Forty9er QRP CW TRX

Forty9er QRP TRX

I had noticed cheap kits from china for the Forty9er. A project originally designed by the NorCal QRP club. The Chinese kits cost £10 with the PCB and all the parts. Which makes a nice little project. They are advertised as being 3 Watt output. The reality is just over 3 watts.

The kit had good instructions and included a circuit diagram. A resistor and capacitor was missing but there were extras for others. I have a draw with bits and pieces in. So the missing parts was not a big issue. This kit does require the builder to wind a couple of inductors. Its not difficult and instructions are included.

The wave output looks clean and is stable. Its crystal controlled. So this is expected.

The Frequency plot of the output looks good. No meaningful harmonics can be seen.

A lot of people have said these kits dont reach the advertised 3 watts. The above image shows mine being driven into a dummy load. It is putting out 4 watts.

I decided to build a battery pack to power the forty9er. Which contains 3 parallel 18650 battery holders. All connected to an 18650 charger. This increases the current capacity and puts out just under 12 Volts.  The charger will charge the Cells when power is applied. When power is drawn it will supply power. Its very light weight and small.

Centre Plate and spreaders

Below is a picture of the centre plate and four telescopic fiberglass spreaders.


The clamps that hold them in place are for car exhausts. They come with the U shaped metal supports. reducing crushing of the fiberglass poles. The poles are 4 meters long when extended. So it will support a 20 meter antenna.

Portable Moxon / Delta

I decided to build a portable and light frame for a HF Moxon or Delta Loop Antenna.

HF Moxon / Delta plate

HF Moxon / Delta plate

Above you can see the centre plate. It is 1 CM thick Perspex. Its dimensions are the same as a4 paper. They are sold on ebay for a few pound. very cheap, strong and light. perfect for portable use.

There are holes drilled for four spreaders, these are to support the moxon.

There are additional holes drilled that allow me to remove two spreaders and fix one perpendicular to the plate. This creates a very large triangle to support a delta loop.





Nearly finished

Here we have the back of the case, showing the data and USB leads.


Left Is the delay circuit and opto-isolated PTT switch, I have also added a DC blocking capacitor, which does not appear in the circuit diagram. This is to stop the PTT line voltage triggering the VOX.

A Case and input !

The case is getting there, a switch to inhibit the PTT, Green LED to show power for the USB and a red LED to show that the interface is in PTT mode.


Left is pre-sets to control the volume in and out. It also has a common mode choke to protect the USB, which is a new addition to the circuit. Centre is the Audio isolation and VOX. Right is the start of a delay circuit.