Yaesu FRG-7700 Communications Receiver

General Description

The Yaesu FRG-7700 is a communications receiver designed for demanding shortwave listeners. It utilizes an advanced frequency synthesizer to cover the range of 150 kHz to 29.9 MHz, supporting AM, SSB (USB, LSB), CW, and FM reception modes. The receiver offers three bandwidth options for AM reception, allowing users to select the most appropriate IF bandwidth based on interference levels and fidelity requirements. An optional memory unit allows storage and recall of up to twelve frequencies, simplifying the monitoring of multiple stations. The FRG-7700 features a high-sensitivity design, excellent selectivity, a combined digital and analog display of the operating frequency, and a built-in digital quartz clock with programmable on/off timer functions. The timer can also control peripheral equipment like tape recorders for unattended recording. Key performance features include an effective noise blanker, selectable fast/slow AGC, an adjustable audio filter for improved interference rejection, an easy-to-read S-meter, and two RF attenuators for strong signal conditions. For FM operation, a squelch control is included. Interface jacks are provided for tape recorder control, audio output, receiver muting, and headphone listening, making the FRG-7700 a versatile receiver.

Image Description: A front view of the Yaesu FRG-7700 communications receiver, showing its various controls, displays, and speaker grille.

Specifications

• Frequency Range: 150 kHz - 29.999 MHz (30 bands)
• Modes: AM, SSB (USB, LSB), CW, FM
• Sensitivity:
  • 0.15 MHz - 0.3 MHz: AM: 30 μV / 500 Ω; SSB/CW: 3 μV / 500 Ω
  • 0.3 MHz - 2 MHz: AM: 25 μV / 500 Ω; SSB/CW: 2 μV / 500 Ω
  • 2 MHz - 29.999 MHz: AM: 5 μV / 50 Ω; SSB/CW: 0.5 μV / 50 Ω; FM: 1 μV / 50 Ω
• Selectivity:
  • AM W (Wide): 12 kHz (-6 dB), 25 kHz (-50 dB)
  • AM M (Medium): 6 kHz (-6 dB), 15 kHz (-50 dB)
  • AM N (Narrow): 2.7 kHz (-6 dB), 8 kHz (-50 dB)
  • SSB/CW: 2.7 kHz (-6 dB), 8 kHz (-50 dB)
  • FM: 15 kHz (-6 dB), 30 kHz (-40 dB)
• Stability: Less than ±1 kHz from 1 to 30 minutes after power ON; Less than ±300 Hz after 30 minutes warm-up.
• Antenna Impedance: 0.15 MHz - 2 MHz: 500 ohms (unbalanced); 2 MHz - 29.999 MHz: 50 ohms (unbalanced)
• Audio Output: 1.5 Watts (8 ohms, 10% THD)
• Speaker Impedance: 8 ohms (internal); 4-16 ohms (external)
• Power Requirement: 100 / 120 / 220 / 240 volts, AC 50 / 60 Hz
• Power Consumption: Standby: 10 VA; ON: 33 VA (without Memory Unit), 39 VA (with Memory Unit)
• Size: 334(W) x 129(H) x 225(D) mm
• Weight: Approx. 6 kg (6.5 kg with Memory Unit)

Semiconductor Complement

The FRG-7700 utilizes a comprehensive complement of Integrated Circuits (ICs), Field-Effect Transistors (FETs), and transistors, including specific models such as HD10551P, MB8718, MC4044P, 2SK107-3, 2SC945AQ, and various diodes and LEDs.

Accessories

Packaged accessories include an AC Power Cable, extra fuses (1A for 100-120V, 0.5A for 220-240V), a 10-meter wire for antenna, and extender feet with pads.

Available Options

• Memory Unit
• Memory/Clock Backup Batteries (AA Size)

Controls and Switches

Front Panel:

• SPEAKER: Internal speaker.
• POWER: Main ON/OFF switch. Can be controlled by the clock timer.
• PHONES: 1/4" headphone jack. Disables internal speaker when used.
• REC: Miniature phone jack for recording output (approx. 100 mV fixed).
• MODE: Selects reception mode: LSB/CW, USB, AM N (Narrow), AM M (Medium), AM W (Wide), FM.
• AGC: Selects Automatic Gain Control decay time: SLOW (for AM) or FAST (for CW/SSB).
• NB: Noise Blanker switch to reduce pulse-type noise.
• AF GAIN: Controls speaker volume.
• TONE: Adjusts high-frequency audio response to minimize interference.
• S-METER: Indicates relative signal strength.
• AM, PM: Indicators for the clock.
• MAIN DIAL: Tunes the operating frequency.
• DIGITAL DISPLAY: Shows operating frequency or time, selected via the FUNCTION switch.
• ATT: Attenuator control to reduce receiver preamplifier gain for strong signals.
• M FINE: Fine-tuning control during memory operation (±1 kHz).
• SQL: Squelch control, usable only in FM mode to silence receiver until a signal is present.
• CONTROL SWITCHES (TIMER, DIM, M, MR): TIMER activates the power control timer. DIM dims display and lamp intensity. M stores a frequency into memory. MR recalls stored frequencies.
• BAND: Selects 1 MHz segments of the HF spectrum (0-29 MHz) and includes presets for amateur radio bands.
• M CH: Selects the desired memory channel.
• FUNCTION: Selects Digital Display functions: FREQ, CLOCK, ON, OFF, SLEEP.
• CLOCK SETTING SWITCHES (HOUR, MINUTE, HOUR SET, TIMER CLEAR): Used for setting the clock and timer functions.

Rear Panel:

• COAX ANT: UHF type coaxial connector for antenna input.
• AC: AC power cable input.
• ATT: Rear panel Attenuator switch (LOCAL/DX).
• AC LINE FUSE: Fuse holder for AC line fuse.
• REMOTE (N.O., N.C.): RCA type jacks for controlling peripheral equipment via the timer.
• AC VOLTAGE SELECTOR: Selects the proper input AC voltage.
• ACC: 5-pin DIN accessory jack for AGC voltage, 11V DC line, and mute line.
• EXT SP: External speaker connection jack.
• SW/BC, BC, E, MUTE: Antenna and ground connection terminals. SW/BC and BC for long-wire antennas, E for ground, MUTE for receiver muting.

Image Description: A detailed diagram of the front panel of the FRG-7700, with numbered labels pointing to each control and switch.

Image Description: A diagram of the rear panel of the FRG-7700, with numbered labels pointing to each connection and control.

Image Description: A table showing the SINPO code and its corresponding signal strength, interference, degrading effect of noise, propagation disturbance, and overall rating.

Image Description: A diagram illustrating antenna connections for shortwave and broadcast bands, including coaxial and long-wire antenna setups.

Image Description: A diagram showing ACC (Accessory) connections for the FRG-7700, detailing the pinout of a 5-pin DIN connector.

Installation

Proper installation is crucial for optimal performance and to prevent damage. Key steps include:

• Unpacking and Initial Inspection: Carefully unpack and inspect the unit for any physical damage. Check the freedom of action of knobs and switches.
• AC Voltage Selection: Ensure the rear panel voltage selector matches your local AC supply voltage. Use the correct fuse rating (1A for 100/120V, 0.5A for 220/240V).
• Backup Battery Installation: For memory-equipped units, install three AA penlight cells, observing correct polarity.
• Ground Connection: Connect the unit to a good earth ground using the 'E' terminal on the rear panel.
• Antenna Installation: For LF/MF reception (below 2 MHz), a long wire connected to the BC terminal is recommended. For shortwave (SW) reception (above 2 MHz), a resonant 50-ohm antenna, such as a dipole, fed with coaxial cable is ideal. Formulas for calculating dipole length are provided: Length (feet) ≈ 468 / frequency (MHz) and Length (meters) ≈ 142.5 / frequency (MHz).
• Remote Terminal Connections: Use the REMOTE terminals (N.O., N.C.) for controlling peripheral equipment like tape recorders via the timer function.
• Mute Connection: Connect the MUTE terminal to ground to silence the receiver when used with a transmitter.
• Physical Location: Ensure adequate ventilation around the cabinet. Avoid extremely hot environments (above 40°C) without provision for cooling.
• Interconnection with YR-901 Morse Code/Teletype Reader: The YR-901 option allows display of Morse Code and RTTY signals on a video monitor. Interconnection diagrams are provided.
• Memory Unit Installation: Follow specific instructions for connecting the optional Memory Unit to the receiver's bottom panel.
• Bottom Panel Feet: Extender feet can be installed to adjust the viewing angle.

Image Description: A diagram illustrating the AC voltage selector on the rear panel, showing how to adjust it with a screwdriver.

Image Description: Figure 1 shows the installation of three AA batteries for the memory backup feature.

Image Description: Figure 2 illustrates the process of removing a cover to access the memory unit installation area.

Image Description: Figure 3 shows the internal connections for the optional Memory Unit.

Image Description: Figure 4 shows the mounting of the Memory Unit using self-tapping screws.

Image Description: Figure 5 illustrates the installation of extender feet on the bottom panel of the receiver.

Image Description: A diagram showing the interconnection between the FRG-7700, YR-901, YVM-1, and SP-901 units.

Operation

Frequency Selection: Use the BAND switch to select the 1 MHz segment and the MAIN DIAL to tune the specific frequency. The digital display provides kHz resolution.

AM Broadcast Reception: Set MODE to AM M, tune for maximum S-meter reading. Use AM N for heavy interference and AM W for best fidelity in clear conditions. Adjust TONE for audio clarity and use ATT for strong signals. Press NB to reduce impulse noise. Adjust AGC (FAST/SLOW) for fading conditions.

Amateur Radio (HAM) Band Reception:

• SSB Voice Signals: Set MODE to LSB (below 10 MHz) or USB (above 10 MHz). Tune for clarity, adjust AF GAIN for volume. Use FAST AGC for rapid fading. Press NB for pulse noise. Use TONE and ATT to reduce adjacent frequency interference.
• Morse Code (CW) Reception: Set MODE to USB or LSB/CW. Tune for a comfortable listening pitch.
• Frequency Modulation (FM) Reception: Set MODE to FM. Tune for best fidelity. Use SQL to silence the receiver until a signal is present.

Memory Operation: Store frequencies by tuning to a station, selecting a memory channel (M CH), and pressing M. Recall stored frequencies by pressing MR and selecting the channel. Press MR again to return to main dial tuning. M FINE allows ±1 kHz fine-tuning of memorized frequencies.

Digital Clock Operation: Set the FUNCTION switch to CLOCK. Use HOUR and MINUTE buttons to set the time. Use HOUR SET to reset minutes/seconds to zero for precise alignment with a time standard. Ensure correct AM/PM indication.

Timer Operation: Four timer functions are available: ON Timer, OFF Timer, ON/OFF Timer, and SLEEP Timer. Program desired times using the FUNCTION switch (ON, OFF, SLEEP) and the HOUR/MINUTE buttons. Activate the timer by pressing the TIMER switch. Use TIMER CLEAR to cancel programmed times or turn off the receiver early.

Notes Regarding Propagation of Shortwave Signals: Shortwave signals rely on ionospheric reflection. Optimal frequencies vary with time of day, season, and solar activity. Daytime listening is generally best on higher frequencies (12-14 MHz and up), while nighttime listening favors lower frequencies (2-15 MHz). Sunrise/sunset periods often provide peak propagation. Understanding broadcast station schedules and aiming antennas for specific reception areas are key to successful long-distance listening.

Image Description: A diagram illustrating the concept of radio wave propagation, showing single and double hops, skip zones, and surface waves.

Image Description: A block diagram of the FRG-7700 receiver, showing the signal flow through various units including the PLL Unit, SW Unit, FM Unit, and Main Unit.

Maintenance and Alignment

The FRG-7700 is factory-aligned. Realignment should only be performed by experienced personnel using proper test equipment if a malfunction is confirmed to be due to misalignment.

• Main Unit Adjustments: Includes counter clock frequency adjustment, SSB carrier frequency adjustment (USB/LSB), first and second IF adjustments, S-meter sensitivity and full scale adjustment, NB adjustment, and trap adjustment. Specific test points and trimmer capacitor locations are indicated in diagrams.
• PLL Unit Adjustments: Includes PLL reference oscillator adjustment, PLL local alignment (adjusting transformers for maximum meter reading), and VCV (Voltage Controlled Voltage) line adjustment for various band switch positions.
• Memory Unit Adjustments: Includes M FINE adjustment and VCV line adjustment for memory operations.

Image Description: A top view of the Main Unit board with numbered components and test points indicated for alignment procedures.

Image Description: A bottom view of the Main Unit board with numbered components indicated for alignment procedures.

Image Description: A view of the Memory Unit board with labeled test points and adjustment points (T6001, TP6001, Q6021 PIN 9, T6002, T6003, T6008).

Parts List

A comprehensive parts list is provided, detailing components for the Main Unit, VFO Unit, FM Unit, Power Supply Unit, Switch Unit, and optional Memory Unit. This list includes part numbers, descriptions, and quantities for transistors, ICs, diodes, resistors, capacitors, inductors, transformers, switches, connectors, and modules.

GILFER ASSOCIATES, INC. Modifications

Gilfer Associates offered modifications to the FRG-7700 in April 1982 to improve selectivity. These modifications involved replacing manufacturer-installed filters with new ones providing narrower bandwidths at -6 dB and -60 dB points. Additional upgrades included adding precision ceramic resonators, increasing IF stage gain, and offering options for DC input provision and 12-channel memory installation.