The remote compass rose display (left) and the DF unit (right) connected with the data/power cable.  The "diamond" symbol indicates the "north" point on the compass rose.
Click in image for a larger version.

Using an "Outboard" (remote) compass rose
with the
Montreal Doppler II or III unit.

Important note:
  This is NOT an official page of VE2EMM - please read the disclaimer at the bottom of this page.

Adding a remote compass rose display:

There are at least two good reasons for having an outboard compass rose display:

The "Alternate" compass rose display firmware:

While there is no reason why Jacques' original formware would not work using this same scheme, you might also consider using the "Alternate Compass Rose Firmware" to provide extra functionality such as multi-colored display and configurability.  Please note that this page describes a compass-rose display unit using the Alternate Compass Rose Firmware.

Getting a compass rose display board:

It has been reported that Jacques is willing to sell an individual compass rose display board, but since they are typically paired with the main board, availability may be limited.  Fortunately, Jacques has made the circuit board pattern available on his web site and you (or your group) can make them yourself.

One currently-popular method uses a special transfer paper specifically designed for use in a laser printer that produces resist traces on circuit board material.  Another popular method that uses cheaper materials but more "elbow grease" is described here and it uses standard glossy laserjet photo paper fed through a laser printer:  The circuit board pictured uses this latter technique and was kindly prepared by Brett, N7KG and drilled by me using a #70 carbide bit.

If etching/drilling isn't your cup of tea, you can build it on standard perfboard or simply contact Jacques and get a board when one becomes available.
Using the compass rose with the Montreal Doppler II unit.

Using the Alternate Firmware, this same software may be used with the older Montreal Doppler II unit to provide a compass-rose display. 

This firmware adds the capability of a synchronous data stream to the Doppler II:  For more information on how it is connected, see the Doppler II modifications page. 

Note:  It is unknown if just the Compass Rose display board is available from Jacques:  You may have to "build your own" display board.  The schematic and layout of the board may be found on Jacques Doppler III page.

Interfacing an outboard compass rose display board:

The mechanical interface:

For both the outboard and main doppler unit, I chose RJ-45 connectors extricated from a junked piece of equipment.  Using this type of connector allows a cable to be easily attached/detached at any time and with a few inexpensive tools, can be replicated.  Furthermore, a standard 4-wire "modular plug" telephone cable (the "wall" cable) will plug into it, ignoring the 4 "outer" pins.

The only real problem with this type of connector is that it is usually designed with the intention of being mounted on a circuit board rather than simply flush-mounted on a panel.  In my case, I simply used metal-filled epoxy to bond the jack to the case on the DF unit while I used retaining screws and a fashioned bracket on the outboard compass rose display board.  There are numerous other connector possibilities, but it is recommended that you make the outboard display's connector different from the others so that something else cannot accidentally be connected to it.

The electrical interface - the "DF" unit:

Electrically interfacing to the DF unit isn't difficult - but it is important to keep in mind that one would want to protect the main processor from damage.  This task is fairly easy because there are only four wires that need to be connected to the compass rose:
Schematic of the interface for the "outboard" compass rose.
Click in image for a readable version.

For the DATA and CLOCK lines, I simply used a series 2.2k resistor on each lead.  This resistor provides several functions: Having the series resistor also means that one may "hot switch" the outboard display - that is connect/disconnect it without fear of damaging or glitching the main unit.  Additionally, the worst that can happen if the cable is miswired/shorted out is to blow the power fuse on the main DF unit.
The data/power connector and the mode selector switch on the outboard compass rose display.  This particular "CD Wallet" has a flat back, making it easy to mount the connector and switch.
Click in image for a larger version.

The electrical interface - the "Display" unit:

The interfacing on the other end of the cable (at the outboard compass rose display itself) is slightly more complicated, but still quite simple:  It simply consists of a logic buffer and a 5 volt regulator.

The logic buffer is simply a few transistors and resistor that take the inputted clock/data signals and regenerate them while providing circuit protection.  As can be seen from the schematic, the input to the first transistor of each stage is well-protected by a 10k resistor.  This circuit, being between the Compass Rose's processor and the outside world, offers excellent protection against any likely fault (overvoltage, reverse polarity, etc.) that is likely to occur.

The 5 volt regulator is simply a 78L05 (although one could go overkill and use the bigger 7805 instead) with a reverse-polarity diode in series.  With the protection offered by the regulator and logic buffer, there is no way that either the compass rose display or the main DF unit could be damaged by cable miswiring (other than, maybe, blowing a fuse if the cable were shorted out.)

None of the components shown are critical:  Practically any small-signal NPN transistor will work, and the resistors could probably be anything from 4.7 to 22k.  The reverse-polarity diode could be almost any diode capable of handling a few hundred milliamps, and the value of the capacitors isn't critical.

I'm sure that it will be pointed out that there are other ways to provide logic buffering (such as using a 74HC14 Schmidt trigger, a 4049 or 4050, and a few resistors, etc.) but I figured that anyone building this would have some NPN transistors and few 10k resistors (although anything from 4.7k through 22k should work fine) laying around.  Because the signalling rate for the data and clock signals is, at most, a few 10's of kilobits per second, there is nothing too critical about the way it needs to be handled.
A side view of the internal circuit board, showing the smaller perfboard containing the interface and voltage regulator circuit.
Click in image for a larger version.

Getting it together...

I looked around for a suitable enclosure for a while, considering several possibilities:

As is plain from the pictures, I chose the latter.  I was able to find a "CD Wallet" constructed of black ABS.  It seemed to fit the most important criteria:  It was about the right size, fairly rugged, it looked pretty good, and it was cheap.  A further feature that should be considered when choosing a case is its color:  Black (or another dark color) provides better contrast between the lit LED and the surroundings.

The board was mounted using hexagonal standoffs from Radio Shack, the mode switch is an SPST momentary center-off snap-in rocker type from Mouser Electronics, and the RJ-45 jack was retained using screws and a homebrew bracket (a piece of circuit board.)  As can be seen, the interface board (with the logic buffer and 5 volt regulator) is constructed on a piece of perf board and is soldered (using short wire leads) to one edge of the display board.  When choosing a standoff and mounting the LEDs, make certain that, when the LEDs are fully seated in their holes, that the height of the processor in its socket is considered:   If the LED leads and/or standoffs are too short, the top of the processor may hit the case when mounting the board.

As may be seen from the pictures, various symbols and labels were added to denote the "North" LED as well as the other three cardinal points.  Additionally, the positions/functions of the mode switch are also labeled.  For a visibility on the black plastic, I simply used a silver "Sharpie" (tm) marker, filling in the areas masked by "invisible" tape.  After the ink dried, the tape was removed and the written labels added using a fine-tipped permanent marker.

Locating the holes for the LEDs:

For the case shown in the pictures, once I drilled the holes for mounting the board (something that I did before installing any components) I bolted the board flush with the plastic case and using a very small drill bit, I marked the position of each pair of LED leads (all 37.)  When the board was removed, I had marks indicating where each LED would go and drilled a hole at each location.

An alternate approach would be to mount the LEDs just under a clear window in the case of your choice as this would eliminate the need for drilling a hole for each of the LEDs.  If this is done it is recommended that one provides a dark background for the LEDs to enhance contrast.  This could be done by spraypainting the top of the board black, or by mounting some dark material (such as black paper or felt, a disc of black plastic,etc.)

Mounting the LEDs:

Once the holes for the LEDs have been drilled and all of the other components on the circuit board have been installed, a remaining task is to mount and space each of the LEDs on the board with a lead length that will cause the lens of the LEDs to protrude equally through the holes.  If you have never done this sort of thing before, it is actually very easy:

Of course, when the board is removed and reinstalled, one will have to be careful to make sure that each LED is lined up with its hole and that the leads don't bend as one pushed everything into place.

The Mode switch:

The "mode" switch is a square, snap-in momentary SPDT type (a CW Industries model GRS-4013C-0001 switch, available from Mouser Electronics.)  This switch is simply mounted on the side of the enclosure and is marked as seen in the pictures as to its function(s.)


Operation of the outboard compass rose is very simple:  Just connect it, set it to the mode that you like, and place it wherever you feel is the best location.

With its smaller size, it is practical to place this unit on the dashboard of a vehicle, set it for the "Mirror" mode (where the display is flipped) and use it as a "heads-up display" at night, with the bearing reflecting in the windshield.  Note that if placed on the dashboard, one may want to put a small shield around the display so that the LEDs themselves aren't visible from the side view, but only the reflection itself.  Because most windshields are quite slanted, the positioning of the compass rose display will vary greatly and it is possible that installation of such a device in some vehicles such that the reflection may be seen will be a challenge.
Inside the outboard compass rose display.  This shows the backside of the board as well as the panel on which the jack and switch was mounted.  The regulator/interface board is mounted along the top edge of the display board.
Click in image for a larger version.

Useful operational tips:

(The above instructions apply to both the Doppler III running either Jacques' original firmware, or either a Doppler II or Doppler III running my alternate firmware.)


For information about the availability of this firmware, please go here.

If you plan to use this compass rose with the older Doppler II unit, you may have to make your own circuit board.  It has been reported that Jacques is willing to sell just the compass rose display board, but that the availability of these may be limited due to their being made as a pair with the companion main Doppler III board.


While the code used in the doppler unit itself was originally based on that of the original Montreal Doppler II DF unit by Jacques Brodeur, VE2EMM, the code for this compass-rose display was not..  Because this work was my own and was not done with his involvement, Jacques cannot reasonably be asked to offer any support or assistance regarding its operation!

Although good faith efforts have been made to make certain that the operation of the hardware/firmware is as described, it is possible that "undocumented features" (bugs) may be present:  It is through testing, use, and feedback from the users that projects such as this may be improved, and the user is asked to be understanding of this fact.  This firmware is strictly intended only for non-commerical amateur-radio use and any other use is in violation of applicable laws.

Always exercise common sense and good judgement when placing electronic items in a vehicle as to avoid driver distraction.  Not only can the driver be distracted by any display, but also by "fiddling" with it to adjust it or keep it from sliding around.  It is soley up to the user to utilize this equipment in a manner safe to anyone on or near the road!

Do you have any questions on this or other DF-related topics?  Go here.

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KA7OEI - 20060619

Since 12/2010: