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Author Topic: Cantenna dummy load resistor  (Read 6475 times)
K3GM
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« Reply #15 on: September 16, 2017, 07:34:09 AM »

At one time (I have one) the Cantenna was filled with transformer oil that contained PCBs.....
  

Was the Cantenna kit ever supplied with oil?  I built mine in 1980, and had to furnish the oil myself.  I'm almost positive that even then the instructions said to avoid transformer oil due to the presence of PCB's.  I used non-toxic mineral oil, cleaning out my corner drug store.  It was my first piece of "test" equipment and is under the operating desk today.
« Last Edit: September 16, 2017, 07:38:47 AM by K3GM » Logged
K8AXW
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« Reply #16 on: September 16, 2017, 09:36:33 AM »

I can't recall the Cantenna being supplied with oil.  The Cantenna assembly manual said to fill the can with "transformer oil or mineral oil to within 3/4" of the top of the can."  I can't find any indication of "avoiding oil with PCBs."

AS I RECALL, back when I bought and assembled my Cantenna, ALL transformer oil contained PCBs.  It wasn't until many years later that someone discovered that transformer oil contained PCBs and OSHA then required all power companies, including industr, to change out their transformer oil to one that didn't contain PCBs.  I know it cost our company big bucks because we generated our own power and had huge transformers all over the plant.

The Cantenna curves indicate:

The transformer oil is rated at 1000w for 10 minutes.

Mineral oil is rated at 1000w for approximately 1 minute.

The transformer oil is rated at 750w for 12 minutes.

The mineral oil is rated at 750w for 6 minutes.

The Cantenna Curves indicate that transformer oil and mineral oil are essentially the same at 400w for 30 minutes. 





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W8JX
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« Reply #17 on: September 16, 2017, 10:04:48 AM »

I can't recall the Cantenna being supplied with oil.  The Cantenna assembly manual said to fill the can with "transformer oil or mineral oil to within 3/4" of the top of the can."  I can't find any indication of "avoiding oil with PCBs."

AS I RECALL, back when I bought and assembled my Cantenna, ALL transformer oil contained PCBs.  It wasn't until many years later that someone discovered that transformer oil contained PCBs and OSHA then required all power companies, including industr, to change out their transformer oil to one that didn't contain PCBs.  I know it cost our company big bucks because we generated our own power and had huge transformers all over the plant.

The Cantenna curves indicate:

The transformer oil is rated at 1000w for 10 minutes.

Mineral oil is rated at 1000w for approximately 1 minute.

The transformer oil is rated at 750w for 12 minutes.

The mineral oil is rated at 750w for 6 minutes.

The Cantenna Curves indicate that transformer oil and mineral oil are essentially the same at 400w for 30 minutes. 



I suspect this because mineral oil is more viscous than transformer oil the impedes convective currents in oil and causes resistor to heat up quicker. (you will notice that as wattage decreases the difference decreases too. I suspect 10w non detergent motor oil would be closer to transformer oil curve. 
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Ham since 1969....  Old School 20wpm REAL Extra Class..
KM1H
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« Reply #18 on: September 16, 2017, 05:44:00 PM »

PCB's were outlawed in the late 60's for new construction and utility companies gradually changed over as needed, I doubt if any PCB's are still in commercial use. There are still many PCB full HV caps floating around at hamfests and online and as long as they are not leaking there is no toxicity from use or storage. PCB's are still the best HV insulating fluid developed

My ancient custom 3000W Bird load, built for RCA, is full of PCB's and Im still living and breathing fine after 30+ years of using it..as are the two big 4000V filter caps in my 1500W 2M amp I built about 35 years ago with NOS caps from the 70's.

Much ado about nothing scare tactics. The real effects are decades behind us when it was treated like water or other harmless liquids.
I doubt if anyone here washes their hands in or drinks anti freeze either.
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KJ6TSX
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« Reply #19 on: September 16, 2017, 09:30:36 PM »

I know this goes against our principles but HRO has the cantenna dummy load with oil for about as much as you would buy 4 quarts of good motor oil??
follow the linkhttp://www.hamradio.com/detail.cfm?pid=H0-001066

Have fun
George
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K7KBN
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« Reply #20 on: September 17, 2017, 08:27:42 AM »

A visit to your area's electrical maintenance shop might yield a gallon or two of good quality, PCB-free transformer oil from one of their nearly-empty barrels.  A dozen donuts taken along just might seal the deal.
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Pat K7KBN
CWO4 USNR Ret.
K2DFC
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« Reply #21 on: September 17, 2017, 08:45:19 AM »

My Cantenna is close to 50 years old. I filled it with mineral oil. Used to get it at Drug Stores. Recently popped the top on the Cantenna and the 50 year old oil is still crystal clear. Transformer oil was always much more expensive. I'm sure today's oil wouldn't have the PCB's but you will pay a premium price for it. Go with mineral oil.
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K8AXW
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« Reply #22 on: September 17, 2017, 11:14:50 AM »

Quote
Much ado about nothing scare tactics. The real effects are decades behind us when it was treated like water or other harmless liquids.
I doubt if anyone here washes their hands in or drinks anti freeze either.

Some of our electricians did in fact "wash their hands" in PCB laden transformer oil....but then wiped it off with a rag and washed their hands later with soap and water.  I don't recall ANY of them dying with cancer.

Quote
A visit to your area's electrical maintenance shop might yield a gallon or two of good quality, PCB-free transformer oil from one of their nearly-empty barrels.  A dozen donuts taken along just might seal the deal.

Wonderful idea!

JX:  Heath mentions in the Cantenna assembly manual: "Do not (Emphasis by Heath) use any type of motor oil.  The vaporizing temperature of motor oil is too low and would cause excess vapor."  I suspect this was the case 30-40 years ago and is no longer valid.  Frankly, I find this hard to believe.

Quote
I know this goes against our principles but HRO has the cantenna dummy load with oil for about as much as you would buy 4 quarts of good motor oil??
follow the linkhttp://www.hamradio.com/detail.cfm?pid=H0-001066

The price of the cantenna shown at your link is $70.00 and with shipping with oil would make it much higher.  Even empty at $70.00 and shipping makes for some very expensive motor oil.  A lot more expensive than the lard I use in my vehicles!

The exchange of oil for donuts is the winner!  I did the same with my in-plant tin shop.  They made me two nesting cookie sheets for my wife and I came back with a couple dozen of my wife's top-o-the line chocolate chip cookies.  From then I was in like Flynn!   Grin
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W8JX
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« Reply #23 on: September 18, 2017, 06:15:55 AM »

JX:  Heath mentions in the Cantenna assembly manual: "Do not (Emphasis by Heath) use any type of motor oil.  The vaporizing temperature of motor oil is too low and would cause excess vapor."  I suspect this was the case 30-40 years ago and is no longer valid.  Frankly, I find this hard to believe.

Motor oil does no easily vaporize because if it did you would not be able to keep it in your engine long and would be constantly adding to it plus SA rated oil is non detergent oil and vapor would be no worse than mineral oil vapor. I would suggest that the reason they might be against it is because of different types of oil on market in weights and grades and if it said motor oil they would use any they could find rather than straight 10w non detergent oil. (SD was just coming out when cantenna first shipped too) SA rated oil is non detergent and was the mainstay through early 30's. It also was always straight weight rated oil (ie 10w, 20 etc) and is 100 % pure oil. (It was replaced in 30's with SB that has a very small amount of anti scuff additive for pistons and that's it) Newer multi-viscosity oil is some thing you would not want to use not just because of detergents and additives but also because of VI (viscosity improver) added to it. VI starts cooking out of oil around 300 degrees and leave hard carbon like deposits that can build up over time. (many cars that were not properly maintained suffered from higher oil consumption due to stuck piston rings caused by VI cooking out on them as oil ages) In 50's SB was replaced by SC with was first grade with detergents and each newer grade has more additives.

Furthermore consider this, mineral oil is a byproduct of crude oil and has a lower flash point that motor oil (335 vs 410 and flash point is were oil gives off enough vapor to burn without a wick, not where oil itself flashes to burn)






 
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Ham since 1969....  Old School 20wpm REAL Extra Class..
N3QE
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« Reply #24 on: September 18, 2017, 07:26:47 AM »

I have an Ameriton AL-80B I need to not only test....but probably run long enough to regetter the 3-500Z tube.

Have you applied filament and HV to the tube? If you already have, and it did not flash over, then I don't see any need to regetter the tube.

Just get on the air and use it.

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K8AXW
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« Reply #25 on: September 18, 2017, 09:11:58 AM »

JX:  Good info that I never knew.  Many thanks.
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KC4ZGP
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« Reply #26 on: September 18, 2017, 11:23:26 AM »


Say I wonder how my amplifier would do if I submerged the heatsink in a pan of motor oil. I could get rid of the noisy fans eh?

Kraus

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K3GM
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« Reply #27 on: September 19, 2017, 06:26:06 AM »

I did some digging, and found that motor oil does indeed have a higher flashpoint than mineral oil, about 100 degrees higher.  The problem with using ANY kind of motor oil is they're a chemical soup of additives, of which any of them can attack the resistor element.  One other reason.  I've never seen a Cantenna (mine included) that does not have some kind of oil residue or film on the top.  Mine even appear to slightly leak at bottom seam.  I would much rather clean up mineral oil than motor oil.  Even fresh out of the bottle, the latter has a chemical odor to it.
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K2DFC
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« Reply #28 on: September 19, 2017, 06:46:47 AM »

Why the debate. Just get a gallon on mineral oil and your set for life.
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W8JX
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« Reply #29 on: September 19, 2017, 07:38:38 AM »

The problem with using ANY kind of motor oil is they're a chemical soup of additives, of which any of them can attack the resistor element.

I guess you missed the memo, SA rated non detergent oil has NO additives and is 100% pure oil and can still be found at farm stores (because a lot of old tractors used it in their hydraulic systems) and some car parts places. Approx 20% of all motor oil still sold is SA or SB rated. (SB is non detergent too and only has a tiny bit of anti scuff additive for pistons). Some hard core engine builder still break engines in on SA or SB oil to speed up break in.

Get some 10w SA non detergent oil and it will work fine. (BTW, the "w" does not stand for weight it stands for winter flow rating as you can find plain 10 and 20w-20 that is flow rated at cold and high temps)
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Ham since 1969....  Old School 20wpm REAL Extra Class..
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