SSB exciter project - 1st MIXER

One of the projects I want to get "under my belt" is an SSB exciter. It has always seemed to me to be a black art or magic to generate SSB signals. I mean I know on paper how its done, but to build a system...? That's another matter. Anyway I have started, this is the plan



The first mixer will generate DSB signals at 11MHz, this will be sent to a xtal filter with a bandwidth of 2.5-3kHz, this sill then go to a 2nd mixer with inputs at 4 or 18MHz to be mixed down to 7MHz LSB or USB, finally there will an output amp to give at least +10dBm output.

The mixers will be the commercial SBL-1 double balanced mixers which have an excellent performance.

1ST MIXER

Here's my schematic for the 1st mixer



The RF input is at a relatively high level to switch the internal mixer diodes, it comes straight from the "0" output of a Si5351 frequency synthesiser. The audio input is via a 51R "load" resistor, it currently comes from my Audio Synthesiser (see previous posting) which has an LM386 output amplifier. The level is 200-300mVrms. The RF output is across the 20uH choke (10t/FT37-43) loaded by a 150R resistor - which will be the input impedance for the xtal filter.

Here's the breadboard



OUTPUT

These are two shots of the output. I used a simple Elektor SDR receiver, via a 40dB attenuator and into my MacBook running the Cubic SDR program.





I am running it at 11MHz. As you can see the output is the two sidebands 1kHz away from the centre frequency.