Tucker Tin Ssb Transmitter

Fig. 3- W3TLN SSB transceiver.
Fig- 4, The Little Feller,

signal is sampled and used for automatic gain control, to prevent limiting in the linear amps.

The W2EWL phasing exciter

This exciter is a filter type, and has been highly popular with those likiog filter exciters. One of equal popularity among the phasing set was W2EW L\s "Cheap and Easy SSB/' originally described in QST for March, 1956, The block diagram of this unit appears in Fig. 2; the schematic is in the ARRL publication mentioned earlier.

Like the W61 luV rig, this uses a conventional audio pre-amp without about the same characteristics; it feeds a cathode follower for impedance matching, and the audio then goes through a low-pass filter to remove everything above about 3 kc before reaching a commercial phase-shift network.

Output pi the phase-shift network feeds a pair of triode amplifiers, which in turn drive (through transformers) a four-diode balanced modulator,

The rf input to the balanced modulator originates in a 9 mc crystal oscillator, passes through an if phase-shift network, and then meets the audio in the balanced modulators. A tank circuit in the balanced-modulator output does the phase addition and cancellation which gets rid of one sideband, and a voltage amplifier brings the wanted sideband up a bit in level before it reaches the mixer.

The mixer's other input is from a YFO operating near 5 mc, and mixer output goes to a pair of 1625s (or 807's) which feed the antenna directly.

The SSB transceiver

\ be great similarity between a SSB transmitter and a SSB receiver has prompted several designers to combine the two into a single system; quite a number of SSB transceivers are now on the market. One of the original designs was that by W3TLN. described in June, 1959, in QST, Fi^. 3 shows the block diagram of this unit.

Audio in the W3TLN unit comes from a carbon mike, eliminating the pre-amp used in the other two systems examined. It goes directly to a bride-type balanced modulator, which gets its rf from an 8553 kc crystal oscillator. Output of the modulator goes to a filter which passes 8550-8552*7 kc, and the sideband which gets through the filter is then amplified by two class A voltage amplifiers.

In the transmit position, output of these amplifiers goes to the transmitting mixer, which receives its other input from a variable crvstal oscillator which can tune some 50 kc on 15 meters. Mixer output feeds a 12BY7 driver, which in turn pushes a pair of 1625Ts which are hooked to the antenna.

In the receive position, incoming signals go through a caseode rf amplifier into the receiving mixer, which also is fed by the YXO; output of this mixer goes to the filter input, and the output of the amplifiers following the filter is switched to a product detector which gets its BFO signal from the 8553 kc crystal oscillator.

Switching from transmit to receive is done primarily b\ supplying or removing plate voltage from the various tubes; only two signal-carrying leads are switched, one at the antenna and (he other at the // amplifier output.

The Little Feller

One of the simplest of all single-sideband transmitting systems is Lester Earnshaw's i j *

"Tucker Tin Two" apparently first described in I he Sidebander'1 and later picked up and modified by a number of other people. One1 of the most interesting versions of this system was "The Little Feller/' first put together by W50RH and reduced to duplicatable form by W5BCS, and described by them jointly in the November, 1962, VHP Horizons.

Fig* 4 shows the block diagram of "The Little Feller/' and you'll notice that it uses only four tubes (outside of the power supply) to give SSB output in the 50 mc band*

Audio passes through a 12ATT preamplifier, although a carbon mike is used (purpose ol the carbon mike is to reduce highs without resorting to an audio filter). It passes through a homebrew phasing network consisting of two capacitors and one resistor, then goes to a pair of two-diode balanced modulators.


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