Bob Campbell wrote:
John Smith wrote:
Dave wrote:

...
http://www.eham.net/forums/Elmers/1574

Uh, yeah, I guess your reference to a dummy load is helpful, in some
other reality ...

I was just happy to see someone in that thread pop up with the warning
about PCBs in old transformer oil. I couldn't believe someone said they
actually got power company transformer oil!
After I refurbished my Cantenna (needed a new globar resistor and cleaning),
I was able to get a gallon from my local power company (free gratis). It
took a few phone calls to find the supervisor of the transformer shop. At
the rate their pump runs, the trick was getting /only/ one gallon!

I considered mineral oil but learned transformer oil has better thermal
characteristics. I now have a homebrew air-cooled dummy load that will
handle over a kilowatt continuously.

Bryan WA7PRC

On Jan 3, 12:31*am, "Bryan" wrote:
Bob Campbell wrote:
John Smith wrote:
Dave wrote:

...
http://www.eham.net/forums/Elmers/1574

Uh, yeah, I guess your reference to a dummy load is helpful, in some
other reality ...

I was just happy to see someone in that thread pop up with the warning
about PCBs in old transformer oil. * I couldn't believe someone said they
actually got power company transformer oil!

After I refurbished my Cantenna (needed a new globar resistor and cleaning),
I was able to get a gallon from my local power company (free gratis). *It
took a few phone calls to find the supervisor of the transformer shop. *At
the rate their pump runs, the trick was getting /only/ one gallon!

I considered mineral oil but learned transformer oil has better thermal
characteristics. *I now have a homebrew air-cooled dummy load that will
handle over a kilowatt continuously.

Bryan WA7PRC

I used Shell Diala for years in radar systems. The last time I changed
the oil we used somrthing else, probably cheaper. The main ingredient
in all odf it is mineral oil but it has a few additives. Local PoCO
uses the same. We got some from them one time and they had a RR tank
car full of it.

Jimmie

Billy Burpelson wrote:

...
And swallowing something is -not- being "introduced directly into the
body"? I would have thought otherwise...

John Smith wrote:

I mean, "Come on!" You have to ask that?

A hypodermic needles injection is "directly." A swallowed substance is
directly introduced into the digestive tract, where it is the
assimilated into the blood ...

Huh? Are we both saying the same thing?

If a substance is injected by a hypodermic needle and then 'assimilated
into the blood', how is that different from you saying "A swallowed
substance is directly introduced into the digestive tract, where it is
the[n] assimilated into the blood ..."?

Seems like it gets into the blood stream (and is thus circulated around
the entire body) in -either- case. So your point is...?

Back to my original, bottom line question: is silicone in the blood
stream good for you or bad for you? (and yes, I DO have to ask, because
your response seems to make no sense).

Regards,
Billy

Billy Burpelson wrote:

Back to my original, bottom line question: is silicone in the blood
stream good for you or bad for you? (and yes, I DO have to ask, because
your response seems to make no sense).

Yes. Ask the women whose breast implants broke.

- 73 de Mike N3LI -

In rec.radio.amateur.antenna Mike Coslo wrote:
Billy Burpelson wrote:

Back to my original, bottom line question: is silicone in the blood
stream good for you or bad for you? (and yes, I DO have to ask, because
your response seems to make no sense).

Yes. Ask the women whose breast implants broke.


Or you could ask the Mayo Clinic which says the only problem is the
formation of scar tissue, which happens with any foreign object in
the body.

http://www.mayoclinic.com/health/bre...plants/AN01212

--
Jim Pennino

Remove .spam.sux to reply.

In rec.radio.amateur.antenna Billy Burpelson wrote:

Billy Burpelson wrote:

...
And swallowing something is -not- being "introduced directly into the
body"? I would have thought otherwise...

John Smith wrote:

I mean, "Come on!" You have to ask that?

A hypodermic needles injection is "directly." A swallowed substance is
directly introduced into the digestive tract, where it is the
assimilated into the blood ...

Huh? Are we both saying the same thing?

If a substance is injected by a hypodermic needle and then 'assimilated
into the blood', how is that different from you saying "A swallowed
substance is directly introduced into the digestive tract, where it is
the[n] assimilated into the blood ..."?

Seems like it gets into the blood stream (and is thus circulated around
the entire body) in -either- case. So your point is...?

Back to my original, bottom line question: is silicone in the blood
stream good for you or bad for you? (and yes, I DO have to ask, because
your response seems to make no sense).

It is not very likely to be "good" for you and depending on how much, it
could be "bad" for you.

But there is the bottom line question of how could an oranically inert
substance get into the blood stream other than through direct injection?

The question is like asking if glass in the blood stream is a problem.

--
Jim Pennino

Remove .spam.sux to reply.

On Fri, 2 Jan 2009 01:35:16 -0500, "NoSPAM"
wrote:

However, the Cantenna relies on natural
convection of the oil for cooling and the higher viscosity of commonly
available silicone oils will limit the power handling capability of the
Cantenna.

So, a low density fluid would be the better choice? If that were the
prime criteria, I would think that water or antifreeze would be the
best. If having convection currents agitate the fluid is important,
it would be easy enough to install a paddle stirrer and thermometer.
Oh wait. This is ham radio. Forget the thermometer.

I'm also wondering if the electrical characteristics of water are an
issue for an HF dummy load. Even if someone dumps salt water into the
paint can, the conduction losses to ground from the resistor to the
can ground can't be all that much below 30MHz.

Thermal Conductivity Viscosity
W/mK cSt @20c
Water 0.6 0.9
AF (glycol) 0.24 2.0
Water+AF 0.8(?) 1.5 50%/50%
Silicon Oil 0.1 varies radically
Mineral Oil 0.138 34.5
Fluorinert FC-77 0.063 0.75

Ok, I see why. Water has 1/5th of the thermal conductivity of mineral
oil. 50/50 water and antifreeze won't work. That raises the boiling
point but ruins the thermal conductivity. Pure ethylene glycol looks
tolerable. Other than the health and ecology issues, any reason that
100% antifreeze won't work?

Incidentally my theory is that the Heath engineers of the 1960's used
mineral oil because that's what's inside a Lava Lamp. They were
probably designing Heathkit Lava Lamps but when that failed, they had
to do something useful with the mineral oil.

Remember that the Cantenna must be de-rated when used for long
duty cycles, and a high viscosity oil will lower the power rating still
more. Also remember that silicone oils are not cheap (and my buddy at Dow
would only send me small samples).

Well, if you want expensive and near perfect, there's 3M Fluoinert.
http://en.wikipedia.org/wiki/Fluorinert
http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxTE5X46EVuQEcuZgVs 6EVs6E666666--
About $400/liter for recycled FC-77 and $2,200/liter for the new
FC-770 stuff from various 3M dealers. A 1 gallon cantenna required
3.78 liters or about $1,500 in recycled FC-77. For those hams that
want the very best. Gold plated paint can is optional.

I would suggest using modern RF terminations made by Bourns and other
companies. These are designed to be bolted to a large heatsink. The
CHF9838CNF series is rated for 50 ohms, 250 watts, VSWR below 1.1 from DC
to 2.2 GHz. It only costs $27.50 in single lot quantities. I think this
is higher than the continuous rating of the Cantenna. I don't know for
sure as I disposed of my Cantenna years ago. Digi-Key sells these Bourns
terminations if you want one.

Nice. Thanks.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CHF9838CNF500L-ND
http://www.mouser.com/Search/Refine.aspx?Msid=65210000&Keyword=CHF9838CNF500L
http://www.bourns.com/data/global/PDFs/CHF9838CNF.pdf
I kinda prefer to use 4ea 200 ohm loads in parallel. In a previous
power amp design, I had to dump 200 watts into a load if the antenna
failed. The thermal resistance of the flange mount was too high for
one device to handle the load at the rated temperatures. However, 4
devices did the trick.

Barry L. Ornitz, PhD WA4VZQ
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In article ,
Jeff Liebermann wrote:

I'm also wondering if the electrical characteristics of water are an
issue for an HF dummy load. Even if someone dumps salt water into the
paint can, the conduction losses to ground from the resistor to the
can ground can't be all that much below 30MHz.

It's probably not worth much, but here's some anecdotal evidence. About 50
years ago several of us at W8LT (The Ohio State University amateur radio
club) needed a low-power dummy load to be used at moderate frequencies (e.g.
20 meters). I came up with the idea of immersing a 2 watt, 51 ohm carbon
resistor in a large glass of Columbus, Ohio tap water. We found that at 14
MHz putting the resistor under water made negligible change in observed SWR,
which surprised me because Columbus water (unlike the stuff we're blessed
with here in the Vancouver, BC area which comes right from the mountain
snow-pack) was fairly hard. This also indicated that the water didn't put
too much capacitance in parallel with the resistance. Water-cooling did
allow the 2 watt resistor to absorb a fair bit more power than 2 watts, at
least for a while until the water heated up too much.

Thermal Conductivity Viscosity
W/mK cSt @20c
Water 0.6 0.9
AF (glycol) 0.24 2.0
Water+AF 0.8(?) 1.5 50%/50%
Silicon Oil 0.1 varies radically
Mineral Oil 0.138 34.5
Fluorinert FC-77 0.063 0.75

Ok, I see why. Water has 1/5th of the thermal conductivity of mineral
oil.

It's still a heck of a lot better than air.

As I recall, we were in a hurry, we had the resistor, and we didn't have any
suitable oil on hand.

David. ex-W8EZE

--
David Ryeburn

To send e-mail, use "ca" instead of "caz".

On Sat, 03 Jan 2009 18:53:59 -0800, Jeff Liebermann
wrote:

Thermal Conductivity Viscosity
W/mK cSt @20c
Water 0.6 0.9
AF (glycol) 0.24 2.0
Water+AF 0.8(?) 1.5 50%/50%
Silicon Oil 0.1 varies radically
Mineral Oil 0.138 34.5
Fluorinert FC-77 0.063 0.75

Air 0.025
Copper 370.
Diamond 1000.

Ok, I see why. Water has 1/5th of the thermal conductivity of mineral
oil. 50/50 water and antifreeze won't work. That raises the boiling
point but ruins the thermal conductivity. Pure ethylene glycol looks
tolerable. Other than the health and ecology issues, any reason that
100% antifreeze won't work?

Sorry, I goofed. Vicodin etc. It should be the higher the W/mK, the
better the thermal conductivity.

So why is Fluorinert favored for cooling when it has such a lousy
thermal conductivity?
http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxTE5X46EVuQEcuZgVs 6EVs6E666666--
Since it's usually circulated with a pump and involves direct
immersion, is it because of it's low viscosity and superior electrical
characteristics?

It would also appear that water has 5 times the thermal conductivity
than mineral oil. So, why use mineral oil?

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
On Sat, 03 Jan 2009 18:53:59 -0800, Jeff Liebermann
wrote:

Thermal Conductivity Viscosity
W/mK cSt @20c
Water 0.6 0.9
AF (glycol) 0.24 2.0
Water+AF 0.8(?) 1.5 50%/50%
Silicon Oil 0.1 varies radically
Mineral Oil 0.138 34.5
Fluorinert FC-77 0.063 0.75

Air 0.025
Copper 370.
Diamond 1000.

Ok, I see why. Water has 1/5th of the thermal conductivity of mineral
oil. 50/50 water and antifreeze won't work. That raises the boiling
point but ruins the thermal conductivity. Pure ethylene glycol looks
tolerable. Other than the health and ecology issues, any reason that
100% antifreeze won't work?

Sorry, I goofed. Vicodin etc. It should be the higher the W/mK, the
better the thermal conductivity.

So why is Fluorinert favored for cooling when it has such a lousy
thermal conductivity?
http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxTE5X46EVuQEcuZgVs 6EVs6E666666--
Since it's usually circulated with a pump and involves direct
immersion, is it because of it's low viscosity and superior electrical
characteristics?

It would also appear that water has 5 times the thermal conductivity
than mineral oil. So, why use mineral oil?


It doesn't turn to steam or otherwise evaporate.

Dave WD9BDZ