On Sat, 05 Oct 2013 15:24:01 -0500, John S
wrote:

The microwave oven test is not very useful. The microwave will test
whatever at about 2450MHz. I doubt he is trying to make a loading coil
for anything near that frequency.

Actually, it's very useful. In my admittedly limited experience,
anything that survives the microwave oven test, will usually work
nicely at HF frequencies. Those that get warm in the oven, might
work ok. Those that melt, burn or explode, will probably not work
very well at HF. While testing at 1000 times the frequency, and 30
times the power, might be considered overkill, it does yield some
useful information.

Incidentally, the loss tangent changes over frequency on many
materials. See table at:
http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_5.html

There are other resources for that information. Please search.

Well, there's the loss tangent tables for various materials.
http://www.rfcafe.com/references/electrical/dielectric-constants-strengths.htm
Is that what you mean? The problem here is that the ABS or PVC coil
form is hollow. There's only a little plastic and plenty of air. If
the PVC tube were thin enough, it might be considered air core.

You are correct. But, the losses (percentage-wise) will be the same
barring heating effects.

The losses are fairly small, but the effects on the material at
different power levels quite different. For example, a 1dB power loss
at the 5 watt level will produce about 1 watt of heat. That same 1dB
loss at 150 watts will produce 30 watts of heat, which will probably
melt the coil form.

It wouldn't be air core considering that it would be over
wood (dry and waterproofed) or PVC pipe.

For a hollow PVC or ABS pipe, it's mostly air core. (For a solid wood
coil form, it's all wood with some absorbed water.) I'm not sure how
to calculate the effective dielectric constant of a hollow plastic
pipe. Probably by measuring the inductance of a surrounding coil with
and without the pipe, and calculating what dielectric constant was
necessary to produce the change. Unfortunately, that doesn't help
calculate the combined losses or loss tangent.

Most posters here do not state all of the facts initially. That's
because most of their ideas are still brewing in the brain and some of
the details are not formalized. It is the reason we ask for other
people's inputs. Cut him some slack and continue to ask how you can help.

Of course. However, I post far too many "answers" in far too many
newsgroups and mailing lists to remember everyones situation. If I'm
expected to spend my time answering a question or solving a problem, I
expect to be provided with:
1. What problem are you trying to solve? A one line description is
sufficient.
2. What do you have to work with? (Equipment, site limitations,
available test equipment, numbers, numbers, numbers).
3. What have you done so far and what happened?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Saturday, October 5, 2013 7:44:30 PM UTC-5, Jeff Liebermann wrote:
On Sat, 05 Oct 2013 15:24:01 -0500, John S

wrote:



The microwave oven test is not very useful. The microwave will test

whatever at about 2450MHz. I doubt he is trying to make a loading coil

for anything near that frequency.



Actually, it's very useful. In my admittedly limited experience,

anything that survives the microwave oven test, will usually work

nicely at HF frequencies. Those that get warm in the oven, might

work ok. Those that melt, burn or explode, will probably not work

very well at HF. While testing at 1000 times the frequency, and 30

times the power, might be considered overkill, it does yield some

useful information.

I had always heard that if one were to use PVC, the gray type was
the best vs the white. I've used gray PVC for mobile whip loading
coils for years and never really noticed any real problems.
But, I do not run high power, and 100w is the max I run.
I've always had good results with the antennas, and noticed no
noticeable performance loss vs say an open type bug catcher coil.
There may be some, but it's small enough not to be a problem.

When I first started using the gray PVC, I stuck it in the
microwave with a glass of water, and it did not get warm at all.
I have heard the white PVC can be more of a problem.

On 10/6/2013 2:32 AM, wrote:
On Saturday, October 5, 2013 7:44:30 PM UTC-5, Jeff Liebermann wrote:
On Sat, 05 Oct 2013 15:24:01 -0500, John S

wrote:



The microwave oven test is not very useful. The microwave will test

whatever at about 2450MHz. I doubt he is trying to make a loading coil

for anything near that frequency.



Actually, it's very useful. In my admittedly limited experience,

anything that survives the microwave oven test, will usually work

nicely at HF frequencies. Those that get warm in the oven, might

work ok. Those that melt, burn or explode, will probably not work

very well at HF. While testing at 1000 times the frequency, and 30

times the power, might be considered overkill, it does yield some

useful information.

I had always heard that if one were to use PVC, the gray type was
the best vs the white. I've used gray PVC for mobile whip loading
coils for years and never really noticed any real problems.
But, I do not run high power, and 100w is the max I run.
I've always had good results with the antennas, and noticed no
noticeable performance loss vs say an open type bug catcher coil.
There may be some, but it's small enough not to be a problem.

When I first started using the gray PVC, I stuck it in the
microwave with a glass of water, and it did not get warm at all.
I have heard the white PVC can be more of a problem.


The guys that build high Q inductors for crystal radios use
styrene pipe couplers.
http://www.genovaproducts.com/docs/P...og.pdf#page=37
Note: S prefix denotes styrene.
I see references to both Lowes and Home depot having these in stock.
I think styrene will deform at a lower temperature than PVC.
Mikek

On Sun, 6 Oct 2013 00:32:22 -0700 (PDT), wrote:

I had always heard that if one were to use PVC, the gray type was
the best vs the white. I've used gray PVC for mobile whip loading
coils for years and never really noticed any real problems.
But, I do not run high power, and 100w is the max I run.
I've always had good results with the antennas, and noticed no
noticeable performance loss vs say an open type bug catcher coil.
There may be some, but it's small enough not to be a problem.

When I first started using the gray PVC, I stuck it in the
microwave with a glass of water, and it did not get warm at all.
I have heard the white PVC can be more of a problem.

http://lists.contesting.com/_towertalk/2006-12/msg00091.html

I ran tests at 2.4GHz about 15 years ago. The plan was to use PVC
pipe as a 2.4GHz antenna radome. While heating is obviously not an
issue at 1 watt, even small losses and detuning were deemed
intolerable. I couldn't measure any difference between grey or white
as long as the pipe was the same thickness. However, things went awry
when I tried to build prototypes out of a mix of different brands of
white PVC pipe. The dielectric constant was all over the map causing
the resonance point to move around. After determining that even a
single supplier can't keep their electrical characteristics
consistent, we switched to the more expensive fiberglass tubing and
lived happily thereafter.

Another potential problem with a base loaded vertical is not power,
but voltage. At 5 watts, there's not going to be much voltage across
the coil. At 150 watts, it might arc. No calcs today. Gotta run and
watch the solar satellite outage today.
http://en.wikipedia.org/wiki/Sun_outage

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 10/6/2013 10:24 AM, Jeff Liebermann wrote:
Gotta run and
watch the solar satellite outage today.
http://en.wikipedia.org/wiki/Sun_outage

Sorta like watching paint dry.

On Sun, 06 Oct 2013 14:42:31 -0500, John S
wrote:

On 10/6/2013 10:24 AM, Jeff Liebermann wrote:
Gotta run and
watch the solar satellite outage today.
http://en.wikipedia.org/wiki/Sun_outage

Sorta like watching paint dry.

Ummm... no, it's not like watching paint dry.

I live in a forest of 50 meter redwood and fir trees. If you want to
receive TV or digital audio from a satellite, you need to find or make
a hole in the trees. During the solar satellite outage is the perfect
time to do this. Any place where the sun is shining during the
approximately 4 minutes of the outage is a good dish location. This
is my house in 2008:
http://802.11junk.com/jeffl/pics/DBS/
It's also a good time to check if any tree branches are blocking
reception as they cast a shadow on the dish. Note the branch shadows:
http://802.11junk.com/jeffl/pics/DBS/slides/101d.html
At 13 and 30GHz, the Fresnel Zone is about the same diameter as the
dish, so any hole in the trees bigger than the dish will work (until
the wind blows).

This year, I was at a customer with a similar problem. During the 4
minutes, we both ran around the property, taking photos of prospective
dish locations. We also discovered that his existing Exede dish had a
few branch shadows, which explains why it needs to be moved. We found
what I think will be a good location, as soon as the concrete sets.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 10/6/2013 10:24 AM, Jeff Liebermann wrote: Gotta run and
watch the solar satellite outage today.
http://en.wikipedia.org/wiki/Sun_outage


I lost several minutes of the nascar race on ESPN and then a while
later on radio, a syndicated program (Bob Brinker) was out for 3 to 6
minutes. It all happened (approximately) between 3:45 and 4:20.
Was that the sun outage?
Mikek

On Sun, 06 Oct 2013 16:37:56 -0500, amdx wrote:

On 10/6/2013 10:24 AM, Jeff Liebermann wrote: Gotta run and
watch the solar satellite outage today.
http://en.wikipedia.org/wiki/Sun_outage

I lost several minutes of the nascar race on ESPN and then a while
later on radio, a syndicated program (Bob Brinker) was out for 3 to 6
minutes. It all happened (approximately) between 3:45 and 4:20.
Was that the sun outage?
Mikek

Unless the downlink was in Hawaii, it's unlikely that it was directly
caused by the sun outage. It happend on Viasat-1 (Wild Blue or Exede)
today at about 12:25PM. The earth rotates at:
24hrs * 60min/hr / 360deg = 4 min/deg
With a difference of about 3.5 hrs (210 minutes), the earth will have
rotated:
210min / 4 min/deg = 52 degree longitude or about:
122w + 52 = 174w
which is almost at the International Date Line. A more sane guess
would be that what you were watching was recorded between 12PM and 2PM
for delayed broadcast somewhere in the continental USA, during which
time there was a solar outage.

A 3 to 6 minute outage implies 1 or 2 meter receive dish.

Most stations know about the problem and usually have something
pre-recorded available to fill in the outage. I'm rather surprised
that ESPN wasn't paying attention.

Grind your own numbers:
http://www.satellite-calculations.com/Satellite/suninterference.php

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sunday, October 6, 2013 10:24:55 AM UTC-5, Jeff Liebermann wrote:

Another potential problem with a base loaded vertical is not power,

but voltage. At 5 watts, there's not going to be much voltage across

the coil. At 150 watts, it might arc. No calcs today. Gotta run and

watch the solar satellite outage today.

http://en.wikipedia.org/wiki/Sun_outage

I haven't had any problems with 100w. Mine are center to above
center loading though. Usually not base loaded.
In the normal driving mode, it's almost exactly center loaded.
But I have a solid mast I add below the glass whip when parked,
and then it's probably 2/3 up from the base or so.
These antennas are basically plastic bugcatchers. And you
could use two back to back as a dipole that could fit in a
fairly tight area.