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The Regenerodyne Receiver is one of the variety of superheterodyne receiver types incorporating a regenerative final detector which both determines the receiver's overall selectivity (Q), and it's own product detection, in cases where the final detector is called upon to operate in autodyne mode. It is well suited for AM reception, and serves well as a cw receiver.

It would be helpful at this point to review the different common types of regenerative superhet receivers.

Regenerative Superhet Background

For discussion purposes, a regenerative superhet is a superheterodyne receiver which uses a regenerative/ autodyne final detector. We are not considering conventional superhets with regenerative RF or IF/ Q-multiplying circuits.

Probably the most well known and oldest of the regenerative superhet receiver types is the "Super Gainer", developed in the late 1930s by Frank Jones. This receiver utilizes a relatively conventional converter and a fixed, often very low frequency regenerative detector. The local oscillator in the front end of the Super Gainer provides receiver tuning as most single conversion superhets. The fixed regenerative detector, often tuning as low as 50 - 100 kHz, provided enough selectivity so as to compete with more complex HF receivers of the day. The chief drawback to the Super Gainer apart from the well known signal handling dynamics common to all regenerative detectors, is image rejection owing to a typically very low frequency IF and typically simple front end tuning circuitry. These receivers were however, in their day, well known for their sensitivity and selectivity which could rival most moderately priced commercial receivers made at the time (1935 - 1940, approx.)

Another variety of the regenerative superhet is what has been called the Band Imaging Superhet. These were common handbook "Simple Super"s, again, popular for economy and simple design. These receivers typically utilized a 1700 kHz IF which could tune both 80 and 40 meters when using a 5 mHz local oscillator. Either the 40 and 80 meter Amateur Bands could be "imaged", each being 1700 kHz from the local oscillator signal. Again, a fixed tuned regenerative detector (1700 kHz) was employed for reasons similar to the Super Gainer. Images in these receivers were better than the low frequency IF Super Gainers owing to the higher IF frequency. The detector is typically less selective than the Super Gainer due to the higher operating frequency, although still quite selective compared to inexpensive shortwave sets manufactured in the 1950s, the era in which these band imaging regenerative superhets were most commonly known. They served quite nicely as beginner and novice receivers, although they still exhibited typical regenerative detector signal handling characteristics (locking/ blocking in the presence of a strong signal.) These band-imaging regenerative superhets largely vanished by the late 1950s. A few solid state project receiver versions may have been published well into the 1960s.

The Regenerodyne

The Regenerodyne was first developed and named by Gary Johanson, WD4NKA, as a result of experiments in making a simple, portable, and smaller sized receiver utilizing vintage parts (primarily, tubes). The idea was to build a receiver from parts available up to WW2. The design goal was physical and electrical stability, sensitivity with a very small antenna, spartan simplicity, excellent dependability, and independence from manufactured parts. In this instance, the only IF transformer is hand wound.

The Regenerodyne concept is not unlike the design architecture surrounding many solid state Direct Conversion receiver projects of the 1970s which involved a detector that tuned a low frequency band such as 80 or 160 meters, utilizing xtal converters to provide higher band coverage. The lowest frequency stage provides the tuning for the whole receiver. It was noticed by WD4NKA that this approach seemed not to be applied, historically, to the regenerative receiver. The different types of regenerative superhets followed the common architecture using the converter as the stage that tunes the receiver, feeding a fixed detector such as the Super Gainer.

The first successful Regenerodyne that met all design criteria was built in 1988, using a 6SN7 twin triode as a combination Armstrong regen detector that tuned 2.5 - 3.0 kHz, and one stage of audio. The xtal converters were solid state in the prototype using a 2n2222a xtal Pierce local oscillator injecting a 40673 dual gate mosfet at gate 2, the output being untuned, inductively coupled to the regenerative detector's grid tuning coil. The tunable regenerative detector provided all necessary gain and selectivity to tune across an approximately 400 kHz "IF window". This provided more than enough range for the HF amateur bands.

The prototype showed amazing sensitivity and image rejection when using a single tuned front end. Band selection is a simple matter of changing local oscillator xtals rather than coils, and if local oscillator xtals were chosen correctly, the tuner needed no recalibration from band to band, something unknown to the band imaging regen supers.

Lower frequency tuning and crystal controlled high frequency converters combined to create a very stable regenerative superhet. Crystal control of the converter stages make band changing very simple. The 3 mHz IF provides excellent front end image control. Low parts count and home made IF transformers make the Regenerodyne architecture not only the simplest of superhets, but also the least expensive. WD4NKA's third Regenerodyne (also called 'R-dyne') has been a continuously used part of his station for over 25 years, still being used in special events such as Novice Rig Round-up.

Upon a detailed search, it was discovered, amazingly, that this circuit was either never before published in it's current form, or if it had, it went un-named and faded into obscurity. WD4NKA provided the name "Regenerodyne" to distinguish it from the other regenerative superhets.

Independently, Professor Arnaldo Antich Coro of Radio Habana also worked on a very similar regenerative receiver concept, essentially the same radio independently naming it the "Regenerodino". Professor Coro is the developer and driving force behind the now well known "Islander" and "Islander II" receivers. Coro and Johanson (WD4NKA) collaborated in the development of the schematic design program "'TubePad'".