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.

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 G0MBV



 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.

    

Very pleased with the results of this radio that i have now added a headphone socket just to finish it off. Movie below showing it working.

 

FM Receiver

 My first attempt at building an fm receiver.
I chose to use a very similar design for the chassis and casing as i did on my reflex receiver except chose black perspex.



 Matchbox Radio

   

The circuit i used is below, based on the modern version of the ZN414 (TA7642). Works well. I found that my ipod headphones work much better than a crystal earpeice. 32 ohm. Last photo i included an on/off switch. Just need a micro sized 200pf tuning capacitor now as ive just preset this one with my favourite station.

 Vintage looking MW Radio


   


 This was built using the circuit above and just a headphone out socket. I used brown perspex that i sanded for the front panel to make it look like paxolin. The 9volt battery is to power the Led tuning indicator just above the dial. The sensitivity and selectivity is really good with this circuit and ferrite rod layout, makes you wonder why we need superhet designs. The audio is extremly clear and very warm sounding. Proberbly my best build yet.

The tuning dial is a Muirhead Direct drive dial from the 50's. I purchased this from ebay. It was brand new still in it's original box. Not bad for 8 quid considering its solid brass and bakelite.