Guys, I've mentioned this caviet before:
http://n2.nabble.com/Ref-Osc-Cal-Method-4-td2595451.html#a2595451 The way the K3 implements the passband shift, the same signal, with the same VFO setting, will have a different audio beat note if the SHIFT control is changed. * So your calibrations with your atomic standards are no better than the delta F that takes place when you vary the shift control. If you want to measure frequency with the K3 BW and SHIFT *always* set to the same values then OK. However, calibrating at 50Hz BW and normalized SHIFT and then changing to SSB bandwidths and declaring that some stations are "on frequency" and others aren't is stretching it. * I've discussed this with Wayne and it's considered IP. Wes N7WS --- On Tue, 11/17/09, juergen piezo <plebia...@yahoo.com> wrote: From: juergen piezo <plebia...@yahoo.com> Subject: Re: [Elecraft] K3 frequency accuracy versus displayed precision To: elecraft@mailman.qth.net Date: Tuesday, November 17, 2009, 12:53 AM Hi Paul I find the same thing, I have checked the clubs K3's against a rubidium standard that was calibrated to a cesium standard. The K3 is spot on, the only limitation being its 1hz calibration step limit for the TCXO. I wonder what use the yet to be released external standard interface will be when we can only adjust the TCXO in 1 hz steps. Its amazing how far off frequency most stations are when you use a radio thats dead on, the typical average being 40 to 80hz off. The K3 sounds so good on RX these days, its easy to pick stations that are off frequency by even a few HZ. The radios that I have found to be consistently on frequency are the IC7700 and IC7800. The SSB stations that impress me the most for being on frequency are the different Aeronautical control towers. These control towers have such excellent audio quality and they are always spot on frequency. Its a shame that more ham stations cant sound so professional and clear like these aeronautical SSB stations. I have always wondered what brand of transmitter they use? The excessive bass and ESSB audio that we hear so often just sounds so awful in comparison. Excessive bass and ESSB is just not good audio for SSB use. (I dont want to start a SSB debate!) but ESSB bassy audio sucks in comparison to these commercial SSB stations! John --- On Mon, 11/16/09, Paul Kirley <pkir...@fuse.net> wrote: > From: Paul Kirley <pkir...@fuse.net> > Subject: [Elecraft] K3 frequency accuracy versus displayed precision > To: elecraft@mailman.qth.net > Date: Monday, November 16, 2009, 6:28 PM > The K3 is capable of displaying > frequencies to 1 Hz. It can > be calibrated to somewhat less than 1 Hz against WWV > (method 2). > > Because I wanted to see if my K3 serial 1322 was capable > of > measuring frequency to its displayed precision, I decided > to > attempt the November 11/12 ARRL Frequency Measuring Test. > > I warmed up my K3 for about two hours because--even with > the > optional TCXO--my K3 drifts almost 0.1 ppm per degree > Centigrade > from 25C to 30C, the latter part of its warmup range this > time > of year at my QTH. (0.1 ppm is almost 1 Hz on 40 > meters.) > > Then I carefully used method 2 to calibrate against 10 MHz > WWV, > checking after exiting REF CAL by tuning across WWV on CW > with > SPOT activated to see that the beat notes were similar on > each > side of zero beat for 1 and 2 Hz off frequency. (A > lack of > similarity indicates that a small tweak of REF CAL is > needed.) > Tuning past WWV's carrier on CW with SPOT enabled also > provides > practice for the real thing. > > When W1AW (and each of the other FMT stations) began its > call-up, > I tuned its frequency to be centered in the passband with > the DSP > set at 50 Hz bandwidth. When the long dashes began, I > turned on > SPOT and zero-beated against the sidetone with 1 Hz fine > tuning. > > After recording the result, I moved on to the other > frequencies > and stations that had been specified in the ARRL FMT > announcement. I was able to copy and measure 4 of the > 5 tests, > with one station on one frequency being inaudible at my > QTH. > > Result: my K3 was within 1 Hz on all 4 readings, that > is, its > accuracy matched its displayed precision--after warmup and > careful calibration. > > 73, Paul W8TM > > ______________________________________________________________ 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
