Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to use
for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"

In news:7pnrj.1378$J93.474@trndny08 "RP"
wrote:

Hi I need to building a 4 ohm 1500 watt "cantenna paint can style"
dummy load for audio and guitar amp work. I have forgotten what type
of oil to use for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.

MFJ sells the correct "transformer oil" by the gallon for $30/gal, but the
manual for their version of the cantenna says you can use "mineral oil".

http://www.mfjenterprises.com/Produc...oductid=MFJ-21

http://www.mfjenterprises.com/man/pdf/MFJ-250X.pdf

--
Bert Hyman St. Paul, MN

"RP" wrote in message
news:7pnrj.1378$J93.474@trndny08...
Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to
use for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"


See E-Ham Article
http://www.eham.net/forums/Elmers/33528

Also a construction article with oil recommendation

http://www.k4eaa.com/dummy.html

Lamont

"RP" wrote in message
news:7pnrj.1378$J93.474@trndny08...
Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy load
for audio and guitar amp work. I have forgotten what type of oil to use for
heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"


In another life, I worked at a Motorola commercial 2-way radio shop. We used
Heathkit Cantennas for all of our test benches. All were filled with mineral
oil. Ran that way for years, never a problem.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

"In theory, there isn't any difference between theory and practice. In
practice, there is." - Yogi Berra

On Sat, 09 Feb 2008 19:45:07 GMT, "RP"
wrote:

Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to use
for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"

The idea of using a cantenna for audio is new to me.

I would be inclined to use distilled water for continuous use and tap
water if use is intermittent. Cheap & trivial risks!

As I think back of all the lash ups I have used to build and test
power supplies through the years I think you have led me to a much
more practical solution!

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

On Feb 9, 1:45*pm, "RP" wrote:
Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to use
for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"

I used 'baby oil' - the local pharmacy had a bunch marked down 80% as
it was close to expiration. It is just scented mineral oil - what
could 'expire' in that? It works fine in my cantenna, and smells
better than anything else in the shack.

73 - NM0S

On 2008-02-09, RP wrote:
Id like something easy to get (like peanut or something with a high
flashpoint).

Use mineral oil. Don't use any kind of food oil -- it will go rancid.

--
Ben Jackson AD7GD

http://www.ben.com/

RP wrote:
Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to
use
for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
Joe "NOSPAM"

Hi Joe,

I recently revived a Cantenna. When it came time to refill, I considered
mineral oil and decided to go with transfomer oil because of the better
thermal characteristic. Others have suggested that you can buy it from MFJ,
but I found it as close as my local power company. It was no big deal for
them to give me a gallon. ^5

Your audio dummy load sounds interesting. You might consider keeping an eye
on the oil temperature, as my Cantenna gets noticeably warm fairly
quickly... can't drive it at 1KW sinewave for very long. I envision a
thermistor comparator audible indicator.

73,
Bryan WA7PRC

Hi I need to building a 4 ohm 1500 watt "cantenna paint can style" dummy
load for audio and guitar amp work. I have forgotten what type of oil to use
for heat transfer.
Id like something easy to get (like peanut or something with a high
flashpoint).
Don't want to loose the house.
==============================
Assuming a resistance wire load made from thick galvanised fencing wire
( freq is low ;no RF) carrying up to sqrt 1500/4 equals approx 20
amperes , I would just use a large paint can filled with motor oil.

The 2 dummy load connections can be best made with heavy duty insulated
panel sockets with screwed head to be fitted in the can's lid. The stiff
resistance element can be fitted unsupported and kept free from the can

I also use motor oil for RF dummy loads with metal oxyde resistors and
over the years the resistance hasn't changed.

To prevent the oil filled (paint)can 'weeping' oil it is important that
the can's vertical and bottom seals are tight by applying solder inside.
Depending on the type and duration of testing ,the heat capacity of the
dummy load can be increased by placing the lower part of the can in
(flowing) cold water.
The can's lid should have a small vent hole (1-2 mm)

Frank GM0CSZ / KN6WH

To prevent the oil filled (paint)can 'weeping' oil it is important that
the can's vertical and bottom seals are tight by applying solder inside.
------------
That hasn't been my experience, but if one must solder, for sure don't
use a lined can. And then after soldering, clean and apply a
protective coating on the outside to cover all areas where heat has
discolored the metal... because these areas will be far more prone to
rust.
==========
It is hardly possible that rust develops when the can is filled with
(any) oil.
Another way to prevent oil weeping from the can is to cover the seams
internally with 2 component-expoxy adhesive.I had a motor oil filled
dummy load in operation for 15 years without problems , resistance
measured remained constant (50.3 Ohms) over that period.
That dummy load was made with 20 ea 1000 Ohms ,2Watt carbon film
resistors. With so many resistors in parallel the inductance of the
device is sufficiently low for use up to VHF frequencies.

Frank GM0CSZ / KN6WH