From: "Dr. Barry L. Ornitz" <ornitz@usa.net>
Newsgroups: rec.radio.amateur.homebrew
Subject: Re: Raising coil Q in regen RX - Materials and Q-dope
Date: Wed, 31 Jan 2001 02:28:32 -0500

"Boatanchor Bob NA4G" <na4g@weedcon3.cropsci.ncsu.edu> wrote
in message news:9577k0$abg$1@uni00nw.unity.ncsu.edu about
regenerative receivers.

Excellent advice, Bob!

> Enamel is good, or teflon coated is good.

With large wire spacings and large coil diameter, the
dielectric is not too important.  I would prefer enamel wire
from a motor shop to vinyl covered house wire, however,
because of the much higher loss of plasticized PVC.

>> - ribbed former, or better no former at all
>>   (easier with thick wire)
>
> Use a ribbed former with good insulating properties. Glass
> would be good, or isolantite.  I find that at usual regen
> frequencies, acrylic works good, too.

Actually acrylic will have lower dielectric losses than
glass and many ceramics.

>> - another option: two or more side spacers instead of a
>> full former (this is quite common in big coils in old
>> transmitting equipment)
>
> This was typical of better quality regens in the so called
> "low-loss" era of the early to mid 1920's.  It still works
> fine today.

These are easy to make with Plexiglas or Lucite too.  Just
file notches to hold the wire.

>> Have you ever heard of a special glue for use on coils?
>> Does Araldite ring a bell?  I last heard about it perhaps
>  20 years ago.
>
> That would be the early electron microscopy era, where it
> was used as an embedding medium for thin sections?  Is it
> still available?

Araldite is a trade name for many related adhesives and
resins.  Today most are generically known as epoxy.  Their
dielectric loss properties are not as good as the the old
standby, polystyrene Q-dope.

> I would expect teflon would do well, too, but cost an arm
> and a leg to machine.

Teflon is easy to machine unless you need precision
tolerances.  Then you need to cool it in liquid nitrogen
first.  :-)   It is somewhat expensive.  Acrylic tubing is
availabe from most plastics distributors.  A section cut
from a plastic soft drink bottle (polyethylene
terephthalate) makes a reasonably low loss dielectric but it
may be too flimsy.

Q-dope is still sold, but you can easily make your own.  Get
a pint glass bottle and fill it about 3/4 full of toluene
(which can still be bought at Home Depot around here).  Add
polystyrene peanuts.  You would be amazed at how many will
go in the bottle.  Soon you will have a rather sticky mess
that looks much like a liquid with fur-balls in it.  Cap the
bottle tightly and let it sit for a few weeks.  Think of the
polymer chains as blobs of tangled spaghetti.  In the
solvent, they will eventually untangle and uncoil.  This
takes a while so don't think they did not dissolve if the
solution looks cloudy the next day.

Eventually almost all of the polystyrene peanuts will
dissolve.  You may have some sediment (often pigments and
contaminants) at the bottom of the bottle.  Add some
additional toluene if the solution is too viscous (thick to
non-chemists).

When using toluene or any other flammable solvent, stay well
away from flames or sparks.  Avoid breathing the fumes and
work in a well ventilated area.  Acetone is usually an
acceptable substitute for the toluene and it is far less
toxic.  I have made quite acceptable coil dope either way.

[Some trivia...  Originally coil dope took its name from
solutions of cellulose esters, which the original coil dopes
were made from.  In the early days, these were cellulose
nitrate and later came cellulose acetate, propionate, or
butyrate.  In manufacturing these esters, the solutions are
still known as dopes.  Likewise in cloth wing aricraft, the
fabric coatings are called dopes.  I have no idea of the
origin of the term, however.  Of course, sniffing too much
of the solvents will turn you into one! (And destroy your
liver too!)]

        73,  Barry     WA4VZQ     ornitz@usa.net

From: "Dr. Barry L. Ornitz" <ornitz@usa.net>
Newsgroups: rec.radio.amateur.homebrew
Subject: Re: Raising coil Q in regen RX - Materials and Q-dope
Date: Thu, 1 Feb 2001 03:22:39 -0500

Hi Dick,

Since your questions will be likely asked by others too,
I'll answer them here.

"Dick Carroll" <dixie@townsqr.com> wrote in message
news:95au17$6bv$0@208.207.71.176...
> Thanks for this good information. My bottle of Q-dope
> always dries out long before it is empty, and usually
> can't be opened.

Drip some fresh solvent into the bottle-cap threads.  This
often softens the dried plastic.

>   Question: You said "polystyrene" peanuts. Are they the
> same matereial as what are almost universally known as
> "styrofoam" peanuts, or they the more rarely seen tough,
> spongy pellets that appear to be cut off pieces of rod?

The crunchy kind.  Styofoam is just one trademarked name
(Dow, I think).  I usually use the generic names since when
I worked in the chemical industry and wrote reports, I was
taught to avoid  using such trademarks and copyrighted
names.

> Also: Can one thin commercial Q-dope with acetone to
> prevent it from drying out? I keep a pint of acetone on
> hand. Or should I go looking for some Tolulene?

Look on the bottle to see which solvent is currently being
used.  You will have better luck thinning it with the same
solvent.  Recognizing which is used by smell is second
nature to me, but thinking about it, I find it hard to
describe either smell.  To me toluene smells sweeter than
acetone.  Since you have acetone, you should recognize its
smell. Polystyrene is somewhat more soluble in toluene than
it is in acetone.

I generally recommend acetone as a good, general purpose
solvent for many applications because it is far less toxic
than most others.  It is generally considered about the same
toxicity as isopropyl alcohol.  It is a good polar solvent,
where toluene is non-polar.  For general degreasing, where a
non-polar solvent is desired, I usually use painter's
naphtha (or Stoddard solvent, the main ingredient in WD-40,
which is a highly refined kerosene distillation cut).

All of these are very flammable, and while acetone and
naphtha are not terribly toxic, toluene is fairly bad.  It
is best to avoid breathing the vapors of any solvent.  So
work in a very well ventilated area and use safety glasses.
If you need to wipe something down with a solvent-soaked
rag, wear protective gloves.  The nitrile (Buna N) gloves
are generally best with solvents.

        73,  Barry     WA4VZQ     ornitz@usa.net

From: "Dr. Barry L. Ornitz" <ornitz@usa.net>
Newsgroups: rec.radio.amateur.homebrew
Subject: Acetone
Date: Thu, 1 Feb 2001 19:51:56 -0500

<glass2@glass2.lexington.ibm.com> wrote in message
news:95bu1f$h54$2@ausnews.austin.ibm.com...
> I seem to remember a warning on the last can of Acetone that I
> bought warning that it may be a liver carcinogen (I'm not sure
> whether this is due to the Acetone itself, or due to a contaminant
> in it).  In any case, please be sure to read and heed all
> appropriate warnings on the container.  Additionally, it may be
> worth obtaining a MSDS on the chemicals in use.

Acetone is listed as being non-carcinogenic by NTP, IARC,
ACGIH and OSHA.  I used to work for the company whose long
history of safely working with acetone convinced the EPA to
remove it from the SARA 313 list (Eastman Kodak).

Like most solvents, acetone can certainly harm the liver and
kidneys.  Just as it is a good degreaser for cleaning parts,
it also dissolves the fat from cells in the liver and
kidney.  Skin dermatitis may result from this same action on
the skin.  This is the reason I suggested the use of Nitrile
gloves, safety glasses, and working in a well ventilated
area.  As I noted, acetone is similar to isopropyl alcohol
in its toxicity.  Drinking an ounce will probably not kill
you (but the hangover and other nasty effects may make you
wish it did).  Ethyl alcohol (ethanol - the drinking kind)
will also de-fat your liver and kidneys, and also cause
intoxication and brain damage.

But if you compare the toxicity of acetone, isopropanol, and
ethanol to commercial brake and carbureter cleaners, brake
fluid, antifreeze, gasoline, etc. - you will find them to be
pretty tame in comparison.  This is not to say you should
treat them as harmless; it merely says you should treat the
other materials with considerable care.

            73,  Barry     WA4VZQ     ornitz@usa.net

From: "Dr. Barry L. Ornitz" <ornitz@usa.net>
Newsgroups: rec.radio.amateur.homebrew
Subject: Re: Acetone
Date: Sat, 3 Feb 2001 02:23:42 -0500

"Kawaya" <on5wv@RadioLink.net> wrote in message
news:4mdl7tkbjtd257u4sdiv4l5l3fd1r2n9ol@4ax.com...

> How does MethylEthylKetone compare to Acetone?

It is somewhat more toxic than acetone, but still less
dangerous than the chlorinated solvents or aromatics
(benzene, toluene, xylene).  It is not considered a
carcinogen.  The odor of MEK does not bother me too much,
but the odor of methyl isobutyl ketone can give me a
headache within minutes.

As a comparison, the permissible exposure levels and short
term maximum exposure levels for acetone and methyl ethyl
ketone (MEK) are shown below:

                    Acetone             Methyl Ethyl Ketone
OSHA PEL            1000 ppm                 200 ppm
OSHA STEL                                    300 ppm
ACGIH PEL            750                     200 ppm
ACGIH STEL          1000 ppm                 300 ppm

OSHA - Occupational Safety and Health Administration
ACGIH - Americal Council of Government and Industrial
Hygienists
ppm - part per million (by volume in air)

        73,  Barry      WA4VZQ     ornitz@usa.net