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Ken,=20
You can buy transformer oil from Ameritron or MFJ for $24.95/Gallon. =
Transformer=20
oil has better thermal properties than mineral oil and thus will give =
better power=20
handling than with mineral oil (MFJ gives derating curves for their =
dummy load=20
using both transformer oil and mineral oil). Per the MFJ-250 manual, =
motor oil is=20
not recommended for use in dummy loads due to its low vaporization =
temperature.
By the way, if you find a lower priced source for transformer oil, let =
me know,=20
I need a couple more gallons for an upcoming project=20
73 de Mike, W4EF.......... =20
P.S. Since your dummy load is of unknown origin, you may want to =
properly dispose of=20
the old oil as it might contain PCB's which are known to be carcinogenic =
when burned. =20
----- Original Message -----=20
From: Ken Barber=20
To: Radio-contesting.com=20
Sent: Sunday, September 30, 2001 5:03 PM
Subject: [AMPS] transformer oil
Hi,
I purchased an old military 1000 watt dummy load at a hamfest today. =
It is quite large and has industrial size radiators. I ran 500 watts =
into it for about 5 minutes. I noticed that the input area where the =
"N" connector is fastened got quite warm, whereas the rest of the dummy =
load didn't seem to get warm at all. I opened it up and found that the =
oil is low and would not completely cover up the resistive element and =
that the oil is rather dirty. I saw in a radio handbook that =
transformer oil may be obtained from the local power company, so I will =
try them as a source. If you know of another source, please let me know =
who it is.
I know nothing about oil and heat transfer, so could someone explain =
why one could not use motor oil or mineral oil or cooking oil such as =
olive oil ? Secondly, should the transformer oil be filled right up to =
the top of the dummy load or should there be a little room for =
expansion?
73,
Ken W2DTC
=20
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</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3D"Courier New" size=3D2>Ken, </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2>You can buy transformer =
oil from=20
Ameritron or MFJ for $24.95/Gallon. T</FONT><FONT face=3D"Courier New"=20
size=3D2>ransformer </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>oil has better thermal =
properties than=20
mineral oil and thus will give better power </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>handling than with mineral oil =
(MFJ gives=20
derating curves for their dummy load </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>using both transformer =
</FONT><FONT=20
face=3D"Courier New" size=3D2>oil and mineral oil). Per the MFJ-250 =
manual, motor=20
oil is </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>not recommended for use in =
</FONT><FONT=20
face=3D"Courier New" size=3D2>dummy loads due to its low vaporization=20
temperature.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2>By the way, if you find a lower =
priced=20
source for transformer oil, let me know, </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>I need a couple more gallons =
for an=20
upcoming project</FONT> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2></FONT> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2>73 de Mike, =
W4EF.......... =20
</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3D"Courier New" size=3D2>P.S. Since your dummy load is =
of unknown=20
origin, you may want to properly dispose of </FONT></DIV>
<DIV><FONT face=3D"Courier New" size=3D2>the old </FONT><FONT =
face=3D"Courier New"=20
size=3D2>oil as it might contain PCB's which are known to be =
carcinogenic when=20
burned. </FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A href=3D"mailto:kenw2dtc@home.com"; title=3Dkenw2dtc@home.com>Ken =
Barber</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
href=3D"mailto:amps@contesting.com"=20
title=3Damps@contesting.com>Radio-contesting.com</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Sunday, September 30, =
2001 5:03=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> [AMPS] transformer =
oil</DIV>
<DIV><BR></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS" =
size=3D4>Hi,</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS" size=3D4> I purchased =
an=20
old military 1000 watt dummy load at a hamfest today. =
It is=20
quite large and has industrial size radiators. I ran 500 =
watts into=20
it for about 5 minutes. I noticed that the input area where =
the "N"=20
connector is fastened got quite warm, whereas the rest of the dummy =
load=20
didn't seem to get warm at =
all. </FONT></STRONG><STRONG><FONT=20
face=3D"Comic Sans MS" size=3D4>I opened it up and found that the oil =
is low and=20
would not completely cover up the resistive element and that the=20
oil is rather =
dirty. </FONT></STRONG><STRONG><FONT=20
face=3D"Comic Sans MS" size=3D4>I saw in a radio handbook =
that transformer=20
oil may be obtained from the local power company, so I will try =
them as a=20
source. If you know of another source, please let me know who it =
is.</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS" size=3D4> I know =
nothing about oil=20
and heat transfer, so could someone explain why one could not use =
motor oil or=20
mineral oil or cooking oil such as olive oil ? Secondly, =
should the=20
transformer oil be filled right up to the top of the dummy =
load or should=20
there be a little room for expansion?</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS" =
size=3D4>73,</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS" size=3D4>Ken =
W2DTC</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=3D"Comic Sans MS"=20
size=3D4></FONT></STRONG> </DIV></BLOCKQUOTE></BODY></HTML>
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