Ronja Twibright Labs

Building Ronja Inferno Receiver

Building Ronja Inferno Receiver



We are going to build a tin box with lid here. Box will be equipped with mounting brackets and wire leads. Finally we'll solder receiver electronics inside. The result without the lid will look like this except for mounting brackets:
Gallery[59b] Gallery[16b] Gallery[684]
Postscript / PDF / EPS / BIG png / DXF (qcad)

Box Template

Print this template on a calibrated printer. You can also use RX and airwire TX template together.


Bracket Template

If you plan to build optical head and the pipe has diameter less than 105mm, skip this box and the next one.

Subtract box width (normally 92mm) from the optical head's pipe inner diameter. If you don't plan to build optical head, assume 145mm. Select the template according to the resulting number from the Side template list and print it. The template is for two boxes, you need just half of it.

Make the brackets

  • Drill the side template out and bend it. Wash the template off in warm water.
  • Solder the M4 nuts over the holes from the inside.
Receiver box
Postscript / PDF / EPS / BIG png / DXF (qcad)

Main box

Note the picture shows an older type of the box.

  • Glue the box template on tinned steel plate.
  • Cut and drill out.
  • Bump the indicated points.
  • Bend into a box shape.
  • Remove the template with warm water
  • Solder the corners up
  • Solder the partitions (strips with square notches) inside the box. The strip positions are given by the bumps on the bottom. Solder all along their gap, not just in several points.


Solder on brackets/nuts

If you have brackets, then solder the brackets to the case, otherwise solder bare M4 nuts from the outer side over the 4mm holes.

SFH203F in hole


Put the SFH203F detector into the 5mm hole in the case and solder anode to the box. The Anode (A, the longer pin) is described in the lower left corner of the schematic (below). When inserting the detector into the hole, make sure the detector is perpendicular to the plane (is not askew) and about 1/3 of the plastic body is protruding out. The chip must be inside otherwise catches intereference!

After soldering, fix it from the inner side using the thermal glue gun (optional, recommended).



Put the cable grommets into the 8mm holes. Note: the box in the picture should have mounting brackets soldered on.
Gallery[167] Gallery[16a]

Cutting cables

Cut the following types and lengths of cables:
3shielded single-conductor20cm
Postscript / PDF / EPS / BIG png / SVG (Inkscape)


Strip 29mm of the outer insulation from the shielded cable on both sides. Strip 4mm of the inner insulation from the shielded cable on both sides.

Cover all bare ends with solder.

Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Installing cable leads

Put the bare ends through the grommets as seen in the picture. Leave the middle cable's shield unconnected but solder the remaining shields to the box. Seal the cables inside the grommets with sillicone sealant (you can also use thermal glue, it is faster). Seal from both inside and outside of the grommets. When sealing the outside take care not to occupy the place where the lid will be (the rim of the box).
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Copper stubs

The cables ends that are not inserted into the box need copper stubs. Solder 6 stubs made from 4mm^2 uninsulated solid copper wire.
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Colour insulation

Insulate the stubs with colour duct tapes according to the diagram.

Making the coil

Take the 8.5mm bit bit and wind a 10-turn coil on it from the insulated1mm^2 hard copper wire.
Placement of selected components inside the receiver

Key components

Place some important components into the box according to the drawing. Fix them by soldering on their ground lead. If they don't have any ground lead and you mind them rolling all around inside the box, you can glue them down using thermal glue gun.
Gallery[16b] Gallery[16c] Gallery[16d] Gallery[16e]
Gallery[16f] Gallery[170] Gallery[173]
INFO We are going to place components according to a schematic. There are arrows in the schematic labeled "P*" where "*" varies. They don't mean any component, they are just test points.

Stereo picture

You can view a stereo picture of populated RX to get a notion how the components are mounted inside prior to starting soldering them down. Please note there should be mounting brackets instead of the screws:

Now the following components are already installed in the box:

  • U101
  • PD101
  • R105
  • R112
  • C174
  • Q101
  • Q102
  • Q103
  • J101
  • J102
  • J103
  • J104
  • J105
  • J106
  PostScriptPostScript + Gzip PDF
Color Dark inferno_receiver_01.pdf
Light inferno_receiver_00.pdf
Small inferno_receiver_02.pdf
B/W Dark inferno_receiver_11.pdf
Light inferno_receiver_10.pdf
Small inferno_receiver_12.pdf
inferno_receiver.sch (gschem) Component lists Seznamy součástek


Place the remaining components according to the schematic in this sequence:
  • C168 close to J101
  • C165 close to J101
  • C178 close to J103
  • C179 close to J103
  • C163 close to U101
  • C164 close to U101
  • C154 close to Q101
  • C153 close to Q101
  • L102
  • R101
  • C173
  • C167
  • D101
  • R103
  • C152
  • C161
  • C155
  • C151
  • C177
  • C175
  • L101
  • R122
  • C172
  • D103
  • C162
  • C157
  • D102
  • R102
  • R104
  • C156
  • R111
  • R113
  • R108
  • R109
  • R110
  • R115
  • C158
  • C166
  • R117
  • R120
  • R119
  • R107
  • C169
  • R116
  • R121
  • C178
  • R114
  • R118
  • C160
  • C170
  • C159
  • C171

Correctness check

Take the schematic and a multimeter and check everything except R106 (still missing). Check that the topology is OK (i. e. the wires lead where they should lead). Measure every resistor with a multimeter (sometimes it will show less if there is a current path around). Check every capacitor visually where the value is visible. Check every diode and transistor junction with diode measuring function of the multimeter. Scrawl out every part and wire you check on the schematic with a pencil. Check visually all soldered joints for quality and resolder all joints where suspicion may arise.


Connect 12V regulated supply: + to J101 (red) and - to J102 (black). Set multimeter to 200mA and put red probe to P104A and black probe to P104. Measure current.

Disconnect from power. Select R106 according to this table:

Current [mA]R106 [Ohm]

Solder the R106 into the receiver.

Schematic inside the lid

Print the small schematic (see above). Overwrite all part numbers that have been installed different than in schematic. Overwrite all resistor values that have been changed during tuning. Write down amplification factors of both 2N3904 transistors. Glue the paper on the inner side of the lid.

Postscript / PDF / EPS / BIG png / SVG (Inkscape)


Print out the Ronja 10M Receiver label. Fill in the label and stick on the outer side of the lid.

Washers and nuts

Save the 4 M4 washers and 4 M4 nuts for future mounting.

An expected information missing here?