Availability of chips for the DF (Direction-Finding) gear:

• Q:  Where can I get this firmware?
• A: This firmware is now available in the form of pre-programmed PICs (only) be available from the author:  Please send email if you have any questions.  Note that these chips are usually shipped code-protected.
  
• Q:  Which chips are used?
• A:  The main processor for the Doppler I uses a PIC18F4620;  The Compass rose uses the PIC16F819 or the PIC16F88;  The Comb Filter use the PIC16F819 or the PIC16F88 - although there is one minor wiring change between the two;  The "mini" comb filter uses the PIC12F683;  The Doppler III "Clock" can use either the PIC12F675 or PIC12F683.  There is no functional difference between the compass rose, comb filter or clock generator with the different chips - it's just that I started using the larger-memory chips (e.g. PIC12F683, PIC16F88) when they became available.
• Q:  Why has the firmware been available on two different types of processors?
• A:  Originally, the PIC16F877A had been used, but due to "feature creep" it was required that a chip with more program memory and RAM, so the code was ported to the PIC18F4620 - and the '4620 is also a bit faster for the same clock speed owing to a broader instruction set.  If one were to upgrade from older firmware, either one may be used with no modifications.  If you can think of some feature that would be advantageous to add, please feel free to contact me to see.
  
• Q:  How much do the chips cost?
• A:  Recently, I have been charging as follows (all prices in US Dollars)  Please note that these prices are subject to change!:
• $15 - Main processor for Doppler II or Doppler III alternate firmware using the PIC18F4620  - you must specify whether you want the Doppler II or Doppler III firmware.  If, for some reason, you really want the PIC16F877, let me know.
  
• $12 - Main processor for the Doppler I alternate firmware.  This is implemented using the 18F2620.
  
• $7 - Compass rose display chip.  This chip is required for the Doppler III, as are certain minor modifications - see the Compass Rose page for more info.
• $5 - "Clock generator" chip.  If you already have a working Doppler III and wish to change to the alternate firmware, you will not need this chip:  You will only need it if you are building it and do not already have the chips.  This clock generator is not required for the Doppler II.  Also note that the .HEX file may be found below if you have the ability to obtain and program PIC12F675 or PIC12F683's yourself.
  
• $7 - Comb Filter to remove the switching tone from the received audio.  This is for the "full-sized" comb filter.  Important note:  This filter is designed to filter a tone of precisely 500.8 Hz - the switching frequency of the original Doppler II firmware and the alternate firmware for both the Doppler I, II and III units:  If used on the original Doppler III firmware, a different frequency will be required - please note this if you are interested!
• $5 - The "mini Comb Filter."  This works much like the above comb filter, except that it has fewer available modes and it uses an 8-pin PIC in a smaller package.
• $5 - A PIC-based TDOA unit.  If you are interested in this unit, please note that its firmware is still being developed, but the prototype seems to work nicely - but if you get one, I expect feedback from you as to how to improve it!
  
• Shipping/handling and "hassle factor" - While this will vary depending on the destination, if you order just one or two of the smaller chips (8 or 18 pin) then shipping/handling will probably be $3.50 for domestic U.S. mail.  If you order a complete set of chips for the Doppler III, it will probably be be in the $5-$6 area.  Please ask!  Please note that any incurred taxes and/or tariffs are the responsibility of the recipient of the chips.  International mailing costs will likely be a bit higher as I need to jump through ever-more hoops at the post office these days!
  

If you are interested in any of those, the same general rules outlined above apply, but feel free to contact me for more information.

Doppler III Filter Clock object code:

If you have the chip and the means to do so, please note that object code for the Doppler III filter clock is available here in the event that you wish to program it yourself. 

Note that this code is functionally identical to the original - but is not in any way based on the original code as I'd not ever seen the code at the time that I wrote it.  This .HEX file is targeted to be programmed into a PIC12F675 and simply outputs a 98.04 kHz signal with a 20 MHz input drive signal - that is, it simply divides the 20 MHz input by 204 by using a bunch of "watchdog restart" instructions to delay toggles of the output clock line.  This filter clock rate yields a bandpass frequency very close to 500 Hz.

The .HEX code for programming this same functionality into a PIC12F683 is available on request.

Other chips that are available:

There are a few other chips that are available that aren't related to amateur radio direction finding, including:

• Comb filter for removal of mains hum - This is based on the PIC16F88 and it's a comb filter that removes 100 or 120 Hz components and its harmonics.  This was designed for use with analog receivers used for free-space, through-the-air optical communications where there was some "interference" from mains-powered light sources that cause hum and buzz.  Since such lighting operates on both sides of the AC waveform, the frequency at which it occurs is TWICE that of the AC mains frequency.  This device can be configured for use with either 50 Hz or 60 Hz mains.  Note that it is often the case that hum on cables contains significant energy at the mains frequency (50 or 60 Hz) and that this filter may not remove it since it operates only on the even-numbered harmonics of the mains frequency!

•  "Mini" Pulse-width modulator for LEDs and Lasers - Based on the 8-pin PIC16F283, this PIC takes audio input (up to 5 volts peak-peak) and pulse-width modulates an output at a rate of 19.5 kHz.  This chip also includes an audio AGC using external resistors and an op amp to select the gain as well as built-in tone generation features.  This chip is intended to be used with an external op amp for the microphone/line level audio amplification and it is used to drive high-power LEDs (using an external transistor) or even inexpensive laser pointers.

•  A PIC-based VU meter - Based on a PIC16F88, there's not a page for this (yet) but this takes inputted audio and outputs a linearized voltage based on the audio level input - that is, level differenced in dB correlate with differences in output voltage.  The practical dynamic range for this device is about 50dB.  It can also output a serial data stream with the output levels encoded in ASCII text.  For this, there's no guarantee that the ballistics of the "meter" are exactly like that of a "real" VU meter, but it does give a reasonably accurate indication.  It is also possible for this meter to give the minimum and maximum readings over a window of time (e.g. a few seconds.)
  

• PIC-based intervalometer - No web page for this yet, either, but this device (based on the PIC12F683) interfaces with a digital (or even film!) camera and will provide a programmable interval for time-lapse pictures.  For cameras with a corded shutter release mechanism, a simple transistor-based circuit will trigger the camera while for those cameras that have only wireless shutter release, one simply gets a cheap remote and hacks it up so that this device can "press" the button.  This unit easily provides interval timing from seconds to hours.  The units that I've built operated from a pair of AAA cells, but it could easily operate from a single 3 volt lithium coin cell.
  

•  PIC-Based tone generator - Original built into a modulator for high-power LEDs, this simple tone generator (based on the PIC12F683) produces reasonable-quality sine waves from a 20 Hz to 2.457 kHz as well as a few "fixed" frequency tones and some attention-getting tone sequences.
  

Solar panel charge controller:

Here are the .HEX files for the solar panel charge controller as described on the web page:  "A Simple, effective, yet inefficient solar charge controller!"

• Version 2c targeted for the PIC12F675
• Version 2c targeted for the PIC12F683
  

For additional questions about any of these, or for pricing and availability, please contact me using the link at the bottom of this page, but generally the pricing will be comparable to the chips listed above.

The only components that are available from me are the pre-programmed chips themselves.  Here's a short list of the sorts of things that are not available - and why:

• Complete kits.  Producing a complete kit is a task in itself and I am not prepared to do it at this time.  Also, I have had a number of people "promise" to purchase a complete kit if I were to put it together.  On some occasions I have reluctantly done so, but in several of these cases, those individuals simply have not kept their word, so I am simply not doing that anymore!
• Assembled and tested kits.  One of the advantages of assembling a kit or a project is the experience one gains and the fun in doing so.  Unfortunately, going unto production of an item crosses this line and what had been a fun project can become more of a arduous task.  As with "kitting" parts, I'm simply not set up to do this - and if I were, I'd have to charge more for my time in doing-so than it would likely cost to purchase a commercially-produced unit.
• The source code.  The simple answer is NO, but there have been certain exceptions in the past.  Why?  While I am sure that there are a lot of people that have genuine intellectual curiosity in how things work, there are also many people with interests that are less than academic!  I'm happy to determine this ona case-by-case basis.
  
• The "object" code.  Normally, no - but:  In certain cases - as in working with people to develop new and/or enhanced features - I am willing to email .HEX files so that they can test new firmware.  In the cases that I have done this in the past, I have been able to determine to my satisfaction that the other party is genuinely interested in helping with the development of the firmware and is trustable:  In those cases, such interactions have been invaluable in providing insight in how others might use the equipment.  Of course, for the object code to be of any use at all, one must be able to obtain and program the chips for which the code was intended.
• Finally, I get a surprising number of emails from people who would like a lot of information about direction finding and how, exactly, these circuits work.  While most people are genuinely interested in learning about these things, on one or two occasions it became clear that this person was in the middle of a class project and clearly had not done his/her homework and was hoping simply to avoid due-diligence - and now the deadline was fast-approaching!  Having said this, I'm more than happy to offer some help, but I will not do your homework for you!
  

Disclaimer:

This code was originally based on that of the original Montreal Doppler II DF unit by Jacques Brodeur, VE2EMM, and full credit is given to him for this fine work.

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-commercial 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 want to get some chips, or do you have any questions on this or other DF-related topics?  Go here.

This page updated on 20170912