DFD2 instructions. 

BEFORE BEGINNING CONSTRUCTION

There a 3 general steps to complete assembly and packaging of  the DFD-2.

INSTALLATION NOTES:

The final installation is limited only by your imagination and the physical space available to you.  Model 2 of the DFD has inputs for 3 signals, which are typically RCA  or BNC type chassis mount connectors.  You may also wish to have an on/off  switch, power selection (AC or battery),  or other optional controls.  You may also need to provide lights for display edge lighting or power to the  optional back-lit display module.  Knowing these things before you begin PCB assembly will allow you to install the correct wires and cables (coax) during board assembly.

Attach the power supply, or battery leads, to the  marked pads on the back of  the board near the bottom.  Be sure to observe polarity with the negative lead to the grounded pad.

Attach each of the signal cables from the rear of the board at the indicated pair of pads.  Note that the pad connected to the capacitor is the center conductor and the other pad (connected to the diodes)  terminates the shield of the cable.  You may use low capacity  RF coaxial cable (RG174). three wire audio/video cables work well.  Use the video cable for the HFO signal.
 a.  The top pair of pads is the BFO signal input.
 b.  The center pair of pads is the VFO signal.
c. The bottom pair of pads is the HFO signal.

Carefully inspect all of your solder connections, and the polarity of the diodes, voltage regulator,  the electrolytic capacitor, and the IC’s.

Adjust the contrast control fully counter-clockwise. Apply power from 8 to 18VDC. You should see some frequency displayed. Adjust the contrast control for the desired effect. Adjust the coarse and fine trim-pots until the IF frequency of your unit is displayed. (Custom micro-controllers have this value pre-stored and it should be displayed. It is best to remove the 4046 chips during setting of the offset to prevent noise from triggering the inputs.

(General purpose DFD2 only)
Install the zero ohm jumpers on the four post header to determine the +/- of each frequency input.
Top Jumper off is plus for RF = HFO + VFO +/- BFO(IF),
jumper on is minus for RF = HFO - VFO +/- BFO(IF).
Bottom jumper off is plus for RF = HFO +/- VFO + BFO (IF),
jumper on is minus for RF = HFO +/- VFO - BFO (IF) .
If you can’t figure this out, just try all four combinations and see which one gives the right answer.

(Custom DFD2s)
The top zero ohm jumper selects 100Hz resolution (jumper off) or 10Hz resolution (jumper on)
The bottom zero ohm jumper selects display format (where USB is used as an example of the operating mode display):
10 Hz resolution: 12.345.67MHz USB (jumper off) or 12.345.670 USB (jumper on)
100Hz resolution: 12.345.6 MHz USB (jumper off) or 12.345.600 USB (jumper on)

Using the LED back-lit display
The back-lit module has a block of LEDs behind the LCD display. It is powered from pins 15 and 16 with pin 15 being plus and pin 16 being minus (usually ground). The voltage drop across the LEDs is 4VDC. The current can range from 20ma. To 150ma. The dropping resistor required is R = (V-4)/I where I is the desired current and V is the supply voltage.

One method that works well is to power it from the 78L05 regulator on DFD2 as follows:
On top of the display module, solder an insulated jumper wire from pin 1 (ground) to pin 16. Solder a 33ohm 1/8watt resistor from pin 2 (+5VDC) to pin 15. This supplies 30ma which is about a bright as a car radio dial at night.


YAESU FT-101

CONNECTING TO THE FT-101 TRANSCEIVER

Cabling options:

1)  You may use the remote VFO plug (octal) if:
a.  You are sure that you, or anyone else that you may sell the rig to in the future, will never want to install a Yaesu remote VFO;
b.  You have a spare octal, male plug;
c.  You are willing to work in a very restricted space.

2)  You may bring cables out of the rear of the rig and terminate them with RCA or BNC connectors at the Digital Frequency Display unit if:
a.  You are not concerned with affecting the resale value of the FT-101 by drilling holes in the rear panel;
b.  You want to avoid soldering to an octal plug in a very congested location.

3)  You may install RCA or BNC chassis mount jacks on the rear panel if:
a.  You want the modification to appear as inconspicuous as possible;
b.  You don’t want cables that cannot be disconnected at the rear panel;
c.  You are willing to very accurately measure and drill mounting holes in a very small space.

Yaesu FT-101 signals

The BFO signal (3.1793 MHz) is approximately a 3 volt (peak-to-peak) signal that may be tapped in either of two different places.  It appears on pin 6 of board 1184A and is carried by a short piece of coaxial cable to pin 5 of board 1183A.  Each board has a convenient grounded pin for shield connection, but board 1183A is easier to reach with a small soldering iron.

After routing the new cable (or mini-coax, which ever you have chosen) from the rear panel to the area of  the board chosen,  solder a .01 disk ceramic capacitor to the center conductor of the cable.  Then solder the free lead of the capacitor to the chosen pin of the board edge connector and the shield to the nearest grounded pin on the edge connector.

The Local Oscillator signal (approximately 6MHz above the displayed signal, or 8 to 36 MHz) is approximately a 3 volt (peak-to-peak) signal that is available at the test point near the top edge of board 1181A.

You have 2 cabling options here.  The first option is to route the cable from the rear panel toward the front of the transceiver, and the openings around the tuning dial.  Use these openings to pass the cable to the top of the chassis.  While viewing the FT-101 from the normal operating position in front of the rig, route this cable up over the tuning shaft and to the right of the chassis.  Solder a .01 disk ceramic capacitor to the center conductor and a small ground lug to the shield.  Solder the free lead of the capacitor to the test point at the top of board 1181A,  and attach the ground lug under the adjacent control’s mounting nut and lock-washer.

CAUTION. This method of installation means that you must disconnect the ground lug in order to remove the board from its edge connector.

AN ALTERNATIVE installation method is to install the blocking capacitor (.01 disk ceramic) on the board between the test point and unused pin 15.  This will allow easy removal of  board 1181A.  However,  it requires soldering the coax to the edge connector for board 1181A in a very congested area.  In this alternative installation the cable stays on the underside of the chassis and is soldered to pin 15, with the shield is soldered to pin 18 of the edge connector for board 1181A.

The VFO signal (approximately 9 MHz) is about a 1 volt (peak-to-peak) signal available at pin 11 of board 1180A.  After routing the cable from the rear of the chassis, solder a .01 disk ceramic capacitor to the center conductor.  Solder the free capacitor lead to pin 11 and the shield to pin 10 of board 1180A.

(The VFO signal also appears on the remote VFO adapter (octal) plug.  In the beta unit this signal appeared to be a little dirty causing erratic operation until the unit had warmed up for awhile. This may be peculiar to that one unit.)


DFD2 assembly instructions.

DFD2a.jpg (13272 bytes) Begin by placing solder globs on the four rectangular

pads for the surface mount TCXO.

DFD2b.jpg (9629 bytes)
Carefully Position the TCXO with pin 1 as shown and
remelt the solder globs while pushing down on
that side of the device until all four pads of
the TCXO are soldered.  You can check
by looking at the edge view to verify that
solder has flowed onto the TCXO terminals. 
If later the unit shows only 8 black squares
on the display it may be because one or
more of these terminals
did not properly reflow solder.
DFD2c.jpg (14751 bytes) Next mount the IC sockets and display header.
DFD2d.jpg (19789 bytes)
Next install and solder all resistors and the six
back to back diodes.
DFD2e.jpg (18539 bytes)
Then install and solder 9 each .1 uF capacitors
DFD2f.jpg (12194 bytes)
Next install the 78L05 voltage regulator, the 10uF
electrolytic and, if a general purpose programmable DFD2,
the two 15 turn trimpots.  These are not used with
custom chips for Collins, Kenwood etc.
 
+ Terminal of 10uF electrolytic in hole closest to edge of
PCB.  Flat side of 78L05 toward IC sockets.
DFD2i.jpg (12902 bytes)
On the back side of the PCB install and solder the
10K contrast control (adjust it fully CCW)
and the 25K calibration control.
Later when assembly is complete calibration
consists of connecting the unit to a known
accurate frequency, or by zero beating the TCXO
against 20MHz WWV, and  adjusting this 25 turn pot.
DFD2j.jpg (17707 bytes)
Next, Install the ICs. If this is a general purpose
DFD2 then leave the 74HC4046 chips off until you have
set the IF offset.  This will insure that the input
frequencies are all zero.
 

DFD2l.jpg (8065 bytes)

Mount the 14 pin female header on the display
module soldering only one pin. 
Then verify the connector is at a right angle to the
module, remelting the soldered pin and adjusting
the connector if necessary. 
Then solder the remaining pins.
Plug the module into the DFD2 PCB.
At this point you can plug the counter board into
the module and power them with a 9 volt battery.
You should see something displayed. 
What you see at this point is not important as some
inputs are still floating until final assembly in your
enclosure.If this is a general purpose DFD2 then set
the IF offset by adjusting the 15 turn trimpots.  Then
install the 74HC4046 chips.

wpe1.jpg (18051 bytes)

Parts List (appearance of parts may vary depending on what I have in stock)

1     PCB
1     18 pin socket
4     16 pin sockets
1     male 14 pin display header
1     female 14 pin display socket.
6     1N4148 diodes
9     .1uF capacitors (blue)
1     100 ohm resistor
2     1K ohm resistors
1     10K contrast control (3/4 turn black and yellow)
2    10K 15 turn trimpots (general purpose DFD2 only)
1    25 Turn trimpot (value may vary as I have in stock)
1     20MHz TCXO module (silver surface mount)
1    PIC16C71 programmed for application.
1    74HC153 data selector
3     74HC4046 input amplifiers.
1    16X1 LCD display module (may be backlit if ordered as option.)
1    78L05 voltage regulator
Setting OFFSET (general purpose DFD2 only)
Top trimpot is COARSE, bottom is FINE.  Set offset by first turning CCW until reading of zero is obtained.
Adjust COARSE CW until frequency just less than desired offset is displayed. 
Then adjust FINE CW until desired offset is obtained.
 
CALIBRATION
  • There are many ways to calibrate a frequency counter depending on available test equipment.
  • The simplest is to zero beat a signal generator agains WWV (receiver bfo off) while measuring the generators frequency with the counter.
    • Adjust the 25 turn trimpot on the back of the PCB to obtain the WWV frequency (20 MHz) on the counters display.
    • Or listen to TCXO on receiver while zero beating it to WWV on 20MHz.
  • Any other KNOWN frequency can also be used.
Installation
It is possible to overdrive the inputs causing erratic frequencies to be displayed.   A 10K trimpot can be used to set the levels going into the DFD2.
the levels should be set only slightly greater than required for a stable display.   Set the BFO input first, then the VFO and finally the HFO (usually on 10mtr band).
pwr conditioning.jpg (37132 bytes)
This is the power conditioning module supplied as part of the plug-n-play fully assembled digital dials.
Something similar is recommended for DFD2 applications to provide level controls.
The 7805 part is to power a backlit display option.

Dfd2schr.jpg (50600 bytes)