[Elecraft] Difference in dummy loads

[Don Wilhelm]

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 <mikekopacki at gmail.com> 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?