This page contains archive information about changes / updates to this website, and any mistakes that have been detected / corrected.

If you want e-mail notification of any changes / updates, send me an e-mail with the phrase "DOPPLER WEBSITE UPDATE" in the subject field, and I will add you to the list.

20 December 1999 :

First release of website information... parts list full of errors, but otherwise OK.

10 January 2000 :

(1) Changes to component values for R1, R2, R3, R4, R11, C1 through C9, C14 and C15

R1, R2 and R11 previously = 10K, now = 100K

R3 and R4 previously = 100K, now = 1.0 Meg

C1 through C9, C14 and C15 previously = 1.0 uF, now = 0.1 uF

INFO : it was difficult to find 1.0 uF capacitors that were physically small enough to fit on the main PC board. They were available from Newark, but they cost over $5 each. Also available from Jameco, but I wanted at least two ( inexpensive ) sources for each part. Therefore, all the 1.0 uF capacitors were replaced with 0.1 uF capacitors. Changes to several resistor values were necessary to maintain the same frequency response / sensitivity with the new capacitor values. The original values will work fine... this change simply makes it easier / cheaper to find parts.

(2) Parts list was updated with correct circuit designations, and p/n's from three different sources.

(3) Schematic diagrams were also updated with new component values.

(4) I also added this page, ( the one you are reading now ) and a page containing some photographs of the prototype D/F unit, titled "PHOTOS".

(5) Results from a second field test were added to the page titled "FIELD TESTS".

(6) The "home page" was re-organized... the sequential order of the links was re-arranged. "Next Page" links ( at the bottom of individual pages ) were also re-organized, where necessary.

(7) The "Intro" page had some information added to the text, about availability of "Heathkit style" kits, and about ( commercial ) rental units.

18 January 2000 :

While assembling the 3rd, 4th and 5th units using information from this website, errors were discovered in the parts list and in the antenna board pictorial.

The parts list showed two different values for resistors R1, R2, and R11... they were listed both as 10K and as 100K resistors... 100K is correct. This mistake was generated by the 10 January update. The parts list has now been corrected.

The orientation of diode D20 on the antenna board was wrong... the cathode end of the diode should face towards the board edge. The antenna board pictorial has now been corrected.

23 January 2000 :

A digital readout option was added to the site. Several new pages were added, describing a 3 - digit numeric readout for the Doppler. Home page was reorganized, with new links provided for the readout option.

6 February 2000 :

A new page was added, dealing with the filter circuits in greater detail, and providing the design equations for the LPF. It also offers an explanation why a single resonant BPF was not employed in this D/F design.

The "cool links" page was removed, since no-one was using it.

All the images ( except photos ) were converted to black and white to accelerate download speeds. Many were also "re-sized" slightly, to eliminate the horizontal scroll bar on the browser window.

Several pages were re-organized, and the "NEXT PAGE" links were updated to reflect the new page sequence. OPTIONS and CONTACT/ORDER pages were combined together into a single page, MORE PRINCIPLES was re-named and broken up into two separate pages, to allow new/extra information about integration, including some speculation about possible benefits of using an "active integration" SCF.

4 March 2000 :

The parts list for the digital readout was completed, including alternative p/n's for LED digits with different colors.

In the "DOPPLER THEORY" section, one sentence in the page titled "PULSES" was changed (near the bottom of the page) because it was somewhat confusing... no effect on the actual D/F design.

I added my call sign and e-mail address at the top of the front page, as a crude attempt to give this D/F some kind of unique "name".

10 March 2000 :

An error was discovered on the artwork for the display board... the ground connection for the 74138 chip was corrected... ( sorry... use a wire jumper if you have already made these boards with the old artwork )

I have added 4 more photographs, showing the PC boards after installation of all the parts, but before final assembly.

4 April 2000 :

A link to a German language website was added... contains photos of a unit completely constructed ( including PC board fab ) by Raimund Jakob, DG9MAQ.... very nice photos, very well done... field testing in progress, at this time.

A portable TDOA Doppler was also added to the site... parts list not yet completed, and the unit has not been assembled or tested, but I expect no serious problems. Prototype will probably be finished in 4 - 8 weeks. Aside from the parts list, all the other web pages for this unit are ( essentially ) completed. Photos and field test results will follow completion of the prototype.

5 May 2000 :

Minor "cosmetic" changes... after upgrading my browser to the latest version, I found several "anomalies" in the displays on various pages, most notably the lack of proper column alignment in the parts lists, and some "accidental" boldface type on a few pages. Nothing "technical" was changed on the website.

8 May 2000 :

A mistake was found on the INSTALLATION page for the DIGITAL READOUT option... Capacitor C20 was identified as the capacitor to change from 0.1 uF to 0.0022 uF. In fact, capacitor C19 is the capacitor to change to 0.0022 uF. The page has now been corrected. ( Sorry... )

9 May 2000 :

The parts list for the portable Doppler unit was finished with vendor p/n's.

A hobbyist pointed out that the electrolytic capacitors on the input / outputs of the voltage regulator chips on the main and antenna PC boards was listed in the parts list as 22 uF, but the schematic diagram shows 1.0 uF caps. In fact, any value 1.0 uF or above is OK. I updated the schematic to prevent confusion.

10 MAY 2000 :

A serial RS232 interface was added to the website. It employs a PIC 16F84 microcomputer which was "added on" to the digital readout option boards.

Links were re-arranged, and ( in many cases ) RE-NAMED, so if you bookmarked a page on a previous visit and can't find it now, blame me.... The pages were re-named so I could interpet the website traffic reports more easily... the new names are more descriptive.

17 May 2000 :

Some items in the TDOA parts list did not have vendor p/n's. I thought it was completed on 9 May, but apparently I was mistaken. The list is now completed, except for the 10 ohm 1/2 watt resistor, which serves as the dummy load for speaker audio... too bad.

21May 2000 :

Minor changes in various non-technical pages, to increase clarity... OPTIONS page was edited, and some of the information was moved to the INTRO page, where it seemed more appropriate. Information about possible "kits" was removed, as no-one has enquired about them. A paragraph was added to the end of DIGIT_INSTALL, dealing with a potential problem that can occur when the digital readout is employed with other types of Doppler units.

24 May 2000 :

While assembling the first TDOA unit, it was discovered that the PC artwork for the DETECTOR board had a minor problem... the pads for the two trimpots ( VR1 and VR2 ) were "mirror - imaged" on the artwork... as a result, the trimpots had to be installed on the solder side of the PC board, instead of the component side. The PC artwork has now been corrected.

28 May 2000 :

Several flaws with the TDOA unit have been discovered, while constructing the first unit.... more than I would have expected, and enough to warrant rendering an apology to anyone who has preceeded me in building it.... sorry.

The "D" input of the D-type flip-flop ( U5, pin 5 ) was originally connected to U5 pin 1, which will prevent the flip-flop from toggling... it should actually be tied to U5, pin 2. This error existed on the schematic AND the PC artwork, which have now ( both ) been corrected.

One side of resistor R20 was not connected to ground on the PC artwork, but the schematic is/was correct.

The mounting holes for the PC board have been moved downward by 0.1 inch to allow the board to fit in the SerPac enclosure... otherwise, U5 will interfere with the 9 volt battery compartment.

Resistors R11 and R13 were not listed in the parts list.

Resistors R9 and R10 were reduced to 2.2K to increase the maximum size of the deadband.

Resistors R12 and R14 were reduced to 2.2K to increase the "farside" earpiece attenuation to 20 db.

The website has been updated with all these corrections. Furthermore, results of a preliminary field test were added to the INTRO page. The "primer" for EMI/RFI shielding "tricks" was removed from the page titled DETAILS. Additional sections were also added to DETAILS, describing some "bench test" methods, and some notes on headset construction. Basically, every page dealing with the TDOA unit has been changed, to some degree.

3 June 2000 :

Preliminary bench checks of the DIGITAL READOUT and the SERIAL RS232 INTERFACE were completed. A temporary webpage called "TESTS" was added in the section for the digital readout, describing the problems found, and their corrections.

4 June 2000 :

The corrections for the DIGITAL READOUT have been permanently incorporated into the website. The "temporary" TEST webpage was removed and replaced with a final version. Other changes were made to almost every webpage in the DIGITAL READOUT section, so take a second look at ALL of them. For the record, these are the flaws that were discovered in the first DIGITAL READOUT unit :

R60 was added to bias U17's input at 2.5 volts. ( COUNTER board ) There was not enough input signal to drive the chip without it. Schematics, PC artwork, and parts lists have been updated to include R60.

C39 ( at U17 input ) was reduced from 0.1 uF to 1000 pF, to generate a very narrow RESET pulse for the counter chips. Schematics and parts list were updated with this change.

U27 ( voltage regulator chip ) needs a heat sink. Comment were added in the section titled INSTALL.

The "calculated" value of 2200 pF for C19 proved to be incorrect. This cap is located in the 555 oscillator, on the MAIN board, and must be changed when the digital readout is installed, to increase the clock frequency to ( approx. ) 360 KHz. I used a 1000 pF cap, but 800 pF would be better. Comments about this "change of a change" were added to the section titled INSTALL.

An "anti - jitter" circuit was added to the design, to reduce jitter in the LSD readout. The circuit was installed on the COUNTER board, and consists of U29, R61, R62, C41, C42, and D34. Schematics, parts list, and PC artwork for the COUNTER board were all updated to include this mod, and comments were added in the section titled CIRCUIT, as well as a schematic for the mod.

An "inhibit" mod for the zero-crossing detector was described, ( with schematic ) but not incorporated into the design. The description and schematic was included in the section titled TESTS. The mod overcomes some timing instability problems with the 555 CALIB 1-shot that manifest whenever it is adjusted for a pulse duration of 360 degrees or greater. The mod involved two resistors and one diode, installed on the MAIN board. It is not essential, but reccomended, because it allows the FULL RANGE of the CALIB trimpot to be employed... it was previously limited to about 330 degrees. With this mod installed, the CALIB range well exceeds 360 degrees, with no ill effects.

Some remarks were added to the TESTS webpage regarding temperature stability of the CALIB 1-shot and ( possibly ) the LPF as well... both circuits are a potential source of temperature sensitivity which might ruin the calibration of the digital readout. These problems were not obvious with a "low resolution" ( compass ) display, but became obvious with the digital display.

28 July 2000 :

While testing the first anti-jitter circuit in the digital readout, some schematic flaws were discovered regarding U17 on the DIVIDER board. The section of U17 in the divide by 45 circuit had the wrong pin numbers. ( now corrected )

The anti-jitter circuit itself ( U29 ) suffered "self - oscillation" because the "A" input on pin 1 is ( apparently ) not REALLY "edge triggered", as the spec sheet indicates. If this input is low when the signal at pin 3 returns high, the 1-shot will trigger. because pin 1 is NORMALLY low, this lead to self-oscillation, and random readout values. To fix the problem, I moved the trigger source from U9 pin 6 to U9 pin 5, which is normally high. Schematics have been updated.

I also experienced some intermittant triggering of U29, due to insufficient trigger amplitude applied to U9 pin 5 on the main board. I had previously reduced the value of C18 from 0.1 uF to 0.01 uF, to eliminate a 15 degree "difference" between the numeric value from the RS232 output, and the value displayed on the digital readout. This was due to the fact that the digital readout triggers on the falling edge of the ( U9 - 6 ) pulse, but the RS232 triggers on the rising edge of this pulse. As a result of the reduction of C18, the signal amplitude at U9 - 5 was not sufficient to ensure reliable triggering, due to slow dv/dt of the 555 output pulse... I reduced the value of R19 from 1.0 K to 470 ohms, to increase the amplitude, and restore reliable triggering.

This information ( regarding C18 and R19 ) will eventually be included in the INSTALLATION section of the RS232 portion of the website, since these changes are only required if the user employs both the digital readout and the RS232 output, simeltaneously...

A new section was added to the SERIAL RS232 section of the website, providing an IBM / PC display program, available for download. Written in Microsoft QuickBasic 4.0 and compiled to run alone, source code is available ( free ) from me if an e-mail is sent to me, requesting it.

2 August 2000 :

Minor changes in text and/or content on several webpages, but important changes in the following pages :


The trigger source for the 1-shot was changed on the ANTI-JITTER schematic from U9-6 to U9-5. I thought I had previously done this, but a close look a the entire website revealed this was not true. ( sorry ) See the entry for 28 July for an explanation of this change.


An improved version of the display software was uploaded to the site... minor changes, really... biggest change was the addition of identifiers at the cardinal points of the azimuth scale, "X:EXIT" was changed to "Q:QUIT". A different display method was employed, which reduces "screen flash" considerably, whenever the azimuth scale or cursor is rotated. Default DECAY is now 0.95, ( previous = 0.90 ) default FOCUS is now 0.8. ( previous = 0.5 )


All the PC artwork drawings were updated to include a new resistor, ( R60 ) installed on the COUNTER PC board... see entry for 28 July for an explanation.

Various minor changes in the remaining pages :

For the main DF unit:


For the digital readout :


For the RS232 OPTION :


13 August 2000 :

An electronic compass option was added to the website, containing four new pages that describe the compass. The Home page was updated, and some "NEXT PAGE" links were updated to include the new COMPASS information.

Construction of the RS232 prototype PC board revealed that the trigger source for the "360 rollover" signal produced a pulse that was too narrow for reliable operation of the PIC chip... as a result, the RS232 message sometimes contained bearings numbering 400 and above.. the source for this signal was changed to U6, pin 11, ( "D" bit of the 74LS93 on the MAIN board ) which was available on the RS232 board at the input of C39... the artwork on the website has been updated, ( both sides of the RS232 board had artwork changes ) as well as the schematic for the RS232 interface.

If you have already made some of these boards ( with the old artwork ) simply cut the track running to pin 1 of the PIC chip, and install a wire jumper from PIC pin 1 to the wire pad feeding C39.

18 August 2000 :

A mod was identified for the 555 oscillator on the MAIN board, to achieve a 360 KHz clock frequency, as required by the DIGITAL READOUT and RS232 SERIAL INTERFACE options. The mod is described in the DIGITAL READOUT section of the website, under "INSTALL". Apparently, 300 KHz is the approximate upper limit for the basic 555 oscillator circuit, and it was necessary to add additional feedback to the timing cap to achieve the higher frequency.

The mod involves changing the value of one capacitor ( C19 ) and adding one capacitor and one resistor. The value of the resistor can be adjusted to "fine tune" the frequency... with NO resistor ( = 0 ohms ) the frequency reaches over 800 KHz.

13 October 2000 :

I added a new webpage called "PALM DISPLAY SOFTWARE" which contains downloads for a display program, written to run on PALM PDA devices... small, inexpensive computers. The new webpage is located in the SERIAL RS232 section of the website.

24 October 2000 :

I recieved a compiler software upgrade from NSBasic and used it to re-generate the Palm display program. The 3 download files for the Palm display were ( therefore ) updated today... Users MIGHT see a slight increase in speed, when using real signals from a DF...

26 October 2000 :

Very embarrasing, but not serious... I found a dumb flaw in the PIC code, all three versions. ( DF with compass, DF without compass, compass only ) Seems I was transmitting 9 bits in each ASCII character... 8 data bits and a "no parity" bit... ( should have been 8 bits, total )

For reasons unknown to me, the IBM display program never suffered any adverse reactions to this fact, but the Palm display refused to accept it... took a while to figure out the reason, because I assumed the PIC code was OK, because it was driving the IBM display without any problems...

Anyway, it is now fixed... I have also adjusted the baud rate very slightly, it was about 2 percent higher than 1200 baud... should be less than 1 percent error now.

All 3 source files and all 3 object files for the PIC device have been updated on the website, with these changes. These changes should only impact people who use a Palm display device.

11 November 2000 :

A miniature radome antenna was added to the website. A photo was added to the RS232 INTRO page, and to the COMPASS INTRO page. The HOME page was re-arranged, and the OPTIONS page was changed to clarify prices and options.

25 November 2000 :

Brief field tests were performed on the new mini-antenna at 450 and 800 MHz, with good results... The INTRODUCTION page for the mini-antenna was updated with this information, including a description of the test methods... The antenna had previously been tested ( successfully ) at 150 MHz.

2 March 2001 :

A new version of PIC DF software was added to the compass section of the website... the "MAGDOPP" program automatically adds the compass heading to the DF reading, and ( therefore ) directly reports all DF bearings in magnetic degrees, instead of relative degrees... the message format was restored to the original Agrello DF format, which makes the DF message compatible with other types of display software, ( GPSS, etc. ) as well as APRS...

If the compass suffers a failure ( or is not installed ) error - detection subroutines will detect this fact, and change the compass heading value to 000 degrees. This has the effect of restoring the ( reported ) DF bearings to relative degrees, rather than magnetic degrees.

12 May 2001 :

A single board computer ( SBC ) was added to the website, using the MicroMint 80C52 chip. PC boards designed with ExpressPCB CAD. The SBC has a built - in 8K BASIC - 52 interpeter, 8K of RAM, 8K of EPROM, an RS232 port, and an integral EPROM programmer that can "EPROM save" BASIC programs. The interpeter can "coldboot" directly from the EPROM at "power on", and run the ( EPROM saved ) BASIC program. Also room for an 18 pin PIC chip, for I/O.

16 June 2001 :

I added a download program for the 8052 single board computer, ( SBC ) in the webpage titled "SBC_SOFTWARE". The download program allows an IBM computer to automatically download a text file ( containing a BASIC-52 program ) to the SBC, using a user-defined COM port, baud rate, and download filename.

23 August 2001 :

Minor changes to several web pages, mostly to remove the offer of "undrilled" PC boards, since my source for those boards has failed... Several changes in the INTRO page, to clarify ( I hope ) all the "stuff" on this website.

25 October 2001 :

I added a photograph of the 8052 single board computer ( SBC ) to the SBC_INTRO webpage.

2 November 2001 :

Some flaws were discovered by a website visitor in the schematic diagram for the TDOA DETECTOR unit. The PCB artwork was correct. The schematic has been updated to agree with the PCB artwork.

Pins 8 and 9 of U2C were transposed on the schematic, so were pins 10 and 11 on U2D.

Also on the schematic, the RT and LT identities of the outputs of U2 ( driving U2A and U2B ) were also transposed, and the U5 output driving U2A was shown connected to U5, pin 2. In fact, it was connected to U5 pin 1.

9 November 2001 :

RS232 board schematic : The trigger source for the CALIB 1-shot was changed from U3 pin 3 to U9 pin 6. The PIC software triggers on the positive edge, so taking the trigger from U3 pin 3 will result in an RS232 display which never changes. This problem was discovered when a friend built the DF. The PCB artwork for the RS232 board identifies U9-6 as the trigger source, so it was just a matter of luck that this flaw was discovered. ( sorry )

15 November 2001 :

I added some warnings to the DIGIT INSTALL page, ( in the section for the DIGITAL READOUT option ) regarding problems I have observed with the 555 clock circuit. This circuit is installed on the MAIN board of the original DF unit, but it must be modified to increase its output frequency from 8 KHz to 360 KHz, whenever the digital readout or the RS232 interface options are employed.

30 December 2001 :

I updated some obsolete links to the website of Precision Navigation, which is the company that makes the electronic compass module, used on this website.

24 January 2002 :

Someone reported problems with the SCF on the MAIN board of the BASIC DF unit, causing a "false" DF signal, even when no audio was connected to the DF. Others have ( from time to time ) been confused by the ground connections for the capacitors used in this filter, since there is a ( minor ) disagreement between the schematic and the PC board.

I added a few paragraphs to the page titled "CIRCUIT" in the section for "THE BASIC DF", to explain the ground connections. I also describe a "fix" for the problem of "false" DF signals. The false signal is caused by internal ( capacitive ) leakage in U2, running from the switch control pins ( 9, 10, and 11 ) to the signal pins, where the filter capacitors are connected. It is usually weak enough to be ignored, when a "real" DF signal is applied to the DF input.

My apologies to anyone who has suffered as a result of this "flaw"... it can ( no doubt ) be VERY confusing to anyone who does not have previous experience with circuit or component imperfections.

10 February 2002 :

I discovered a pin that was improperly numbered on the compass picture, in the section titled COMP_CIRCUIT. There were two pins on the compass picture with the same pin number. ( P6 ) The schematic was correct, only the picture was wrong. ( now corrected )

12 May 2002 :

At long last, I completed a Yagi Polar Plot DF and added it to the website...2 new pages describing the instrument were added to the website. A link to these two pages is provided near the top of the HOME page.

22 May 2002 :

For the YagPlot DF : I added a zipped download file for YagPlot and MathLib because some folks were having trouble downloading and running the regular download files. Located in same place as the regular downloads, on the YAGI_INTRO page.

12 September 2002 :

Several changes in the website... all web pages were changed to an ARIEL font, and the HOME page was re-organised, but no links were deleted... just "moved around".

The TDOA will no longer be offered by me... it was never popular, and simply not worth the effort to offer it...

The PNI V2X compass is no longer available, and this fact is noted on several web pages relating to the compass. Refer to the INTRO page for more detailed information about how I am dealing with this "situation"... I still have a few, which I will ONLY sell with a complete DF system, until I can finish making my own compass.

Several new issues regarding the ANTENNA board for the BASIC DF unit...

The PIN diodes for the ANTENNA board which is used in the BASIC DF unit are becoming impossible to obtain... I have noted this fact in several web pages relating to the ANTENNA board... I will try to obtain Motorola MPN3404 PIN diodes as a substitute, for use in assembled / tested ANTENNA boards, but it is best to enquire if you intend to buy this board from me... the MPN3404 diodes are obsolete, and may not be available, even from me, even for my own a&t boards...

Furthermore, the ANTENNA board for the BASIC DF that is displayed on the website is no longer available from me, but I now have an improved ANTENNA board which is the same size, same mounting footprint, and same schematic. It is a "re-designed" version of the original ANTENNA board, which should work much better into the higher VHF regions of the spectrum... I have not had time to really test it, to prove this, but I truly believe it is superior...

The new ANTENNA board is not displayed on the website because I suffered a computer "crash", and wiped out the CAD file for it. Fortunately, I already had the photo artwork delivered to my PCB vendor, so they are still available. Unfortunately, I cannot provide a pictorial diagram, showing the location of the various components. ( lost in the crash )

The schematic is identical to the original ANTENNA board, so anyone "clever" can simply compare the schematic with the ( new ) PC board, and "figure out" where the components go... or they can buy an assembled / tested board from me...

Messy and ugly, but there it is...

7 October 2002 :

A new display board for the Doppler was added to the website. It offers a combined pelorus and numeric readout in a single board, and is driven with ( standard ) RS232 Agrello messages, as well as my own "extended Agrello" message. It can be retrofitted to my own DF ( if the RS232 board is installed ) as well as other DFs that generate Agrello RS232 messages. See the new web page for details, there is a link on the front page of the website.

12 October 2002 :

The SquawkBox T-hunt transmitter was added to the website. This is a miniature, fully synthesized 2-Meter FM transmitter ( 50 milliwatts ) with a voice record / playback chip, and built-in mike with a RECORD button. Built specifically for 2-meter amateur T-hunts. Available only assembled / tested, but all technical information ( except the CAD file for the PC board ) is provided to those who purchase, to allow modifications or changes. Available ONLY to licensed amateur radio operators.

15 February 2003 :

For the digital readout and / or the RS232 options, I added a section on the page titled DIGIT_INSTALL, regarding an alternative to the NE555 oscillator chip. This chip must generate a signal of approx. 360 KHz when used with the digital readout or RS232 option, but the 555 chip does not behave very well above 250 KHz, and usually requires a lot of attention to the individual 555 chip, to make it work properly.

In February 2003, I decided to create a replacement for the 555 chip, using an 8 - pin 12C508 PIC micro to "simulate" a 555 chip. It worked out quite well, so I added it to the website, ( on the DIGIT_INSTALL page ) along with the assembly source code for the chip. For DF units I ship in the future, I will use this type of oscillator, simply to avoid the struggle of making the 555 chip work properly at 360 KHz.

1 August 2003 :

At long last, a completely new Doppler design was completed and posted to this website. Using a single microcomputer chip to achieve almost all functions, it is called PicoDopp... much simpler than the original website Doppler, with RS232 and IrDA outputs. A banner was added to the front page of the website, leading to several new pages describing it, and describing optional accessories. It is "backwards compatible" with earlier antenna boards and the MultiDisplay board. No compass, though.( not yet... December )

6 May 2004 :

The e-mail link to Sr. Ruben Martinez was removed, it appears he has shut down that address... inquiries en espaniol should be directed to me, ( ) I will try to get them translated by friends if mio espaniol es no bueno...

The 80C52 single board computer was moved to the website of Design Consultants, and the web pages ( on this website ) were changed to automatically re-direct web browsers to that website, after a 20 second delay. All the information is still free, and available there... the SBC is not really a radio DF type of project, and I recently assisted with the creation of the Design Consultants website, which is brand new. ( April 2004 ) Moving the SBC project there was intended to generate some traffic on this new website, and promote it's "web visibility" in search engines.

17 February 2005 :

The old DF design ( the one described on this website ) is no longer available for sale, either as assembled / tested boards or as bare boards. Since the introduction of the new PicoDopp DF, ( see it [HERE] ) no-one has enquired about this old design in over a year. Some items are still available on the new website, such as the MultiDisplay and the SquawkBox. The PicoDopp is a better performer, and has more features.