FRG - 7700

Manufactured by Yaesu Musen Company Ltd., Tokyo.

In 1977 Yaesu adopted the technical principle of the Wadley loop circuit from their first general coverage receiver FRG-7 and equipped the set with a frequency counter with red LED display and a digital clock. This receiver FRG-7000 was replaced in 1981 by the FRG-7700, which was a next-generation digital technology tabletop receiver equipped with a PLL synthesiser circuit and could be fitted with an optional extension for 12 frequency memories.

Yaesu FRG-7700

Technical data

Power supply


  • 334 x 129 x 225 mm, weight 6.5 kg



The FRG - 7700 with its anthracite-coloured metal cabinet measures 33.4 x 12.9 x 22.5 cm, has a weight of 6.5 kg and is thus the same size as its predecessors. It is designed for mains operation, the mains voltage can be switched from 100 - 240 volts. The receiver can be easily tilted with screwable feet.

The loudspeaker is mounted behind a square cover on the left side of the front panel and performs well, below it is the mains switch and the sockets for headphones and tape output. To the right is the mode switch, which can be used to switch between LSB/USB with the narrow IF filter, AM with three filter bandwidths and narrowband FM, which used in the shortwave range mainly by CB radio operators. Slightly above, two small push-buttons select the AGC characteristic, the decay speed of the automatic gain control, and activate the noise limiter, which is of little effect. To the left below the main tuning knob is the volume control / tone control, which is designed as a double potentiometer, to the right the fine tuning, which is only active in memory mode, the squelch control, which is effective in FM, and above it the ATT control.

In case of overloading, the input signal can be attenuated continuously as with the classic RF gain control; an additional attenuator can be switched at the rear of the set. At the bottom right, the second largest knob is the band switch, with which the thirty 1 MHz ranges can be selected. Above it is the selector to access 12 stored frequencies, if the memory option is installed. Four small touch keys are used to store and recall frequencies and dim the display. The rotary switch above is used to switch the clock display, timer on/off time and set the display to frequency display, the small buttons next to it are needed for the clock and timer functions.

The main tuning knob is very easy to grip and has a finger recess. The FRG-7700 was one of the last tabletop receivers to have a fully usable analog circular scale, on which reception frequencies can also be read with an accuracy of 5 kHz. BUt that is much easier reading the yellow LED digits of the frequency display, which is located directly above. The S-meter, which is a relatively large analog instrument, displays quite generously, but its calibration with S-units meets the requirements for sets in the amateur radio sector.

The rear panel has a 50 Ohm coax and high impedance terminals to connect long wire antennas, there is no integrated telescopic antenna. Next to the antenna terminals there is an additional attenuator switch. Two sockets are used to communicate the switching status of the digital timer, but only low voltages devices can be connected. With the help of a simple circuit using a relay, the mains voltage of a tape recorder can be controlled. Behind the screwed cover, the optional electronic frequency memory for the 12 frequency memories can be installed. Three UM-3 back-up batteries for retaining the memory contents even when the mains voltage is switched off, they are located behind a cover on the bottom side of the set.

In practical use, the FRG-7700 is straightforward and certainly easier to operate than its predecessors. After switching on, the desired 1 MHz band is set with the band switch, the remaining three kHz digits are tuned with the main tuning knob. For normal AM reception, the medium-wide IF filter is usually fine; with interfering adjacent channel stations, the result can be improved with the narrow IF filter; the wide AM filter can only be used in exceptional cases with very undisturbed stations and then gives excellent sound. With very strong signals, e.g. from long-wire antennas, which quickly cause the S-meter to deflect to the limit, the attenuator must be activated; unfortunately, no optical warning indicates that it is active.

With the memory unit, twelve frequencies can be stored with the selector switch in the desired position by pressing the M key. Pressing MR recalls the frequency, a corresponding small light signals the memory operation, the frequency can now only be adjusted slightly +/- 1 - 1.5 kHz with the fine tuning, the main tuning is now no longer active. In memory mode, the received frequency deviates slightly from the frequency set in the display when the fine tuning is detuned. Since fine tuning of SSB stations with the main tuning knob can be problematic, especially when using a radioteletype converter, it is recommended to store the frequency in memory and work with fine tuning.

The FRG-7700, with its superior sensitivity and, once allowed to warm up for an hour, good stability, can still easily satisfy the needs of a programme listener who wants to hear the external services of European and international broadcasters. It is also sufficient for DXing in the tropical bands or for listening to amateur radio and utility stations. The filters are not very steep; higher-quality filters, as commonly found in commercial grade shortwave receivers, could be installed thanks to the common intermediate frequency of 455 kHz.

When you read the manual, you easily recognize the origin of the receiver from a amateur radio company, the signal path and the installation of optional components are described and an alignment instructions and component list as well as the complete circuit diagram are included. One is not at all used to this in consumer grade sets made by Sony or Grundig. The FRG-7700 or its successor, the FRG-8800, are a good choice to enter DXing.

Numerous accessories were available for the FRG-7700, which can also enrich a shack when used standalone. The FRA-7700 active antenna with an integrated telescopic antenna was supplied with its necessary operating voltage from the receiver. It is tunable and the gain is adjustable, so no wideband signal is fed to the input stage, which could lead to overload receivers with a poor front end. A very popular accessory is the passive antenna tuner FRT-7700, which tunes long-wire antennas from two switchable connectors. Thanks to the preselector effect, not the entire short-wave spectrum but only the tuned signal reaches the input stage. A VHF converter allowed reception of the VHF amateur radio bands and came in the same format. For RTTY reception, the Yaesu YR-901 decoder could be used.

Technical principle

The HF signal passes from the antenna socket via the attenuator stage, a low-pass filter that eliminates high frequency interference, and octave band-pass filters switched by diodes to an amplifier stage equipped with low-noise dual-gate MOS FETs and to the first mixer, where an oscillator frequency generated by a PLL synthesiser is fed in and the signal is converted to the high first intermediate frequency of 48.055 MHz. After conversion to the second IF of 455 kHz, the signal reaches the IF filter bank via a ceramic 20 kHz bandpass filter and the noise limiter built with diodes. After diode demodulation of AM signals or the product detector for single sideband reception, the AF signal is amplified and fed to the loudspeaker.


The set is equipped with solid state components.

Technical documentation


Further information

en/frg-7700.txt · Zuletzt geändert: 2022/12/25 18:16 von mb