Elecraft K1 Modifications

ATTN: This content will not be updated because I do not have a K1 anymore.

AGC Problem Solved
LCD Backlight Kit Added
160m Band Filter Board Module
BFO Changed to USB
VFO Spread Out
Power Increased
12m/10m Mod

AGC

When the strong signals came into my receiver, I was very surprised because of the loud sound. So I changed some capacitor on the RF Board of my K1.

C31 to 1uF (from 2.2uF)
C67 to 0.1uF (from 2.2uF)

References:
K1_AGC_Notes (from Elecraft Reflector)
[Elecraft] K1 revisited

LCD Backlight

Elecraft now presents K1BKLTKIT, the LCD backlight mod kit. I put it into my K1. So I can operate even if it is dark. Not so bright, but easy to read.

160m Band Filter Board

The K1 covers 80m to 15m (4-band or 2-band), but Don, W3FPR modified two-band module to 160m. My K1 can be on 160m running 9 watts RF output.

Reference:
[Elecraft] 160M K1 band option (From: Don Wilhelm W3FPR Date: Tue, 10 Feb 2004 22:20:20 -0500)

BFO Changed to USB

The BFO of K1 is LSB but I usually use 17m/15m filter board, so I changed the BFO to USB from LSB by removing and jumpering RFC1 on the RF Board. I can listen to the SSB (USB) stations.

RFC1 removed
and jumpered

Special Thanks:
A staff of Elecraft support team told me how to modify. MNI TNX.

VFO Spread Out

I added a 68pF capacitor in parallel with C2 (120pF) on the RF board to make the VFO range spread out because I want to listen to SSB QSOs. VFO covers about 267kHz, but it is difficult to tune.

p.s.
I removed a cap. because it was so critical to tune.

Power Increased

The output power of my K1 was four watts on 15 meters, so I added a 0.001uF capacitor (as a bypass) in parallel with R30 on the RF board.

160m: 10W (not changed)
80m: 10W (not changed)
17m: 7W (from 6W)
15m: 7W (from 4W)

12m/10m Modification

Special Thanks to Stephanie, VA3UXB
for her suggestions on component values

Parts

a KFL1-2
four T37-6 (yellow) cores (if no KBxx band modules)
a FIL-J1 and a FIL-J2 (if K1 has KAT1)
capacitors (listed below)
crystals (listed below)

Component Values

Ref. Designators		Qty.	Components
Band 1 (24.8MHz)	Band 2 (28.0MHz)	Qty.	12 meters (24MHz)	10 meters (28MHz)
C1, C5	C6, C10	2	100 (or 82) pF	82pF
C2, C4	C7, C9	2	47pF	47pF
C3	C8	1	1pF	1pF
C11, C15	C16, C20	2	270 (or 220) pF	220pF
C12, C14	C17, C19	2	33pF	33pF
C13	C18	1	2pF	2pF
C21, C23	C24, C26	2	68pF	68pF
C22	C25	1	150pF	150pF
L9, L10 (T37-6 core) (yellow)	L11, L12 (T37-6 core) (yellow)	2	0.26uH 8 turns (16cm)	0.26uH 8 turns (16cm)
X1	X2	1	32.8000MHz (fundamental)	36.0000MHz (fundamental)

Mods

Additional mods I did were almost same as Stephanie's:

220pF capacitor added to J7 on the RF board, between pin 7 and 8 of J7.
R11 on the RF board changed from 82-ohm to about 33-ohm (56-ohm added in parallel with 82-ohm).
Compressing the windings on T3 on the RF Board.

In addition to above mods, I added a 0.001uF capacitor in parallel with R30 on the RF board to increase the RF output power.

ATTN: VFO range must be 150kHz or more because K1 covers 12-meter band starting 24.800MHz, but this band begins from 24.890MHz.

RF Output Power

Band	Output
24MHz	7 watts
28MHz	4 watts

References

[Elecraft] K1 on 10 meters: helpful advice (by Wayne Burdick N6KR @ Mon Dec 26 14:44:01 EST 2005)
[Elecraft] 10 meters on K1 - component values (by Stephanie Maks VA3UXB @ Sun Jan 1 12:57:13 EST 2006)

Additional Info: [Elecraft] 4-band K1 module covering 10-20 meters? Also: less-expensive 10/12 m crystals (by Wayne Burdick N6KR @ Sat Jan 7 14:13:04 EST 2006)