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A High-Performance Regenerative Receiver - HiRegen

Updated on September 22, 2015

Regenerative radio receivers (regen) always remain a passion for the amateur constructors. They will be seen by exceptional simplicity, easy to build and also have increased sensitivity and selectivity.
The key circuit of such receiver is an user-controlled RF oscillator. Once the circuit is oscillating you can just tune around and check your reception frequencies.

A new type of regenerative-receiver circuit (HiRegen) is shown in Fig. 1.

Fig. 1 Schematic of the high-performance regenerative receiver (HiRegen)
Fig. 1 Schematic of the high-performance regenerative receiver (HiRegen)

The RF Stage

The transistor T1 is a one-stage RF amplifier in a grounded-base circuit. This allows for a high output impendance, which is absolutely essential for a high selectivity of the tuned circuit (L1C5D1D2). The antenna input signal connects through capacitor C1 to T1 emitter.

The Regenerative Detector

The tuned circuit is comprised of inductor L1, capacitors C5 (trimmer) and C15, along with tuning diodes D1 and D2. Positive feedback, controlled with Regen potentiometer P1 and related components, allows the stage to be brought into controlled oscillation. This oscillator configuration is very stable. The signal is amplified by positive feedback, while at the same time the „Q‟ of the tuned circuit is increased, narrowing the reception bandwidth. Both a CW carrier (carrying Morse code) and amplitude-modulated (AM) waveforms are increased in amplitude as regeneration is advanced. When the stage breaks into oscillation, CW signals are then heard as a „beat note‟ between the carrier and the slightly-offset oscillator frequency. Single-sideband (SSB) modulation can be recovered this way as well. To hear AM broadcasts the regeneration is generally held just below the point of oscillation. Diodes D1-D2, a voltage-variable capacitors, are used to tune the oscillator. A low-cost plastic 100 Kohm potentiometer is used as the main tuning control (P3). For fine tuning a 10 Kohm potentiometer is used (P2). For setting the frequency range the trimmer (C5) is adjusted. Detection is done at the level of T4 and T5 transistors. The output signal from the detector is the differential type. R11C11 and R12C12 groups are low-pass filters for audio signal.

This detector presents more advantages over the classic ones. First of all, the gain of the detector is higher than in classical variants due to special configuration T3-T4-T5. On the other hand, regeneration control is done in DC which shows the advantage of a good stability. Also, regeneration control is made using widespread potentiometers instead of variables capacitors.

Audio Power Amplifier

In this stage has been used the widespread circuit LM386. Its amplification has been set at 52 by R17.

Circuit Design

To analyze the circuit (RF), I have used the programs TINA from Texas Instruments and LTspice IV from Linear Technology. For PCB design I have used the Altium Designer package. All the electronic parts have been carefully selected and dimensioned.

Fig. 2 RF Simulation using TINA software
Fig. 2 RF Simulation using TINA software

The Kit

This project is available as a kit. The kit will supply most on board components. This also includes the PCB. It does not include the potentiometers, the coil, the speaker and the battery. Table 1 shows the components that are included in the kit.

ID
Device Type/Value
Obs.
PCB
80 x 90 x 1.6 mm
FR4, single side, solder mask, silk screening
IC1
LM386N-3
Audio Amplifier, 8 ohm, 700 mW
T1, T2
2N3906
pnp Transistor
T3
J113
JFET
T4, T5
2N3904
npn Transistor
D1, D2, D3
1N4007
Diode
DZ1
BZX79-B6V2
Zener Diode 6.2 V
C1, C15
100 nF
Ceramic disc
C2, C3, C4, C6, C7, C8, C9, C10, C16, C20
100 nF
Multilayer ceramic
C11, C12, C13, C14, C21
47 nF
Multilayer ceramic
C5
Trimmer 6 - 50 pF
MURATA TZ3Z500F169B00
C17
100 uF/16 V
Aluminium Electrolytic
C18
10 uF/16 V
Aluminium Electrolytic
C19
330 uF/16 V
Aluminium Electrolytic
C22
220 uF/16 V
Aluminium Electrolytic
R1, R3, R5
4.7 K
0.25 W
R2
10 K
0.25 W
R4
47 K
0.25 W
R6, R8, R9, R11, R12, R13, R14, R17
1 K
0.25 W
R7, R10
510 ohm
0.25 W
R15
100 K
0.25 W
R16
10 ohm
0.25 W
Table 1. Parts included in kit

The following items (Table 2) you will need to supply yourself.

ID
Type/Value
Obs.
P1, P2
10 K, Potentiometer
Linear
P3
100 K, Potentiometer
Linear
P4
10 K, Potentiometer
Logarithmic with switch
LS1
Speaker
8 ohm, 500 mW
BAT
9V Battery
 
L1
4 uH, Air Coil
16 Turns, 20 mm diameter, 16 mm length
Antenna/GND
Connector
 
Table 2. Parts NOT included in kit

Potentiometers can be mounted on the control panel using wires, but there is the possibility of installing them directly on the PCB. You can choose the types of potentiometers and knobs as you like to build your control panel. When you will assemble the kit you must be sure to done the three connections on the PCB denoted by J1, J2 and J3.

Fig. 3 The Printed Circuit Board of HiRegen
Fig. 3 The Printed Circuit Board of HiRegen
Fig. 4 Top view of the circuit completely assembled
Fig. 4 Top view of the circuit completely assembled
Fig. 5 3D view of the circuit completely assembled
Fig. 5 3D view of the circuit completely assembled
Fig. 6 Coil Placement on PCB
Fig. 6 Coil Placement on PCB

The Frequency Range

Using a 4-μH coil you get a frequency range of 7.7 ... 11 MHz including 31-meter broadcasting band. This coil is made on a plastic support diameter of 20 mm with 16 turns on a length of 16 mm. After setting the midpoint of the band with C5 you get a variation in the frequency of 1 MHz using potentiometers P2 and P3. To accurately adjust the frequency range, you can measure signal frequency in source of transistor T3. Of course, for this procedure, the circuit must be brought in a state of oscillation by adjusting potentiometer P1.

Kit Price

The price structure is as follows:

1. Gerber files provided via email

For an amount of 5 USD you will receive the necessary manufacturing PCB gerber files via email. You will also receive the printed circuit images, in case you want to build PCB by any other than the industrial methods. So you can order online to printed circuit for example at MakePCB.com (Single Layer, 1.6mm, 35um, Lead Free Tin, Solder Mask Color Green, Silkscreen One Side, No, No, No, Standard, Single PCB, 80mm, 90mm).

2. The kit according to Table 1

The price for the kit is 22 EUR + postage for the European Community and 30 USD + postage for the rest of the world.


To order, deposit the amount for the chosen item to my Paypal at naga@ack.ro. For any inquiry or clarification, send email to the same address. Please checking it twice your delivery address.


Item
Area
Price
Postage
Gerber Files
Worldwide
5 USD
-
Kit
European Community
22 EURO
10 EURO
PCB only
European Community
12 EURO
10 EURO
Kit
The rest of the world
30 USD
13 USD
PCB only
The rest of the world
16 USD
13 USD
Table 3. The Price Structure

Testimonials

The following testimonials are received by email:

- "Your receiver (seen on SciTec) is by far the most interesting regenerative I have seen in a few years", February 08, 2013, Filippo Cattaneo, Italy

- "Just wanted to inform you that I have finished construction of the regenerative receiver circuit (using parts from my junkbox and the PCB, trimmer and LM386N3 which you supplied). The receiver works fine, I connected a short wire (3 meters or so) to the antenna input and immediately heard a SW broadcaster (Italian language program) with good signal strength. The board (with dangling wires) should still be placed in a decent cabinet. And I should probably use shielded wire for connection of the volume control and speaker. Since increasing the amount of regeneration now results first in RF oscillation of the detector (which is of course OK and is audible as an increase of background noise) but if the amount of regeneration is further increased, the audio amplifier starts to oscillate at a few hundred Hz resulting in a loud howl. The regen control works nice, the amount of positive feedback can be set just below or just above the level required for oscillation. My coil has a slightly larger diameter than yours (because of the availability of a good former) and is wound of wire with 1 mm thickness. I may attempt to receive the 40m amateur band. Thanks for a nice project!" August 23, 2014, Aren van Waarde, Groningen, Netherlands a.van.waarde@hetnet.nl

Comments

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    • profile image

      Serge 3 years ago

      Good Regen , good reception - all work OK

    • SciTec profile image
      Author

      Neculai Agavriloaei 3 years ago from Romania

      Yes, the radio receiver can work in the 3.5 MHz band. To work in any other frequency band you have to recalculate the LC circuit and find a suitable value for the resistance R6.

    • profile image

      YANNI 3 years ago

      Great job !This receiver can work at 3.5mhz with a different coil?

    • profile image

      SebastianT 4 years ago

      I will build this set, I am very interested in its operation.

    • profile image

      DrM 4 years ago

      An atypical regenerative receiver in which the signal is fed to a detector stage which acts as a differential amplifier. This amplifier performs the mixing action which demodulates the modulated RF signal.

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      Cecil Bayona 4 years ago

      The Postal services will most likely be your cheapest option for sending the kits to International destinations. You may want to check with your Post Office. It may take a little longer than Express service but there should be a substantial difference in cost, most of us are willing to a little delay when connected to a substantial savings in shipping cost. I hope you work something out.

      Cecil Bayona - k5nwa

    • profile image

      ianm8 4 years ago

      OK. thanks for your answers. I'll wait for process to purchase Gerber file. :) Can you find someone to help in US? World wide shipping from there is pretty good. The softrock kit is a good example. I'm in Australia so I know all about shipping issues! Always costs more to ship to Australia. :)

      Cheers, Ian

    • SciTec profile image
      Author

      Neculai Agavriloaei 4 years ago from Romania

      Hi

      This is now corrected in the parts list in Table 1.

      C11, C12, C13, C14 and C21 are 47nF.

      Thank you Ian !

    • profile image

      ianm8 4 years ago

      Hi

      The parts list shows C11, C12, C13, C14, C21 as 100n but they are 47n on the schematic.

      BTW, is there a youtube of the working receiver? That would be awesome!

      Cheers, Ian

    • profile image

      ianm8 4 years ago

      This is great! What's the highest frequency it will go to with a different coil? How do we buy the kit?

      Cheers, Ian

    • profile image

      Ian 4 years ago

      This is great! How do I order the kit?

      thanks!