dummy load plans wanted.
 

plans wanted for high power dummyload.needs to beable to take 300w
continious (up to 6hrs) at up to 144mhz. based in UK so source of high
power resistor required also..
thanks g0zen

i keep setting my heathkit cantenna on fire!!!

"zindazenda" wrote in message
...
plans wanted for high power dummyload.needs to beable to take 300w
continious (up to 6hrs) at up to 144mhz. based in UK so source of high
power resistor required also..
thanks g0zen

i keep setting my heathkit cantenna on fire!!!


You might think about some additional cooling for the cantenna. What I'm
thinking is to get a heat exchanger, pump the coolant from the cantenna
through it with a small circulating pump, and back into the cantenna. You
can probably use an automobile heater core for the heat exchanger, and an
automobile blower to cool the heater core. You should be able to find
those at good junkyard. You should find circulating pumps from many surplus
dealers on the net, such as http://www.surplussales.com,
http://www.herbach.com, http://www.surpluscenter.com and others.
ISTR that the cantenna is rated for 100W, but don't remember if it's
continuous or not. But the additional cooling should certainly boost the
power dissipation capabilities significantly.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!

"zindazenda" wrote in message
...
plans wanted for high power dummyload.needs to beable to take 300w
continious (up to 6hrs) at up to 144mhz. based in UK so source of high
power resistor required also..
thanks g0zen

i keep setting my heathkit cantenna on fire!!!


You might think about some additional cooling for the cantenna. What I'm
thinking is to get a heat exchanger, pump the coolant from the cantenna
through it with a small circulating pump, and back into the cantenna. You
can probably use an automobile heater core for the heat exchanger, and an
automobile blower to cool the heater core. You should be able to find
those at good junkyard. You should find circulating pumps from many surplus
dealers on the net, such as http://www.surplussales.com,
http://www.herbach.com, http://www.surpluscenter.com and others.
ISTR that the cantenna is rated for 100W, but don't remember if it's
continuous or not. But the additional cooling should certainly boost the
power dissipation capabilities significantly.
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!

If a Heath Cantenna is overheating all that much that indicates that it is
being used at well beyond its rated power. Added cooling is not necessarily a
solution. The stress on the resistor comes from thermal sources as well as
electrical sources. Even with "adequate" cooling, if you exceed the current
handling capability of the non-inductive resistor it will shorten its life.

An alternative solution is not to use a Cantenna at all. Use an inductive
resistor with an adequate rating and an antenna tuner to tune out the
reactance. Another approach is to use a 40m antenna as a dummy load. Wait
until evening, tune up on top of a foreign broadcast station, and use that for
testing purposes.

73s

If a Heath Cantenna is overheating all that much that indicates that it is
being used at well beyond its rated power. Added cooling is not necessarily a
solution. The stress on the resistor comes from thermal sources as well as
electrical sources. Even with "adequate" cooling, if you exceed the current
handling capability of the non-inductive resistor it will shorten its life.

An alternative solution is not to use a Cantenna at all. Use an inductive
resistor with an adequate rating and an antenna tuner to tune out the
reactance. Another approach is to use a 40m antenna as a dummy load. Wait
until evening, tune up on top of a foreign broadcast station, and use that for
testing purposes.

73s

ok found plans for bigger dummy load..but need supplier of non inductive 50r
resistor..needs to take full legal load for long as possible..intend to use
ARRL suppy dummy load design..
"K9SQG" wrote in message
...
If a Heath Cantenna is overheating all that much that indicates that it is
being used at well beyond its rated power. Added cooling is not
necessarily a
solution. The stress on the resistor comes from thermal sources as well
as
electrical sources. Even with "adequate" cooling, if you exceed the
current
handling capability of the non-inductive resistor it will shorten its
life.

An alternative solution is not to use a Cantenna at all. Use an inductive
resistor with an adequate rating and an antenna tuner to tune out the
reactance. Another approach is to use a 40m antenna as a dummy load.
Wait
until evening, tune up on top of a foreign broadcast station, and use that
for
testing purposes.

73s

ok found plans for bigger dummy load..but need supplier of non inductive 50r
resistor..needs to take full legal load for long as possible..intend to use
ARRL suppy dummy load design..
"K9SQG" wrote in message
...
If a Heath Cantenna is overheating all that much that indicates that it is
being used at well beyond its rated power. Added cooling is not
necessarily a
solution. The stress on the resistor comes from thermal sources as well
as
electrical sources. Even with "adequate" cooling, if you exceed the
current
handling capability of the non-inductive resistor it will shorten its
life.

An alternative solution is not to use a Cantenna at all. Use an inductive
resistor with an adequate rating and an antenna tuner to tune out the
reactance. Another approach is to use a 40m antenna as a dummy load.
Wait
until evening, tune up on top of a foreign broadcast station, and use that
for
testing purposes.

73s