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A Clean Vintage Ham Radio Transmitter: The Collins 32S-3
24 September 2024 at 10:54
In an article on IMD and splatter, tech guru Rob Sherwood noted that the cleanest tranmitter he had ever owened was the Colling 32S-3. Here is the article. https://soldersmoke.blogspot.com/2024/09/sherwood-its-time-to-clean-up-our.html
In it, you will see thar Rob has the spectrum anayser two tone test to prove his point.
This got me wondering: Why was the Collins transmitter so clean. Today I looked at some ot the tech info on this rig. I think I have found the answer. The Collins Collectors Association has a great page on the 32S-3: https://collinsradio.org/cca-collins-historical-archives/the-equipment-of-collins-radio/the-grey-boxes/32s-3/
The key lines are these:
Click on the paragraphs or go to the link for a clearer view
I think the explanation of Collins'32S-3 cleanliness is due to 1) Thermatrons in the final stages and 2) Negative feedback to take down any IMD products that might appear due to non-linearities in the finals.
There is nothing magical in that technique. Heck, we could homebrew that today. We could build HDR stations (perhaps transistor-tube hybrids) that would be cleaner than their commercial SDR cousins.
