Sorry, that is twenty resistors, not fifty. wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog)
> On Aug 25, 2018, at 5:35 PM, Walter Underwood <wun...@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 <marklgoldb...@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@mailman.qth.net> 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:Elecraft@mailman.qth.net >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to marklgoldb...@gmail.com >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to wun...@wunderwood.org > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to wun...@wunderwood.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
