K3 TX Calib Dummy Load Recommendations
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K3 TX Calib Dummy Load Recommendations
 
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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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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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 < [hidden email]> 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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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In reply to this post by Elecraft mailing list
Any decent commercial nominally 50 ohm 100W+ DL ought to work fine, as long as it isn’t a piece of junk that falls apart at 50 MHz. It doesn’t need to be NIST traceable :-)
Grant NQ5T K3 #2091 KX3 #8342 > On Aug 25, 2018, at 7:09 PM, Steve Lawrence via Elecraft <[hidden email]> wrote: > > What are recommended dummy loads to consider for use when running the K3 TX Calibration? > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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In reply to this post by Mark Goldberg
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 <[hidden email]> 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 <[hidden email]> > 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 < > > [hidden email]> 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:[hidden email] > >> > >> This list hosted by: http://www.qsl.net > >> Please help support this email list: http://www.qsl.net/donate.html > >> Message delivered to [hidden email] > >> > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[hidden email] > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > Message delivered to [hidden email] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] -- -+-+-+-+- 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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In reply to this post by Mark Goldberg
While one can measure a dummy load with an ohm meter, this is only the
DC resistance of the resistive element. It does not assure that it is non-reactive as reactance is an AC component related to frequency. Dummy loads should appear as 50 ohms at all frequencies within the range where they are expected to be used. A good dummy load will be rated at 50 ohms from DC to 500 MHz or higher. A better way to verify a dummy load is to use an antenna analyzer such as a MFJ-259, an Autec, or Comet CAA-500 or RigExpert AA-30, etc. Do connect the dummy load direct to the instrument without a jumper cable and sweep the range of frequencies desired. Any value measured other than 50 ohms and with a SWR greater than 1.1:1 is deemed not satisfactory for a dummy load. Another method is to use a return loss bridge or a vector network analyzer. Don't be mislead by the numbers printed on the label. I have two of the "gallon can" oil filled types. They measure noticeably different values than 50 ohms and get quite reactive above 30 MHz. From this source you will find 100 watt Decibel Product dummy loads DB4303B for $50 each. http://www.nm3e.com/loadSampler.htm#LoadSampler <http://www.nm3e.com/loadSampler.htm#LoadSampler> And you will find Bird 100 watt loads, good from DC to 2.4GHz for $85. And if you need one for that legal limit amp, they have a Bird 82C being a 2500 watt water cooled load for $500. Everyone should have a dummy load and an antenna bridge for their station. 73 Bob, K4TAX On 8/25/2018 7:35 PM, Walter Underwood 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 <[hidden email]> 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 < >> [hidden email]> 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:[hidden email] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [hidden email] >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [hidden email] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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For my KX3, I built a dummy load from three 150 ohm 2 watt
resistors and a BNC connector. The resistors are in parallel with a lead going to the center conductor of the connector. The other leads are folded back over the resistors and attached to the ground-side of the connector. The whole outside is then covered with a piece of coax braid. It does well on the antenna analyser test Bob, K4TAX suggests. It lives in a pocket of Rose's case and goes where the radio goes. 73 Bill AE6JV --------------------------------------------------------------------------- Bill Frantz |"After all, if the conventional wisdom was working, the 408-356-8506 | rate of systems being compromised would be going down, www.pwpconsult.com | wouldn't it?" -- Marcus Ranum ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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Try to find carbon resistors as newer film resistors may be reactive.
Older carbon resistors have a tendency to migrate upwards in value. Be sure to check them with a meter. 73 Bob, K4TAX On 8/26/2018 7:50 AM, Bill Frantz wrote: > For my KX3, I built a dummy load from three 150 ohm 2 watt resistors > and a BNC connector. The resistors are in parallel with a lead going > to the center conductor of the connector. The other leads are folded > back over the resistors and attached to the ground-side of the > connector. The whole outside is then covered with a piece of coax > braid. It does well on the antenna analyser test Bob, K4TAX suggests. > > It lives in a pocket of Rose's case and goes where the radio goes. > > 73 Bill AE6JV > > --------------------------------------------------------------------------- > > Bill Frantz |"After all, if the conventional wisdom was > working, the > 408-356-8506 | rate of systems being compromised would be going > down, > www.pwpconsult.com | wouldn't it?" -- Marcus Ranum > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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In reply to this post by Bill Frantz
Some of the best dummy loads are built from Caddox Thick Film Resistors.
The 50 ohm resistors are non-reactive and flat up through 500 MHz. They MUST be mounted on a heatsink to achieve their power rating. Using careful wiring practices (close to zero length leads), you can wire 4 of the 25 watt versions in series-parallel for a 100 ohm dummy load, but there is a 100 watt version available that will do a better job. 73, Don W3FPR On 8/26/2018 8:50 AM, Bill Frantz wrote: > For my KX3, I built a dummy load from three 150 ohm 2 watt resistors and > a BNC connector. The resistors are in parallel with a lead going to the > center conductor of the connector. The other leads are folded back over > the resistors and attached to the ground-side of the connector. The > whole outside is then covered with a piece of coax braid. It does well > on the antenna analyser test Bob, K4TAX suggests. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Elecraft mailing list
I have a db Products 50 watt dummy load which was sold on ebay as
surplus cellular test equipment. That should mean it's good to a GHz I guess. Even though it's only 50 watts I have used it briefly at 100. There used to be lots of these on ebay but now all I see are 25 or 30 watt versions. 73, Drew AF2Z On 08/25/18 19:09, Steve Lawrence via Elecraft 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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: K3 TX Calib Dummy Load Recommendations
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In reply to this post by Elecraft mailing list
"What are recommended dummy loads to consider for use when running the K3 TX Calibration?"
____________ Thanks to all who've replied both on and especially off list. The general consensus is that BIRD makes the best dummy loads. Avoiding units that incorporate BeO is a consideration. Others mentioned, in no particular order: Heath / MFJ Cantenna Oak Hills Research RFL 100 db Products Designs that use Caddock film resistors. MFJs. TKS & 73 - Steve WB6RSE ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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