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(5) Temporarily mount the RF relay circuit board onto the inside of the top cover,
making sure the center pin of each SO-239 jack extends into its mating hole on the circuit
board, and that the body of J501 fits through the rectangular cutout on the cover. Because
of variations in manufacturing tolerances, you may need to file slightly the rectangular
cutout for J501 to make sure it fits smoothly into the enclosure lid. Loosely secure the
circuit board to the four corner standoffs with 4-40 x 3/16” screws in order to verify that
the holes line up. Once you’re sure everything fits together properly, solder the pins on
J501.
Do not
solder the pins yet on the coax jacks. Now unscrew the four 4-40 x 3/16”
screws that you just installed, and remove the circuit board from the enclosure.
(6) In the following steps, all components mount on the top of the circuit board. Install a
0.01 µF/50V (marked 103) epoxy coated ceramic capacitor at C501-C507.
(7) Install a 0.1 µF/50V (marked 104) epoxy coated ceramic capacitor at C508.
(8) Install 1N914A diodes at D501-D507, taking care to observe the diode polarity. The
banded end of the diodes is indicated on the silkscreened legend.
(9) Install RF power relays K501– K510. Install these one at a time and make sure the
body of each relay is flush against the circuit board before you solder the pins.
(10)
OPTIONAL STEP. The printed circuit board has provisions for sampling the RF
output from your transceivers and linear amplifiers. Most builders will probably not
need this feature and can omit this step. Note that implementing the RF sampling
feature will require drilling or punching two holes in the RF enclosure in order to
mount two BNC coax jacks. (If desired, users can substitute two RCA phono jacks).
Necessary parts (to be supplied by builder):
BNC Chassis Jacks, qty 2
Capacitor, 15 pF/500V (dipped silver mica), qty 1
Capacitor, 330 pF/ 500V (dipped silver mica), qty 2
Hookup wire or bare tinned wire: 6 in. (approx)
(a) Install the following capacitors:
C509
15 pF/500V, qty 1
C510, C511 330 pF/ 500V, qty 2
(b) Note that the circuit diagram shows a high voltage capacitor C
*
which is part of the capacitive voltage divider that samples the RF
from the selected amplifier. This capacitor is built into the circuit
board copper pattern and has a value of 2.8 pF. Physically, this
capacitor consists of two copper pads, each having a capacitance of
1.4 pF and connected in parallel by a copper trace. If in very high
power applications it is observed that the sampled voltage is too
