Elecraft

KPA1500 Cooling

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P.B. Christensen

KPA1500 Cooling

>"Until it leaks on the LDMOS devices."

Pure water is an insulator. Leakage becomes a problem when water becomes
contaminated with conductive particles. This rarely occurs in closed loop
systems that use distilled water when non-contaminating hoses, fittings, and
heat exchangers are used. My 2KW LDMOS amp uses water cooling in such a
closed system.

My main amplifier at home is an Alpha PA-70V. The amp uses an openly-cooled
vapor-phase system. A pint of distilled water separates 4KV of plate
voltage and chassis ground. Water is in direct contact with the plate. In
time, air particles do contaminate the water (usually in the form of algae)
and the system must be purged and refilled at annual intervals. If leakage
exceeds a predetermined amount, the amp faults and shuts down.

Paul, W9AC

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Re: KPA1500 Cooling

Hi Paul,
I can't remember what we used to use for closed loop cooling. I don't think we used distilled water because it's resistance would increase over time from picking up ions from the metal. In our case it was cooling loops in a copper 37" electrode. I thought it was some kind of antifreeze or maybe an oil? And also isn't distilled water quite reactive?
To many bourbons ago 😊
N2TK, Tony

-----Original Message-----
From: [hidden email] <[hidden email]> On Behalf Of Paul Christensen
Sent: Thursday, July 23, 2020 3:54 PM
To: [hidden email]
Subject: [Elecraft] KPA1500 Cooling

>"Until it leaks on the LDMOS devices."

Pure water is an insulator. Leakage becomes a problem when water becomes contaminated with conductive particles. This rarely occurs in closed loop systems that use distilled water when non-contaminating hoses, fittings, and heat exchangers are used. My 2KW LDMOS amp uses water cooling in such a
closed system.

My main amplifier at home is an Alpha PA-70V. The amp uses an openly-cooled vapor-phase system. A pint of distilled water separates 4KV of plate voltage and chassis ground. Water is in direct contact with the plate. In time, air particles do contaminate the water (usually in the form of algae) and the system must be purged and refilled at annual intervals. If leakage exceeds a predetermined amount, the amp faults and shuts down.

Paul, W9AC

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W2xj

Re: KPA1500 Cooling

glycol and anti freeze.

Sent from my iPad

> On Jul 23, 2020, at 4:49 PM, N2TK via Elecraft <[hidden email]> wrote:
>
> Hi Paul,
> I can't remember what we used to use for closed loop cooling. I don't think we used distilled water because it's resistance would increase over time from picking up ions from the metal. In our case it was cooling loops in a copper 37" electrode. I thought it was some kind of antifreeze or maybe an oil? And also isn't distilled water quite reactive?
> To many bourbons ago 😊
> N2TK, Tony
>
>
> -----Original Message-----
> From: [hidden email] <[hidden email]> On Behalf Of Paul Christensen
> Sent: Thursday, July 23, 2020 3:54 PM
> To: [hidden email]
> Subject: [Elecraft] KPA1500 Cooling
>
>> "Until it leaks on the LDMOS devices."
>
> Pure water is an insulator. Leakage becomes a problem when water becomes contaminated with conductive particles. This rarely occurs in closed loop systems that use distilled water when non-contaminating hoses, fittings, and heat exchangers are used. My 2KW LDMOS amp uses water cooling in such a
> closed system.
>
> My main amplifier at home is an Alpha PA-70V. The amp uses an openly-cooled vapor-phase system. A pint of distilled water separates 4KV of plate voltage and chassis ground. Water is in direct contact with the plate. In time, air particles do contaminate the water (usually in the form of algae) and the system must be purged and refilled at annual intervals. If leakage exceeds a predetermined amount, the amp faults and shuts down.
>
> Paul, W9AC
>
>
> ______________________________________________________________
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Re: KPA1500 Cooling

Tnx Paul

-----Original Message-----
From: W2xj <[hidden email]>
Sent: Thursday, July 23, 2020 5:08 PM
To: [hidden email]
Cc: Paul Christensen <[hidden email]>; [hidden email]
Subject: Re: [Elecraft] KPA1500 Cooling

glycol and anti freeze.

Sent from my iPad

> On Jul 23, 2020, at 4:49 PM, N2TK via Elecraft <[hidden email]> wrote:
>
> Hi Paul,
> I can't remember what we used to use for closed loop cooling. I don't think we used distilled water because it's resistance would increase over time from picking up ions from the metal. In our case it was cooling loops in a copper 37" electrode. I thought it was some kind of antifreeze or maybe an oil? And also isn't distilled water quite reactive?
> To many bourbons ago 😊
> N2TK, Tony
>
>
> -----Original Message-----
> From: [hidden email]
> <[hidden email]> On Behalf Of Paul Christensen
> Sent: Thursday, July 23, 2020 3:54 PM
> To: [hidden email]
> Subject: [Elecraft] KPA1500 Cooling
>
>> "Until it leaks on the LDMOS devices."
>
> Pure water is an insulator. Leakage becomes a problem when water becomes contaminated with conductive particles. This rarely occurs in closed loop systems that use distilled water when non-contaminating hoses, fittings, and heat exchangers are used. My 2KW LDMOS amp uses water cooling in such a
> closed system.
>
> My main amplifier at home is an Alpha PA-70V. The amp uses an openly-cooled vapor-phase system. A pint of distilled water separates 4KV of plate voltage and chassis ground. Water is in direct contact with the plate. In time, air particles do contaminate the water (usually in the form of algae) and the system must be purged and refilled at annual intervals. If leakage exceeds a predetermined amount, the amp faults and shuts down.
>
> Paul, W9AC
>
>
> ______________________________________________________________
> Elecraft mailing list
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Luis V Romero (mobile)

Re: KPA1500 Cooling

In reply to this post by P.B. Christensen

In the analog NTSC days, Harris UHF broadcast transmitters were liquid
cooled by stuff called UCARTHERM-HTF 6141 (If memory serves me).

We called it "Vulcan Blood". It was a special Ethylene Glycol much like
automotive anti-freeze but thicker and with lots of other goodies inside.
It was an interesting MSDS sheet.

An older RCA UHF TV Transmitter I remember "fondly" used distilled water.
There was a resistance sensor on the circulation system that measured the
resistance of the water. The meter pointer on the yellow part of the meter
meant a long Friday overnight to Saturday morning session that week.
Usually quarterly.

And, don't even think of turning the rig off during cold winter nights! The
heat exchanger had no heating element, and if you left the rig off for more
than a couple of hours, the water would freeze and crack it open, which was
a really bad thing to happen.

No snow ever gathered in the vicinity of the heat exchanger exhaust duct.
There could be two feet of snow on the driveway, but there was always a spot
on the side of the building that was not only snow free, but often dry.
Often, the icicles on the adjacent windows were legendary!

Nobody ever thought of bypassing some of that heat into the building...
Those were the days of cheap energy.

Lu - W4LT

-----------=-----------------------=------------------------=---------------
-

Date: Thu, 23 Jul 2020 16:46:00 -0400
From: <[hidden email]>
To: "'Paul Christensen'" <[hidden email]>, <[hidden email]>
Subject: Re: [Elecraft] KPA1500 Cooling
Message-ID: <02b001d66132$4664f990$d32eecb0$@verizon.net>
Content-Type: text/plain; charset="utf-8"

Hi Paul,
I can't remember what we used to use for closed loop cooling. I don't think
we used distilled water because it's resistance would increase over time
from picking up ions from the metal. In our case it was cooling loops in a
copper 37" electrode. I thought it was some kind of antifreeze or maybe an
oil? And also isn't distilled water quite reactive?
To many bourbons ago ?
N2TK, Tony

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Bill Frantz

Re: KPA1500 Cooling

In reply to this post by P.B. Christensen

The Cray-2 computer was cooled with "Fluorinert", a 3M product
which is an electrically insulating, stable fluorocarbon-based fluid.

73 Bill AE6JV

-----------------------------------------------------------------------
Bill Frantz | gets() remains as a monument | Periwinkle
(408)348-7900 | to C's continuing support of | 150
Rivermead Rd #235
www.pwpconsult.com | buffer overruns. |
Peterborough, NH 03458

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Wes Stewart-2

Re: KPA1500 Cooling

The Phoenix Missile was cooled using Coolanol. Insidious stuff. Never wear a
new pair of slacks when you might get near a Phoenix Receiver/Transmitter Unit.
Don't ask me how I know this.

Aircraft carrier Captains hated it leaking all over their carrier decks about as
much as AFB Generals hated SR71s leaking fuel all over their runways. We "dried
up" Phoenix after the Shah was overthrown and the Russians got Phoenix and we
redesigned it to replace klystrons with IMPATTs.

And they paid us to have all this fun.

Wes N7WS

On 7/24/2020 6:56 PM, Bill Frantz wrote:
> The Cray-2 computer was cooled with "Fluorinert", a 3M product which is an
> electrically insulating, stable fluorocarbon-based fluid.
>
> 73 Bill AE6JV
>
> -----------------------------------------------------------------------
> Bill Frantz        | gets() remains as a monument | Periwinkle
> (408)348-7900      | to C's continuing support of | 150 Rivermead Rd #235
> www.pwpconsult.com | buffer overruns.             | Peterborough, NH 03458

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Rich NE1EE

Re: KPA1500 Cooling

In reply to this post by Luis V Romero (mobile)

If you're up to the challenge, hydrogen is a great for cooling. Very nice thermal conductivity and thermal capacity. I've worked on systems that used it for cooling.

~R~
72/73 de Rich NE1EE
On the banks of the Piscataqua

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Re: KPA1500 Cooling

In reply to this post by Bill Frantz

Bill,
That is what I was trying to remember what we used for cooling for the
electrodes in RF plasma tools.
Thanks
N2TK, Tony

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Bill Frantz
Sent: Friday, July 24, 2020 9:56 PM
To: [hidden email]
Subject: Re: [Elecraft] KPA1500 Cooling

The Cray-2 computer was cooled with "Fluorinert", a 3M product which is an
electrically insulating, stable fluorocarbon-based fluid.

73 Bill AE6JV

-----------------------------------------------------------------------
Bill Frantz | gets() remains as a monument | Periwinkle
(408)348-7900 | to C's continuing support of | 150
Rivermead Rd #235
www.pwpconsult.com | buffer overruns. |
Peterborough, NH 03458

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W2xj

Re: KPA1500 Cooling

In reply to this post by Rich NE1EE

I would avoid that in ham or broadcast transmitters due to the potential skill sets (or lack thereof)of end users. Hydrogen is too explosive in the wrong hands.

Sent from my iPad

> On Jul 25, 2020, at 6:41 AM, Rich NE1EE <[hidden email]> wrote:
>
> If you're up to the challenge, hydrogen is a great for cooling. Very nice thermal conductivity and thermal capacity. I've worked on systems that used it for cooling.
>
> ~R~
> 72/73 de Rich NE1EE
> On the banks of the Piscataqua
>
> ______________________________________________________________
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>

RICHARD Martin

Re: KPA1500 Cooling

If you have to use gas, use Helium. It is very good especially at reduced
pressures where the mean free path approaches the dimension of the
container.

Dick Martin KN6AA

On Sat, Jul 25, 2020, 07:37 W2xj <[hidden email]> wrote:

> I would avoid that in ham or broadcast transmitters due to the potential
> skill sets (or lack thereof)of end users. Hydrogen is too explosive in the
> wrong hands.
>
> Sent from my iPad
>
> > On Jul 25, 2020, at 6:41 AM, Rich NE1EE <[hidden email]> wrote:
> >
> > If you're up to the challenge, hydrogen is a great for cooling. Very
> nice thermal conductivity and thermal capacity. I've worked on systems that
> used it for cooling.
> >
> > ~R~
> > 72/73 de Rich NE1EE
> > On the banks of the Piscataqua
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> >
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> >
>
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AI4NS

Re: KPA1500 Cooling

We used helium to cool IR detectors on the RF-4C. It is also fun later. The
last IR system used nitrogen to cool the detectors. Not as much fun.

On Sat, Jul 25, 2020 at 11:35 RICHARD Martin <[hidden email]> wrote:

> If you have to use gas, use Helium. It is very good especially at reduced
> pressures where the mean free path approaches the dimension of the
> container.
>
> Dick Martin KN6AA
>
> On Sat, Jul 25, 2020, 07:37 W2xj <[hidden email]> wrote:
>
> > I would avoid that in ham or broadcast transmitters due to the potential
> > skill sets (or lack thereof)of end users. Hydrogen is too explosive in
> the
> > wrong hands.
> >
> > Sent from my iPad
> >
> > > On Jul 25, 2020, at 6:41 AM, Rich NE1EE <[hidden email]> wrote:
> > >
> > > If you're up to the challenge, hydrogen is a great for cooling. Very
> > nice thermal conductivity and thermal capacity. I've worked on systems
> that
> > used it for cooling.
> > >
> > > ~R~
> > > 72/73 de Rich NE1EE
> > > On the banks of the Piscataqua
> > >
> > > ______________________________________________________________
> > > Elecraft mailing list
> > > Home: http://mailman.qth.net/mailman/listinfo/elecraft
> > > Help: http://mailman.qth.net/mmfaq.htm
> > > Post: mailto:[hidden email]
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> > >
> >
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