4A
This Transmitter was introduced to the amateur radio community in the October 1933 issue of QST.
Crystal Controlled, CW transmitter with built-in power supply for the 160 & 80 meter (28 watts), 40 meter (25 watts), and 20 meter (13.2 watts) amateur radio bands.
In early models the crystal and associated band-changing coils were plugged from the top of the unit.
The production units were a bit different than the artifact shown in the first image.
As production continued, the Power Amplifier Neutralization control was moved to the front panel as well as the crystal module. In addition, the front panel material changed from aluminum to Bakelite.
Construction
The 4A was sold as a kit, all parts included. However, you were responsible to purchase the tubes separately. Like many home-assembled projects of the day - this unit had no top cover, sides or back. To protect yourself from live wires it was best to mount it into a rack.
As Advertised
Ad Copy: "The 4A transmitter marks the entry of the COLLINS line in the extremely low-priced field. The 4A uses a 47 crystal oscillator and parallel 46's in the power amplifier permitting an output of 18 to 20 watts on 1.7, 3.5 or 7 mc. The power amplifier is operated on the crystal frequency in each case. Despite its low cost, the 4A embodies the mechanical and electrical refinements found in the larger COLLINS transmitters. A separate power supply is used for the oscillator to reduce frequency "chirp." Standard COLLINS plug-in coils are employed. A single Weston meter is provided with a switching arrangement to read plate and grid currents. The 4A is ideal for an amateur who wants to start out with a minimum investment and yet have a transmitter which will deliver a high quality C. W. signal. The 4A can also serve as a stand-by transmitter in a high-powered station to be used when full power is not required.
Really surprising results can be obtained and amateurs who are accustomed to think in terms of kilowatts can get a great deal of service and amusement from one of these little transmitters."
Additional text from the 4A Brochure:
The above announcement was first made regarding the 4A transmitter in the April-August issue of the COLLINS SIGNAL and only a moderate amount of importance was attached to it at that time. However, during the intervening months this model has proved to be one of our most important products. It has met a very insistent demand for a low-cost, all band CW transmitter which was not burdened by the extra cost and complication of a lot of meters and tuning controls, but, at the same time, was capable of giving consistent performance.
We have been very much gratified by the letters we have received from the many amateurs who have purchased this transmitter. Transcontinental schedules are maintained regularly with the 4A's and several users have reported working Mexico City, Hawaii and New Zealand within the first week or so of operation.
Some slight refinements have been made in the circuit of the 4A so that the measured output is now 28 watts on 3,500 and 1,700 kcs., 25 watts on 7,000 kcs., and 13.2 watts on 14,000 kcs. Of course, the outfit is crystal controlled with a D. C. note.
We have a few inquiries as to why we, do not incorporate the new "universal exciter" in some of our transmitters. The universal exciter is a very clever arrangement, but no advantage is found over our existing 4A and 1OB circuits. It should be remembered that the output of the universal exciter is scarcely high enough for serious transmission work, unless it is followed by another amplifier, whereas the 4A Transmitter puts out a relatively powerful signal and. it also contains dual power supplies, so that no additional equipment has to be purchased.
We strongly recommend the 4A Transmitter for the consideration of every amateur who wants the most efficient telegraph transmitter obtainable at a very moderate investment.
