Want to build a 5 Gallon "Cantenna" dummy load.

[kv5i]

I found a five gallon metal bucket in good shape and would like to use copper pipe and pieces to duplicate the one gallon version. Is it possible? How?

[Pete, WA2CWA]

From Surplus Sales: mount two of  these in parallel; terminate in a SO-239 mounted to lid
Non-Inductive Termination Resistor
100 Ohm / 200 Watt
(RNI) FR200-100-NI
Memcor Non-Inductive Termination Resistor. Tubular style with tabbed terminals. 100 ohm, 200 watt. 1-1/4" diameter x 11-1/2" long. Use for in-series / parallel for different wattages and resistance values. Type E. Used in Gates / Harris equipment.


Fill can with 5 gallons of mineral oil. Note that a 5 gallon can is way overkill and not necessary unless you have a lot of mineral oil and need some place to store it.

It's cheaper and less messy to just go buy one of these:



http://www.hamradio.com/detail.cfm?pid=H0-001066

[N2DTS]

I have a cantenna I would like to get rid of.
I always worried about a huge nasty fire from using one.
Might as well cool a resistor with gasoline.

I have no idea what oil is in it, and any oil can burn.
I have a nice dry dummy load that takes 1000 watts for a half hour without getting hot.

[WQ9E]

I have some big air cooled units from a broadcast setup I use now but prior to that I used 4 "Cantennas" connected in a series/parallel arrangement when doing initial testing of my homebrew amp.  With three 4CX800 tubes and a big power supply they heated up nicely while I was checking thermal stability in the amp

[W3RSW]

Oil in a cantenna won't easily burn bereft of oxygen from a fully immersed resistor. The vapor on top will if hot enough if an arc occurs from a poor, internal top conmection. Just don't over power the poor cantenna.  Heath put a safety blow off valve on the lid of theirs for exactly those small puffs and only lightly sealed to keep oil from evaporating.

Oh, and if you put 11 1/2 inch resistors in the Gallon Cantenna size illustrated you'll pop your top!

Solder a couple of paint cans together for a lomger cylinder.  There was an article about this not to long ago, maybe in QST? I'll have to locate it.

[w1vtp]

Agree about 5 gallons being overkill.  Assuming 1 KW spec.  Just keep track of the time or temperature.

I have one of the heath cantennas but it's lost in the back room   

Picked up this 500 watt Bird at a 'fester  works just fine

GL es 73, Al

[Jim, W5JO]

If you are worried about high flashpoint oil then cool the resistor (s) with water.  Put and inlet and outlet in the can then a small circulation pump to move the water.  Be sure your pipes are capable of radiating the heat, such as copper, and run a few feet.  You will need to use distilled water.  If that doesn't suit you then put the resistor in the open and put a fan moving air across it .  You will be surprised at how much power can be radiated with either method.

[KG4DAG]

I made a saltwater dummyload that works fine up to over 100W. Since I'm
building a legal limit amp I may have to build a bigger one..

[Detroit47]

When buying a resistors you must be careful not all resistors like oil. They can soak it up and change value. I have a 2.5 k bird load and wouldn't part with it. I also have a cantenna on my station for tune up works great I found this article to be interesting. http://www.orcadxcc.org/content/cantenna_va7jw.pdf.

John N8QPC

[WD8BIL]

Water cooled is the way to go!!

http://www.birdrf.com/en/Products/Terminations_Loads/Coaxial-Terminations/10kW/8730-Series_10-kW-Water-Cooled-Terminations.aspx#.VN4gkXgo6po

[KG4DAG]

FWIW... The SWR plot for my simple saltwater dummy load...

[WBear2GCR]

Please tell us more about the saltwater dummy load? Links?

The aluminum tube around the carborundum resistive load I have read is to improve the performance at HF, apparently by adding a bit of C...

[Jim, W5JO]

My hesitation about salt water is that when it evaporates it leaves a residue.

[kv5i]

Guys, when I say 5 gallon, I mean in both forms. 5kw into a five gallon bucket of transformer oil.
73,
Ed

[Pete, WA2CWA]

Guys, when I say 5 gallon, I mean in both forms. 5kw into a five gallon bucket of transformer oil.
73,
Ed

5 KW Peak or Continuous?
Impedance?
Frequency Range?
 

[KL7OF]

Oven broiler element...

[Opcom]

Agree about 5 gallons being overkill.  Assuming 1 KW spec.  Just keep track of the time or temperature.

I have one of the heath cantennas but it's lost in the back room   

Picked up this 500 watt Bird at a 'fester  works just fine

GL es 73, Al

I use the very same. Perfect! With a couple of fans on it, a bit more juice like a 15 minute 1500W PEP AM test is no problem. All about heat removal.

Shell Diala is good, and silicon based oil is supposedly not flammable. The evil of "Cantenna" oil load things is they all seem to get nasty with greasy dirt after time. Maybe due to the sloshing and required expansion vent. A 'punching ball' balloon, rubber bellows, or some cheap metal bellows as used in the MC Jones dummies might make a nice expansion device.

Why not buy enough resistors for 5KW and let that be the end of it forever. No need for oil, use a metal can and drill a bunch of 1" holes in the bottom and top. Rubber feet and let convection do the work or add a fan if desired.

See this topic using 'microwave' resistors and a big heat sink. It worked out well.
http://amfone.net/Amforum/index.php?topic=22823.msg166314;topicseen#msg166314

[Opcom]

Oven broiler element...

Two spaced close for non inductive. Their resistance changes a lot when cold to hot. A stack of them is perfect for load-banking generators, saves a lot of money.

[W2PFY]

I made a saltwater dummy-load that works fine up to over 100W. Since I'm
building a legal limit amp I may have to build a bigger one..

Will it make Heavy Water?

[K1JJ]

Al has the right idea....

Occasionally these very FB Bird dummy loads show up at flea markets or on eBay at cheap prices.  They are as flat as the ocean.

I bought one at a flea mkt years ago for $10.  A 500 watt rated  load with a fan blowing air thru the fins will easily handle a 1500 watt carrier for a few minutes, no problem.

http://www.ebay.com/itm/Bird-Electrical-500W-50-ohm-dummy-load-/131427970607?pt=LH_DefaultDomain_0&hash=item1e99b7ae2f

T

[KG4DAG]

I made a saltwater dummy-load that works fine up to over 100W. Since I'm
building a legal limit amp I may have to build a bigger one..

Will it make Heavy Water?

No, but it might do cold fusion..

[DMOD]

If you want an oil for a Cantenna type dummy load, this is an excellent fluid with a high flash point:

http://www.schaefferoil.com/281s-heat-transfer-fluid.html


Phil - AC0OB

[Opcom]

If you want an oil for a Cantenna type dummy load, this is an excellent fluid with a high flash point:

http://www.schaefferoil.com/281s-heat-transfer-fluid.html


Phil - AC0OB

That's some top stuff there. Very low coefficent of expansion, would it require vent? Maybe just a membrane.
What about dielectric or insulating properties? I didn't find any volume resitivity.

[DMOD]

Here is the technical data sheet:

http://www.schaefferoil.com/cmss_files/attachmentlibrary/TD%20Sheets/281S.pdf

I use it my cantenna, has good thermal conductivity, and doesn't turn rancid like mineral oil.

Phil

[VE3LYX]

I have a cantenna I would like to get rid of.
I always worried about a huge nasty fire from using one.
Might as well cool a resistor with gasoline.

I have no idea what oil is in it, and any oil can burn.
I have a nice dry dummy load that takes 1000 watts for a half hour without getting hot.

Gasoline BTW only burns in a very narrow AFR. about 8 to 1 - 21 to 1 AFR Much narrower even then diesel. Which is why your electric fuel pump in your car is sitting in your gas tank bare wire connections and all. Without air and oxygen there will be no fire ever. And if not in the AFR window will never happen. Gasoline oil or whatever . Only OXy bearing fuels like Alky and Nitromethane can work in a limited air environment and even both Alkys still require a bunch of it. Ethonal about 8 to 1 and Methonal about 6 to 1 AFR. The laws of nature are carved in stone thankfully.