Yaesu FT-227R Memorizer 2 Meter FM Transceiver User Manual

General Information

The Yaesu FT-227R is a new synthesized 2-meter FM transceiver specifically designed to provide high performance for amateur VHF/FM communications. This completely solid-state unit utilizes Yaesu computer theory and offers 800 digital Phase Lock Loop channels in 5 kHz steps between 144 to 148 MHz.

An 'optical coupling' system eliminates noisy rotary switches, and bright digital LEDs display the selected channel in MHz, 100 kHz, and 1 kHz, ensuring easy readability even in bright sunlight. A memory circuit allows instant recall of any of the 800 channels with a touch of a switch.

In addition to a conventional ±600 kHz repeater split, any transmitter offset frequency can be memorized for operation on odd split frequency repeaters. A built-in tone burst generator supports tone burst accessed repeater operation, fully adjustable for pitch, duration, and level. An optional tone guarded squelch (TGS) provides silent monitoring; in TGS mode, a tone-guarded signal automatically opens the receiver squelch circuit. The tone frequency can be selected within 160 Hz to 250 Hz. The BUSY lamp indicates if the channel is occupied or serves as an alarm if receiver volume is too low.

Advanced circuit design features prevent damage to transistors from high antenna VSWR or reversed power supply polarity. The FT-227R is manufactured with high regard for quality, utilizing a diecast front panel and a heavy gauge metal case for an extremely rugged package that minimizes shock and vibration effects. Channels can be limited to 400 within either 144-146 MHz or 146-148 MHz.

The FT-227R VHF/FM transceiver is supplied complete with all mounting hardware, cables, connectors, and accessories required for a mobile installation. Key components include the transceiver with a built-in 3-inch speaker, a dynamic push-to-talk microphone with a retractable coiled cord, a universal mounting bracket with screws, washers, and nuts, a power cable, a cigarette lighter adapter, spare fuses, a microphone hanger, a miniature phone plug for an external speaker, an accessory plug, and a tap connector.

Installation

Using the Tap Connector

The tap connector is designed for easy power connection without stripping wire insulation. It handles most automotive instrument panel wire sizes. To use, slice the 'hot' lead into the tap connector, insert the transceiver power lead 3/4 of the way in (past the metal connector element), then use pliers to press the metal connector element until it is flush. Fold the hinged cover over and snap it firmly in place. The compact design of the FT-227R makes it ideal for mobile installation, operating directly from a vehicle's 12 Volt battery. For base station use, an AC Power Supply rated 2.5 ampere at 13.8 V DC is required.

General Installation Guidelines

The FT-227R transceiver is primarily designed for mobile service, requiring only an antenna and a 13.8 Volt DC power source. The unit is factory pre-tuned and requires no adjustments for normal operation into a 50 ohm load.

Antenna location is crucial for effective communication range, which is directly related to antenna height. The antenna should always be in the clear and as high as possible, maintaining a minimum distance of 5 feet between the VHF antenna and other antennas. For mobile installations, locate the antenna as far from the engine as practical to minimize ignition noise pickup. In all installations, ensure the antenna VSWR is less than 1.5:1.

Popular mobile antenna types include a 1/4 wave length whip with unity gain or a 5/8 wave length offering approximately 3.5 dB gain. To minimize losses, use the shortest practical length of coaxial cable, avoiding sharp angles or kinks. Use type RG-8/U cable if the transmission line length exceeds 25 feet, while RG-58U is suitable for shorter lengths. For all bends, form the cable into a radius of not less than 10 times its diameter.

Mobile Installation Steps

For mobile service, install the FT-227R where controls, indicators, and the microphone are easily visible and accessible. The unit can be mounted in any position without performance loss, such as under the dash or atop the transmission tunnel. A universal bracket is supplied for this purpose.

Use the universal mounting bracket as a template to locate the mounting holes. Use a 3/16-inch diameter drill for these holes and allow clearance for the transceiver, its controls, and connecting cables. Secure the mounting bracket with the screws, washers, and nuts supplied.
Install the transceiver in the mounting bracket by sliding it into the guide rail and tightening the screws on both sides.
The microphone hanger can be affixed to any convenient place for handling the microphone.

Power Connection and Cables

The supplied power cable can be plugged directly into the vehicle's cigarette lighter receptacle for casual operation. For permanent installation, the lighter plug may be removed, and the leads routed directly to the battery (red for positive, black for negative or ground), or the nearest termination to the battery (e.g., ignition switch, fuse block). If extending power leads, use #16AWG insulated copper wire and avoid extending leads further than required to prevent excessive voltage drop. The frequency may shift to 147.000 MHz or 147.005 MHz if the supply voltage is accidentally opened by a loose contact of the power adapter.

Caution: Before connecting the power cable to the transceiver, check the battery voltage with the engine running (battery charging). If the voltage exceeds 15 Volts DC, the regulator should be readjusted so the highest charging rate does not exceed 15 Volts. Always observe proper polarity when making battery connections. Reversed polarity will not damage the FT-227R due to protective circuitry, but the equipment will not operate under this condition.

Connect the power cable to the POWER receptacle on the rear panel.
Connect the 50 ohm antenna cable to the ANT receptacle on the rear panel.
Connect the microphone cable to the 4-pin microphone receptacle on the front panel.
An external 8 ohm speaker may be connected at the SP receptacle on the rear panel if desired (this automatically disconnects the internal speaker). Use the external speaker plug supplied.

Base Station Installation

As a base station, the FT-227R requires a source of 13.8 Volts DC at 2.5 amperes.

Controls & Switches

The FT-227R is designed for ease of operation, though some controls may be unfamiliar due to its modern computer technology. It is important to understand the function of each control and indicator before operating the equipment.

Front Panel Controls

Channel Selector: An endless optical coupling system selects from 800 channels.
VOL (Volume) inner control: Adjusts the receiver audio output level and turns power off when rotated to an extreme counter-clockwise (CCW) position.
SQL (Squelch) Outer control: Adjusts the receiver squelch threshold sensitivity.
FUNCTION Switch: Selects the transmitting frequency.
- SIMP (Simplex): Simplex operation.
- +600: The transmitting frequency is 600 kHz higher than the receive frequency.
- -600: The transmit frequency is 600 kHz lower than the receive frequency.
- MEM (Memory): Transmits on the memorized frequency.
DIAL Display: The digital display indicates the operating frequency.
METER: Indicates signal strength on receive and relative power output on transmit.
MIC receptacle: A four-pin connector used for microphone input and push-to-talk (PTT) relay actuation.
MEMORY switch: When pressed, the frequency on the dial is memorized, and the 'M' lamp lights up. To release the memorized frequency, press the switch a second time.
5UP switch: Shifts the channel frequency 5 kHz up, and the '5UP' lamp lights up.
TONE SQUELCH switch: Activates an optional TONE SQUELCH circuit when pressed, and the 'TONE SQ' lamp lights up.
MEMORY RECALL switch: When pressed, the memorized frequency is recalled, and the 'MR' lamp lights up.
BUSY indicator: The lamp lights up when a signal is received.
ON AIR indicator: The lamp lights up when in the transmit mode.

Rear Panel Controls

POWER receptacle: A two-pin connector for connection to a 13.8 Volts DC (negative ground) power source, vehicle battery, or AC power supply.
SP (Speaker) receptacle: Provides audio output for an external speaker. Output impedance is 8 ohms, and the internal speaker is disabled when a plug is inserted.
ACC (Accessory) socket: Used for external control of the transceiver.
BURST switch: Applies a short 'tone burst' to the carrier at the start of each transmission when in the 'ON' position. This is normally used only with 'tone access' repeater actuation.
HI/LOW switch: Selects the desired RF power output: 10 Watts in 'HI' position or 1 Watt in 'LOW' position.
ANT (Antenna) receptacle: UHF type coaxial receptacle for connection of the antenna.

Operation

Initial Check

Rotate the VOLUME control switch clockwise to apply power. The meter will illuminate, and the channel frequency will automatically set to 147.000 MHz (with 5 kHz up at depressed position), regardless of the channel knob position. However, a memorized frequency can be retained if the MEMORY switch is left in the depressed position.
Rotate the SQUELCH control fully counter-clockwise.
Adjust the VOLUME control for a normal listening level (background noise or a station if one is transmitting).
When the channel is clear (background noise only), rotate the SQUELCH control clockwise until the receiver is silenced and the BUSY lamp turns off. Perform this step carefully to avoid going beyond the silencing point, which would prevent the receiver from responding to weak signals.
Set the HI-LOW switch on the rear panel to the desired power output position.

Frequency Selection

The channel select knob selects the frequency at every 10 kHz step. Clockwise rotation increases the frequency up to 148.000 MHz, and counter-clockwise rotation reduces it down to 143.990 MHz. When the 5 kHz up switch is pressed, the channel frequency shifts 5 kHz higher. On 148.005 MHz and 143.990 MHz, the transmitter section is automatically disabled to prevent transmission outside amateur bands.

Note: When the memorized frequency is recalled with the channel outside the amateur band (143.990 or 148.005 MHz), the guard circuit remains active, preventing the transmitter from being activated by the PTT switch.

Caution: Channel selection should not be done while the transmitter is keyed.

Memory Operation

Select the desired channel with the channel select knob. Then press the M (Memory) switch; the M lamp lights up, indicating the channel is memorized. The memorized frequency shifts 5 kHz up when the 5UP switch is pressed and shifts down when released. After memorizing, the channel selector knob can be used to select other frequencies. To recall the memorized frequency, press the MR (memory recall) switch.

The MR lamp lights up, and the memorized frequency is displayed on the dial window. When the MR switch is pressed again, the frequency returns to the frequency preset by the channel selector knob. The channel selector knob can then be used to select a new frequency. To release the memorized frequency, press the M switch again.

The memorized frequency is retained when the power is turned off by the front panel switch. However, the memory disappears if the power cord is removed from the power source. The memory circuit functions with the FUNCTION switch in any position. When the FUNCTION switch is in the MEM position, the MR switch is inoperative, and the memorized frequency is transmitted by the PTT switch.

Repeater Operation

The transmitting frequency can be shifted to either the lower or higher side for repeater operation. When the FUNCTION switch is set to +600 kHz, the transmitting frequency shifts 600 kHz up from the displayed receive frequency. With the FUNCTION switch at -600 kHz, the transmitting frequency shifts 600 kHz down.

The MEMORY function can be used with the function switch on the repeater position, and the receive frequency is memorized. For non-standard offset, first memorize the transmit frequency. Then find the receive frequency using the channel selector knob. Set the FUNCTION switch to MEM position. The transceiver will then transmit on the memorized frequency and receive the frequency displayed in the channel window.

Extreme caution should be observed to avoid transmitting outside the amateur bands when the FUNCTION switch is at +600 kHz and MEM POSITION.

If operating on a repeater channel requiring 'tone access,' set the BURST switch on the rear panel to the 'ON' position. The 'tone burst' will be applied to the carrier each time the push-to-talk lever on the microphone is depressed.

Note: Refer to the Tone Adjustments paragraph to change the tone frequency or duration (factory set for 1800 Hz and one second).

When ready to transmit, hold the microphone close to your mouth, depress the push-to-talk lever, and speak distinctly at a normal conversation level. Check that the red 'transmit' indicator illuminates and the meter indicates upward.

Block Diagram

The FT-227R features a comprehensive block diagram illustrating the interconnections and signal flow within its main units. The diagram details the Main Unit (PB-1659), PLL Unit (PB-1757), PLL Control Unit (PB-1773A), and Display Unit (PB-1758/1759). Key sections include the RF amplifier, mixers, IF amplifiers, discriminator, audio amplifier, power amplifier, tone oscillator, voltage-controlled oscillator (VCO), phase-locked loop (PLL) circuitry, and various control and display components. The diagram shows how signals are processed from the antenna input through the receiver chain, and from the microphone input through the transmitter chain, including frequency synthesis and power amplification. It also depicts the interconnections of integrated circuits (ICs), transistors, and other discrete components that form the functional blocks of the transceiver.

Theory of Operation

The transceiver consists of a transmitter and a double conversion superheterodyne receiver, utilizing a digital phase lock loop synthesizer capable of operating on any of the 800 channels within the frequency range of 144 to 148 MHz. Solid-state circuitry is employed throughout, and computer theory is utilized for frequency selection. The transceiver is designed to operate from a 13.8 Volts ±10% negative ground power source.

Transmitter

The transmitter produces a Frequency Modulated (FM) signal. The audio signal from the microphone is set to a proper level by VR201 and amplified by Q201, Q202, and Q203 (2SC372Y). The audio output from Q202 is coupled to the IDC (Instantaneous Deviation Control) circuit, where positive and negative peaks are clipped by diodes D201 and D202 (1S1555). The output from the last amplifier Q203 is fed through a low-pass filter, which attenuates frequencies above the speech range caused by clipping at the level set by the deviation control potentiometer VR202. This speech signal is then applied to a phase modulator varactor diode, D401 (1SV50), which varies the frequency of the 10.7 MHz crystal controlled oscillator, Q401 (2SC372Y).

The frequency modulated 10.7 MHz signal is then amplified by a buffer amplifier Q402 (2SC372Y) and fed to a balanced mixer consisting of Q403 and Q404 (2SK19GR), where the signal is converted up to 144-148 MHz by mixing with the 133.3-137.3 MHz signal delivered from the VCO (voltage controlled oscillator). The output from the balanced mixer is fed through tuned circuits (T404-T407) to an amplifier Q405 (35K40M). T404-T407 are tuned to the transmitting frequency by varactor diodes D403-D406, whose capacitance changes according to the DC output voltage from the PLL circuit. The 144-148 MHz signal is then amplified by amplifier stages Q204 (25C535A), Q206 (2SC2053), Q207 (2SC730), and Q208 (MRF212), which delivers 10 Watts of RF energy through a diode switch and low pass filter into a 50 ohm load.

Diodes D205 and D211 (1S188FM) rectify a small portion of the RF output and apply the resultant DC voltage to the meter, which indicates relative power output from the transmitter. The DC output from D205 is also delivered to the lamp driver Q209 and Q210 (2SC372Y), which turns the ON AIR lamp on during transmission.

If the transmitter is keyed without an antenna connected, or if a high VSWR exists, the reflected power is detected through T202 and a diode D208 (1S188FM), which produces DC voltage. Q211 (2SC372Y) conducts with this DC voltage, causing a decrease in Q212 (2SC372Y)'s collector current. This drops the collector voltage of Q213 (2SA496), causing Q11 (2SD235) to decrease current and supply voltage to the PA amplifier, lowering power to prevent damage. The threshold level is set by VR205. This circuit is also used to switch the output power down to 1 Watt when the HI-LOW switch is set to LOW. The amount of power reduction can be adjusted with VR206.

The antenna change-over circuit consists of switching diodes D206 and D207 (M1301). The tone burst circuit consists of a timing generator and a gated multivibrator. With the BURST switch in the 'ON' position, a DC voltage is applied to the tone burst circuit. When the transmitter is keyed, Q214 (2SC372Y) conducts and triggers the one-shot multivibrator Q215 (MC14011B). The other half of Q215 generates a tone signal, which is amplified by a buffer Q216 (2SC372Y) and applied to the microphone circuit of the transmitter. The tone frequency is adjustable by VR207, while the output level (deviation) is adjustable by VR209, and the burst duration by VR208.

Receiver Section

The input signal from the antenna is fed through a low-pass filter (L1, L214, L213, C1, C243-C245) and the diode change-over switch (D206, D207, L212) to the FET amplifier Q101 (3SK51). The amplified signal is then applied through four stage high Q coax resonators to the first mixer Q102 (3SK51). The use of a dual gate FET RF amplifier together with high Q coax resonators minimizes effects of cross modulation and other spurious responses while providing a low noise figure for the receiver front end.

The 144 to 148 MHz signal is heterodyned with the first local oscillator, producing a 10.7 MHz first IF signal. The first local oscillator is delivered from the PLL (Phase Lock Loop) VCO circuit. The first IF signal is fed through a crystal filter XF101, which has a pass band of -7.5 kHz, to the second mixer Q103 (3SK40M). This produces a 455 kHz second IF signal by heterodyning with the 10.245 MHz output signal of the second local oscillator Q104 (2SC372Y). Q105 (2SA564) works as a switch, disconnecting the supply voltage to Q104 when the PLL circuit is unlocked.

The second IF circuit consists of Q106, Q107, Q108 (2SC372Y), and Q109 (µPC577H). The cascade connected ceramic filters CF101 and CF102 provide narrow band selectivity for the receiver, and the limiting action of Q109 removes any amplitude variation to the ceramic discriminator (CD101, D106, and D107 - 1S188FM).

The discriminator produces an audio output in response to a corresponding frequency shift in the IF signal. The output audio signal is amplified by Q113, Q114 (2SC372Y) and applied across the VOLUME control VR1 to the input of the audio amplifier Q116 (µPC575C2). The output from Q116 is applied in series through the ACC socket to the internal speaker. A low-pass filter between Q113 and Q114 attenuates the audio frequency spectrum above 3 kHz to increase readability of the received signal.

A portion of the 455 kHz IF signal is rectified by D103, D104 (1S188FM) for S-meter indication. VR101 is used to adjust the meter sensitivity. When no carrier is present in 455 kHz IF, the high frequency noise at the discriminator output is amplified by Q110 and Q111 (2SC372Y), then detected by D108 and D109 (1S188FM) to produce a DC voltage. This voltage is applied to turn Q112 (2SC372Y) on. With the conduction of Q112, the base of Q113 is grounded to squelch the audio amplifier. When a carrier is present in the 455 kHz IF, the noise is removed from the discriminator output, and the audio amplifier recovers normal operation.

The squelch circuit opening causes Q113 to conduct, causing lamp driver Q115 (2SC372Y) to draw current to light up the BUSY LAMP. The SQUELCH controls, VR2 and VR102, set the threshold level.

Heterodyne Oscillator

The heterodyne signal is generated by the PLL (phase lock loop) circuit, consisting of a VCO (voltage controlled oscillator), a reference crystal oscillator, a programmable divider, and a phase comparator.

The VCO oscillator, Q301 (2SK19GR), generates 133.3-137.3 MHz signals. The oscillator frequency is controlled by a varactor diode D301 (1S2209), which varies the capacitance of a tuned circuit (L301, TC301, C302, and C304) in accordance with a DC voltage supplied from a phase comparator Q309 (TC5081P). The output signal from Q301 is amplified by a buffer amplifier Q302 (3SK40M) and Q303 (2SC535A), and fed through a diode switch, D302 and D303 (1S1555), to the receiver or transmitter mixers.

A portion of the output from Q303 is fed through a buffer amplifier Q304 (3SK40M) to a PLL mixer, Q305 (2SC535A), which produces a 1-5 MHz PLL IF signal by mixing with the PLL heterodyne signal. The PLL heterodyne signal is generated by an overtone crystal controlled oscillator Q310 (2SC373). The crystal frequency is selected by diode switch D315-D320 (1S1555) in accordance with the FUNCTION switch and 5kHz up switch. The output from Q310 is fed to a tripler Q311 (2SC710), which produces the PLL heterodyne signal.

The PLL IF signal is fed through a low pass filter (L305, C331, and C332) to the amplifiers Q306 and Q307 (2SC372Y). The amplified signal is then fed to a programmable divider, Q308 (µPD857C). The crystal oscillator, Q312 (2SC373), generates a 10.24 MHz signal, and its output is fed to the scaler/divider Q308 (µPD857C), where the 10.24 MHz signal generates a 10 kHz reference signal.

The digital phase comparator Q309 (TC5081P) compares the phase of the PLL IF signal with that of the reference signal, and any phase difference is converted into an error correcting voltage. This error correcting voltage is fed to the varactor diode D301, which changes the output signal phase to lock with that of the reference signal. When the VCO is locked, the constant voltage at pin 4 of Q309 is applied to Q316 (MPSA13) to conduct, and in turn Q315 (2SC372Y) cuts off. The 'H' voltage at the collector of Q315 turns Q205 (2SC372Y) to conduct, and it supplies DC voltage to the exciter younger stages Q204 and Q206. When the VCO is unlocked, the DC voltage at the emitter of Q205 drops to prevent normal operation of Q204 and Q206.

PLL Control Section

The optical coupling system utilizes two photo-interrupters Q2 and Q3 (PS-4001) to generate two signal outputs, which are applied to a PLL counter unit. The signal applied to the CK terminal is fed through a waveshaper Q710 (MC14049B) to a BCD up/down counter (Q707 - 10 kHz, Q708 - 100 kHz, and Q709 - 1 MHz), using MC14510B as a clock signal. The signal applied to the U/D terminal is inverted by a unit of Q710 and controls the up-down counter. The output from Q707-Q709 is fed to a 4-bit data selector (Q701-Q703 - MC1451B) and Quad latch (Q704-Q706 - MC14042B), which are used for memory when the MEMORY switch is pressed. The output from Q701-Q703 is fed to a programmable divider, Q308 (µPD857C).

Q711 (MC14081B) for high end and Q712 (MC14028B) for low end cut off Q713 (2SC735Y) to prevent any transmission outside the amateur bands. The BCD signals at the input of the programmable divider are also fed to the LED driver, Q601-Q603 (MSM561), to drive LEDs D601-D603 (TLR 312). A 4-BIT full adder, Q604 (MC14008B), is used as a binary adder to produce a 4-8 display on the MHz range. LED D604 (TLR312) displays 0 or 5 by the 5 UP switch. The display LED will be turned off by Q605 (2SC372Y) when an unlocked signal is received.

Power Supply

A DC 13.8 Volt supply is used for the audio power amplifier Q116, relay, and lamps. The supply voltage to the driver and final power amplifier is regulated by voltage regulator Q11 (2SD235D), which is controlled by the HI/LOW switch and the automatic final protection circuit. Voltage regulator Q605 (µPC14305) regulates the supply voltage at 5 Volts to supply Q308 and the display unit. Q313 (2SC372Y) and D301 (RD6.8EB) regulate the supply voltage at 6 Volts for the VCO and phase comparator. The 5 Volts supply for the PLL control unit is regulated by a zener diode D3 (WZ050) and is connected directly to keep memory when the power switch is turned off with the M switch pressed. A regulated 8 Volt supply using Q117 (µPC14308) is used for all other circuits. When the function switch is at MEM position, D4 (WZ050) supplies 5 Volts to the receiver, and D5 (WZ050) supplies 5 Volts to the transmitter.