Modifications for the Yaesu FT-221
Keying modifications for Yaesu FT-221
Keying modifications for Yaesu FT-221(225) (S/N 130233D)
(circuit diagrams are shown in DUBUS info 1991 nr 1)
By Jan-Martin Noeding, LA8AK, Voielien 39/B, N-4623 Kristiansand S.
Several boards in FT-221 and FT-225 are equal, so this article is
believed to suit either rig. Some of the older FT-221 do not have the
KEY-filter (PB-1568) (I am not sure if this board really helps)
Intentions for modifications: CW-MS TX experiments.
In this article the modifications shown is for maximum speed 200-300
lpm. LA8SJ friendly let me borrow his set to test the experiments,
this limited the amount of modifications.
Status before modification.
FT-221/225 has bad reputation for key-clicks, and tone can be heard by
local stns between the charachters (bad key on/off ratio).
Measurements before modification:
RF measurements (RF RMS mV-meter - eg. LA7MI mV-meter). See fig 1.
Q08 emitter 1.5V rms, Q07 emitter 0.6V rms @ Key-down or SSB.
RX-carrier(PB-1460B pin 22) 0.5-0.55V. FM-out (pin 3) 22mV.
It is not important to measure these voltages very correct, but this
is only for reference before and after modifications to see whether
some bad changes have been made.
Normally just above the minimum level the rig will work with at the
outputs from the board will give output free from overloading other
stages in the rig !
Keying for Q07 may be checked at pin 22 (PB1460) RX CARRIER. Original-
ly key-up RF voltage is as high as 25mV. This is easily reduced a lot.
Modifications PB-1460B MIC AMP (see fig.1)
Q07 2SC372Y was replaced by the RF transistor type BF199, the keying
was improved by 10dB. Oscillator drive to the buffer (Q07) is excessive
so it is important to reduce this. This stage pulled frequency when keyed.
It was found easier and sufficient to use a PASSIVE BUFFER (and voltage divider)
instead of an active stage to solve the problems, Xtal osc emitter resistor R42
is divided into two resistors, 100 and 120 ohm, an 1nF capacitor is
connected between center of the resistors and Q07 base Q (C46).
Control that RF voltage at pin 22 is almost the same
as before. R39/40 is changed as in the circuit diagram. This is not
important for key-up carrier suppression, but for keying-waveform
(key clicks). CW-Modification: R38 is divided into two resistors, 330
and 560 ohm. They were found experimentally in a test circuit. With
0.6V RMS input the emitter-cutoff voltage is increased by 1v DC.
CW FM BUFFER Q01 (2SC372Y). The original values are: R02=1K, R03=6k8,
R04=3k3 (VR10=5k was not found). If other values are used for R03 and
R04 they should be changed. VR10 must be removed, it is connected
between pin 8 and 26 on some models. The emitter resistors are re-
arranged as shown on the circuit diagram. To achieve highest possible
key-up/down ratio this transistor is now operated at much higher gain
than earlier, BF199 is also used for Q01. The excessive RF level is
reduced at the output with an extra resistor (1R5). It it easiest to
use a trimpotmeter here (470 ohm as variable resistor across the point).
The diode D17 1S1555 seems not to give sufficient attenuation when cut-off,
so a BA182 (or 2x BA182 in series) is used instead.
KEY FILTER and SHAPER (see fig.2 and 3)
For normal keying it is possible to change the original board, when
installed, see figure 3. For a simple circuit it was necessary to use
germanium transistor driver (low saturation voltage level).
Good germanium transistor types are: AC125, AC126.
AC162 may have too little current gain. I used OC57 because
this was available, perhaps it is just too low current type.
For FT-7 I tried AC162, but it failed in a similar circuit.
For CW-MS a keying unit like the one shown for IC-202E must be made,
however higher key-up current must be available.
Rewiring (fig. 2 and 3)
The original wiring cannot be used. This because SIDETONE oscillator
is connected to output from KEY-FILTER (I just don't understand why)
This must be changed. New circuit diagram is fig. 3.
To use the 'high' voltage-swing in the keying circuit, which is +8V
some diodes must be connected to KEY input (SSB-GND) to the PB-1499
AF pin 6 + 7 to isolate these connections. 4x 1N4148 are used to
achieve this and have equal operation point for these stages after
RX audio line output.(LINE OUTPUT)
For CW-MS and packet radio audio direct from top of AF gain should be
used to feed the external equipment, to achieve independent audio
FT-221 has bad AGC. It seems not possible to improve the circuit much,
this is because of severely carrier oscillator leakage into the
IF stages. One week was used to solve this, a lot of extra decoupling
capacitors were installed, but it seems impossible. Possibly the only
solution to the AGC problem is to use a combination between the old
circuit and a Plessey SL621/1621 AGC IC.
SIGNAL INTELLIGIBILITY is the most important term for efficient DX-
and contest operation, I suppose you do not wish to ask several times
for locator and other details. When you are not used to the language,
pronounciation, or dialect of the station you work this is of extreme
FT-221 and FT-225 are rather old rigs. They compare to FT-101B/FT-301,
some one should perhaps expect too much, but in fact, several new rigs
have the same troubles, and many other defects than this. So perhaps
it is sometimes better to keep the old rig!
CW Meteorscatter keying.
A simple way is to reduce the capacitor in base circuit of the germanium
driver transistor. A better way is to use the circuit shown for IC202E
with some changes for higher current in key circuit.
Yaesu FT-221R repeater modification
Updating the Yaesu FT-221R
With the recent opening of the 2-meter sub band [144.5-145.5 MHz] to
repeater operation,owners of some excellent transceivers find themselves
unable to use their rigs to key machines on the newly activated
channels.Notable among those radios is the Yaesu FT-221R.In order to
prevent out-of-band operation,only the 146.5MHz and the 1470-MHz switch
positions permit offset transmission.Yaesu engineers did not anticipate
the recent FCC ruling and as manufactured,the 221R cannot work through
repeaters having inputs below 146.0-MHz.The solution I describe below is
simple and does not mutilate the radio.Only two short pieces of wire and
one new offset crystal are required.
Loosen the top cover by pulling up on the four snap fasteners and
carefully pry off the cover.Turn the set upside down on the work table
.Remove the side screws and slowly lift away the bottom shell.The
four-section band switch will be found just behind the front panel.The
second band switch from the panel is designated as S2B, the third section
The solder lugs of each section of the switch [from lugs 1 through 8]
start with number 1 on the left UNDERSIDE of the wafer [looking from the
front panel].Number 2 is the first lug on the left TOPSIDE.Number 3
through 8 follow clockwise so that number 8 is on the extreme right
TOPSIDE of the wafer,as you view the switch with the set upside down.
On the wafer S2B solder an insulated wire about 1-1/2 inches[40 mm]
long to lugs 3 and 7.Lug 3 is not wired at the factory,and lug 7 has a
yellow wire soldered to it. On S2C connect lug 3 to lug 6.Again,lug 3 is
not factory wired; lug 6 is solder to a dark blue wire. Be very
careful,when soldering,not to melt the insulation of surrounding wires. A
helpful idea is to have a friend use to small screwdrivers or similar
instruments to separate,and make a path through,the jungle of wiring
around the switch while you do the soldering.
Now replace the bottom shell. Turn the radio right-side up. Remove the
black plastic cover plate over the LOCAL board and carefully pull out the
board. Just rock and lift it gently out of its edge connector. Plug a
13.9666-MHz crystal [case type HC-25/U ] into position 12 on the offset
/ auxiliary end of the crystal strip.Do Not use socket 9.
At the bottom of the component side of the LOCAL board find connector
contacts 28 and 30. They are contiguous to each other. Immediately above
the contact strips very carefully solder [ with a low heat iron ] a
bonding bridge connecting the printed conductors of 28 and
30.Then,immediately above this solder bridge sever the pc conductor of
number 30. Use a razor blade,or X-acto knife.Be sure the 28 to 30 bridge
remains intact. Replace the LOCAL board in the chassis-mounted
edge-connector. Screw it down tightly.
Turn on the transceiver. Rotate the band switch to 145.0 MHz.Throw
the AUX switch to the UP position and the RPT switch to NORM. Key the
transmitter [ with dummy load ] and adjust the trimmer capacitor of
crystal 12 [ last one on the left , looking from the front panel ] until
the transmit frequency is 600 kHz lower then the receive frequency.
Replace the plastic cover plate over the LOCAL board. Replace the top
cover. The set should now operate through the repeaters on the 144.5-to
145.5-MHz sub band... And surprise!! You are also able to use the 221R
on 1-MHz split repeaters in the 146/147MHz "oddball" band. Just turn the
band switch to 146.0 MHz,the AUX toggle UP, the RPT toggle to either NORM
or REV, as the occasion requires,and you've got 1-MHz split without the
need for an additional crystal.You're actually using one of the
factory-wired crystals as an offset rock without impairing the normal
When I ordered my crystal I also ordered The frequency I use as
simplex and that saves a lot of tuning.I ordered Mine from "Jan
Crystals",They charge as much for one as they do for two.That was the
reason I ordered the simplex one
NOTE: On the LOCAL board contacts at the bottom of board there will be
6 or more contacts in a row then a blank and then another one .The two
that are bridged together are the last two before the blank space.The one
you cut is next to the blank of the two you bridge together.I hope I have
not confused you to much .Have fun!!
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