FT-221 improvements- CW
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If you change Q07 (PB-1460) to BF199, carrier leakage in CW may be reduced by 10-15db. Key on/off ratio will be about 50dB.
If you change the transistor Q01 also to BF199, a further 5dB improvement can be reached giving a 55db on/off ratio.

This was tested with the following set-up:

Converter 10.7MHz to 500KHz (2xBC547 with 11.2MHz xtal).
Siemens 3D344a2a "Pegelmesser-selektiv" (selective voltmeter) with 
+20 - 120dB range, dB/Volts).

The signal output from Q08 was also changed, 100+120 ohm voltage divider with 1nF directly to Q07.I believe that a better figure for keyed carrier on/off ratio would be preferred, but the achieved value is acceptable.

CW MS modification will also be tried, a new PCB for keying must be built, using an LM324=MC3403CP


                 YAESU * FT-221 KEYING
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The PCB for keying, PB-1568 may easily be modified with a BC547 and
OC57(OC75, AC125, AC126) with a simple keyfilter that works(!!)
Some rewiring of the key-line must be done.
The IC 14011/4011 was defective on receipt of this transceiver, so I inserted a 100k resistor to the input of the IC, to avoid static destruction of the IC.

                FT-221 KEYING, FURTHER IMPROVEMENTS
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Some 70dB tx carrier suppression was achieved (in contrast to the poor 40dB) with the earlier mentioned changes to the keying, and using the output transistor running at 3mA (Q01). The drive is adjusted with a resistor (220 ohms) across the output from T01(IF transformer going to pin 3)(PB1460) The diode on the output was also changed, to BA182, because I could not see that the original was operating properly.

73 jan-martin LA8AK @ LA5IV


PORTED AND REALIGNED FROM PC TO AMIGA FORMAT BY BOB G0LBQ - N6XDI.