Page 9 of 16 ft8_II_assy_smd_diode_072020.pdf
20M
[ ] L1 – 0.68 uH – Blue/Gray/Silver/Gold or Blue/Gray/Silver/Silver
[ ] C26 – 100pfd – marked 101
[ ] C27 – 22 pfd – marked 22 or 220
[ ] C28 – 22 pfd – marked 22 or 220
[ ] C29 – 150 pfd – marked 151
[ ] C30 – 330 pfd – marked 331
[ ] C31 – 33 pfd – marked 33 or 330 (don't mix up the 331 and 33 values!)
[ ] C32 – 150 pfd – marked 151
[ ] L2 – 17 turns on T37-2 YELLOW core – make sure turns are snug to the core and more or less
evenly spaced around the core. Loose winding does not work well.
[ ] L3 – 15 turns on T37-2 YELLOW core
[ ] X1 – 14.074 MHz crystal. If you are
not
using the optional VFO, you need to jumper the
“CRYSTAL ENABLE” pads with a clipped piece of a resistor lead. Otherwise
omit
the jumper for
VFO operation.
Winding the toroids:
[ ] Wind each of the L2 and L3 toroids using 12” of the supplied magnet wire. Use the tables
above and wind them in the direction shown in the graphic below and they will align with the pcb
holes. When you are certain of the turn count, trim the leads ~3/8” and
tin them
before installing
the toroids flat on the top of the board, centered on the silkscreen outline. Secure each toroid to
the pcb using two of the supplied plastic zip ties, as shown below.
Be sure to tin the wire ends before installing. The transceiver will not work if you do not
tin the magnet wire. This is a leading cause of failure. Be sure not to pull the wire thru
the hole past where you have it tinned.
Test and set up:
[ ] Apply 12V to 13.8V to the board.
[ ] Verify 9V (+/- 0.25) between pins 8 and 4 of U2. (Optional)
[ ] Remove power
[ ] Install LM358 IC into U2 socket.
The following bias adjustment is made without a band module or optional vfo attached.
[ ] Connect your DMM in series with the positive power supply lead and set the meter to measure
current. To be safe, use the 10A scale.
[ ] Set the V1 (BIAS) trimmer to fully
Clockwise
.
[ ] Apply power to the board again.
[ ] Insert the shorting jumper
(Berg connector)
into the [TEST] SIP pins. This will force the board
into transmit mode. The RED LED should now be on.
[ ] Note the amount of current the board is drawing.
[ ] Slowly adjust the V1 trimmer
Counterclockwise
while watching the current meter. Adjust
until the current
GOES UP
by about 15 ma. This is just enough to put the PA into linear mode.
[ ] Remove power
[ ] Remove the shorting plug from the [TEST] pins.