+++++++++++++++++ From: "Sandy, W5TVW" To: "Elecraft Reflector" Date: Thu, 13 Jun 2002 21:25:15 -0500 Subject: [Elecraft] K1- VFO "jump" A problem cropped up with my K1 a couple of days ago. The frequency of the VFO "jumped" a small amount, perhaps 50-150 Hz. from time to time. If the set was tapped on with the finger smartly, it would "jump" as much as 200 Hz. The amount of the "jump" would be erratic from occurrence to occurrence. I found that the VFO oscillator toroid was "cocked" on the lower nylon washer (next to the PC board.) I was apprehensive that the washer wasn't quite large enough in diameter and lacked a "shoulder" to centralize the core when I assembled it, and proceeded on nevertheless. I dug a fibre washer (like the kind used on binding posts) out of my hardware junkbox that had a raised "shoulder" on it that was just right for the toroid core and fit the mounting screw. It kept the toroid core from "cocking" off center when the nylon screw was tightened. I installed it in place of the lower nylon washer, and respaced the windings on the VFO core to get the desired tuning range coverage on all 4 bands from 40-15 meters. This seems to hold the core central to the mounting screw and I think it will solve my problem. Has anyone else noted this on their K1's? I can supply a scanned drawing of this, but didn't attach it, as on many reflectors, attachments are banned or truncated from the messages posted. 73, Sandy W5TVW K1 #1178 ++++++++++++++++++ Date: Wed, 28 May 2003 12:40:04 -0700 From: Wayne Burdick Organization: Elecraft To: Elecraft Subject: [Elecraft] K1 RIT and VFO counter hysteresis There has been some discussion lately about a change in the K1's displayed VFO frequency on exit from RIT mode. This is due to our use of "hysteresis" (lead/lag updates) in the K1's VFO frequency counter firmware. Applying hysteresis prevents flickering of the 100 Hz digit on the LCD. But as a side-effect, a shift of as much as 200 Hz is possible when changing bands or turning RIT on/off. For those of you who are still awake :) here is further and still more arcane detail: Suppose, due to the hystereis algorithm, you had a "lead" of one count (100 Hz) in one direction at the time RIT is turned on. By the time it is turned off, the counter will have sampled again many times, and it could now exhibit a "lag" of 100 Hz in the other direction. The net (200 Hz) represents the worst-case shift that you would ever see, assuming that VFO drift during the interval is less than 100 Hz. It would be possible to change the firmware to catch this condition explicitly and guarantee that you'd never see the 200 Hz apparent frequency shift. But the truth is that the display is still accurate to within +/- 100 Hz even in this case, which meets the intended spec for the K1 VFO. And of course the VFO itself will exhibit no shift at all--it's just the display that changes. So I think we'll reserve the firmware space for something more interesting! 73, Wayne N6KR +++++++++++++++++