CONCEPT - a flexible QRP TXRX

I have been developing a new Concept over the last few months. Based on the Arduino UNO with added shields to implement a QRP TXRX. This system will be presented to Banbury Amateur Radio Society in June with a view to building the system cooperatively. The basic system is



to have stack of boards, all of which are shown here. By using some or all of these many different applications and modes can be implemented.



In addition to the shields a series of program sketches have been written to provide

1 Universal_VFO. Driving the VFO shield to generate a single frequency, which can be used as a source of RF for experiments or for CW. I have in mind to have an alternative receiver which is a simple Direct Conversion circuit to use also the VFO single output.

2 Universal_SDR. Driving the VFO shield to generate the I & Q outputs for the SDR RX and SDR TX shields

3 Universal_QRSS_KB. For driving the PA shield directly (either a low power version ~200mW) or a 5W PA with slow morse signals for QRSS communication. Text to send can be entered on the computer KB. The SDR RX shield can be used for reception.

4 Universal_WSPR. For generating WSPR transmissions, which again can be used with the 5W or low power PA to make a fixed beacon

5 Universal_HELL_KB. Which generates Hellschrieber signals.

6 WSPR_symbol_generator. A useful tool is a sketch which generates the WSPR symbols for transmission based on your call sign, location and transmit power.

Future sketch development will be for the GPS shield or RTC shield to give accurate timing for the transmissions. The signals to and from the Arduino UNO are



And the table of builds for different applications is



Universal_VFO

The first and most important shield is the Universal_VFO.

It has an added 8 pin connector at the left. This carries four RF signals from the DDS, VFO, BFO I & Q. The idea is that the VFO output can directly drive a PA for digital modes, the BFO can be used in superhet designs (think BITX) and the I & Q can be used for SDR TX & RX. The VFO shield is based on the Si5351 module DDS and has in addition a 74AC74 to generate the I & Q signals.

Universal_SDR_RX

The SDR RX sheild is a conventional SDR design somewhat like the famous Softrock series. Its simplicity belies its performance.



The 8 pin connector carries teh RX input from shields above - the PA or the ATU. The system use is



Which shows the RX configuration.