Kenwood YK-88S, PS-50, SP-430, PS-430, MB-430 Circuit Description, Fig Selectivity control circuit

TS-440S

CIRCUIT DESCRIPTION

t	Signals from the ANT pin are fed into the RAT pin of the R F
	unit via the transmit/receive switching relay . The signals the n
	go to the 10 BPFs through the approx . 20 dB attenuator cir-
	cuit, the first stage of the first IF trap circuit, and the lo w
	pass filters (which pass only 500 kHz or less) . The signal the n
	goes through the second stage of the first IF trap circuit, an d
	is mixed with the VCO signal and converted into the first I F
	signal of 45 .05 MHz in the first mixer, consisting of Q3 an d
	Q4 (2SK125-5) . The VCO circuit consists of Q21 to Q2 4
	(2SC2668Y) and oscillates in four bands from 45 .05 MH z
	to 75 .05 MHz . Oscillator frequencies are controlled by D C
	signals from the PLL unit .
	The first IF signal of 45 .05 MHz is passed through the MC F
	(F1), which is used in both receive and transmit, and is am -
	plified by the first IF amplifier Q5 (3SK74L) . In the secon d
	mixer, consisting of Q6 and Q7 (2SK1 25), the first IF signa l
	is mixed with the heterodyne oscillator signal (36 .22 MHz )
	from the PLL circuit, amplified by Q12 (2SC2668Y) to ob-
	tain the second IF signal (8 .83 MHz) . The second IF signa l
	of 8 .83 MHz goes through the gate of the noise blanker . In
	modes other than FM , the signal then goes through the MC F
	(F2) and is fed into the IF unit through buffer amplifiers Q 8
	and Q9 (2SC2668Y) .

When the optional 8 .83 MHz filter is connected, the secon d IF signal is then fed from the IF unit into the optional filter . In the third mixer, consisting of Q1 and Q2 (3SK73GR), th e second IF signal is mixed with 8 .375 MHz signal generate d by IF unit's heterodyne oscillator circuit, consisting of Q5 3 and Q54 (2SC2458Y), and converted into the third IF signa l (455 kHz) . The third IF signal is then amplified by Q 5 (3SK73GR) . A diode switch is used to route the signal t o either the FM or SSB circuits .

In SSB mode, the third IF signal goes through the SSB cer- amic filter (XF3) . In AM mode, the third IF signal goes throug h the AM ceramic filter (XF4) . In either mode, the third IF sig- nal is then amplified by Q7 and Q8 (3SK73GR) and detected . In FM mode, the third IF signal goes through the FM cerami c filter (XF5) . The signal is then sent to the FM IF, IC2 (M C 3357) for amplification and detection . IC2 also contains an FM noise squelch circuit .

The detected SSB/AM signal is passed through the notch cir - cuit, consisting of hybrid IC IC1 (BX6124) and squelch gat e Q12 (2SC2459BL) . The signal then goes through the AF volume control and is amplified to the appropriate level b y AF amplifier IC7 (UPC2002V) .

1) Selectivity circui t

Figure 4 is a selectivity circuit diagram . In auto mode, th e appropriate bandwidth filter is automatically selected accord - ing to mode . When an optional filter is used, two filters ar e available . Tables 2 and 3 shows the various combinations

of bandwidth available when optional filters are used . In F M mode, the selectivity switch does not operate and a singl e dedicated FM filter is used . Optional filters operate only i n receive and are separate from the filters used in transmit .

AUTO SELECTIVITY CONTRO L

	I—		il aD6		X59—1070—00		1I < ss R
558	21,				01
455 3t_.14					/a	D I	AI
					+R+z.'	,$W	AL T
				D5	02	L aJ
			r p1				< cw R
			I
					R4~~
							fro m
					04
			D4				IC 1 0
							RYR
			~• 14		i	D 2
						j
			D3		0 3
Bew	sj		r al	—i		L_ . J	<A M R
45A	6		L
	45AI	DII
	BowI	la	o		D
					I49 N -	M 2	RX B
455	88 5			(-	0
		D8			D 5
	45S
				a			SELEC-
	BBC				6
							TIVIT Y

AUTO

AUT n

454

GNDI

F/14 — J

Fig . 4 Selectivity control circuit

MANUAL SELECTIVITY CONTROL

7