A dry dummy load is good for up to its power rating - but do not exceed
that rating. The air cooled dummy loads not only require power for the
fan, but may be over-rated for their power spec.
I prefer dry or oil immersed dummy loads.
A good dummy load should present a 1.0 SWR for all the bands of
interest. Check with an antenna analyzer. If you have access to a
vector analyzer, it should show 50 ohms resistive and zero reactance at
all frequencies of interest.
Those home-built with resistors can usually be OK up through 30 MHz, but
may fail at 50 MHz and above - and that includes the 'cantenna' types
(oil immersed resistors). careful construction is required to reduce
the inductance involved in the mounting and assembly.
I have 3 'cantenna' type dummy loads, two for 150 watts In quart cans
and one for 1000 watts in a gallon can. They are OK up through 30 MHz,
but not above that level.
They are good for loads on the transmitter, but are not sufficient for
precise measurement.
I also have 2 precision dummy loads that are good up into the GHz
region. Those are the ones that I use for measurements (up to 100
watts) And for the K3 TX Gain calibration. I have another that I rate
at 50 watts (using a 100 watt Caddock thick film resistor on a heatsink)
that is a good load up through 220 MHz.
None of mine are air cooled.
73,
Don W3FPR
On 7/1/2020 7:45 PM, Eric Norris wrote:
Basically the same thing. I suggest the Vectronics DL-650 (dx engineering)
or a commercial pull from Ridge Equipment. For serious testing, I fire up
my 2GHz, 6kW water-cooled dummy load--louder than 10 KPA-1500s on PCP.
Always get more capacity than you need. --because you'll need it later. If
you get an amp, a high power dummy load is essential for tracking down
possible RFI. I keep a 50-watt dummy load on ANT2 of the K3S for a quick
TXGN CAL, and a DL-2500 on ANT2 of the KPA1500. But then, I love the smell
of a hot dummy load in the morning. It smells like...radio.
73 Eric WD6DBM
On Wed, Jul 1, 2020, 2:44 PM NJMike <[email protected]> wrote:
I need to purchase a dummy load for use with my K2/100. What's the
difference between a dry dummy load and an air cooled dummy load? Which is
better?
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