This document provides instructions for building a simple regenerative radio receiver with a single FET and low component count. The receiver can tune from 3.4 MHz to 8.5 MHz and uses a variable capacitor, coil, resistors, capacitors, FET, battery and regeneration control to receive AM radio broadcasts and SSB transmissions. Testing involves connecting an antenna, ground and audio output, tuning the variable capacitor while adjusting the regeneration control to achieve maximum sensitivity and selectivity at different frequencies across the band.

1. SIMPLE REGENERATIVE
RECEIVER
80 and 40 with one FET and a low
component count

2. COMPONENTS LIST
RESISTORS All 1/8 W carbon
1k0, 2k7, 1M0
10k Linear potentiometer
CAPACITORS
15p ceramic*, 4p7 ceramic*, 150p ceramic, 50p polystyrene,
100p silver mica or polystyrene, 300p polystyrene, 0µ1
polyester film, 2 X 33µ 16v electrolytic
Variable capacitor 208 + 176pF (176p section only used)
* C1a and C1b - selected for optimum selectivity performance:
actual values may differ from guide values shown.
SEMICONDUCTORS
N-channel FET J310 or 2N4416 preferred
2N3819 will do (select on test)

3. COMPONENTS LIST (continued)
MISCELLANEOUS
•4mm. sockets - 3 off (2 red, 1 black) - or piece 4-way choc
block
•Min (3.5mm.) jack socket
•Min switch, SPST
•Slow motion drive for tuning capacitor: 10:1
•Knobs for VC and VR
•3 X 4BA short machine screws (or 4BA studding & nuts) &
washers / spacers (VC mounting); 1 X 4BA m/c screw &
nut + large washer (coil mounting)
•Plastic 35mm. Film can (coil former)
•22g (+/-) insulated hook-up wire for coil (2M approx.)

4. COMPONENTS (continued)
MISCELLANEOUS (continued)
•Printed circuit board, drilled for VC and L1, 150mm. X 100mm.
X 1mm. thick (approx. measurements)
•Shaped 4BA screw(s) and nut(s) - tuning drive retainer.
•Hook-up wire (< 100mm.)
•9v battery (PP3 or equivalent)
• PP3 type battery clip and lead
•Double-sided sticky tape (100mm X 15mm approx.) - to secure
coil turns
•Rubber feet

5. CIRCUIT DIAGRAM
d
g
s

6. COIL CONSTRUCTION
(insulated
hook-up
wire)

7. RECEIVER LAYOUT DIAGRAM (SUGGESTED)

8. KNOW YOUR FET!

9. BEFORE YOU START!
1. Read through the instructions, referring to the
circuit, layout and constructional diagrams.
If there's anything that doesn't make
sense, please ask.
2. When you start construction, keep the
diagrams handy and check each stage as
you go.
3. Tin all leads before you solder them - but
watch out for the polystyrene capacitors:
they melt easily. Use a heatsink if in doubt.
more...

10. BEFORE YOU START! (continued)
4. When placing major components on the
board leave plenty of room to get in and
modify the circuit if necessary.
5. Keep the construction as rigid as possible -
the final receiver will be more stable that
way.

11. INSTRUCTIONS
1. Wind the coil first, making sure that the coils
are secure. Use double-sided tape to
secure windings to the former - see the
diagram. Anchor the winding ends by
passing the wire through two holes pierced
in the former.
2. Mount the tuning capacitor on its back, using
4BA machine screws and spacers. Make
sure that the screws do not foul the
capacitor plates (use washers / spacers
under the screw heads to adjust). Don't fit
the reduction drive at this stage.
more..

12. INSTRUCTIONS (2)
3. Mount the coil base (film can cap) to the
base-board using a 4BA machine screw
with a large washer and nut.
4. Mount Aerial and Earth Sockets to the board
with hot-melt glue.
5. Solder a short length of wire (ca. 50mm. or
so) to one switch way terminal; solder one
lead of the 150pF capacitor to the pole
terminal. Keep the leads short.
more...

13. INSTRUCTIONS (3)
6. Using hot-melt glue, mount the switch on top
of the insulated body of the earth terminal,
making sure that the free lead of the
capacitor can be soldered to ground.
Solder it.
7. Solder the free end of the switch wire to the
VC rear section fixed plates terminal
(LHS).
8. Solder R1 and C2 in parallel. Keep the leads
short (< 10mm.).
9. Solder one end of R1 / C2 to the VC rear
section fixed plates terminal (RHS). more...

14. INSTRUCTIONS (4)
10. Solder C3 and C4 together in series (short
leads); solder the free lead of C3 to the
free end of R1 / C2.
11. Solder the free end of C4 to ground (short
lead).
12. Using hot melt glue, secure the
regeneration potentiometer (VR) in position -
make sure it's at least 10mm. from the front
edge of the board.
13. Solder to ground the rightmost of the three
VR terminals.
more...

15. INSTRUCTIONS (5)
14. Solder C6 (-ve) and R3 to the VR centre
terminal. Solder the free lead (-ve) of C6 to
ground.
15. Solder C7 (+ve) to the remaining (leftmost)
VR terminal. Solder C7 free lead (-ve) to
ground.
16. Solder C5 to the junction of C3 / C4 / R2. It'll
probably help rigidity if this component is
stuck down to the board with hot melt glue.
17. Position the output socket on the right hand
edge of the board. Secure in position with
hot melt glue. more...

16. INSTRUCTIONS (6)
18. Solder the free lead of C5 to the socket tip
terminal. Solder the socket's other terminal
to ground.
19. Solder the battery clip red lead to the
junction of VR with C7. Solder the black
lead to ground.
20. Solder C1a and C1b to Aerial terminals A1
and A2 respectively.
21. Solder the free ends of C1a and C1b
together, and connect (solder) to VC rear
section fixed plates terminal.
more…

17. INSTRUCTIONS (7)
22. Position the coil on its base. Solder the
lower end of the winding to ground.
23. Solder the upper end of the coil winding to
the VC rear section fixed plate terminal.
24. Solder the FET in place:
! (check the leadout diagram for your device) !
gate to junction of C2 / R1 and C3; source
to junction of C3, C4, R2, C5; drain to free lead
of R3.
25. Secure the battery in position. Do not connect
the battery clip at this stage.

18. INSTRUCTIONS (8)
26. Check your wiring, paying special attention
to electrolytic polarities and FET
connections.
27. Fit the reduction drive to VC. Tighten the
grub screws.
28.Secure the drive fixing lugs to the capacitor
using 4BA studding and lock nuts. !Make
sure the stud ends don't foul the
capacitor plates! Solder the lugs to
the studs.
29. Fit knobs to VC drive and VR.

19. TESTING AND OPERATION
1. Connect an audio lead between the receiver
output jack and audio amplifier.
2. Connect an aerial, preferably at least 10M
long, to the aerial terminal.
3. Connect an earth lead to the earth terminal.
Connect the lead free end to a suitable
earth.
4. Switch on the amplifier and turn up the
volume control; connect the receiver
battery clip to the battery.
more...

20. TESTING & OPERATION (2)
5. Advance the regeneration control from the
fully anticlockwise position: a point should
be reached where either stations are
heard, or a rushing sound.
6. If broadcast stations are heard, tune a station
and continue to advance the regen. pot.
until volume is maximum, without the set
starting to howl: this is the point of
maximum sensitivity and selectivity.
more...

21. TESTING & OPERATION (3)
7. As the set is tuned across the band, small
adjustments to VR will maintain the
maximum selectivity / sensitivity point, and
further broadcast stations will be heard.
8. Without C8 switched in, the receiver should
tune 4.5 MHz to 8.5 MHz approximately;
with C8 in circuit the range was 3.4 MHz to
4.6 MHz in the prototype.
more...

22. TESTING & OPERATION (4)
9. To receive s.s.b. transmissions, advance the
regen. pot. until the set just oscillates
(rushing sound), tune for a station and
adjust tuning / regeneration for best
intelligible speech.
10. Each time you re-tune, you'll have to make
adjustments to the regen. pot.. It takes
practice, but the rewards are well
worthwhile.
Good Listening!