Description

1.1 GENERAL. THE MULTI-ELMAC AF-67 Trans-Citer is a ten-tube variable frequency or crystal controlled seven band transmitter or exciter. All circuits are simultaneously switched to the desired band by a single bandswitch lever.Designed as a complete transmitter for mobile or fixed installations, or an exciter to drive a higher power transmitter. When used as an exciter the 500 ohm tap on modulation transformer can be used to drive the higher power modulators.

1.2 DIMENSIONS. The maximum external dimensions of the AF-67 Trans-citer, excluding projections of control knobs, is 11 1/4 inches wide, 7 inches high, and 8 1/2 inches deep behind panel. Approximate weight is 18 pounds.

1.3 CIRCUIT DESCRIPTION. The AF-67 Trans-citer employs a variable frequency oscillator with output on wither 1.75 to 2.0 Mc. or 3.5 to 4.0 Mc. In addition to the V.F.O. feature, two crystal positions are included for operation on two spot frequencies. Any crystal that will work straight through, double of quadruple to the desired frequency may be used. The oscillator circuit employs a voltage regulator tube to maintain the plate voltage at a constant level.

The multiplier stages are broad tuned with a front panel control for peaking the final grid, insuring best performance on all bands. The audio circuit is designed to use either a carbon microphone or a low output microphone such as a crystal or dynamic. A slide switch on the rear apron on the AF-67 Trans-citer sets up the circuit for use with either type of microphone. A reactance tube modulator is incorporated in the variable frequency oscillator circuit for narrow-band-frequency-modulation. The variable frequency oscillator dial scale is directly calibrated in megacycles for each of the amateur bands.

1.4 TUBE COMPLIMENT. The AF-67 Trans-citer is supplied complete with all tubes, tested in the individual unit, as follows: 

1.5 OUTPUT. The AF-67 Trans-citer is designed for use with a resonant antenna coupled to its output with a transmission line of 50 to 300 ohms impedance. Other impedance or balanced lines can be coupled through the use of an antenna tuning device. When used as an exciter the coupling link of the high powered final can be directly connected to the AF-67 with a suitable length of coaxial cable. The MULTI-ELMAC AF-67 is designed for a maximum plate power input of 60 (sixty) watts. Maximum ratings for this Trans-citer are 600 volts at 100 milliamperes; or 500 volts at 120 milliamperes. Full 100% modulation occurs when the modulator plate current swings to about 60% of the final plate current with normal voice frequencies.

1.6 AUDIO. The modulation transformer is provided with a 500 ohm output tap brought to the power plug for driving the grids of high powered modulators. The 5881's will deliver approximately 40 watts of audio with a plate supply of 500 volts.

1.7 POWER SUPPLY. The AF-67 Trans-citer was intentionally designed to use an external power supply in order to permit (a) use of PMR-6A receiver power supply to supply the low level stages, (b) use of the AF-67 Trans-citer with an AC operated power supply at a fixed or portable location, (c) use of a dynamotor or vibrator supply in mobile installations, or (d) use of the Trans-citer as a driver-exciter for high powered transmitters. A suitable MULTI-ELMAC power supply MODEL PS-2V for portable or fixed station operation from 115 volt AC lines is available.

1.8 POWER CONNECTOR. A 15 prong female connector is provided with each unit. The 15 prong connector allows all circuits to be arranged for maximum flexibility. Making it possible to use the AF-67 Trans-citer in various types of installations.
1.9 ACCESSORIES. The following accessories are available for use with the AF-67 Trans-citer:

PS-2V --- A universal 115 volt AC power supply. (Supplies 6 or 12 volts AC for filaments and two separate high voltages.)
CFS-1 --- Cable with a 15 prong female connector and fanning strip to connect the AF-67 to the PS-2V power supply.

Multi-Elmac AF-67 White Paper

AF-67 Mods & Maintenance by John Conley, W7ZFB