For a bit of fun and to get back in to electronics I decided to build a 40 meter receiver.
The pictures below document the progress of the build.
It was good to get back into the hobby again and this simple project was a great re-introduction.
I won’t go into the details of how and why I decided on this particular make and model but to put it simply lots of internet searching and reading of reviews directed me this way.
Below are some pictures of the stages of the build.
All the parts to build the radio.
Labeled each item to make it easier to identify the parts and reduce the chance of putting the wrong component somewhere.
Some components added to the board.
Nearly all the components in their correct places. I was careful to place them in the right place first time. A little extra time here can save a lot of frustration down the road when it comes to testing. ( and can also save you from the embarrassing cloud of smoke 🙂 )
I also put the components in the board so the resistors all read from left to right and top to bottom and capacitors values were readable from the front. For obvious reasons this isn’t possible with polarized components. This doesn’t make any electrical difference but it looks nice and makes it easy to read component values later. I’ve always liked to do things neatly and methodically.
Next is cutting the pot shafts to length so the control knobs fit properly.
Drill the case
Board placed in the case to check the holes line up properly. Looks like I got it right!
Once everything was put in place and I wired up the connectors it was time to do another quick check then power it up.
Everything went well after powering it up, and I used the local oscillator from another radio close by to set the top and bottom of the band. I also tuned it by peaking the signal from the same source. Later I’ll do more fine adjustments with a signal generator and frequency counter to calibrate the tuning control and peak the signal.
In operation with my 40 meter half wave dipole connected the receiver seems to work reasonably well. There’s no sign of overloading or annoying harmonic interference like I’ve experienced with other simple direct conversion radios. One thing I did find really useful was a good ground connection which seemed to clean up the received signal to noise ratio.
If you are planning to build this little kit I would strongly recommend a metal case as stray capacitance does affect its operation.
I may be tempted to build a 20 meter version some time.
Even though I have a modern all singing and dancing HF transceiver I keep going back to this one as its really enjoyable listening to the band on something I built my self.
One modification I may do is to alter the RF gain control to a switch and use the control on the front case for a further fine tune control.
For a home built kit radio as simple as this one once its warmed up for at least 15 minutes it doesn’t drift, but you have to remember that with any direct conversion radio receiver you hear both upper and lower side band so I think the extra fine tune control may be beneficial especially if there’s another station very close to the target one.
I hope this little write up and set of pictures is useful to anyone thinking about building this radio.
73’s Cameron – AF7DK