Yaesu FT-75 / FT-75B

The President of the United States is Richard M. Nixon and the Vice President is Spiro T. Agnew. Cigarette advertisements are banned from American television, the Ed Sullivan Show goes off the air, Apollo 15 astronauts become the first to ride in a lunar rover, and women gain the right to vote in Switzerland.

And the Honda Z600 sedan was invading our shores worldwide.

The Honda 600 was the first “mass market” car sold by Honda. The N600 sedan was introduced to the US market in 1969, and the sportier Z600 coupe followed in 1971. Powered by a two-cylinder motorcycle engine with 36 cubic inches and 36 horsepower — small cars, just over 10 feet long, weighing about 1300 pounds.

Oh yeah, we were talking about radio weren’t we? So let’s see if we can do a little mobile operation with the FT-75.

Photos from the original Japanese FT-75 owner’s manual. The FT-75 is shown going mobile, under the dash in the Honda Z600.

Introduced in 1971 as a compact amateur band transceiver that operated from 3.5 to 28 MHz in SSB and CW modes.

The FT-75 is a hybrid high frequency transceiver that sports a single 12DQ6B final amplifier tube driven by the popular 12BY7A driver tube as found in many Yaesu products during this time. Specifications for the FT-75 vary because it was originally introduced in Japan to meet JARL specifications — the single 12DQ6B final is rated at 20 watts.

Later the transceiver was reintroduced as the FT-75B sold elsewhere in the world. The FT-75B is rated at 30 watts P.E.P. input power low, or 100 watts input power if set up for high power by use of the matching FP-75 AC supply or the DC-75B mobile supply. To achieve the higher power over that of the original FT-75, the “B” model used two 12G-B7 final amplifier tubes.

The FT-75 transceiver is crystal controlled while at the same time it uses a VCXO front panel control. For those too young to know: a VCXO is a Variable Crystal Oscillator. The VCXO allows a frequency shift of several kHz above and below the crystal operating frequency — much like a fine tune or RIT control found on modern transceivers.

Another unique feature of the FT-75(B) mobile transceiver is that there are no final amplifier tuning controls accessible from the front panel while driving. Other than the VCXO, there is a bare minimum of controls for volume and squelch. The transceiver is hybrid — part solid state with tube-type final amplifier stage. Loading and plate tune controls are on the rear panel and, once set, should be left alone.

One advantage of the FT-75(B) is that it is pre-tuned and allows for quick QSY, has an effective noise blanker and squelch circuitry — ideal for simple and safe mobile operation as well as home station use.

Although primarily sold as a compact mobile transceiver, the FP-75 desktop power supply was sold as an option for base station operation. Users in the United States should be aware that the FP-75 power supply originally intended for use with the FT-75 was not intended for export — the supply is set up for 100 VAC / 60 CPS standard house current in Japan.

To overcome the 100 VAC transformer installed in the power supply from Japan, two transformers were wired together in a make-shift auto-transformer configuration. An old Yaesu FP-4 (12 VDC) export power supply transformer with 100/117/220 VAC primary taps proved useful — applying 117 VAC to the US primary winding yielded the other voltages on the primary side for step-up or step-down.

Much like a Variac, but using only the fixed primary windings, voltage can effectively be dropped to the required 100 VAC/60 cps as used in Japan. The secondary winding still exists but is not used in this configuration.

Auto-transformers are frequently used to convert local power line voltage to some other value needed for equipment — most often 117 V to 240 V, or 240 V to 117 V, or in this case to the required 100 VAC. Unlike an isolation transformer, auto-transformers use common windings. A 3 amp fuse was installed between the first and second transformer to protect the power supply.

If you attempt high-voltage repairs, take your time, solder your connections properly, and do it neat or don’t do it at all.

An FP-75B was recently sold on eBay with the mobile DC-75 multivibrator power supply.

FT-75 VXO Frequency Card — a credit-card-sized chart for listing channels and crystal frequencies. In the VXO box, enter the number shown on your VXO front panel. The VXO shifts crystal frequency a couple of kilohertz; the front panel markings have no absolute frequency significance.

FT-75 Final Amplifier — single 12DQ6B:

FT-75B Final Amplifier — dual 12G-B7:

The AN212 audio amplifier IC is installed in a metal TO-3 type transistor case. This was later replaced by the AN-214 flat-pack audio IC commonly seen in Yaesu products through the 1970s.

PB-1149 — IF frequency of 5173.9 kHz and the SSB crystal filter XF-51A. This particular IF center frequency and crystal filter were not used in any other Yaesu product. PB-1152A — microphone amplifier and 1st SSB oscillator circuitry.

Construction of the Yaesu FT-2 Auto VHF transceiver looks remarkably similar to the FT-75 of the same timeframe.

• FT-75B owner’s manual (PDF)
• Yaesu Musen Journal FT-75 review (Japanese, December 1971)

The word MUSEN is the Japanese word for wireless — Yaesu Wireless Company. The Journal date uses the Showa-era calendar: number 46 indicates the 46th year of Emperor Hirohito’s reign (Showa 46 = 1971).

The date shows 47. 3. 15 — believed to be the date of manufacture: the 47th year of Showa (1972), third month (March), 15th day.

There’s a good reason the warranty was valid only in Japan when you consider the FP-75 with its 100 VAC transformer as noted above.