[Elecraft] K3 TX Calib Dummy Load Recommendations

[Mark Goldberg]

A good one that you know is 50 ohms over the range of frequencies and power
you want to use it at. Unfortunately, any particular model may be good or
bad, depending on how it has been used or abused. Is there any way you can
get access to an analyzer to determine if the dummy load is good? I have a
Vector Network Analyzer, but few hams will have one of those.

Also, if you really want to do a real calibration, you should have a
calibrated reference to check against. Lots of devices can be 5-10% off if
not calibrated, worse if abused or damaged. A Bird meter is only specified
to I think 5% of the full scale. So if it is a 200W full scale, it could be
10W off. So 100W might read 110W or 90W.  I've got a calibrated Spectrum
Analyzer and Signal Generator that I use to calibrate all my other stuff
against, but again, few Hams will have similar or spend to keep them in
calibration.

In general, oil filled dummy loads with fins like the Birds shown lower on
this page are going to be good, but expensive:

https://www.birdrf.com/Products/Test%20and%20Measurement/Loads/Coaxial-Terminations.aspx

You can find similar ones used, hopefully not abused and not filled with
PCBs.

I've got a similar one that must be decades old and it works well and is
pretty close to 50 ohms over the HF range. I have not opened it to see what
it is filled with!

73,

Mark
W7MLG


On Sat, Aug 25, 2018 at 4:09 PM, Steve Lawrence via Elecraft <
elecraft at mailman.qth.net> wrote:

> What are recommended dummy loads to consider for use when running the K3
> TX Calibration?
>
> Thanks - Steve WB6RSE
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