Dave, I followed the problem you described on the group and this is the reason i do some measurements around the power output because i was a little bit anxious!
At the beginning, my only 2 "ham" references were my MiniVNA output (calibrated at my office at -2.04 dBm , 7.040MHz with 50 Ohms load) and a 25W MCE/Weinschel bi-directional attenuator (calibrated as 50.1 Ohms and 29.83 dB attenuation) These 2 "references" have permitted to "verify" the "coupling" factor of my LP-100A RF Sensor as 29.12 db for the 29.1 dB used by Larry!! The LP-100A is now my 3rd "ham" reference instrument. I also do some peak/average power ratio measurements for different digi modes and results were ok between 0 db (FSK) and 15 dB (EasyPAL during digital picture transmission) (the 2 extremes "tested" with software running in my PC). After that, i do also power output measurements with and without ALC (with a lot of caution!) for the K3 and.found something like ~ 1dB more power without ALC (ONLY for TESTING!) With ALC ON, i measured a mean error < +/- 0.1 dB between 1W and 12W and < 0.45 dB between 13W and 20W. (may be due to the activation of the PA?) During all these measurements, i have my "old" TDS 220 scope (1Gs/s 100MHz BW) connected at my -30dB "dummy load" output for monitoring in case of distortion and/or oscillation but all was ok and i'm very satisfied with these results.The measured P-P values divided by 2*SQR(2) gave me a good confirmation for the RMS value. One more (and last precision...), all measurements were done with a sinus audio single tone, except for peak/average ratio measurements done with some available digi modes. 73 QRO fr Rudolf, HB9ARI Dave G4AON wrote: > Rudolf, the problem is not one associated with the accuracy of the K3 > meter, but one of the ALC being fairly "slack" with the end result that > a fluctuating audio input from speech or from a sound card on many data > modes results in widely varying power, unfortunately often exceeding the > level set by the power control. An oscilloscope or peak reading > Wattmeter, such as the LP-100, will catch and display the peaks far > better than can be read from the K3 meter. > > I hope Elecraft continue their efforts to fix this irritating problem, > as not only does it make the use of some digital modes tedious, but > running a linear on SSB results in power levels which often exceed the > legal power limit - even when being very careful to set the drive level > (UK power limit 400W, using an Acom 1000 which does not use ALC feedback). > > 73 Dave, G4AON > K3/100 #80 > ------------- > <SNIP> > > I've done some measurements some time ago with my K3 #1212 and i had the > following values: > > K3 power set to 20W, f=7.040MHz 25W 50 Ohms dummy load MCE/Weinschel > LP-100A Wattmeter > mode USB 1 kHz sine audio at rear line-input, level adjusted to have the > desired ALC bar configuration > <SNIP> > Rudolf, HB9ARI > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
