Not that there in any paucity of pocket receiver or that they are too expensive, or that there are hardly any well known circuit that we decided to design"another one".Its not just another one.
The True Pocket Receiver
No doubt,dozens of mode are commercially available but they aren't truly pocket sized(rather pocket over sized).Not many,leave alone the corner a shirt pocket,fit into a normal shirt pocket leaving enough space to even tack a wallet.Well that's the reason we though of designing a pocket receiver small enough to fit into a shirt pocket or clip on to a belt that is - pocket receiver in the true sense.And that exactly is what we have here.
How it Works?
The circuit is given in Schematic1 . It uses an 8-pin DIP ZN415 radio receiver chip from Ferranti.The circuit has an edge over the ZN414 in having an in-built amplifier stage. The circuit uses a tuned circuit based on L1 and VC1 serves as a tuning control.L1 detects the signals and passes them on to IC1,which in turn, drives high impedance headphones.That's all.
Contruction
The circuit can be hooked on to a general purpose PCB after cutting a few trackers on the PCB as shown in Schematic 2.The IC socket is mounted first,followed by resistors and capacitors.No on/off switch is needed as the nominal current consumption is 5mA and upon disconnecting headphone it drops to a few hundred microamperes.
The coil can be made by winding 50 turn of 200 um wire on to a flat ferrite slab of suitable length(the longer the better).The circuit can be enclosed in any small plastic or acrylic enclosure of the size of a small matchbox.The antenna coil may be fixed by melting the point plastic with a hot iron.
The True Pocket Receiver
No doubt,dozens of mode are commercially available but they aren't truly pocket sized(rather pocket over sized).Not many,leave alone the corner a shirt pocket,fit into a normal shirt pocket leaving enough space to even tack a wallet.Well that's the reason we though of designing a pocket receiver small enough to fit into a shirt pocket or clip on to a belt that is - pocket receiver in the true sense.And that exactly is what we have here.
How it Works?
The circuit is given in Schematic1 . It uses an 8-pin DIP ZN415 radio receiver chip from Ferranti.The circuit has an edge over the ZN414 in having an in-built amplifier stage. The circuit uses a tuned circuit based on L1 and VC1 serves as a tuning control.L1 detects the signals and passes them on to IC1,which in turn, drives high impedance headphones.That's all.
Contruction
The circuit can be hooked on to a general purpose PCB after cutting a few trackers on the PCB as shown in Schematic 2.The IC socket is mounted first,followed by resistors and capacitors.No on/off switch is needed as the nominal current consumption is 5mA and upon disconnecting headphone it drops to a few hundred microamperes.
The coil can be made by winding 50 turn of 200 um wire on to a flat ferrite slab of suitable length(the longer the better).The circuit can be enclosed in any small plastic or acrylic enclosure of the size of a small matchbox.The antenna coil may be fixed by melting the point plastic with a hot iron.
The genuinely pocket sized receiver,s circuit
The additional add-on amplifier for desktop operation
