Ted Bruce wrote:
Cecil,
I'm pretty sure that Plexiglass is a trade name for acrylic panels.
That stuff is not at all durable.

There's a picture of the Plexiglas® panel on my web page that
was taken ten years ago in Arizona and I'm still using it.
It's the 1/2 inch thick stuff, is still in good shape, and
is still performing its function perfectly. My Piper Plastics
properties chart says the effect of sunlight on Acrylic is "nil".
The main reason that I used acrylic was - it was a 50 cent piece
of stuff from the odds and ends box at a plastics place in Phoenix.
I also used it and some acrylic rods to build an air-core mobile
loading coil about 15 years ago. That coil is still in good shape.

On the othe hand, Lexan (trade
name) is polycarbonate, which is very durable.

Yep, Lexan® is the stuff used in Airplane windows and is easy
to machine. It is superior to acrylic in every way. If I had
used polycarbonate, it would probably still be performing its
function perfectly. (My '96 GMC Sierra Pickup with 180,000 miles
on it is still performing its function perfectly. :-)
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil,
FB on the thick Plexiglas! I was thinking along the lines of window
pane thickness. I put a couple of 2 x 4 feet 1/8" Plexiglas panels on
the back porch to keep the dog from clawing the screen out. She made
very quick work of those :)

I went back to Home Depot and replaced them with Lexan, and nooo
problem!

I have your page bookmarked, Cecil...I'll go there and take a look.

As I said before, Lexan is a trade name for polycarbonate. That's the
stuff I curse at when trying to open a package that typically hangs
on hooks in a store. Even using scissors, it's very tough to cut. A
few year ago, when my son had an RC car, the bodies were made out of
polycarbonate, and you painted them on the inside. Very
indestructable in that applicaton.


On Wed, 23 Mar 2005 09:13:34 -0600, Cecil Moore
wrote:

Ted Bruce wrote:
Cecil,
I'm pretty sure that Plexiglass is a trade name for acrylic panels.
That stuff is not at all durable.

There's a picture of the Plexiglas® panel on my web page that
was taken ten years ago in Arizona and I'm still using it.
It's the 1/2 inch thick stuff, is still in good shape, and
is still performing its function perfectly. My Piper Plastics
properties chart says the effect of sunlight on Acrylic is "nil".
The main reason that I used acrylic was - it was a 50 cent piece
of stuff from the odds and ends box at a plastics place in Phoenix.
I also used it and some acrylic rods to build an air-core mobile
loading coil about 15 years ago. That coil is still in good shape.

On the othe hand, Lexan (trade
name) is polycarbonate, which is very durable.

Yep, Lexan® is the stuff used in Airplane windows and is easy
to machine. It is superior to acrylic in every way. If I had
used polycarbonate, it would probably still be performing its
function perfectly. (My '96 GMC Sierra Pickup with 180,000 miles
on it is still performing its function perfectly. :-)

Roy,
What wiould be the property of a polymer like acrilic or polycarbonate
to determine its effectiveness as an insulator or a dielectric?
Volume resistivity?

Tnx,
Ted KX4OM

On Fri, 18 Mar 2005 17:23:36 -0800, Roy Lewallen
wrote:

---snip---

Ted Bruce wrote:
Roy,
What wiould be the property of a polymer like acrilic or polycarbonate
to determine its effectiveness as an insulator or a dielectric?
Volume resistivity?

Tnx,
Ted KX4OM

Volume resistivity is a useful measure only at DC.

To determine a dielectric's lossiness at RF, look at the loss tangent,
dissipation factor, or power factor. Loss tangent and dissipation factor
are the same thing, and when loss is low, power factor is also the same
for practical purposes. You'll find these in tables and descriptions of
the electrical properties of insulators. Some searching will usually
turn them up on the web if you don't have access to the appropriate
reference books. Note that the loss properties are usually a function of
frequency, so use the value at approximately the frequency of interest.

In some situations, the capacitance of the dielectric can be important,
such as when you're using it as a coil form or antenna covering. For
that, look at the dielectric constant or relative permittivity (which
are the same thing). This also changes somewhat with frequency.

Roy Lewallen, W7EL

I should also mention that the requirements for an insulator depend
heavily on the application. An insulator which results in a lot of loss
when a large electric field is present might produce negligible loss
when the field is weak. For example, an insulator at the base of a very
short or half wavelength high vertical, or at the end of a dipole, has
to be pretty good in order to minimize loss, because the electric field
is high at those points. On the other hand, a poor quality insulator is
just fine at the base of a quarter wave high vertical or the center of a
half wave dipole, since the electric field is low at those points.

Roy Lewallen, W7EL

I see 31 Mix snap-on beads listed by DXEngineering as effective in reducing
ignition noise by placing them on ignition wires. (0.275 inches)

I have several questions about their application for ignition wires:

1. Where along the wire should they be placed (at the plug, at the
distributor, middle of wire)?

2. Should they be stacked next to each other for better effect (series
butted up against one another) and if so, how many, and again, where along
the wire?

3. How many should be used and as above, how should they be "clustered"?

They come in packs of 10 and since I have a For Taurus ('95) 3.0 V6, I have
6 wires to deal with. 2 packs would yield 20 chokes, for example, and
perhaps a silly way to look at it would be to put one at each end of each
wire and one in the middle of each wire, using 3 per wire or 18 of the 20
available.

4. Are these likely to be significant help on either HF or VHF?

5. Can anyone recommend a really good set of ignition wires for best RFI
suppression?

(and yes, I'm aware of the fuel pump noise problem...but I'm concentrating
on ignition noise at the moment)

TIA

....hasan, N0AN

On Wed, 30 Mar 2005 06:33:36 -0600, hasan schiers wrote:

I see 31 Mix snap-on beads listed by DXEngineering as effective in reducing
ignition noise by placing them on ignition wires. (0.275 inches)

I have several questions about their application for ignition wires:

1. Where along the wire should they be placed (at the plug, at the
distributor, middle of wire)?

2. Should they be stacked next to each other for better effect (series
butted up against one another) and if so, how many, and again, where along
the wire?

3. How many should be used and as above, how should they be "clustered"?

They come in packs of 10 and since I have a For Taurus ('95) 3.0 V6, I have
6 wires to deal with. 2 packs would yield 20 chokes, for example, and
perhaps a silly way to look at it would be to put one at each end of each
wire and one in the middle of each wire, using 3 per wire or 18 of the 20
available.

4. Are these likely to be significant help on either HF or VHF?

5. Can anyone recommend a really good set of ignition wires for best RFI
suppression?

(and yes, I'm aware of the fuel pump noise problem...but I'm concentrating
on ignition noise at the moment)

TIA

...hasan, N0AN

Buy a package. Try it. Report back to the news group what you observed.

On Wed, 30 Mar 2005 06:33:36 -0600, "hasan schiers"
wrote:

Hi Hasan,

By the numbers:

1. Where along the wire should they be placed (at the plug, at the
distributor, middle of wire)?

Doesn't matter.

2. Should they be stacked next to each other for better effect (series
butted up against one another) and if so, how many, and again, where along
the wire?

Doesn't matter.

3. How many should be used and as above, how should they be "clustered"?

Until you achieve relief (you haven't described why you want to do
this).

4. Are these likely to be significant help on either HF or VHF?

By the presumption of this indicating a receiver problem with HF or
VHF, I would offer that most (modern) cars do not display such
problems. You could be chasing the wrong solution. However, at the
bottom line, they could help.

5. Can anyone recommend a really good set of ignition wires for best RFI
suppression?

Standard resistive wires. It sounds like you substituted straight
wires for the factory set when they wore out. That is generally a
poor choice for two reasons. One (presumably) is due to ignition
interference with communications. The other is lowered fuel economy
and power.

The application of ferrites to straight wires is introducing resistive
loss into the ignition current path. This is normally the job of
resistive wire. Introducing such loss is actually a boon. The loss
retards spark extinction (means that the spark will burn longer with a
resistance in the path). Longer burn time means more complete
ignition. This also means that the longer burn time equates to fewer
HF spurious products. This is called win-win.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

5. Can anyone recommend a really good set of ignition wires for best RFI
suppression?


Standard resistive wires. It sounds like you substituted straight
wires for the factory set when they wore out. That is generally a
poor choice for two reasons. One (presumably) is due to ignition
interference with communications. The other is lowered fuel economy
and power.

The application of ferrites to straight wires is introducing resistive
loss into the ignition current path. This is normally the job of
resistive wire. Introducing such loss is actually a boon. The loss
retards spark extinction (means that the spark will burn longer with a
resistance in the path). Longer burn time means more complete
ignition. This also means that the longer burn time equates to fewer
HF spurious products. This is called win-win.

73's
Richard Clark, KB7QHC

Bosch, and at least one other company whose name I've forgotten, used to
make a solid wire ignition cable that was coiled internally into a very
long choke. I used them 15 years ago on one of my vehicles that had a
noisy ignition system, and they were fairly effective, better than
resistor wires were on that car. I am not sure if they are still made,
but asking at your FLAPS should give you a quick answer.

tom
K0TAR

Oh, FLAPS is short for Friendly Local Auto Parts Store.

Hi Richard,

(BTW, I was looking to reduce ignition noise to my D700 in the car,
specifically in the VHF region). I have replaced the plugs, cap and rotor. I
haven't replaced the ignition wires. I was thinking "chokes" on the wires
might do it, but after thinking about it more, and relocating the articles
on RFI/EMI suppression wires, it was apparent that no snap-on chokes would
work as well as the wires noted below by magnecor.

I now remember (from 10 years ago) what the ignition wires were that were
claimed by hams as the best for reducing ignition noise generation.
"Magnecor"...as in magnecor.com.

That is what I put in, and they are getting pretty old , 10 years and 198K
miles on the car/wires.

Instead of using the 31 mix chokes, I think my money would be better spent
getting another set of wires.

In the end, perhaps the only thing that would have helped would have been to
buy enough of the snap-on chokes to cover the wires completely, which makes
no economic sense.

To the "gentleman" who suggested (without offering any information or
responses to my questions) that I buy the chokes, put them on and report
back...sorry, I'm not providing information, I'm soliciting it. Your
response didn't provide any info, didn't bother to respond to ANY of the
questions, and just contained a rather pointless recommendation....if you
didn't understand that I wanted someone who "knew" or had thought about the
problem to offer an opinion as to the efficacy of 31 mix chokes in this
application BEFORE I bothered to buy them, you missed a rather obvious
point....duh! This "gentleman" also provides no real name, and no amateur
callsign. The typical smart-ass troll.

Thanks to the others (on-list and private), including Richard, who
responded. One of the responses led me back to the source of my ten year old
wires and how to replace them...I had no idea if the company was still in
business or not, nor could I remember their name. They are still there, and
I'm going to order a wire-set this morning.

73,

p.s., I might add for learning sake, several of your answers, Richard, beg a
"why not". (As in, why doesn't it matter which end, distributor or plug
would be more effective, Stacking chokes vs. spacing them out along the
wires doesn't matter? Why not?)

Your observation that most modern cars don't have ignition noise is
borderlline laughable for two reasons:

1. It's not true...most in fact do create quite a bit of RFI to HF radios
and some are quite problematic even at two meters.

2. I spend my spare money on radios/antennas and computers, not new
cars...which my '95 Ford Taurus with 198K miles on it testifies to. It is
very well maintained, but old. (and NOISY from an RFI/Ignition point of
view).

Thanks for taking the time to respond. (to all) 73

....hasan, N0AN

"Richard Clark" wrote in message
...
On Wed, 30 Mar 2005 06:33:36 -0600, "hasan schiers"
wrote:

Hi Hasan,

By the numbers:

1. Where along the wire should they be placed (at the plug, at the
distributor, middle of wire)?

Doesn't matter.

2. Should they be stacked next to each other for better effect (series
butted up against one another) and if so, how many, and again, where along
the wire?

Doesn't matter.

3. How many should be used and as above, how should they be "clustered"?

Until you achieve relief (you haven't described why you want to do
this).

4. Are these likely to be significant help on either HF or VHF?

By the presumption of this indicating a receiver problem with HF or
VHF, I would offer that most (modern) cars do not display such
problems. You could be chasing the wrong solution. However, at the
bottom line, they could help.

5. Can anyone recommend a really good set of ignition wires for best RFI
suppression?

Standard resistive wires. It sounds like you substituted straight
wires for the factory set when they wore out. That is generally a
poor choice for two reasons. One (presumably) is due to ignition
interference with communications. The other is lowered fuel economy
and power.

The application of ferrites to straight wires is introducing resistive
loss into the ignition current path. This is normally the job of
resistive wire. Introducing such loss is actually a boon. The loss
retards spark extinction (means that the spark will burn longer with a
resistance in the path). Longer burn time means more complete
ignition. This also means that the longer burn time equates to fewer
HF spurious products. This is called win-win.

73's
Richard Clark, KB7QHC