[Elecraft] K3 + LP100A + Dummy Load

[Edward R. Cole]

Just a comment on dummy loads:

I do a lot of ham radio work at VHF and higher (up to 10-GHz), so 
making good power measurements involves having a good 50-ohm 
termination (load).  For most of my testing I have several coaxial 
loads:  A 25w Termaline (Bird) is used a lot in the shack as it tests 
Z=51 + j0 on my MFJ-269B antenna analyzer and shows zero reflected on 
a Bird43 power meter.  Some of the other loads show 52 or even 54 
ohms on the MFJ, and not quite resistive (I marked all them so I 
would know).  In all cases resistance measurement with an ohmmeter 
agrees with the R parameter in the complex impedance equation.

I even have a 500w Sierra termination (door stop load) which has a 
integral power meter, but it is not exactly 50-ohms and the meter is 
not in agreement with the Bird43, so I use it as a safe load for high 
power but not for high accuracy measurements.  I have seen coax loads 
shift way off 50-ohms due to overheating from too much or too long a 
transmission.

I bought some of the Cadsoft 100w surface-mount attenuators to use in 
a 900-MHz amplifier to permit driving with 10w exciter.  They were in 
the $12 range from Mouser.

One can make very fine 50-ohm loads using them on a proper heat sink 
at a fraction of the cost of coaxial loads.


73, Ed - KL7UW, WD2XSH/45
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