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 :
10 January 2000 :
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 :
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 :
6 February 2000 :
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 :
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 :
I have added 4 more photographs, showing the PC boards after installation of all the parts, but before final assembly.
4 April 2000 :
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 :
8 May 2000 :
9 May 2000 :
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 :
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 :
21May 2000 :
24 May 2000 :
28 May 2000 :
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 :
4 June 2000 :
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 :
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 :
DIGITAL READOUT : CIRCUIT page :
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.
SERIAL RS232 : DISPLAY SOFTWARE page :
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 )
SERIAL RS232 : DRAWINGS page :
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 :
ANTI-JITTER SCHEMATIC ( in the CIRCUIT page )
For the RS232 OPTION :
INTRO...CHIP...PROGRAM...SOURCE ( adjusted the columns )...DISPLAY _SOFTWARE ( changed the image for the display screen )...DRAWINGS/SOLDER SIDE...DRAWINGS/COMPONENT SIDE... DRAWINGS/PARTS_LAYOUT...DRAWINGS/SCHEMATIC.
13 August 2000 :
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 :
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 :
24 October 2000 :
26 October 2000 :
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 :
25 November 2000 :
2 March 2001 :
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 :
16 June 2001 :
23 August 2001 :
25 October 2001 :
2 November 2001 :
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 :
15 November 2001 :
30 December 2001 :
24 January 2002 :
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 :
12 May 2002 :
22 May 2002 :
12 September 2002 :
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 :
12 October 2002 :
15 February 2003 :
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 :
6 May 2004 :
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 :