DIY Audio Projects Forum

Hi! My name is Andrei, I was born in Romania in 1987 and one of my hobbies is electronics. In the following lines I will present to you a simple MW radio.

The radio consists of two sections: R.F. and A.F. I combined the R.F. section with adjustable selectivity from this reference:
http://www.zen22142.zen.co.uk/Circuits/rf/ZN414.htm and also from here: http://braincambre500.freeservers.com/M ... ceiver.htm

The A.F. section is from here: http://www.radiomuseum.org/forum/mk484_ ... mk484.html
and here: http://radiosammlung.homepage.t-online.de/seite8.html

The result? A performance receiver, sensitive (and selective, if it is adjusted or at night), with a high quality of sound.

I used a small Medium Wave antenna from a walkman with digital radio and a variable capacitor (VC) with two sections connected in parallel from an old russian radio (2x280pF).

I read on the Internet that if you live in an area with strong signals and you want to achive good performance and quality with this 3 pin IC (MK484,ZN414 etc) you have to:
A) use a small or smaller ferrite rod;
B) use a variable supply to adjust the IC voltage (0-1,4V);
C) use two coils for the ferrite rod: main coil - L1 (for tunning) and second coil - L2 (inductive).
You can try A, B or C, each of them improving the performance of the receiver. But, if you use all of them (A+B+C) your receiver will work very well!

The HP Jack allows you to connect a headphones and switch between internal speaker and headphones.

The DC 9V Jack allows you to connect an external power supply of 9V to the receiver and switch between internal 9Vbattery and external power supply.

Here is a record from the radio.The local station Iasi @ 1053KHz

Also,here are some pictures when the radio was "on tests".
And the final diagram of the completed receiver.

Hi Andrei,
this is a very nice radio project. Also your documentation is very detailed.
I like to discuss anything radio. I hope that you found a solution to get a goldcap.
If you get a problem with TA7642 selectivity and strong stations, there are some more solutions possible.

You wrote:

A) use a small or smaller ferrite rod;
B) use a variable supply to adjust the IC voltage (0-1,4V);
C) use two coils for the ferrite rod: main coil - L1 (for tunning) and second coil - L2 (inductive)

I agree with you in point C. I think to use a smaller feritte rod or adjust the voltage down,
is not the right way to go. Try a tapped main coil and look also to my pictured solutions for
this problem if you use a Long Wire Antenna. Try also a filter with a feritte rod.
Fine your work

´til the next time....

Joe

P.S Do you have a data sheet from TDA7052 ?

Hi,again.I'm new @this el.forum. I like it.It is similar to our romanian forum: http://www.elforum.ro
Most of the datasheets are here: http://www.datasheetcatalog.com

There,on my diagram,are noticed all the equivalents for the IC-TRF AM.Download it,and zoom+.

I know,the ideea of tap the coil..it is similar to the inductive L1and L2.Yes,the voltage matter..for adjusting the accuracy of a high-power AM transmitter.I combined 3 sollutions to have a clear and relatively pretty to good selectivity.

I made,after this receiver,on a test board some test with different types of antenna and I noticed that the receiver works with:
a-AM (MW or LW) ferrite loopstick antena
b-AM loop antena (without ferrite rode,but on higher diameter..let's say 50-60 wires at about 50 mm diameter)
c-red core AM oscilator
d-inductance (there are some inductances smaller like a 0,25W rezistor,you know..100uH =>I put 3 x 100uH in series and it worked)
e-without any antena..only a short wire for a local station..

Hi Andrei,

do you have ever tried shortwave with the TA7642?
I have some good results with it, but a real Audion with feedback gets to the shortwave frequencies better success.

Greetings

Joe

Yes..but it is a little bit difficult.Radio Iasi -local station is about 400KW power and at day I hear"Iasi"at background if I'm trying to receive SW..For this reason I found that good results I can receive with smal inductances 10 uH 20uH (in series) 15uH (mixt..) small like 0,25W resistors.With this I can eliminate the noise of local station which at day interfering.
My luck is that Iasi broadcast betwen 6:00 and 22:00 after 22:00 i can receive clear about 12..13 stations ..9 of them only at night with feding.

Yeah Andrei,

this is a very strong station 400KW.
Please give me the name and the frequence of this local station.
I will try to receive it in Berlin/Germany.
Fading is the normal situatuion on shortwave frequencies....also with a super.
13 stations is a good result. If you need, I will give you a very simple Short Wave Audion
schematic with an EF95 tube and also one with a transistor. The amplifier is LM 386.

Cheers

Joe

I have never worked with a vacuum.I wish I could work,one day.I don't have vacuum and also the socket for the vacuum.
Radio Iasi is on MW at 1053KHz and it broadcast between 6:00 and 22:00 Romanian hour (GMT+2)everyday.The power is 400kW.
You could try to tune it if you have maybe a digital radio..but I thought that you could also tune it with a high quality portable radio too in the night...so..when here is 21..at you is ...20..After 19:00 or after 20:00.For long distance I sugest to keep the radio near the window or,go outside or at the balcony if you live in a block of flats.