Sunday 1 September 2013

Sudden Transmitter Shield

After the fun and games with my original Arduino Transmitter Shield and experiments with an ugly version of George, g3rjv's "Sudden" transmitter, I've now closed the loop and built the first prototype of a "Sudden Transmitter Shield"...

The shield includes a buffer/amplifier stage on the input, allowing it either to derive RF from the "RF Bus" which is a common feature of all my Arduino devices (driven by the Kanga/m0xpd DDS Shield) or from any other source (such as a mixer for sideband signals). The shield also hosts a power supply to derive 5V for the Arduino from the conventional "radio" 12V power supply. The DDS Shield is pretty power-hungry and when its 5V is derived from the 12V line by a linear regulator, there's quite a lot of power dissipated - so I think it best to have all the "hot" objects (like this regulator and the PA final) on one shield, where they can sit basking at the top of the "stack".

The keying arrangements follow those used in my own "Ugly Weekender-derived" Tx shield, whilst the remainder of the circuit follows George's words and music closely.

Here's the system with the individual functional blocks annotated...

You can see that I've not fully populated the Rx Mute section - 'cos I've no 2N7000's in stock!

Anybody who doesn't know the Sudden can learn all about it (and learn a lot of useful practical tips besides) by downloading the excellent construction manual from the G-QRP site.

On test, my Sudden Transmitter Shield delivered a nice clean signal through a test 40m Low Pass Filter, when driven by a 7 MHz signal from the Kanga/m0xpd DDS Shield running in the Kanga "Enhanced VFO".

It produced "a shade less than 2 Watts", just as George said it should...

We're looking at ways of making this transmitter shield available for purchase as a kit - once that's sorted, I'll post the complete schematic, in true open-source spirit!

 ...-.- de m0xpd

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