I'm nuts for minimalist solutions...as the wise old engineers would say "It's easy to make a circuit work if there's no limit on parts or cost". Early television mogul Earl "Mad Man" Muntz fumed about "overengineering" and gained notoriety by snipping out components until the picture or sound stopped working, then told his engineer "Well I guess you have to put that part back In". But to my way of thinking, minimalist designs aren't just corner-cutting, and often take advantage of unique capabilities of components or circuits to accomplish a task in an an elegant way. That's why I was instantly intrigued by a thread on Radioboard about using an LM386 audio amplifier IC as a regenerative AM broadcast band radio. Here's a link to that site and I suggest reading it to the end as multiple improved circuits and tradeoffs are discussed: http://theradioboard.com/rb/viewtopic.php?f=4&t=6413&sid=07d79a1d8c3cb46ad619ac2ba35b7502 The LM386 was invented by Ernie Leroy Long at Motorola in 1969. It was originally for part of a fuel injection system for a Ford vehicle and integrates 8 transistors in an 8 pin DIP package that runs from 9 to 12 volts DC. It has become ubiqitous for low-cost audio amplification in millions of devices from toys to QRP rigs. Occasionally I've seen deviations from the reference design in the databooks but credit goes to user "Selenium" at Radioboard for being the first to figure out how to introduce regeneration and apply it as a complete AM radio receiver, not just the audio section of one. Interestingly this wasn't the first application of an audio IC as a regenerative detector - the discussion above included a datasheet for the 1956 vintage Westinghouse WC183 hearing aid amplifier that shows one. It seems like this idea has been a long time coming! I think this simple circuit can be the basis of a number of interesting projects - it sure doesn't take much to make one and try it out. With a high-Q coils many signals should be audible with a minimal antenna (or none) in urban areas. Current consumption is low enough that battery operation is feasible and loudspeaker volume always beats having to wear a pair of ear-squeezers! The recenerative circuit was invented by Major Edwin Armstong in 1912 while still an undergraduate at Columbia University and patented in 1914. While he later went on to develop the superheterodyne receiver and FM, in my view the elegant simplicity of regeneration is his crowning acheivement. Here is the schematic I used - see the link above for other variations and feel free to experiment: |
Crystal Replacement
Posted: 08/226/2024
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Making SMT "no lead" parts easier to use
SMT is the future - but how can we actually use parts without leads? ... READ MORE |
Crystal Replacement
Posted: 02/38/2024
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How good can a crummy receiver be?
Hundreds of different simple SDR receivers have been designed around Dan Tayloe's Quadrature Sampling Detector or QSD. Mine add nothing to the state of the art, and in fact subtract things, as I like minimalist solutions and the QSD is right in that sweet spot. Following the evolution of Tayloe's design I delete the resistors in series with the sample lines for inst... READ MORE |
Technical
Posted: 02/37/2024
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What's in a number (3253)?
The FST3253 dual four-to-one mux/demux IC has long been used as a "Tayloe Detector" or QSD (and QSE) in low-cost SDRs. They provide incredible performance for such a simple circuit, converting RF to baseband IQ with low loss and the ultimate in simplicity. Unfortunately the original FST3253 part has become obsolete and while substitutes are available, this is where the... READ MORE |
Vintage Ham Radio
Posted: 02/32/2024
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The Stancor 10P Transmitter
There weren't really many commercial transmitters in the 1930s as most hams built their own. But many of the ones that were offered came from the transformer companies who had two chances to profit. First, from those who would buy the kit, and two, from those would would see it in the (free) booklets the companies provided to their distributors who would then sell the iron to ham... READ MORE |
Vintage Ham Radio
Posted: 12/355/2023
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The Care and Feeding of the EF Johnson Courier amplifier
The EF Johnson "Courier" is a grid-driven amplifier using two 811A tubes. Switching is provided for operating in either class C for CW or as a class B linear amplifier for AM or SSB. Rated power is 500 watts input for CW, 500 watts PEP input for SSB, and 200 watts input for double-sideband AM with carrier. Since all amateur power levels were meas... READ MORE |
Historic
Posted: 11/329/2023
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TV Duplexer
Some things are interesting, even if totally useless nowadays. Such is the case with the Philco 426-3034 Crossover Kit for UHF TV. What the heck is that? Well, back in the late 50s, UHF television stations operating on channels 14-83 started to appear in many areas of the US where viewers had a VHF-only TV antenna, and in many cases an externa UHF converter was... READ MORE |
Crystal Replacement
Posted: 11/327/2023
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Replacing failed crystals
For decades, quartz crystals were used everywhere a stable frequency source was needed, even in some applications that depended on overtone (harmonic) behavior into the VHF range. These crystals were less stable and more dependent on circuit parameters that fundamental types and thus more problematic. Such was the case with the 94 MHz crystal in the 2 meter converter ... READ MORE |
Historic
Posted: 11/315/2023
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My Own Ham Radio Story by W9RAN
Everyone has a story of how they got involved in ham radio - this is mine. It started much earlier, including receiving a Knight Kit Span Master shortwave radio for Christmas in about 1963, at age 12. I'll never forget the night my dad and I finished building it and I wanted to try it out. It came with a 50 ft. antenna which was still coiled up - but ... READ MORE |
Technical
Posted: 09/267/2023
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Hot to simulate vacuum tubes in LTSpice
LTSice is a powerful simulation tool that is provided free by Linear Technology Corp. It comes with a complete library of passive and common analog solid-state components but if you want to use it to simulate vacuum tubes, it doesen't work as-is. Even though triode and pentode symbols can be found in the "Misc" folder, they are just schematic symbols and... READ MORE |
Friends Remembered
Posted: 07/208/2023
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Merv Schweigert, K9FD (SK)
Comments from Robert Nickels W9RAN, July 27, 2023: There is nothing worse for a ham radio operator than to see a beloved friends callsign with the letters "SK" behind them. Yet sadly, that's what happened on July 23, 2023, when I learned of the passsing of Merv Schweigert, K9FD. While many of our ham radio interests were different - Me... READ MORE |
Paul Stoffregen is the creator of the Teensy microcomputer and related products and has authored a vast amount of exceptionally good and useful public domain software to go with it. As the old saying goes "no good deed goes unpunished" and in the course of answering customer and would-be customer questions, Paul has written over 18,000 replies. From that he's ... READ MORE
- Robert Nickels (ranickels), 12/10/2018
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The VERSA-TR kit designed by RAN Technology Inc. is available from our friends at Hayseed Hamfest. Please direct all order-related questions to them at https://hayseedhamfest.com/pages/contact-us... READ MORE
- Robert Nickels (ranickels), 11/11/2018
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