Kenwood Comprehensive Guide to PS-50 Marine Radio Performance and Features

TS-440S

CIRCUIT DESCRIPTIO N

waves changing from continuous waves to relatively low duty pulses . Q1 is driven by this voltage waveform to control Q2 , which is connected to the collector of Q4 in series and mo- tor drive voltage is generated .

If the motor turns too fast, the SWR value will be smalle r than the motor stop value because of the inertia of the mo- tor . As a result, the motor will continue to operate even if

TUNE STO P

ADJ IC8 c/4

the motor stop signal is sent and the SWR value will con- tinue to be greater than the motor stop value, causing th e motor stop signal to turn off . That is, the motor will not sto p and it will be difficult to obtain a match . If the motor spee d is too slow, it will take a long time to satisfy a matching con - dition . The TS-440 therefore controls the motor speed ac - cording to changes in SWR .

Q 5

Triangular wov e generator

Fig . 7 Antenna tuner circuit

The antenna coupler is a T type . Six relays RL100 to RL10 5 are used to change taps within the range 3 .5 MHz to 30 MHz .

2) Cooling fan circuit

The final unit contains the temperature-sensitive thermisto r TH1 thermally coupled with final transistor Q4 . When tem- perature on the surface of Q4 reaches approx . 50°C, the fa n start comparator Q9B operates (H level), causing Q8 to tur n on to operate the fan . During operation of the fan, tempera - ture protection comparator Q9A is at a L level, so the tem- perature protection circuit does not operate .

When temperature on the surface of Q4 goes down to 45°C , the cooling fan turns off .

Comparato r output

Q9 B

V

/45° /50°	0° Bo°	Temperature ° C
FAN OFF FAN ON	Thermal	Therma l
	protection OFF protection ON

Fig . 8 temperature protection operatio n

•Final temperature protection circuit

When the temperature of the final transistor Q4 rises u p to approx . 80°C, the temperature protection comparato r Q9A turns on (H level), Q1 in the filter unit also turns on , and a minus DC voltage is supplied to the ALC line, reduc - ing the transmitter output to zero . (The TS-440 does not return to a receive state .) When the temperature of th e final transistor Q4 falls to approx . 70°C, the protectio n circuits turns off allowing the transmitter to operate again .

•SWR protection circuit

When antenna VSWR is bad, or the reflected wave is to o large, because the auto antenna is tuning for example, L4 2 and L43 detect the state and its output is rectified . Th e rectified signal is then amplified by Q2 to control the AL C voltage so that drive power is reduced . As a result, loa d on the final unit is reduced .

•SWR automatic arithmetic circuit

The TS-440 uses the automatic arithmetic circuit in th e AT-250 . The forward wave voltage VSF and reflecte d wave voltage VSR from the filter unit are fed into the ana - log arithmetic circuit of the switch unit, and used to se t the voltage level of IC8 pin 2 (5 V +VsR/VSF) . Output vol- tage from the pin 2 is shifted by IC5 to move the needl e in the SWR meter .

IC5 contains a level shift/meter amplifier and an auto tune r V-I convertor . IC7 contains a square wave generator an d a voltage comparator . IC8 contains an integration circuit . Q3 and Q4 are used to switch forward and reflected wave input signals alternately .

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