Minikits EME157B2, Руководство пользователя, Страница: 2 / 6

the board, only the bottom side. To assist construction
especially winding and mounting the coils, please refer to the
pictures on the Kits webpage.
www.minikits.com.au/eme157.htm
2. The first part of construction is to snap the two circuit
boards apart and cut away the break offs and file the edges
clean. The two board will be soldered together once all the
onboard components have been fitted.
3. Next install the small EME180 PC board and BF998R on
the bottom side of the board as shown in the PCB overlay
diagram. It may be easier to solder the small PC board to
the main EME157 board first before soldering the BF998R.
One lead on the BF998R is fatter and this is the source
connection, ( S ). Next tack solder one lead of the BF998R
to the small board, and check that you have the MesFET the
correct way around before completely soldering into place.
4. Fit the two 1N5711 schottky diodes as shown on the bot-
tom PCB overlay diagram. This a modification to the original
design to help protect the BF998R from damage. The diodes
will have to be fitted like SMD components with one end of
each diodes lead soldered directly to the strip-line on the
board. The other end of each diode can be mounted through
the holes in the PCB like a conventional components, and
flush cut.
5. Next you can start soldering the Resistors, Capacitors, and
remaining Diodes to the board. Make sure that you check the
correct orientation for the Diodes and Electrolytic Capacitors
before soldering in place.
6. Fit the 78L08 Regulator, BC547 Transistor, and 2N7000
FET to the board noting that the polarity of these components
are correct.
7. Next wind coil L2. For ( 144MHz the coil is 9 Turns of
0.9mm TCW around a 5mm drill bit and space the coils length
to 15mm long ) Refer to the picture on the web site listed
in the parts list for the correct way to wind and space L2.
The wire needs to be wound around the drill bit the
correct way so that it will fit the board. Fit the coil to the
PC board and sit the bottom of the coil 2mm above the
board and then solder into place.
8. Next wind coil L1. For ( 144MHz the coil is 16 turns of
0.3mm ECW wound 270 degrees around the brown T37-0
Toroid ). Once again refer to the web site pictures to make
sure you wind it around the core correctly. Cut the ends
of the wire short enough so that they can be connected to
the hole in the board and also to L2. For ( 144MHz L1 is
connected to the 3rd turn from the ground end of L2 ).
9. Next wind the BN29-1050 2 hole Balun core L3. For
( 144MHz wind 2 turns of 0.3mm ECW through the core A to
B then make a 15mm loop and twist the loop together for a
tap, and then wind a further 1.5 turns B to C ). One turn is
when the wire passes through one hole of the 2 hole
Balun, and then around through the second hole.
Passing through one hole is only a half a turn. Refer to
the web site pictures on how this is mounted to the PC board.
It can be a bit tricky and you need to remember which end of
the wire has the 2 turns to the tapping point for connection A
the BF998R Drain output connection.
10. Next wind the coil L4. For ( 144MHz the coil is 20 turns of
0.4mm ECW wound 240 degrees around the yellow T50-6
Toroid ). Once again refer to the webpage picture to make
sure that you wind it around the core correctly. Cut the
ends of the wire long enough so that they can be easily
connected through the holes in the board.
11. It is suggested that the Relays only be mounted after
the two PCB’s are soldered together, and the BNC sock-
ets are fitted in section 12. below.
12. The Preamplifier is designed to use the supplied sub PC
board to mount two BNC bulkhead connectors. This makes it
easy to use in conjunction with the optional GME mast head
amplifier enclosure. Simply tack solder the sub board to the
edge of the main board, and check the alignment, and make
sure that it fits into the masthead enclosure correctly. Don’t
fully solder until you have checked that the BNC
connectors can be fitted and the nuts done up without
fouling on the main board. Recheck the whole Preamp
assembly in the box before soldering the boards fully
together on both sides of the main board.
13. Fit the BNC sockets to the sub PCB, and do them up
tightly to avoid them loosening over time. Solder 0.7mm TCW
from the board connections to the sockets. Other connectors
should not be used as the diameter of the connectors may not
fit the GME masthead enclosure. If TNC connectors are avail-
able then these may be able to be used if they don’t foul on
the enclosure.
14. Cables greater than 6.5mm diameter will not fit through
the masthead enclosure, so cables like LMR240 are highly
recommended for low loss short runs. It is suggested that the
pre-amplifier be mounted close to the antenna feed point, and
a short length of LMR240 type cable be used to connect to the
antenna. On the output of the pre-amplifier a length of
LMR240UF ( ultra flex ) can be used to route around antenna
rotators to connect to the low loss feed line to the Radio room.
15. Mount the two Relays to the board. Make sure that you
flow the solder well as the connections need to be able to
handle high RF current in Transmit mode.
Copyright © Mini-Kits www.minikits.com.au Revised 29/12/2014
2M VHF PRE-AMPLIFIER EME157B2
Rev4