wrote in message
...

Modern dielectric oil (aka transformer oil) is refined mineral oil
with an antioxidant (tocopherol, BHA, or BHT) added to retard
spoiling.

Mineral oil does not "spoil" in the sense that animal or vegetable fats
(long chain carboxylic acids) do. Tocopherol (Vitamin E),
butylated-hydroxyanisole and butylated-hydroxytoluene are used (in the low
part per million range) to prevent oxidation of the oil which produces
"sludge" and "varnish" (here used as referring to deposits from
hydrocarbons such as gasoline on fuel tanks and carburetters). All three
compounds are also used in the food industry - to prevent spoilage. :-)

Shell Diala AX
ExxonMobil Univolt 65

are the two major kinds (there's one from Castrol,too)

Both are sold (in 5 gallon pails, typically, as a minimum quantity) by
"jobbers" which can be found on the mfr's website (you enter a zip
code and gives you the distributors within X miles), or by looking in
the yellow pages under Oil,Lubricants-Jobbers. Used to be in the $4-5/
gallon range, but I just was talking to someone who had to pay around
$50 for a 5gallon pail. (probably a hangover from $100/bbl crude
prices)

You *can* use USP White Mineral Oil (laxative) available in pints at
the drugstore, gallons at the feedstore (If you've got a colicky
horse, gallons are the quantity wanted), but it's
a) more expensive
b) not water content controlled

For HV dielectric purposes water content (in the ppm range) is
important. So is particulate contamination. For a dummy load,
probably not so much.

The partioning coefficient of agricultural grade white mineral oil is
greater than one million. Dissolved water will have no measurable effect
on the dummy load.

Another inexpensive source of mineral oil without many additives is
hydraulic oil (as used in, say, tractors, etc.).

Even "straight weight" motor oil without additives/detergents can work
(look for the SAE 10,15, or 20 viscosities).. it can be VERY cheap on
sale as a "loss leader" to get folks into the store (since nobody in
their right mind would actually run this in an engine)

For good natural convection around and through the Kanthal-Globar silicon
carbide resistor used in the Cantenna, I would use no higher a viscosity
oil than SAE 5.

For a dummy load, viscosity IS important, because convective flow is
important. (viscosity change with temperature, too...)

Most organic oils are less viscous at higher temperatures. This is good in
the Cantenna application. The lubricating properties of the oil are
unimportant here.

Silicone would be massive overkill, and we won't even get into
Fluorinert. BTW, if you spill mineral oil, it cleans up nicely with
detergent and water.. the same cannot be said of silicone or FC-xx..
Silicone oils are almost impossible to remove.

This is an excellent point. Freon TF®
(1,1,2-trichloro-1,2,2-trifluoroethane) was excellent for removing silicone
oils and greases, and it had a number of physical properties that made it
ideal for many electronic applications. It is too bad that it is banned as
a ozone destroying chlorofluorocarbon. In looking at some of the
alternatives for cleaning away silicone oils, I would suggest looking at
Caig Laboratories (makers of DeoxIT®) CaiKleen NF which is mainly
1,1,1,3,3-pentafluoropropane. Unfortunately its boiling point is 15 C (59
F) and it is quite expensive.

Good post, Jim!

73, Dr. Barry L. Ornitz WA4VZQ

Art Unwin wrote:
On Jan 1, 9:49 am, "KC8QJP" wrote:
"John Passaneau" wrote in message

... KC8QJP wrote:
a crisco can works well
Sometimes you can get empty paint cans at professional paint supplies
stores. They are nice as they are clean and shiny.
John W3JXP
Thanks for the tip!

Yes. I did that The new can had a plastic type coating on the inside
to prevent any possible leaks and corrosion, a great improvement over
cans of yesteryear that leaked on to the floor over time. Same story
for the lid., Cost me something like $3 and well worth it.
Art
The hole in the lid of a Heathkit Cantenna was to allow for expansion
due to heat buildup in the oil during heavy use. Make sure you allow for
this expansion in any sealed container if you roll your own cantenna.

Dave WD9BDZ

NoSPAM wrote:
wrote in message
...

Modern dielectric oil (aka transformer oil) is refined mineral oil
with an antioxidant (tocopherol, BHA, or BHT) added to retard
spoiling.

Mineral oil does not "spoil" in the sense that animal or vegetable fats
(long chain carboxylic acids) do. Tocopherol (Vitamin E),
butylated-hydroxyanisole and butylated-hydroxytoluene are used (in the
low part per million range) to prevent oxidation of the oil which
produces "sludge" and "varnish" (here used as referring to deposits from
hydrocarbons such as gasoline on fuel tanks and carburetters). All
three compounds are also used in the food industry - to prevent
spoilage. :-)

Shell Diala AX
ExxonMobil Univolt 65

are the two major kinds (there's one from Castrol,too)

Both are sold (in 5 gallon pails, typically, as a minimum quantity) by
"jobbers" which can be found on the mfr's website (you enter a zip
code and gives you the distributors within X miles), or by looking in
the yellow pages under Oil,Lubricants-Jobbers. Used to be in the $4-5/
gallon range, but I just was talking to someone who had to pay around
$50 for a 5gallon pail. (probably a hangover from $100/bbl crude
prices)

You *can* use USP White Mineral Oil (laxative) available in pints at
the drugstore, gallons at the feedstore (If you've got a colicky
horse, gallons are the quantity wanted), but it's
a) more expensive
b) not water content controlled

For HV dielectric purposes water content (in the ppm range) is
important. So is particulate contamination. For a dummy load,
probably not so much.

The partioning coefficient of agricultural grade white mineral oil is
greater than one million. Dissolved water will have no measurable
effect on the dummy load.

Another inexpensive source of mineral oil without many additives is
hydraulic oil (as used in, say, tractors, etc.).

Even "straight weight" motor oil without additives/detergents can work
(look for the SAE 10,15, or 20 viscosities).. it can be VERY cheap on
sale as a "loss leader" to get folks into the store (since nobody in
their right mind would actually run this in an engine)

For good natural convection around and through the Kanthal-Globar
silicon carbide resistor used in the Cantenna, I would use no higher a
viscosity oil than SAE 5.

For a dummy load, viscosity IS important, because convective flow is
important. (viscosity change with temperature, too...)

Most organic oils are less viscous at higher temperatures. This is good
in the Cantenna application. The lubricating properties of the oil are
unimportant here.

Silicone would be massive overkill, and we won't even get into
Fluorinert. BTW, if you spill mineral oil, it cleans up nicely with
detergent and water.. the same cannot be said of silicone or FC-xx..
Silicone oils are almost impossible to remove.

This is an excellent point. Freon TF®
(1,1,2-trichloro-1,2,2-trifluoroethane) was excellent for removing
silicone oils and greases, and it had a number of physical properties
that made it ideal for many electronic applications. It is too bad that
it is banned as a ozone destroying chlorofluorocarbon. In looking at
some of the alternatives for cleaning away silicone oils, I would
suggest looking at Caig Laboratories (makers of DeoxIT®) CaiKleen NF
which is mainly 1,1,1,3,3-pentafluoropropane. Unfortunately its boiling
point is 15 C (59 F) and it is quite expensive.

Good post, Jim!

73, Dr. Barry L. Ornitz WA4VZQ

Hi all:

Great post with lots of good info. But look for a power line transformer
there are very high voltages and a lot of power. In a Ham dummy load the
max voltage on the resistor would be about 275V at 1500w. Unless your a
CB'er you will not see more than that. So hundreds, my self includeDd
Ham's have use common mineral oil from the drug store with fine results.
So go for it. The last time I was took part in filling a dummy load was
back in the seventy's. I was helping friend move into a new house and
set up the ham shack. We needed to get new oil for the dummy load as we
had dumped the old oil rather than move it full and take the chance of
it spilling. So we went to the store and got the oil and along with it
we picked up some water glasses and repair parts for a toilet. The check
out girl looked at us kind of funny and I really did my friend
reputation in by telling her we had found a new way to turn on...


John Passaneau, W3JXP

John Passaneau wrote:


Great post with lots of good info. But look for a power line transformer
there are very high voltages and a lot of power. In a Ham dummy load the
max voltage on the resistor would be about 275V at 1500w. Unless your a
CB'er you will not see more than that. So hundreds, my self includeDd
Ham's have use common mineral oil from the drug store with fine results.


The issue isn't the water content or particulate contamination (which
affect the HV behavior) but the viscosity. Diala AX (for instance) is
quite low viscosity. 9.7 cSt/56 SUS at 40C, 2.3cSt/34SUS at 100C

http://www.nttworldwide.com/docs/diala-ax.pdf

9cSt (mm^2/s) is about the dividing line between SAW 20 and 30 AT 100C,
so Diala AX is a lot less viscous than even 20 weight motor oil (2.3cSt
vs 9.3 cSt)

The typical Mineral Oil, USP, heavy at a drug store is around 34cSt
viscosity (3-4 times heavier).

Diala pours pretty readily.. I'd say about like half and half, but not
as thick as whipping cream.

That's important for the heat transfer, because you need the circulation
inside the load (unless you're just pulsing it..) By the way, that's
why the rating on the Cantenna is different for USP mineral oil and
insulating oil.
http://www.mfjenterprises.com/man/pdf/MFJ-250.pdf

for 10minute duration, the rating is about 60% when using mineral oil
instead of transformer oil.

For long durations, the whole thing gets hot and reaches thermal
equilibrium.

For short durations, the lower viscosity transformer oil moves the heat
away from the resistor faster keeping it at lower temperature.


That said, most hams aren't going to run their dummy load at full power
for 10 minutes at a crack.

On Jan 1, 8:34*pm, "Bob Campbell" wrote:
"JIMMIE" wrote in message

...

Nothing wrong with PoCo oil. They havent used PCBs in years. We use
the same stuff at work made by Shell . Its just mineral oil with a few
additives.

That's good to know.

I have a 200 watt air cooled dummy load made of 2 watt resistors. I
was curious as to how much power it could safley disipate if placed in
a gallon container of mineral oil. It seems to handle 200 watts
continuously with just a muffin fan on it.

Jimmie

JIMMIE wrote:
On Jan 1, 8:34 pm, "Bob Campbell" wrote:
"JIMMIE" wrote in message

...

Nothing wrong with PoCo oil. They havent used PCBs in years. We use
the same stuff at work made by Shell . Its just mineral oil with a few
additives.
That's good to know.

I have a 200 watt air cooled dummy load made of 2 watt resistors. I
was curious as to how much power it could safley disipate if placed in
a gallon container of mineral oil. It seems to handle 200 watts
continuously with just a muffin fan on it.

Jimmie

Not an easy question to answer. allot depends on how the thing is made.
How much power it can handle is controlled by how fast the heat can be
moved away. It doesn't matter if it's oil or air. In oil the speed is
set by how obstructed the path the hot oil would need to travel to get
away from the part thats making the heat. I think the resistor in a
cantenna in free air is only good for about 50 watts but it designed for
the smooth passage of the oil around the resistor. I don't think that
your mass of 2 watt resistors will allow the oil to pass freely enough
to get to a KW for vary long. If you used a pump to move the oil it
would work better in the same way that a fan works.

John Passaneau

One other thing might check out, is the Salt Water Dummy Loads
(on several web sites). One mearly uses (can, Jar with lid),
and with metal plates attached to coax connector, filled
with salt water - Fill with water, then with ohm meter , add
Salt until the brine hits 50 ohms! Tho, don't know how high
frequency it is reliable to, should work to at least 50 MHz.
Jim NN7K


John Passaneau wrote:
JIMMIE wrote:
On Jan 1, 8:34 pm, "Bob Campbell" wrote:
"JIMMIE" wrote in message

...


Nothing wrong with PoCo oil. They havent used PCBs in years. We use
the same stuff at work made by Shell . Its just mineral oil with a few
additives.
That's good to know.

I have a 200 watt air cooled dummy load made of 2 watt resistors. I
was curious as to how much power it could safley disipate if placed in
a gallon container of mineral oil. It seems to handle 200 watts
continuously with just a muffin fan on it.

Jimmie

Not an easy question to answer. allot depends on how the thing is made.
How much power it can handle is controlled by how fast the heat can be
moved away. It doesn't matter if it's oil or air. In oil the speed is
set by how obstructed the path the hot oil would need to travel to get
away from the part thats making the heat. I think the resistor in a
cantenna in free air is only good for about 50 watts but it designed for
the smooth passage of the oil around the resistor. I don't think that
your mass of 2 watt resistors will allow the oil to pass freely enough
to get to a KW for vary long. If you used a pump to move the oil it
would work better in the same way that a fan works.

John Passaneau

"Jim-NN7K" . wrote in message
...
One other thing might check out, is the Salt Water Dummy Loads
(on several web sites). One mearly uses (can, Jar with lid),
and with metal plates attached to coax connector, filled
with salt water - Fill with water, then with ohm meter , add
Salt until the brine hits 50 ohms! Tho, don't know how high
frequency it is reliable to, should work to at least 50 MHz.
Jim NN7K


Back in the mid-1960's there was an article in QST where they did this.
The load will definitely be frequency dependent as demonstrated by
experimental results. Also the salt used will effect the results. From a
theoretical standpoint, the mobility of ions is dependent on the size of
the ion. The bigger the ion, the slower it will move. This conveniently
explains much of what is seen in ground losses and is why electrolytic
capacitors are essentially useless above 1 MHz. The ions cannot move fast
enough in the small times seen per cycle, so the current falls off. Ion
mobility also decreases as the temperature drops which explains why
electrolytic capacitors also do poorly at low temperatures.

I have done as Jim suggested when testing a kilowatt amplifier on 80
Meters. The load is useless if the water boils!

73, Dr. Barry L. Ornitz WA4VZQ

On Fri, 16 Jan 2009 16:59:29 -0500, "NoSPAM"
wrote:

I have done as Jim suggested when testing a kilowatt amplifier on 80
Meters. The load is useless if the water boils!

Is this the dawn of another debate over power in standing waves?

73's
Richard Clark, KB7QHC

"Jim-NN7K" . wrote in message
...
One other thing might check out, is the Salt Water Dummy Loads
(on several web sites). One mearly uses (can, Jar with lid),
and with metal plates attached to coax connector, filled
with salt water - Fill with water, then with ohm meter , add
Salt until the brine hits 50 ohms! Tho, don't know how high
frequency it is reliable to, should work to at least 50 MHz.
Jim NN7K

Generator tests (60 or 400 Hz, multi-KW) are routinely performed with a
trailer-mounted device called a load bank, where plates are immersed into a
tank of salt water. The depth of the plates determines the load resistance.