Well, that's what I get for reading this list while at work and trying to "multi-task" with other stuff...
W4ZV states that the P3 display is NOT controlling the K3, but "it's actually the other way around". Now this makes more sense. Let me know if I have understood this correctly: The P3 display *follows* the K3 within a 1.4 Hz, but displays the frequency ROUNDED OFF to 50 Hz. That is, the GRANULARITY of the P3 display, versus the granularity of the K3 display is 50 Hz versus the 1 Hz accuracy displayed by the K3. So, aftr all of the careful calibration is done and the rig and the K3 are warmed up and ready, when I QSY to a peak on the screen, gents, how close to the actual frequency of the displayed signal on the P3 do I come on the K3? My Christmas list is written in pencil... -lu-w4lt- Date: Thu, 12 Aug 2010 07:06:05 -0700 (PDT) From: Bill W4ZV <btipp...@alum.mit.edu> Subject: [Elecraft] P3 Reference Calibraton Error To: elecraft@mailman.qth.net Message-ID: <1281621965933-5416204.p...@n2.nabble.com> Content-Type: text/plain; charset=us-ascii Brett Howard wrote: > > The center follows the K3 you can tell where it is based on the fact > that there is a K3 next to you. So long as you've got the two synced > and don't have a center offset in you know where the center is. > Correct. I believe his confusion is thinking the P3 display is controlling the K3, but it's actually the other way around. 1. First calibrate the K3 to WWV using the K3 Manual procedure. With a good ear (or other methods) you can do this to <<1 Hz. The K3 should be reading 15.000.000 with FINE resolution and you should hear no beating or change in pitch when switching between UCW and LCW. 2. The P3's Center line tracks the K3 so P3 CF is exactly indicating the K3's frequency (15.000.000) even though the display is rounded (i.e. 15.000.0). So far we have not touched our P3 at all. 3. Next calibrate the P3's spectrum display per the manual procedure by using Ref Cal to shift the spectrum display so that it centers on the center line. Use the minimum SPAN (2.0 kHz) and adjust Ref Cal in 10 Hz steps until the spectrum display is best aligned on the center line. I find this easiest to do if you set SCALE = 10 and adjust REF LVL so the signal peak is mid-scale in the P3 display. Adjust Ref Cal so the signal shoulders are symmetrical about the center, or as close to symmetrical as possible, given the 10 Hz adjustment resolution. Potential sources of error are: 1. Drift in K3 reference oscillator (49.38 MHz). 2. Drift in P3 reference oscillator (60 MHz). 3. Adjustment resolution of the P3's Ref Cal steps. Adjustment steps are 10 Hz (at the P3's 60 MHz clock). At WWV's 15 MHz (1/4 of 60 MHz), each adjustment step is 1/4 of 10 Hz = 2.5 Hz, which results in a maximum 1/2 step uncertainty (1.25 Hz) in adjustment resolution when centering the P3 display. The P3's adjustment error (e.g. 1.25 Hz at 15 MHz) is accurate enough to easily hit 50 Hz bandwidth filters when using the minimum SPAN (even assuming some reference oscillator drift). There may be other minor rounding errors in the DSP but I'll let the nit-pickers argue over that. 73, Bill ______________________________________________________________ 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
