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 <[email protected]> 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 <[email protected]> > 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 < > > [email protected]> wrote: > > > >> What are recommended dummy loads to consider for use when running the K3 > >> TX Calibration? > >> > >> Thanks - Steve WB6RSE > >> ______________________________________________________________ > >> Elecraft mailing list > >> Home: http://mailman.qth.net/mailman/listinfo/elecraft > >> Help: http://mailman.qth.net/mmfaq.htm > >> Post: mailto:[email protected] > >> > >> This list hosted by: http://www.qsl.net > >> Please help support this email list: http://www.qsl.net/donate.html > >> Message delivered to [email protected] > >> > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] -- -+-+-+-+- Jenny Everywhere's Infinite: Quark Time http://quarktime.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
