Alternate firmware for the
Montreal Doppler II and III RDF units

Important note about the Doppler II:


The late Jacques Brodeur, VE2EMM, designed an excellent microprocessor-based "doppler" type DF unit described at VE2EMM's Montreal Doppler II page that drives the antenna switching circuit, updates the display, and does signal processing to determine the bearing.  Please note that this firmware was not supported by Jacques himself - please read the disclaimer.

This unit works along the same principles that the so-called "Roanoake" DF units do - but the addition of a microprocessor (to do the generation of switching signals and processing of the received audio) adds additional flexibility.  For a bit of information about the newer Montreal Doppler III unit, go to the "Montreal Doppler III" page.

This "Alternate Version" firmware is based on the original code written by Jacques for the Montreal Doppler II but these new features have been added independently without Jacques' direct involvement.  Note that it contains equivalents of some of the features found in the newer Montreal Doppler III unit as well as a few others!

Preliminary operating instructions for this firmware may be found on the Operating Manual page.

This new firmware has the following modifications/improvements:
The arrangement of the main display of this new firmware showing dual graphical and numerical bearing displays:  This display is identical for both the Montreal II and III versions.
Go to the Operating Manual page for more information.

Use of the "alternate" firmware on the Montreal Doppler II:

While it is possible to simply "plug in" the alternate firmware into a Doppler II with no modifications at all, the use of some of the features on the Montreal Doppler II require some simple board modifications - go the Doppler II Modification page for more information.  With the alternate firmware, if all of the listed modifications are performed, the feature set of the Doppler II is the same as that of the Doppler III.

Perhaps the most useful feature for users of a Doppler II that haven't added the switched-capacitor filter is the addition of the sliding average.  As mentioned above, this simulates, in software, much of the effect of the 8-capacitor "Roanoake-style" switched capacitor filter present in the Doppler I and Doppler III.  To be certain, the most flexible combination is to add such a filter to the Doppler II so that you have both.  If you have a Doppler II without the 8-capacitor switched-capacitor filter you will notice an immediate benefit in terms of filtering.

Use of the "alternate" firmware on the Montreal Doppler III:

Because of the similarity between the hardware on the Doppler II and Doppler III units, it wasn't too difficult to modify the code to be able to work with either platform, the desired hardware configuration being selectable at compile time.  This new firmware does everything that its Doppler II equivalent does as well as taking advantage of the Doppler III's added hardware:

Preliminary operating instructions for this firmware may be found on the Operating Manual page.

For information about obtaining the chips containing the described firmware, please refer to this web page:


This code was originally based on that of the original Montreal Doppler II DF unit by the late Jacques Brodeur, VE2EMM, and full credit is given to him for this fine work.  Because the additional modifications are my own and were not done with his involvement!

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.

Additional note:  Neither the author or UARC officially endorse any vendors mentioned above or assume any responsibility for the use of the devices/products described herein.  The level and satisfaction of performance of any of the above is largely based on the skill and experience of the operator.  Your mileage may vary.

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

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This page updated on 20120316

Since 12/2010: