[Elecraft] K3 TX Calib Dummy Load Recommendations

[Gwen Patton]

The QRPGuys QRP tuner kit I built is very nice, but don't go over its 12W
limit, or you'll blow the diode.

Thankfully, I have a pile of them on hand just in case. ;)

Gwen NG3P

On Sat, Aug 25, 2018 at 8:36 PM Walter Underwood <wunder at wunderwood.org>
wrote:

> I built the Oak Hills Research RFL-100 dummy load kit. It is supposed to
> be good to
> 144 MHz, so it should be fine at 50. If you’ve never built a kit, this is
> a good one to
> start with. The kit is $50. I got the $5 BNC option, since my shack is
> 100% BNC.
>
> http://www.ohr.com/rfl100.htm
>
> Here are some photos of my build. Mine measured 49.9 Ω, which is within
> 0.2%.
> My Ohmmeter is accurate to +/-0.5%, so I’ll take that as a solid 50 Ω.
> Because the
> dummy load is built with 50 resistors, part tolerances will average out.
>
> https://observer.wunderwood.org/2016/12/31/building-a-dummy-load/
>
> wunder
> K6WRU
> Walter Underwood
> CM87wj
> http://observer.wunderwood.org/ (my blog)
>
> > On Aug 25, 2018, at 4:49 PM, Mark Goldberg <marklgoldberg at gmail.com>
> wrote:
> >
> > 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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