MOBO4_3 (BETA) 10_Transmitter PA

Install Bottomside Rs and Cs

Install U14

U14 - the voltage monitor - would normally be associated electronically with the next phase. However, due to the close quarters around this tiny IC, it is installed during this phase. Take great care to avoid solder bridges, since, once this phase is completed, getting access to the IC will be quite difficult.

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	U14	ZXCT1021 low sense voltage monitor	ZXCT1021	SOT-23-5		Take ESD precautions

Install Topside Rs, Cs, and Ferrite

FB2 is an SMT RF choke - no winding required :>}. The parts supplied include an extra BN43-2402 for those who would prefer to wind this choke: 6T #30 for 56uH.

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	FB2	FERRITE CHIP 120 OHM 500MA 0805		SMT		SMT (optional:6T (8") #30 on BN43-2402 for 56uH)
❏	C18	0.1 uF		SMT 0805
❏	C26	0.1 uF	(smt) black stripe	SMT 1206
❏	C48	0.1 uF		SMT 0805		Install C48 before installing C28
❏	C29	0.1 uF	(smt) black stripe	SMT 1206
❏	C44	0.1 uF		SMT 0805
❏	C49	0.1 uF		SMT 0805
❏	R31	750 ohm 1%		SMT 0805 1/8W
❏	R57	499 ohm 1%		SMT 0805 1/8W
❏	R58	499 ohm 1%		SMT 0805 1/8W
❏	R60	33 ohm 1%		SMT 0805 1/8W
❏	R61	1 k ohm 1%		SMT 0805 1/8W
❏	L01	0.47 uH 20%		SMT 1210
❏	C28	220 uF/16Vdc		Electrolytic

Wind and Install Inductors

Wind and install the transformers and chokes (refer to the preceding stage for transformer winding instructions).

Transformers

T2

T2 is wound on the larger BN43-202, using 4 turns of a a bifilar length (16" total) of #26 (or heavier) wire.

Note that T2 is erroneously shown on the PCB as being installed to the bottom (Cu) side; this is an error. T2 must be installed to the top (Cmp) side in the 4 holes provided.

Use a continuity checker to separate out the 2 pairs of windings. One winding goes to the left 2 holes, and the other winding goes to the right 2 holes. This way, the flat surfaces of the BN core faces east-west.

T5

T5 is wound on a BN43-2402 binocular core using 5 turns of a bifilar length of #30 wire (11" total wire length)

One winding goes to the left two holes and one winding goes to the right 2 holes.

The core is oriented so that its two holes are in a vertical (north-south) row.

Choke

FB1 is wound on a BN 43-2402 binocular core with a 4 inch length #26 (or thicker) magnet wire. The number of turns Is 3. The inductance (for turns verification purposes only) should be about 11.7 uH

Install Connectors

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	P20	header, 2-pin		Header		TP1 - Drain Current Test Point 1 Jumper 1-2 for normal Op. Unjumper to measure drain current with external Ammeter
❏	P20_Shunt	shunt, 2-pin		Shunt		Install shunt for normal operation; remove to measure drain current

Install Transistors and Heatsinks

In mounting the large heatsink, use only the nylon spacer for the pcb bottom on the side closer to the USB connector. This is to avoid shorting to the nearby traces. On the other side and for the pcb top, try to replace the nylon spacers with metal spacers. We recommended putting a "star" metal spacer because it conducts RF but has fair thermal isolation. Therefore you will have good RF grounding of the heatsink via 3 of the pcb surfaces.

Make sure that the Heatsink has a good ground to the Mobo PCB through the mounting screws, preferably using a locking washer. If the Heatsink is not grounded, you WILL get VHF oscillation in the PA.

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	Q06	2N3866 NPN Transistor		TO-39
❏	Q04	RD16HHF1 MOSFET RF OUTPUT TRANSISTOR	RD16HHF1	TO-220		Take ESD precautions
❏	Q04_heatsink	TO-220 heatskink		Misc		Heatsink mounting hardware to be supplied by kit buyer. Suggested that external star washers in conjunction with metallic flat washers be used. Heatsink must be at ground potential for best amplifier stability.