chips with the firmware for the Projects
described at this web site
Availability of chips for the DF
Q: Where can I get
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.
chips are used?
A: The main
processor for the Doppler I uses a PIC16F876A; The
Compass rose and Comb Filter use the PIC16F819;
The "mini" comb filter uses the PIC12F683; The
Doppler III "Clock" uses the PIC12F675. A
PIC16F877A is currently used for the main processor for
the Doppler II and Doppler III alternate firmware
although testing is being done with the PIC18F series.
Q: Why is the
firmware available on two different types of
A: The PIC16F877A
has been used as it has been large enough to accommodate
the current feature set although the addition of more
features will likely require the use of the larger
processors - which may be plugged in with no
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
A: Recently, I
have been charging as follows (all prices in US
Dollars) Please note that these prices are
subject to change!:
$13 - Main processor
for Doppler II or Doppler III
alternate firmware - you must specify whether you
want the Doppler II or Doppler III firmware.For the version using the PIC18F series, the main
processor will be $15.
$12 - Main processor
for the Doppler I alternate firmware.
$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 for this processor may be found below
if you have the ability to obtain and program
$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.
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!
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
How to pay:
Typically, payment is via PayPal. Even though they
get their "cut", I find that well worth letting them
go through the hassle of transferring money - particularly
for overseas transactions.
If you are interested in some of these chips, contact
me using the link below and ask for the payment address.
Please make sure that you contact me
for the PayPal payment address and to verify all information before
you send any money: I want to make sure that any
questions that you may have are properly answered before you
spend your money, make sure that you get what
you really intend to get, as well as to verify the
you know how much these chips actually cost, you can see
that I'm not trying to get rich!
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:
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!
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
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.
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.
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.
What is NOT available:
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
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
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!
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.