Modifications for the Yaesu FT-221


19-07-1998 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 modification.

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 level.

Other problems.

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 importance.
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.



22-08-1998 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 as S2C.

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 function.

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!!

73s
Herman A.Tucker
[email protected]