The 75A-4 Receiver and the KWS-1 Transmitter

A genuine piece of history and for me a real time machine.

Operation Position #2

SSB/CW Receiver
KWS-1 Kilowatt SSB/CW Transmitter

Click on the photo for the complete story of the 75A-4 used at W4THU.

The Gold Dust Twins

I can remember my high school days very well. They were exciting times. It was 1959 and I had a brand-new ham license. My first rig was a Knight T-50 and a BC-348. It was all I could afford as a teenager. Ads in the magazines and photos of "shacks" featured the incredible Collins "Gold Dust Twins." It is said that they were called that because they were so expensive. Together the 75A-4 and the KWS-1 sold for around $2500. That was really big bucks in those days, so there weren't many of these rigs made. If I recall correctly, there were only about 1600 KWS-1 transmitters and around 6000 75A-4's. No one really knows how many are left.

As all teenagers do, I had my dreams. Besides all the usual images of girls and cars, I dreamed of owning a 75A-4. I knew I'd never be able to afford a KWS-1. In 1995, the dream finally came true and with the help of Floyd Soo, W8RO, I made a deal for my own Gold Dust Twins. Arrangements were made and I was off on a 56 hour round trip to northwest Arkansas to pick up my boyhood dream. Was it worth all the money and effort? Absolutely! For me, the Twins are more than just a boyhood dream, they are a "time machine." Simply sitting in front of the glow of the rig'sdials and lighted speaker, listening to the golden tones of quality SSB or CW emanating from the 312A-1 speaker and adjusting that silky feeling tuning knob does no less than transport me back in time when ham radio was still magic and I was young. These were dreams. This is real.

The 75A-4

The 75A-4 is a very special radio receiver. There was nothing like it when it was produced in 1955. It broke the molds and set all the standards of performance and it, in combination with the KWS-1 made SSB a practical, reliable reality. Up to this point in SSB's infancy, most receivers where modified AM receivers and few were up to the task. Missing from the formula in the early 1950's receivers were the necessary stability, good product detectors, AVC (now AGC) systems, clean oscillators and excellent, yet simple, filters and accurate BFO's to select the proper sideband. Collins radio brought it all together in one magnificent receiver, the 75A-4. They did it so well that it's a receiver that's still perfectly capable of handling the tough QRM conditions we find on today's ham bands. Click on the photo for more of the 75A-4 story.


As far as I can tell, except for the 4:1 tuning knob, this KWS-1 is bone stock, unmodified and unrestored. It has a moderately low serial number and uses 4X150's in the final amplifier. There doesn't seem to be any reason to change the finals to the 4CX250's used in later units since I get a full 600 watts output and nothing seems to be protesting.

I have to say that the KWS-1 is fun to operate. Most of the time, I think of a transmitter as just that, a transmitter. If it works OK and produces quality modulation, that's it. However, the KWS-1 is totally unique. No linear amp is required. Instead of just 100 watts output, this rig goes all the way from microphone to 1 KW input, or about 600 watts of RF out to the antenna. It is truly a radio with personality. It produces a big, loud, great sounding signals. The entire transmitter is all in one, tabletop, cabinet. The power supply sits next to the operating desk. Incidently, the power supply pedestal weighs in at around 120 pounds.

As you can see, there are no modern accessories at this operating position. I wanted to keep the appearance of this station as close to the original advertising photographs as possible. That doesn't mean that I've abandoned operating aids like the monitor scope. What I have done is to run the KWS-1's transmission line through the coax switches in the main operating position. That way, I can use the transmatch, monitor scope, computing watt meter and have a choice of all available antennas. The two desks for operating positions #1 (the modern gear) and #2 (the Twins) form an "L" and the monitor scope is placed as close to the "Twins" as possible for easy viewing from both the "Twins" operating position and from the modern station at operating position #1. I do the same thing with the S-Line and it's adjacent operating position.

The microphone is the old standard, a D-104. A new cartridge has been installed, so the D-104 performs like new, even though it is nearly as old as the KWS-1. After a couple of tests on the air, the general opinion was that the D-105 sounded better than the 10DA or the Turner mic which is now on another rig.

Collins stuff
Here are a couple of interesting collectables sitting on the top of the KWS-1 power supply.
312A-1 Lighted Speaker and 302C-1 wattmeter.

If you'd like to join in the fun, or just hear these rigs on the air, drop by the Collins nets on Tuesday evenings at 9 PM eastern time on 3805 KHz and on Thurday evenings on 3875 KHz, again at 9 PM eastern time. On most nights one or more Gold Dust Twins will be one the net. While you're there, check in and say hello. Everyone is welcome. You don't have to be running Collins gear, just tell them you dropped by to hear the Gold Dust Twins, a genuine piece of history.

There is also a west coast net which meets on 3895 KHz at 8 p.m. PST on Friday nights. You may be able to catch someone running the Gold Dust Twins on that net. The largest Collins Collector's association net is held each Sunday at 2000 Z on 14263 KHz. You'll hear mostly S-Lines and KWM-2's on this net, but the "Twins" show up occasionally.

Hamshack Index


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