I have an LP100A as well as TX Mon for the P3. But, I also do admit that my reason for having the LP100A is not to have an accurate reading of power but rather to have a reasonable good indicator of power and SWR. I got the LP100A long before I had my K3 or P3 so if I were doing it all over again, the power meters on the KPA500 or the P3 TX Mon are good enough. I like to know whether I am putting out 100 watts or 2 watts. I really don’t care to know if it is 100 watts or 95 or 105 watts.
I think these days, the best thing about the LP100A is that it is yet another lighted up display that looks cool for any visiting guests. 73, phil, K7PEH > On Aug 21, 2015, at 7:38 PM, Bob McGraw - K4TAX <rmcg...@blomand.net> wrote: > > A comment here, has anyone thought to use a Bird 43P with a 100 watt HF slug? > Or maybe a TelePost LP-100a? Both are equally good regarding power > measurements but only when the load is 50 ohms resistive. > > 73 > Bob, K4TAX > K3S s/n 10,163 > > On 8/21/2015 8:15 PM, Don Wilhelm wrote: >> In a slightly related note - for those who are using an oscilloscope to >> measure the RF voltage at the output, instead of converting everything to >> RMS and doing the power calculation, I can give you a shortcut. The formula >> for power by observing the RF voltage across a 50 ohm dummy load is Vp-p >> squared, and then divided by 400. If the load is not 50 ohms, then it is >> Vp-p squared and divided by 8 times R. >> >> The derivation is left to "the student" - Hint, use SQRT 2 in your >> derivation rather than 1.414 or .707 because the radicals will cancel out - >> the numbers will only cause confusion, but will produce a similar result. >> I use this easy formula at the workbench often when determining power >> output, it is especially useful at power levels of 10 watts and below. Yes, >> I do have an oscilloscope probe permanently connected directly across my >> dummy load just for this purpose as well as for looking at relative RF >> voltages during an alignment. >> >> 73, >> Don W3FPR >> >> On 8/21/2015 3:34 PM, Bill Breeden wrote: >>> >>> It's important to remember that RF power expressed in watts is always based >>> on RMS values. If RF watts are calculated by measuring the voltage across >>> a known load, the voltage must be expressed as an RMS value to correctly >>> calculate the power in watts. Watts are watts. There is no such thing as >>> "peak to peak" or "RMS watts" when expressing RF power in watts. >>> >> >> ______________________________________________________________ >> 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 rmcg...@blomand.net >> >> >> > > > ______________________________________________________________ > 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 phys...@mac.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 arch...@mail-archive.com
