Note
Ham Radio, Sep 1977, p. 104. (with reference t0o a Mark 4 version)
QST, Oct 1977, p. 123.
QST, Apr 1979, p. 145. (MMC-432/28S)
Three units of primary interest to amateurs are the MMT 144/128, MMT 432/128, and the MMT 432/ 28 Mark 4. The first number in the designation indicates the frequency of the band of operation, in this case either 144 MHz or 432 MHz. The second number indicates the frequency of the input (or output) signal required for mixing (or as an IF output). Thus the 432/128 will allow operation in the amateur 432-434 MHz range, with an input of 28 MHz for transmitting and an IF output of 28 MHz for receiving.
The MMT 432/28 Mark 4 is broadbanded to cover a 4 MHz range. This feature was incorporated to allow operation of both weak-signal (432 MHz) and Oscar 8 (436 MHz).
Two additional units, the MMT 432/50 and the MMT 438/ATV, were also available.
Power output from the transverters is nominally 10 watts PEP. Input, and output impedance is 50 ohms, with BNC fittings on the enclosure for connection. There is a separate connector for the 28 MHz IF output to the receiver, marked 28 MHz OUTPUT. A connector is provided for a separate 144-MHz (or 432-MHz, as the case may be) input, but the connector is not wired up. Instructions are given to enable the user to connect this input jack if desired.
Normally, the 432 or 144 MHz input jack serves as both transmitting and receiving connections. Separating the two functions would be useful if you wanted to drive a linear amplifier while transmitting. PIN diodes perform the internal switching function.
DC power required for the transverters is in the range of 12 to 14 volts for both units. Quiescent current for the 144-MHz model is 300 mA; for the 432 unit it is 180 mA. Current drain rises to approximately 2 amperes on peaks for both units.
Drive power required for full output on both models is 500 milliwatts, but there is an internal attenuator that may be jumpered out of the circuit to allow the use of an input as low as 5 milliwatts of drive.
Other features worth noting are a receive converter noise figure of approximately 2.5 dB (144 MHz) and 3 dB (432 MHz); a cast-aluminum enclosure for good shielding and mechanical stability; and a crystal oscillator that starts high enough to avoid the need for a large number of multipliers and their spurious products–101 MHz for the 432 unit and
116 MHz for the 144 transverter.
MMT 144/28, $199.95
MMT 432/28 , $229.95
MMT 432/28 Mark 4, $249.95