DIY Audio Projects Forum

Here are presented different types of TRF radios with ZN414 and its equivalents (MK484,YS414,TA7642,UTC7642,LMF501T,LA1050) or it derivates (ZN415 and ZN416 which incorporates a small audio amplifier).

I hope them will help you and,also make your work easyer.

Here are others interesting diagrams for all you those passionated by radio.

Here are the datasheets for the 3pin IC TRF Radios.

Another two hot diagrams with 3pin IC and electronic tune with varactor diode.
Sorry for posible translations mistakes.I hardly translated first into Romanian and,then in English.

I wish you good luck to construction of these radios.
Andrei

Hello Andrei,

this is a fine collection of circuit diagrams with
TA7642. Thank you for the files. It is a real
little treasure of schematics and a cool selection of options with TA, MK and ZN.

So..... I also understand your solutions for selectivity A,B,C
in your radio post.

Yes ..to translate is a hard job, but I think it is very interesting
to make conversation in a foreign language.

I have the same problem.

Greetings

Joe

I also sugest to download the attachements.Are very important.

Here is another radio diagram from "Radio and Electronics Cookbook" with ZN415E.

21 A portable radio for medium waves

Introduction
The ZN415E integrated circuit (IC) can be used to make a very efficient AM portable MW broadcast radio with a built-in loudspeaker. Here’s how!

The circuit
Figure 1 shows the circuit diagram of the portable radio. It’s not as complicated as it may appear, especially after you have got started. L1 is a coil of wire mounted on a ferrite rod, acting as an aerial; VC1 is a variable capacitor which works, with L1, to tune in different stations. IC1 contains circuits of its own which boost the selected signal and it includes a detector which extracts the audio signal from the incoming RF signal. Earphones could be connected to the output of IC1 (between pins 4 and 5), but the output would not be powerful enough to drive a loudspeaker.

More sound
This is where IC2, an LM386 comes in. This is a small audio power amplifier which produces audio signals with enough power to drive a small loudspeaker, LS1. The radio uses a 6 volt battery, which is made by connecting four 1.5 volt AA cells in series (4 × 1.5 V = 6 V) using a battery holder designed for this purpose. Although a 6 V supply is ideal for IC2, it is far too great for IC1, which needs only about 1.3 V. This lower voltage is provided from the 6 V supply by TR1 (an npn transistor), R2 and LED1 (a light-emitting diode). When current passes through an LED (see the description of the LED in this series) a reasonably constant voltage of 1.9 V appears between the anode and the cathode. Because of the voltage (0.6 V) that always exists between the base and emitter of a working transistor, the voltage on the emitter is about 1.9 V – 0.6 V = 1.3 V, and this is used as the power supply for IC1.

To keep the radio as simple as possible, no volume control has been fitted.Instead, you can use the directional properties of the ferrite rod aerial (see the information on ferrites in this book) to reduce the volume by rotating the set about a vertical axis using the handle provided.

Parts list

Resistors: all 0.25 watt, 5% tolerance
R1: 68 ohms
R2: 5.6 kilohms
R3: 10 ohms

Capacitors
C1, C4: 10 nanofarads (nF) or 0.01 microfarad ceramic
C2, C3, C7: 100 nanofarads (nF) or 0.1 microfarad ceramic
C5, C8, C9: 100 microfarads electrolytic,at least 10 V
C6: 10 microfarads electrolytic,at least 25 V

Semiconductors
IC1: ZN415E radio chip
IC2: LM386 audio power amplifier
LED1: 3 mm green LED
TR1: BC548 npn transistor

Additional items
LS1: Miniature 8 ohm loudspeaker
S1: Miniature SPST toggle switch
Ferrite rod Length approx. 100 mm
24 SWG enamelled copper wire (L=75 turns)

VC1: Tuning capacitor 140 to 300 picofarads (pF)
Tuning knob
8-pin DIL IC sockets (two required)
4 × AA-size battery holder (long)
PP3-type clip for battery holder
Plastic box approx. 158 × 95 × 54 mm
0.1 inch Veroboard, min. size 32 holes × 10 strips

Plus
Stranded insulated conductor for flying leads
Multicore solder
Materials for handle and speaker grille
Double-sided sticky tape or Blu-Tack
Sellotape
Glue
Four AA-size 1.5 V batteries

Schematic with sensitivity adjustment:
OA79 is a Ge diode.
*TIL209A is a RED LED with U=1,8V

Here are another interesting links:

http://bbradio.web.infoseek.co.jp/501t41/501t41.html
http://bbradio.web.infoseek.co.jp/501t01/501t01.html

Try a google translation (relatively..but I think that the diagram tells you the most)