[TowerTalk] Fwd: Fwd: Oil For Dummy Load

Fri Dec 4 18:10:15 EST 2015

I noticed, when I was experimenting with liquid cooled loads I found that mineral oil had some effect on the SWR. FREON had the lowest effect. I never tried water. Antifreeze might work but it might also have an effect on the SWR. In my loads the resistors were in direct contact with the coolant.

Hans - N2JFS

-----Original Message-----
From: Perry K4PWO <k4pwo at comcast.net>
To: 'Roger (K8RI) on TT' <K8RI-on-TowerTalk at tm.net>; towertalk <towertalk at contesting.com>
Sent: Fri, Dec 4, 2015 1:57 pm
Subject: Re: [TowerTalk] Fwd: Oil For Dummy Load

That brings up another thought... how would ethaline glycol (anti-freeze)
work as dummy load coolant?

Perry

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Roger
(K8RI) on TT
Sent: Friday, December 04, 2015 12:51 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Fwd: Oil For Dummy Load

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 at 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 at contesting.com>
> To: 'TowerTalk'  <TowerTalk at 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 at 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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