DDS VFO CW Exciter

Here is the next part of my home brew CW transmitter. An Arduino and AD9850 are providing the DDS VFO signal. Q1 is a buffer to isolate the AD9850. I am not sure that it is needed, but its there to stop the gain stage from loading it up. Q3 is an amplifier that takes the 400mV P-P DDS signal and amplifies it to 8/9V P-P or there abouts into a 50ohm load. Thats about 200mW, enough drive to supply something like the QRP Labs 10w Linear. My plan is to design an amp to follow on from this that will provide 30 to 50w. More on that to come. Q2 is a PNP switch, pulling the base to ground turns lets power flow to Q3 thus keying the transmitter on and off. Simple but works.

Here is the schematic.

The PCB as laid out in Ecad.

Here is the board as built, if you are not colour blind and can read the colours on R5 you will notice i stuffed up here HAHAHA. Also Q1 silk screen is backwards.

Signal output into 50 ohm load at J2. This jumps up to about 10V P-P into the QRP Labs Linear amp. Not sure why yet.

Schematic PDF: CW-Buffer-Amp

Board Gerber Files: DDS-CW-Buffer-Amp

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