Ron's Home brew Radio Page

Reflex Receiver Mk1

I was looking to build a medium wave portable radio for use in the bedroom or even in the bathroom while having a bath. I fancied building a crystal set but knew the limitations regarding an outside antenna and headphones etc then I came across this circuit and decided to have a go at building it. I was quite suprised how well this little radio performed. I am able to receive around 8 strong stations and several weaker foreign ones also. This receiver is based on the reflex design. It uses 1 transistor and the well known LM386 audio ic.

I built this circuit on a small piece of veroboard (stripboard) and found it fairly straight forward. The base is chipboard and front panel is white perspex/acrylic A5 sheet purchased from ebay for 1.80 Pounds

The coil was wound on a 120mm ferrite rod consisting of 50 turns of 28awg copper wire at one end and ten turns loose wound for the feedback winding at the other.

The only problems i had were that it was a little quiet for me, I managed to get around this by increasing the number of turns on the feedback coil from 3 to around 10. Dont go much above this or it will go into oscillation. You can fine tune the feedback by sliding the feedback coil up and down the ferrite rod. I thought the protractor was a nice touch. I drilled a hole just behind the tuning knob and inserted an orange LED from behind. This illuminates the dial on a night. I couldn't find a decent 8ohm speaker but had two 4ohm ones going spare so i just wired these in series to make the 8 ohm load.

Volume is now quite good and certainly loud enough for a table or bedside radio. No external aerial is required.

My Attempt at building the Reflex receiver.

The brass strip i used is manufactured by K&S metals and was purchased from the local model shop. Handles are from B&Q and control knobs from maplins. All other parts were just from the junk box. I have plenty of parts available for this project if you get stuck. Would also love to hear any comments you have on this project. Mail me at ronstv@me.com

Reflex Receiver Mk2

Im in the process of building the Mk2 version with quite a few improvements. I will add some photo's shortly. Differences include seperate audio amplifier board upgraded to 4watts output, much neater layout, ability to drive a seperate speaker and more.