In order to hear the 2m FM band, I made a simple radio.
In these days I began to use the transistor having ft over 1GHz. They can make gain over 40dB when they are used on IF amplifier. They can oscillate over 100MHz direct. Can you believe that? You can believe that when you make this machine. This machine is a simple single conversion receiver. Oscillator is made with varicap in order to avoid the body effect. This oscillator makes small QRH. But as a radio for SWL, It do not makes any problem.
Mixer convertor is made by dual gate FET. This is a basic usage of circuit of this FET transistor.
IF amplifier has 40dB gain only with 1 transistor. FM detector is called as Wise detector. The characteristic is shown on the fig.3.
The output impedance of Wise detector is very high. Therefore the input impedance of an audio AMP must be very high. Therefore I used a FET , on the front of the audio AMP. This AMP uses a very good output transformer named ST-47. Therefore the frequency characteristic of it is very good. See fig 4! This amplifier has 50mW power output. It is enough for the headphone.
I have jointed the antenna for this gear. I could hear the QSO on my city inside and that of nearby towns.
From: Mohan Mathew[SMTP:email@example.com] Sent: Tuesday, July 17, 2001 16:32 To: firstname.lastname@example.org Subject: Valuable Doubts! Hello Om.Kazuhiro Sunamura, I am a fellow SWL from
Dear Mohan These transistors and coils are all famous in
1.Converter FET no: 3sk60. Maker
2.IF transistor no: All IFT are 455KHz AM radio usage. I do not know the number of it.
3.AF amplifier no(1&2): 1st 2sk327: I do not have detailed data now. Sorry! You can use any type of FET here. 2nd:2sc1740: Maker -Rohm. Usage=AF,RF,OSC,SW. Pc=300mW,hfe=120 to 820. FT=180MHz
4.Osc transistor no: 2sc2347: Maker = Toshiba. Usage = mixer. Pc= 250mW. FT=650MHz: Please use Silicone Epitaquisial transistor made to use on VHF mixer for VHF TV.
5.varactor diode no: 1S553: Please use varicap made for FM 80MHz radio converter!
6.Toroid core no: T50-10. Maker = Amidon.
7.Is the o/p is an audio transformer? : Yes. 600: 8 ohms Audio transformer . named as ST47 . Maker = Sansui.