss have to be in order to detract
from an HF antenna's performance when used as an end insulator? When you
put an object in the microwave oven for a minute with a glass of water
and the temperature rises 10 degrees C, how "high" is the loss? How
"high" is the loss at HF?

Roy Lewallen, W7EL