Yaesu FT-7(B)

From Wikipedia, the free encyclopedia
Jump to: navigation, search


Yaesu FT-7 and FT-7B

Yaesu FT-7B

.

Yaesu FT-7 is a rugged, solid state and modular built HF amateurband radio transceiver, suitable for fixed and for mobile operation. The set was built by the Yaesu Corporation in Japan in the late 1970s and early 1980s. Its first Japanese release was in 1976. This transceiver was very small for its time; by current modern standards however it is a large mobile set. It is a low-power (QRP) SSB and CW transceiver of which transmitting power is adjustable up from 10 to about 20W. The set is built up with pre-dated synthesisers and microprocessors, has an excellent receiver and a perfect dynamic range with good close-in noise performance which makes tuning across the noisy 80 or 40m bands at night very easy. All features, coupled to a price of $260- (in 1976) made sure that the "Fox Tango 7" as it was known became very popular in the HAM world.

In 1979 its somewhat upgraded successor - the Yaesu FT-7B - was released and as of 1980 this rig was also sold on the European market. FT-7B has fully extended 10 m band coverage in four 500 kHz segments (this was limited to a single 500 kHz segment in the original FT-7 version). The FT-7B also offers Amplitude Modulation (AM) mode. Its transmitting output is adjustable from 5 to 50W maximum by an integrated 50W power amplifier using two 2SC2099 final transistors. It is also equipped with a noise blanker and an RF attenuator. It is a compliment to its manufacturers that even nowadays more than 30 years later FT-7(B)’s are still popular an are often used as a secondary or as a back-up transceiver.

In Europe the sets were imported by the Swiss firm Sommerkamp and sold as Sommerkamp FT-7(B).

Technical description[edit]

Solid state receive and transmit operating in single conversion configuration with premix heterodyne techniques reducing signal distortion in transmit and receive mode. The incoming signal goes via an antenna relay, tuning circuit, to a RF amplifier, passband tuning unit and mixer. The signal is filtered and fed to the audio amplifier and translated into a 3W audio signal. The outgoing signal is going from the microphone via the modulator / demodulator unit to a filter. Then it is amplified and heterodyned, mixed and fed to the final amplifier.

Accessories[edit]

  • VF-7 separate VFO (and only for FT-7);
  • YC-7B digital readout frequency counter (and only for FT-7B);
  • FL-110 linear amplifier 10W in – 90W out;
  • RSL/RSM mobile HF antenna combination consisting of the RSM chassis clamp and 5 antennas for the 80, 40, 20, 15 and 10m amateurbands.

Pro’s[edit]

Both sets are built like a tank! Under normal conditions its "prehistorical" integrated circuits are never subject to malfunction. Based on its other electronic parts and modular design the transceiver is easy to service and to repair. Locate the problem, unplug the circuitboard, fix the problem and put the ciruitboard back into its slot but don't forget to use a little contactspray to avoid bad contacts. That’s all and that’s why the rigs are still being used even today. In spite of its age its receiver sensitivity and selectivity are still very good. Its modulation is very nice. Sometimes they pop up on the 2nd hand market. If you are in a position to buy a standard unmodified rig do so; you won't be sorry!

Contra’s[edit]

The FT-7’s and 7B’s will drift and it takes appx. 30 minutes before its VFO settles down. After that the drift is minimal. There is no other way to check if the VFO settled down or not than by listening to the signals so you have to keep in mind to tune the signal regularly. The optional YC-7B counter is of little help as it initially drifts down at 100 Hz per second. When very strong signals are present, nearby, out of band or otherwise, the frontend can be overwhelmed and blocked. Activation of the attenuator solves the problem (FT-7 had no attenuator).

FT-7 Specs[edit]

  • Freq coverage: 3.5 -4.0, 7.0-7.5, 14.0 – 14.5, 21.0 – 21.5 and 28.5 – 29.0 MHz
  • Powersupply: 13.5V DC @ 3A transmit; 0.4A receive
  • Dimensions: 23x8x29 cm
  • Weight: 5 kg
  • Emission: LSB, USB, CW Power input: 30W DC
  • Carrier suppression: better than 50dB below rated output
  • Unwanted sideband suppression: better than 50dB @ 1000Hz
  • Spurious: better than – 40dB Distortion: better than -31dB
  • Transmitter freq response: 350 – 2700Hz (-6dB)
  • Stability: less than 300Hz drift from cold start, less than 100Hz drift after 30 mins warmup
  • Ant output impedance: 50 Ohms nominal SO-239
  • Microphone output impedance: 500 Ohms nominal
  • Receive sensitivity: 0.25 μV for S/N 10dB
  • Image rejection: better than 50dB
  • IF rejection: better than 50dB
  • Selectivity: -6 dB 2.4 kHz, -60dB 4.0 kHz
  • Audio output: 3W @ 10% THD, 4 Ohms

FT-7B Specs[edit]

  • Freq coverage: 3.5 - 4.0, 7.0 – 7.5, 14.0 -14.5, 21.0 -21.5, 28.0 – 30.0 MHz in 500 kHz segments.
  • Powersupply: max 13.6V @10A transmit; 0.6A receive
  • Dimensions: 23 x 8 x 32 cm with heatsink
  • Weight: 5.5 kg
  • Emission: AM, SSB, CW
  • Power input: 100W DC SSB/CW, 25W AM
  • Carrier suppression: better than 50dB below rated output
  • Unwanted sideband suppression: better than 50dB @ 1000Hz
  • Spurious: better than –40dB *Distortion: better than -31dB
  • Transmitter freq response: 350 – 2700Hz (-6dB)
  • Stability: less than 300Hz drift from cold start, less than 100Hz drift after 30 mins warmup
  • Ant output impedance: 50 Ohms nominal SO-239
  • Microphone output impedance: 500 Ohms nominal
  • Receive sensitivity: 0.25 μV for S/N 10dB
  • Image rejection: better than 60dB 80-15m, better than 50dB 10m
  • IF rejection: better than 50dB
  • Selectivity: 2.4 kHz (-6dB), 4.0 kHz (-60dB)
  • CW audio peak filter: 80Hz (-6dB) adjustable
  • Audio output: 3W @ 10% THD, 4 Ohms

External links[edit]