Ronja Twibright Labs

Installing Ronja 10M Metropolis

Installing and aiming



We are going to install the device. Then an aiming will be performed using visible feedback of the carrier beam from a retroreflector.
Gallery[7b9] Gallery[31c] Gallery[32f] Gallery[574]

RX and TX into heads

Mount the receiver and the transmitter each into one optical head. Press the tube from the side so that it widens temporarily in the slide space. Put on the M4 washers on the receiver and transmitter fastening bolts. Insert both electronic boxes into the tubes and release them. Put on the slide covers and M4 nuts. Tighten slightly.

Assembly overview

Get the notion what the holder and console assembly looks like. This example picture is with Perpendicular console, but other consoles work the same way:
Drawing of Ronja Holder on Ronja Perpendicular Console Rendering of Ronja Holder on Ronja Perpendicula Console

Heads onto holders

Mount both optical heads onto the holders using three M6 screws and three M6 nuts that are attached to each optical head. Put their front caps' heating cables through the 10.5mm holes in the heels.

The following pictures show heads with holders attached. Note: the first picture is missing plate blocks and cross blocks, the second one the cross blocks only.

Gallery[e44] Gallery[101e]


If you are mounting on a chimney make sure the exhaust is not blocked - people have died from that.

Protecting the console from lightning - first step

If Ronja is installed on a metal railing or mast which is already lightning protected, scrape off the paint from all points where the console will rest on the railing or mast.


Mount the console on the mounting support (wall, railing, chimney etc.). Attach the holders with the optical heads onto the console using the M10 bolt included in the console.
Gallery[e4c] Gallery[e4d] Gallery[720] Gallery[721]

Protecting the console from lightning - second step

  • If Ronja is installed indoor, skip this box.
  • If Ronja is installed on a metal railing or mast which is already properly lightning protected, skip this box.
  • Connect the console to the lightning rod conductor of the house using the clamps and lightning conductor included with the console. If the console has 2 non-touching pieces (railing or wall perpendicular console), connect both pieces to the lightning conductor. Before connecting the clamp to the console itself, scrape off paint at all places where the clamp will touch the console. Mount the console on the mounting support (wall, railing, chimney etc.).
Postscript / PDF / EPS / BIG png / SVG (Inkscape)

Overall schematic

Have for a reference this schematic of a complete Ronja installation for wiring.


Cables into caps

Insert signal cabling, power exchange cable, heating cabling and heating exchange cable into the rear caps that come with RX and TX and tighten then down at wire nuts. Connect internal connections to the wire nut: receiver, transmitter, and heating cable stubs.


Connect power exchange's cable grounding clamp to console grounding or to a nearby lightning rod conductor or grounded roof tin. Check with a multimeter that between receiver's and transmitter's M4 bolts protruding through the optical head and lightning conductor, there is less than 0.2 Ohm resistance.

Signal Cabling

Connect the signal cabling into AUI interface's or Twister's 4-terminal wire nut.


Plug the AUI interface or Twister into your PC or switch. If you have Twister, set both switches on it to proper position depending on if you have a PC or a switch. See label at the bottom of Twister for details.

Power on

Turn the PC or switch on. If you have a Twister, plug the power source into wall outlet. The transmitter should shine it's beam at this moment. If it doesn't, something is electrically wrong and check all connections again.


Prepare a multimeter on 20V DC or AC range. Select the range according to the type of your heating power source. Conect the heating cabling into heater transformer 2-terminal wire nut and plug the transformer into wall socket. Measure voltage on the wire nut immediately. If it's 0V instead of something resembling heating source's nominal voltage, then there's a short circuit in the heating wiring and the fuse has probably just blown too.

Retroreflector board

If your track is so long you are going to use more than one retroreflectors, attach these retroreflectors on a waterproof board. Place them so that the resulting shape has a low circumference.


Attach retroreflector (or retroreflectors on a board, or a car warning triangle) on the receiver or as near to the receiver as possible, roughly perpendicular to the track. If you are using car warning triangle and the car warning triangle is that type with just outline and hollow middle then slip the triangle over the receiver's optical head. A retroreflector always reflects exactly back from where the light comes. So a moderate tilt of the retroreflector from future track's axis doesn't matter.
Number of retroreflectors required (those big red triangular with 16cm side)
800mCar warning triangle

Silica gel

Put one bag of sillica gel into each pipe (beside the box with electronics, the bag will touch the box with electronics and thermal shield) and close the cap and screw it down with the screws.


If you don't insert silicagel, there will be moisture inside from two sources - from the original trapped air and then from diffusion through the silicon sealings. This will result in condensation from inner side of the lens and link dropouts. It will also corrode the electronics so after some time (e. g. 1,5 year) all the parts in the electronics suddenly become unreliable and the electronics will have to be thrown away and built again.
Ronja West link in Cybernet, Cimice, Prague, seen from
250m, and the 90mm transmitter

View of a running link

The picture shows what the transmitter beam looks like from 260m distance (130mm diameter transmitter lens) and the big image is the 90mm transmitter in operation from close, out-of-axis view.

Start of aiming

Ask the peer on the other side to switch on his heating (not necessary for anything yet, but to give it time to heat the lens up). Tell the peer to switch off his device (AUI Forte: unplugging from AUI, Twister: unplugging the wall cube). Wait until dark.

Move the transmitter beam on a distant house, wall etc. Play with the focus slide path of the transmitter until you see a sharp image of the LED junction with the wire connected to the crystal.

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

Focusing magic

Move the LED a little bit towards the lens until the wire stops being visible on the crystal's image. Then move on another bit until the crystal outline stops being visible. Tighten down the M4 nuts on the TX focus.
Get the retroreflector reflection using the M10 nuts. Then tighten the M10 nuts. If you have got a torque spanner, then the recommended torque is 70Nm.
Tune for maximum reflection on the retroreflector using the three M8 bolt heads on the fine adjustment. In this stage, observe with your head as close to the transmitter as possible (the retroreflectors are usually of high quality).

Other side of the link

Go to the other side.

Catching signal

Connect 200mV DC voltmeter to the measurement port, switch on the device (plug AUI interface into PC or plug Twister power source into wall outlet), put the RX focus into the middle, and catch the signal with rough adjustment (M10 nuts), then tighten the M10 nuts down.

Unable to catch signal

If you are unable to catch the signal at all and you are suspecting the RX to not work, then try remote control. Take a remote control like from TV set and shine from near into the RX lens. It should make some millivolts.

Fine adjustment

Get the maximum RX level using fine adjustment. Get the maximum RX level using RX focus. Tighten down the RX focus (M4 nuts). Get the maximum level using fine adjustment again. The threshold voltage where the link starts to be able to receive data varies with Q101 gain and ambient light level and if it's the old receiver with songle BAT4x diode (lower voltage) or the newer with two ones higher voltage). It may be as low as 0.1mV in the old and as high as 100mV in the new.

Opposite direction

Perform the same aiming procedure in the opposite direction of the free-space link.

IP setup

Set up your IP network

ping test

Try ronjaping -c packetloss and BER test the same as described in Testing Metropolis: Performance Measurements

FTP test

Download some 60MB file in one direction using FTP. It is recommended to switch off the 10240 byte ticks by "ti" command. Printing them may delay the transfer a bit :) Throughput calculation: Maximum frame on Ethernet has 1518 MAC bytes plus 8 bytes of preamble plus 1 byte of postamble (including End Of Frame Delimiter) plus 12 bytes of interframe gap which is 1539 bytes frame pitch. 18 bytes from 1518 are MAC header which is 1500 bytes of IP data. IP takes another 20 bytes for IP header which is 1480 bytes for TCP datagram. TCP header takes another 20 bytes for it's header so 1460 bytes remain of pure data of the TCP stream. 10,000,000*1460/1539/8 is 1185834.95 bytes per second (1.18583495 MBytes/sec or 1158.04 KiBytes/sec or 1.130 MiBytes/sec.

Here is a summary of data rates on various layers of the network traffic when trasfering a file via FTP. The calculation is based on the following assumptions:

  • The network stack of both operating systems manage to send and receive packets go back-to-back one after another with no excessive delay (the system is fast enough to keep up with the pace)
  • There is no other traffic than tested TCP FTP traffic
  • There are no ARP packets :)
  • The TCP has negotiated full 1480-byte segment size
  • The card support maximum frame size of 1500 bytes. Some advanced cards may support much longer frames.
  • The disk is fast enough or the transfer is memory-to-memory
  • Both systems are unloaded enough so that the scheduler always manages to prepare the critical process on the line before the various buffers overrun. This criterium may be corrupted also by system flushing memory cache to the disk.
Check if your measurement accords to "Pure data (FTP throughput)". However, this is not an authoritative answer, the result may vary depending on system performance. Some advanced cards also permit jumbo frames which may get values with even better bandwidth utilization.
Data Rate Calculations on Various Layers of The Network Traffic
Flux classBits per secondBytes per secondBytes per 1539-byte frame pitchBandwidth utilization [%]
Link (Crystal Clock)
10000.000 k 
9765.625 Ki
  10.000 M 
   9.537 Mi
1250.000 k 
1220.703 Ki
   1.250 M 
   1.192 Mi
Manchester modulated bit slots (RX diode on AUI Forte or Twister shines)
9915.530 k 
9683.134 Ki
   9.916 M 
   9.456 Mi
1239.441 k 
1210.392 Ki
   1.239 M 
   1.182 Mi
Ethernet frame data guarded by Frame Check Sum (FCS) -- from DST MAC to FCS inclusively
9863.548 k 
9632.371 Ki
   9.864 M 
   9.407 Mi
1232.943 k 
1204.046 Ki
   1.233 M 
   1.176 Mi
IP traffic (IP datagrams including IP headers) -- what iptraf shows
9746.589 k 
9518.153 Ki
   9.747 M 
   9.295 Mi
1218.324 k 
1189.769 Ki
   1.218 M 
   1.162 Mi
TCP traffic (TCP datagrams including TCP headers)
9616.634 k 
9391.244 Ki
   9.617 M 
   9.171 Mi
1202.079 k 
1173.906 Ki
   1.202 M 
   1.146 Mi
pure data -- what FTP shows
9486.680 k 
9264.336 Ki
   9.487 M 
   9.047 Mi
1185.835 k 
1158.042 Ki
   1.186 M 
   1.131 Mi

Full-duplex FTP test

Launch two 60MB FTP data transfer in both directions simultaneously. This is a real test of the full-duplexity of the link :) The resulting counts will be a bit lower due to sharing our bandwidth with TCP acknowledgements from the other FTP transfer.
Look at output of the "ifconfig" command. "errors" and "frame" should not increase during traffic. These entries indicate noisy reception. Nonzero numbers in "carrier" are OK. "collisions" should be zero. "dropped" or "overruns" indicate your system has problems with performance on such fast network connections :)


Climb to the roof again and seal all seams on the tube with the sillicone sealant to be sure no humidity or water will leak inside. After the sealant solidifies (typically a day), climb there once more and seal the gaps again. Sealing in a single layer has got a high probability of failure and water leakage which produces unexpected failure after some time of troublefree operation and necessity for relatively complicated drying of the device.


If you don't seal the optical head properly, water will probably get inside. The link may stop working and the electronics may be irreparably destroyed. See a video.


If you are not 100% sure with safety of Ronja installation, call a certified technician to perform a check. The areas may include:
  • Lightning protection safety with accompanied safety from fire hazard
  • Power source fusing with accompanied safety from fire hazard
An expected information missing here?