A Makeshift Crystal Radio Output Transformer - UK Vintage Radio Repair and Restoration Discussion Forum

vu2nan-nandu · 9th Sep 2015, 7:58 pm

This project was part of my initial attempts at homebrewing an output transformer for my 'Loudspeaking Crystal Radio' http://nandustips.blogspot.in/2014/0...h-speaker.html.

An air-core crossover network inductor and a ferrite-core one (from the junkbox) appeared suitable as the primary and secondary windings of the transformer.

The large number of turns of the air-core inductor as primary and the small number of the ferrite one as secondary would give a step-down ratio. With luck, the open ferrite core would enable reasonable coupling.

Testing was simple, with the air-core inductor hooked up to the crystal radio and the ferrite-core one (placed within) connected to the speaker.

The result was encouraging enough for further attempts which culminated in a proper 'Crystal Radio Output Transformer' http://nandustips.blogspot.in/2015/0...ansformer.html.

Regards,

Nandu.

peter_scott · 10th Sep 2015, 9:06 am

Hi Nandu,

How would you rate the volume from your 200kW transmitter?
Could you listen to a radio talk show or play at the other side of the room?

Peter

vu2nan-nandu · 10th Sep 2015, 11:52 am

Hi Peter,

Certainly not across the room but comfortably a couple of feet away.

Regards,

Nandu.

9th Sep 2015, 7:58 pm	#1
vu2nan-nandu Pentode Join Date: Jul 2014 Location: Bangalore, India Posts: 132	A Makeshift Crystal Radio Output Transformer This project was part of my initial attempts at homebrewing an output transformer for my 'Loudspeaking Crystal Radio' http://nandustips.blogspot.in/2014/0...h-speaker.html. An air-core crossover network inductor and a ferrite-core one (from the junkbox) appeared suitable as the primary and secondary windings of the transformer. The large number of turns of the air-core inductor as primary and the small number of the ferrite one as secondary would give a step-down ratio. With luck, the open ferrite core would enable reasonable coupling. Testing was simple, with the air-core inductor hooked up to the crystal radio and the ferrite-core one (placed within) connected to the speaker. The result was encouraging enough for further attempts which culminated in a proper 'Crystal Radio Output Transformer' http://nandustips.blogspot.in/2015/0...ansformer.html. Regards, Nandu. Attached Thumbnails

10th Sep 2015, 9:06 am	#2
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: A Makeshift Crystal Radio Output Transformer Hi Nandu, How would you rate the volume from your 200kW transmitter? Could you listen to a radio talk show or play at the other side of the room? Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

10th Sep 2015, 11:52 am	#3
vu2nan-nandu Pentode Join Date: Jul 2014 Location: Bangalore, India Posts: 132	Re: A Makeshift Crystal Radio Output Transformer Hi Peter, Certainly not across the room but comfortably a couple of feet away. Regards, Nandu. Last edited by vu2nan-nandu; 10th Sep 2015 at 12:04 pm.