[Elecraft] Using RIT - RIT Mod

[alta]

On Friday 05 April 2002 05:45, you wrote:
> Hi folks  -
> I find it a bit frustrating to get the RIT "centered" ...

Tim ...

I had the same problem.  The following mod solved it for me.  I have 
been using this mod for over a year now, and is is very friendly.

... Reed, K7FLY, K1

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RIT FINE/COUSE MOD

***** This is improved Version 2.3, 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 (more fine) or alternatively 220K (not as fine),
(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 1N5711 Shottkey diodes in parallel with the 220K (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.