++++++++++++++++++++++++++++++++++++++++ Date: Thu, 15 Mar 2001 20:43:25 -0800 From: alta Subject: [Elecraft] New K1 mod: RIT Fine/coarse Feature +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 17 Mar 2001 16:57:34 -0800 From: alta Subject: [Elecraft] K1 RIT mod: Coarse/Fine Enh.- ver 2.1 Delete Old versions +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ***** This is improved Version 2.2, which supersedes the others ***** I want the best of both worlds with RIT functionality. I want the RIT control to work *fine* (gradual) when I punch the button after a station drifts toward the edge of the 200 Hz filter, so that the station doesn't totally disappear after the RIT button-push. Or worse, I could mistakenly lock onto the wrong nearby station! And, I want the RIT control to have *coarse* (wide-range) capability for those DX pileups. No room for a switch, so what's a ham to do. I decided to add circuitry to the RIT control so that it is gradual at 12:00, and becomes increasingly coarse as it is rotated left or right. That way, I keep the fine capability where I need it, yet do not lose much of the wide range of the control. I mounted the following components on the front of the microprocessor board, between the volume and RIT pots. I snipped the middle lead from the RIT control and inserted the circuitry (in effect) between: Between the wiper of the pot and the circuit board, I inserted in parallel: (1) 330K ohm resistor, (2) diode, forward, and (3) diode, reverse. Then from the point on the circuit board that the pot originally connected to: (4) 100K resistor to one side of R3 RIT control, and (5) another 100K to other side of R3. (6) Bridge (parallel) each of the two 10Ks that go to the RIT pot with two 33K resistors, one 33K parallelled with each 10Ks. The 33Ks are most easily added to the inside surface of the microprocessor board. Because this will narrow the total RIT range slightly, you may also want to add 10pf or 20pf to C7. I opted to leave C7 at 39pf, and was left with a +- 3 KHz range. If you want the effect to be subtle, with the fine zone between 11:00 and 1:00, use germanium diodes, like 1N34 or 1N60. If you want to increase the fine zone to between 10:00 and 2:00, use Shottkey 1N5711's or silicon power diodes like 1N4004. For even a tad more fine-zone, use small signal silicon diodes. If you want a spot at say 11:30 and 12:30 to have no change at all, remove the afore mentioned 330K resistor. Without the 330K, you can set the control roughly in the middle (between 11:30 and 12:30), and it will always be right on the frequency of the non-RIT mode. :) At first, I opted for the germanium diode solution. After operating for awhile, I decided that the effect was too subtle. So, I finally settled on the 1N4004 diodes in parallel with the 330K (also with the 100Ks as previously described). With these components, the fine zone is between 10:00 and 2:00. The fine zone gently covers a bit beyond what you can hear with the 200 Hz filter engaged, which has increased the pleasure of operating the rig for me. ...... Reed White K7FLY PS - To render the VFO pot [not the RIT pot] somewhat more linear than in the stock K1, while the front panel was off, I also added a 68K resistor between the high voltage side of the VFO pot R1 and its wiper. ++++++++++++++++++++++++++++++++ Date: Fri, 13 Jul 2001 09:36:58 -0500 From: "Jack Scheinuk" Subject: [Elecraft] K1 - RIT Mod Found Very Useful Greetings - I operate strictly CW - filters set 850Hz, 400HZ and 200Hz - found that the RIT of ~ 6kHz was too wide for the narrower filters as a very small angular rotation of the RIT control snapped thru the narrow ranges - so changed C7 to 10 pF (Page 55, RIT and XIT) which reduced the RIT to ~ 1.2 kHz - this really works excellently - - you can smoothly roll on and off the tuned signal easily peaking it using the 200 Hz filter making copying in heavy QRM very easy - and the RIT of ~ 1.2 (.6 either side) is really all that is needed in 99% of all cases. Incidentally, I found that when I changed C7 from 39pF to 10pF I had to re- adjust the VFO coverage range (Page 38, VFO Range Test, VFO Range Adjustment) and recalibrate very slightly (Page 41, Operating Frequency Calibration). 73 - Jack W5WSF Jack Scheinuk, P.E. 7927 Maple St., New Orleans LA 70118 Tel: 504-866-1221 - Fax: 504-866-1258 +++++++++++++++++++++++++++++