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Re: [TowerTalk] Fwd: Oil For Dummy Load

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Fwd: Oil For Dummy Load
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
Date: Fri, 4 Dec 2015 13:50:30 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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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