Using an "Outboard" (remote) compass rose
Montreal Doppler II or III unit.
There are at least two good reasons for having an outboard compass rose display:
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
perfboard or simply contact Jacques and get a board when one becomes
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
from damage. This task is fairly easy because there are only four
wires that need to be connected to the compass rose:
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
logic buffering (such as using a 74HC14 Schmidt trigger, a 4049 or
and a few resistors, etc.) but I figured that anyone building
would have some NPN transistors and few 10k resistors (although
from 4.7k through 22k should work fine) laying around.
the signalling rate for the data and clock signals is, at most, a few
of kilobits per second, there is nothing too critical about the way it
needs to be handled.
Getting it together...
I looked around for a suitable enclosure for a while, considering several possibilities:
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
that one provides a dark background for the LEDs to enhance
This could be done by spraypainting the top of the board black, or by
some dark material (such as black paper or felt, a disc of black
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:
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
of a vehicle, set it for the "Mirror" mode (where the display is
and use it as a "heads-up display" at night, with the bearing
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
aren't visible from the side view, but only the reflection
Because most windshields are quite slanted, the positioning of the
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
be a challenge.
Useful operational tips:
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.Return to the KA7OEI ARDF Page.
KA7OEI - 20060619