Tuesday, 27 November 2018

BARSSBy - The new project (an SSB Exciter)

We have just finished our BARSicle program "LEARN - CODE - BUILD" during which we learned about Digital Synthesisers, RF Power meters and a Direct Conversion RX, we coded using Arduino and built kits of each.

So what's next? Well after the first part of the program which covered topics that could be enjoyed by Foundation Level Amateurs, we planed to move on to those that are permitted to design and build transmitters (and in the mean time get those M6's up to M0's). The overall objective being to build an SSB exciter and a Power Amplifier, with Audio and RF Vox switching, letting us enjoy FT8 digital QSOs.


First the SSB exciter. For this we need a few building blocks:

MIXERS - for generating DSB signals to pass to a Xtal filter to get SSB, and then again to mix to the output frequency.

MIXER This will use a Mini Circuits SBL-1 mixer, rather than the tedious process of winding our own balun toroids.

XTAL FILTER - a ladder filter, component values yet to be chocen

XTALFILTER SSB generation frequency, for a TX on 40m (7MHz) will be in the range 9-11MHz, depending on Xtal availablility


AMP This will serve as a gain block where needed, the AGC input is used to set the gain.

BAND PASS FILTER - again a common general purpose design we have used before in our DCRX.

BPF The frequencies needed for the SSB carrier and the VFO output mixer will be provided by a Si5351 synthesiser - the one from the BARSicle project we previously built. This will allow us to accurately position the carrier for USB or LSB output, and generate a very accurate transmit frequency.

The AF input will come directly from the headphone output of your PC.

Tuesday, 13 November 2018