NR Q Th e Ultimate Re g enerative Receiver. Even so, 18 months passed before I was able to start building my receiver. During that time I did collect some of the parts I would need to complete the project.
From Ebay I acquired an old Army surplus VHF signal generator which yielded a power transformer and choke needed for the vdc power supply and the 6V6 audio output tube I would need.
Also from Ebay came the National PW dial and gearbox used in the receiver. I built mine as much like his as was possible, with heavy emphasis on solid physical construction. The receiver is also built on two chassis — the audio output, selectoject and power supply on one chassis; the detector and audio preamp on the other. Figure 1. Regenerative detector and audio pre-amp. The detector is a 6C4 and works really well with the plate voltage down around vdc. Windings can be close- or wide-spaced.
That would yield continuous coverage from kHz to 19 mHz. Figure 2. Power supply and audio output.
As you can see from the schematic, this receiver drives a speaker. Boy does it ever! It is as sensitive as most modern receivers and selective enough for listening to AM or shortwave broadcasting. For CW use, I have to engage the narrow-band filter between my ears.
To gain some additional selectivity I built in a two-stage regenerative audio filter which can peak and reject any signal in the bandpass. The circuits are very similar, using the same tubes 2 x 12AX7. Figure 3. After completing the receiver and testing it I was amazed at how much performance can be had with such a simple circuit. Selective fade distortion disappears! The vernier dial on the right is the tuning adjustment for the selectoject which covers the entire audio range allowing peaking or nulling of any signal in the bandpass.
Since the bandpass of a regenerative receiver is wide, this is a very handy circuit.
The knob on the left is the audio tone control. I ran the pilot lights off of the 5 vac winding of the power transformer which was unused I use solid state rectifiers. I also put a 10k resistor in series with the pilot lamps — I prefer muted pilot lights.Hello, Login. Visit Our Stores.
It was called the Doerle Twinplex because it used the brand new 19 vacuum tube which contained two triodes in one glass envelope. An illustration of the front of the radio appears on the front cover of our " Shortwave Manual" while the rear of the radio appears on Rock's "Secrets of Homebuilt Regenerative Receivers.
I have to be honest. I wanted to build the Doerle 19 Twinplex simply because of its appearance. It "certainly" couldn't be much of a receiver. Not a single tube regenerative powered by batteries. It was too simple. Too old. Oh, but was I wrong! When I attached the batteries, brought up the filament, and increased the regeneration, the signals came popping in!
Foreign broadcasts, ships at sea, amateur cw and ssb signals, spy stations, WWV and more! More than once signals were so loud I had to rip off the headphones to relieve the pain!
There were signals everywhere! Of the many regenerative receives I've built, this is the most impressive. It's far more than I ever expected. Next, I built a version using the more modern 6SL7 twin triode vacuum tube.
It was even hotter!
How To Build The Twinplex Regenerative Receiver
And then I built a solid state version using three transistors that tunes the region around 10 mHz to provide shortwave broadcasts, WWV and the 30 meter amateur band. It, too, really performs well. You get three different receiver projects in this one book. In a hurry? Build the solid state version while you scrounge the fleamarkets and dealers catalogs for old time components so that you can build the original Twinplex.
Or build a version out of whatever you have on hand. It's easy. This is a project book. You won't get much help with the basics. The other two books do that. Great receiver!This product has been suspended. We will not have any other components available. Your PayPal receipt is your confirmation that we have received your order.
Stock availability and shipping volume can delay shipping. How better to explore the world of shortwave listening than with a regenerative receiver. You connect the receiver to a simple wire antenna, that can be a simple wire in the attic, or one thrown up in a tree.
There is an attenuator that can be switched in at the antenna to prevent strong stations from overloading the input. The LM will drive inexpensive ear buds or a small speaker connected to the rear mounted 3. The chassis and component pcb are pre-cut and forms a sturdy assembly with the printed circuit board as an integral component of the completed unit.
It is powered either by an on-board 9V battery or can use a 12V supply connected to the rear 2. All the electrical, chassis, and mechanical components are included in the kit with the exception of the battery, earbuds, and wire antenna. The receiver is 4. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 2 to 3, depending on your experience.
Click here for assembly manual. Primary Menu Home Gen. Skip to content.This design uses junk box 2NA or 2n transistors.
Its easy to build and offers excellent performance. Here is a preliminary schematic. It works well but I am still tweaking it. Look for revisions to follow. The circuit can use a series resonant Clapp type topology or parallel tank.
I am using 20uH two crappy tiny molded inductors and a pf variable to get in the Mhz range. You get more tuning range for small tuning caps and the the inductor will be smaller. You also eliminate the collector resistor which surely adds phase noise to the clapp version, when oscillating. These are noted on the schematic. It acts like a halfwave detector but with high Z and significant gain. You could use a FET but I thought it would be fun to only use junk-box type transistors.
I am using k and 47k biasing resistors for the detector. The ratio is what matters so 1meg and k will work fine also. In the schematic, I show the detector connected to L1 and C4 which make up the tank circuit for tuning.
Its just another way to conceptualize a regenerative radio. Sensitivity is excellent. The circuit is simple. Video demo showing smooth regeneration transition on a scope. I believe the schematic is only correct for the tdaa or b. This arrangement will not work for standard tda devices which a number of suppliers sell. Yes thanks for pointing this out- you are right. There is a version of that part without the voltage controlled gain feature I believe that is the main difference.
I need to note that in the schematic. Appreciate you catching that. Parasitics are an issue in terms of detuning and modulation. Loading is not. Its a common base topology where the miller capacitance is part of the tank in the parallel tank version and the Z is very high and well matched. Overall it works pretty well and seem pretty easy to build. But Q2 — which, in the parallel tank version, is connected directly to the hot end of the tank via the Q2 base — is common-collector, is it not?
I still get the feeling that the Q2 base due to the large junction capacitances will not have a very high input Z at the base at the RF frequencies at which this receiver is operating, which could lead to more tank damping than if Q1 were used by itself as a common-base Q multiplier with feedback from an inductive or capacitive tank tap back into the emitter.Enter your mobile number or email address below and we'll send you a link to download the free Kindle App.
Then you can start reading Kindle books on your smartphone, tablet, or computer - no Kindle device required. To get the free app, enter your mobile phone number. One vacuum tube! Batter powered! Stunning performance! Classic appearance! Easy to build! You can build one. There isn't much to it. What few secrets you need are revealed in this book. So have some fun. Build one. Read more Read less. Kindle Cloud Reader Read instantly in your browser. Customers who viewed this item also viewed.
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Audible Download Audiobooks. DPReview Digital Photography. Shopbop Designer Fashion Brands. Amazon Business Service for business customers.When we build an electronic project inthe chances are that the active components will be integrated circuits containing an extremely large amount of functionality in a small space.
There was a time when active components such as tubes or transistors were likely to be significantly expensive, and integrated circuits, if they even existed, were out of the reach of most constructors. In those days people still used electronics to do a lot of the same jobs we do today, but they relied on extremely clever circuitry rather than the brute force of a do-anything super-component.
It was not uncommon to see circuits with only a few transistors or tubes that exploited all the capabilities of the devices to deliver something well beyond that which you might expect. One of the first electronic projects I worked on was just such a circuit.
This book built the reader up through a series of steps to a fully-functional 3-transistor Medium Wave AM radio with a small loudspeaker. How on earth could a single transistor form the heart of a radio receiver with enough sensitivity and selectivity to be useful, you ask? The answer lies in an extremely clever circuit: the regenerative detector. Chetvorno [CC0], via Wikimedia Commons. The basic regenerative receiver was patented in by the prolific inventor Edwin Armstrongwho you may also have heard of as the inventor of frequency modulation FM.
In use the coupling was adjusted until just before the point at which the circuit began to oscillate, at which point it was in its regenerative high gain and selectivity mode. The simplicity of a regenerative receiver did not come without problems though.
The coupling adjustment became a small variable capacitor in later designs, and this could be found as a regeneration control on the front panel of a typical receiver. At every retune to a different station this would require readjustment for best performance, resulting in tuning a regenerative radio becoming something of a black art.
In addition, if poorly adjusted they could sometimes oscillate and become transmitters in their own right. When the more complex but superior superhetrodyne receivers another Armstrong invention arrived around a decade later the popularity of regenerative receivers went into decline, and they had almost entirely disappeared by the end of the s. Today they survive in niches such as amateur radio, toy walkie-talkies, toy electronics kits, and unexpectedly in very cheap UHF remote control modules.
K8TND Regenerative Receiver
While most regenerative receivers are designed for AM broadcasts, the principle works at almost any frequency. Go on, have one on your bench! Made a VLF receiver with a pentode triode combo tube in Tuned frequency from 11 to 33 KHz. Tied in sensitive relay to receive code from military transmitters. There was a time when the AM broadcast band was so full of signals from poorly adjusted regen receivers that it made finding the actual stations hard!
This was a big issue back in the day, when receiver tube would dissipate few Watts at anode.
Today with milliWatt power levels in RF transistors, it is much less of an issue. They radiate as well. Not advisable, a pre-amplifier necessarily will alter the entire design. Each stage including the regenerative one must then be fully shielded and separated. Also, This is not an issue in transistorized designs. Regenerative receivers are good but the real magic is in the super-regenerative receiver which really should have an RF buffer amplifier in front of it.
An unusual Regenerative receiver circuit using only bipolar transistors
While regenerative receiver might oscillate if you are doing it wrong, super-regenerative must oscillate if you are doing it right!
Furthermore, it is not good for CW reception. I routinely use regenerative-detector-based receivers of modern design for two-way Morse code ham-radio communication, and they work just fine. Lots of knobs, until someone thought up the notion of ganging the variable capacitors together so only one knob needed.