Distilled water and deionized water have an affinity for metallic ions.
IOW, it's corrosive.
If it's kept in brass or copper, it will leach ions. Brass will take on
a reddish hue and become very brittle.
It's a slow process and as we use it fittings and other metallic
components should last a long time, but if you test the water for
resistivity, or just conduction, over the months the conductivity will
increase. That is caused by metal ions in the water.
If the system drains back into a resivour when not in use, it will last
a very long time.
In a dummy load the water is very good at conducting heat, but in some,
it's a static system with the water in contact 100% of the time.
We used a lot of RF induction heating equipment. I no longer remember
how often we changed the water, but IIRC it was 2 or 3 times per year.
We monitored the resistivity on a weekly basis. When the resistivity in
oms per cubic centimeter dropped to a given level, the water would be
changed,
73
Roger (K8RI)
On 12/4/2015 12:45 PM, TexasRF--- via TowerTalk wrote:
What is wrong with using distilled water, $1.50 per gallon at Walmart?
Works just fine for amplifier cooling, no problem at 2000vdc and 1296 MHz. Not
flammable either!
73,
Gerald K5GW
In a message dated 12/4/2015 11:33:46 A.M. Central Standard Time,
towertalk@contesting.com writes:
I dime in the discussion, why not use something with the lowest viscosity
such as kerosene. That way the heat would be more efficiently removed.
Kerosene has a relatively low flam point so, unless you allow the temperature
to rise too much.
I, myself use a home made dummy load made from resistors packed in TO-220
capsules and mounted on a large, flat heat sink.
Hans - N2JFS.
-----Original Message-----
From: Bryan Swadener via TowerTalk <towertalk@contesting.com>
To: 'TowerTalk' <TowerTalk@contesting.com>
Sent: Tue, Dec 1, 2015 6:44 pm
Subject: Re: [TowerTalk] Oil For Dummy Load
Gary K4FMX asked only about the derating chart.
Fortunately for myself, oil viscosity is immaterial
since my HN31 won't ever see more than ~ 100W again
and I'll never need to change the FREE transformer oil.
Instead, for high power stuff, I use my scrap parts
1500W (100% D/C) DL that uses small flange-mounted
RF resistors. It's actually smaller than my HN-31.
vy 73,
Bryan WA7PRC
----- Original Message -----
From: D. Scott MacKenzie
To: Bryan WA7PRC
Sent: Tuesday, December 1, 2015
Subject: RE: [TowerTalk] Oil For Dummy Load
Unfortunately they don't give the viscosity of the oil. Most transformer
oil is mineral at a viscosity of 10-20 cst @ 40C. However, mineral oil
can
range from 10-1000 cSt. An identical viscosity mineral oil would
perform in
an identical fashion.
-----Original Message-----
From: Bryan WA7PRC
Sent: Tuesday, December 01, 2015 12:53 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Oil For Dummy Load
The chart is here: http://www.tinyurl.com/wa7prc-cantenna
My scrap parts 1500W dummy load is here:
http://www.tinyurl.com/wa7prc-dummy
Though all the parts were free to me, outfits such as Henry Radio
(http://stores.ebay.com/Henry-Radio) sell RF power resistors for
reasonable
cost on ebay.
vy 73 es gl,
Bryan WA7PRC
Date: Mon, 30 Nov 2015
From: Gary K4FMX
Subject: Re: [TowerTalk] Oil For Dummy Load
There used to be a chart on the side of the Heath cantena that showed
the difference between transformer oil and mineral oil as far as
power/time. As I remember it was rather a significant difference.
73
Gary K4FMX
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73
Roger (K8RI)
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