BEFORE BEGINNING CONSTRUCTION
There a 3 general steps to complete assembly and packaging of the DFD-2.
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 ICs.
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 cant figure this out, just try all four combinations and see which one gives the right answer.
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.
CONNECTING TO THE FT-101 TRANSCEIVER
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 dont 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 controls 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.
|Begin by placing solder globs on the four rectangular
pads for the surface mount TCXO.
|Next mount the IC sockets and display header.|
Parts List (appearance of parts may vary depending on what I have in stock)
|Setting OFFSET (general purpose DFD2 only)