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@comcast.net>
To: 'Roger (K8RI) on TT' <K8RI-on-TowerTalk@tm.net>; towertalk
<towertalk@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@contesting.com] On Behalf Of Roger
(K8RI) on TT
Sent: Friday, December 04, 2015 12:51 PM
To: towertalk@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@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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