Saturday, October 31, 2009
Homebrew 5 W linear amplifier for the Softrock SDR
Enough of this QRPp! Now that we know the radio works for sure, lets add some power for those QSB moments.
The 5W amp is in progress and being tested on 40/20m. First tests into dummy load show about 3- 5W out with 1W of drive. Using NB6M's "miniboots" design, here goes, and "yes I know this really needs to go on copper" with proper shielding.
Notice the LPF is already inline, and output reads close to 5W / CW (with 1W drive from the Softrock SDR)
Parts for this 5W amplifier will run you about $8-$10 depending on where you source your components.
Adding several LPF's for each band combination will require mode capacitors and toroid inductors.
The most expensive part (in my case) was the relay (DPDT tx relay switch) at about $2.50. The amplifier design is based on the very popular and very affordable IFR510 MOSFET. Add your choice of LPF for the output stage and make sure to mearure for harmonic suppression.
Be sure to measure for proper harmonic suppression with the LPF inline. A good IMD test can be performed using Rocky's built-in 2-tone generator.
Miniboots reference: http://www.amqrp.org/kits/miniboots/miniboot.htm