Low cost & simple wide band VCO, LM7001 + 74HC04

Sudah lama tidak utak atik rangkaian RF jadi ingin nostalgia, teringat dulu waktu masih punya call sign YD6DEK, main di 100m (am), 80m (SSB) dan 2m (FM).. tiba2 jadi ingin membuat sendiri 80m SSB receiver..

receiver di design untuk bisa cover 2MHz – 7.5Mhz… harusnya ini sudah bisa cover 100m, 80m dan 40m? setelah membuka stok komponen yang ada maka dipilihlah frekwensi IF sebesar 8MHz (saya punya stok cukup banyak crystal 8MHz untuk ladder filter nanti)

oleh karena itu saya perlu VCO dengan range

2   + 8 = 10 MHz

7.5 + 8 = 15,5 MHz

lets start dengan VCO (mungkin nanti saya coba dengan Direct Digital Synthesizer .. import chips :(?)

mendesign VCO yang bisa lock di 10MHz-15.5MHz tidak mudah karena range ini cukup lebar.. setelah mencoba dengan beberapa rangkain VCO dengan BJT, MOSFET serta bereksperiment dengan banyak coil, ternyata pemanfaatan IC TTL 74HC04 memberikan hasil yg memuaskan (lihat skema di berikut)

untuk PLL saya menggunakan IC LM7001 ic ini sudah lawas tapi murah meriah dan ternyata saya masih menyimpan beberapa unit ini, mungkin next time saya coba dengan FLL yang di bangun dari ATMega8  (lihat gambar berikut)

IC PLL LM7001 di control oleh Microcontroller ATMega8 melalui 3 pin dengan mode SPI, 3 buat push button menjadi sarana pengaturan frekwensi UP, DOWN, STORE. UP/DOWN menaikan/menurunkan frekwensi 1 KHz, STORE menyimpan di EEPROM frekwensi terakhir. Untuk detil LM7001 dan chip lainnya silahkan di baca/download datasheet nya pada link di akhir tulisan ini.

‘*******************************************************************************
‘ 80M VCO
‘ PLL LM7001
‘ ATMega8
‘ 16×2 LCD
‘ 10MHz IF Freq
‘*******************************************************************************
$regfile = “m8def.dat”
$crystal = 8000000

$swstack = 32
$hwstack = 32
$framesize = 32

Declare Sub Send_command(byval Pmode As Word , Byval Value As Word )
Declare Sub Init_pll
Declare Sub Incr_pll
Declare Sub Decr_pll
Declare Sub Store_pll
Declare Sub Dsp_freq

‘*******************************************************************************
‘ config pin
‘*******************************************************************************

Config Lcdmode = Port
Config Lcdpin = Pin , Db4 = Portc.3 , Db5 = Portc.2 , Db6 = Portc.1 , Db7 = Portc.0 , E = Portc.4 , Rs = Portc.5
Config Lcd = 16 * 2

Config Portd = Output
Config Portd.5 = Output
Config Portd.6 = Output
Config Portd.7 = Output

Config Pinb.0 = Input
Config Pinb.1 = Input
Config Pinb.2 = Input

Cen Alias Portd.7
Clk Alias Portd.6
Dat Alias Portd.5

‘*******************************************************************************
‘ Variable
‘*******************************************************************************

Dim I As Word
Dim J As Byte
Dim Pmode As Word
Dim Button As Byte
Dim Freq As Word
Dim Efreq As Eram Word At &H10
Dim Sfreq As Word
Dim Dfreq As Word
Dim Sdfreq As String * 5

‘*******************************************************************************
‘ main program
‘*******************************************************************************
Initialization:

   Waitms 100
   Reset Cen
   Reset Clk
   Reset Dat

   Set Portb.0
   Set Portb.1
   Set Portb.2

   Deflcdchar 0 , 32 , 32 , 32 , 32 , 32 , 32 , 31 , 32

   Deflcdchar 0 , 31 , 31 , 32 , 17 , 27 , 27 , 31 , 31                         ‘ antenna symb
   Deflcdchar 1 , 31 , 31 , 31 , 30 , 29 , 11 , 23 , 31                         ‘ memory
   Deflcdchar 2 , 14 , 16 , 12 , 2 , 30 , 9 , 9 , 9                             ‘ S/N

   Deflcdchar 4 , 32 , 32 , 32 , 32 , 32 , 32 , 31 , 32                         ‘ S1
   Deflcdchar 5 , 32 , 32 , 32 , 32 , 1 , 31 , 31 , 32                          ‘ S2
   Deflcdchar 6 , 32 , 32 , 32 , 7 , 31 , 31 , 31 , 32                          ‘ S3
   Deflcdchar 7 , 1 , 7 , 31 , 31 , 31 , 31 , 31 , 32                           ‘ S4

   Cls : Cursor Off
   Locate 1 , 1 : Lcd “80m RX SSB V1.0 “
   Locate 2 , 1 : Lcd “Jalapindai 2010 “
   Waitms 10

Main:

‘   Pmode = 704
‘   Pmode = 896

   Cls
   Locate 1 , 1 : Lcd ”             KHz”
   Locate 2 , 1 : Lcd ” jalapindai.com “
   Call Init_pll
   Call Dsp_freq

   Do
      Button = Pinb And &H07
      Select Case Button
         Case 3 : Call Store_pll
         Case 5 : Call Decr_pll
         Case 6 : Call Incr_pll
      End Select

   Loop

   Goto Main

 End

‘*******************************************************************************
‘ Init PLL
‘*******************************************************************************
Sub Init_pll

   Freq = Efreq
   If Freq = 65535 Then
      Freq = 10000
   End If

   Call Send_command(704 , Freq)
   Call Dsp_freq
   Locate 1 , 1 : Lcd Chr(1)
   Locate 1 , 2 : Lcd Chr(0)

End Sub

‘*******************************************************************************
‘ Incr_PLL
‘*******************************************************************************
Sub Incr_pll

   Incr Freq
   If Freq > 14500 Then
      Freq = 14500
   End If
   Call Send_command(704 , Freq)
   Call Dsp_freq
   Locate 1 , 1 : Lcd ” “

End Sub

‘*******************************************************************************
‘ Decr_PLL
‘*******************************************************************************
Sub Decr_pll

   Decr Freq
   If Freq < 10000 Then
      Freq = 10000
   End If
   Call Send_command(704 , Freq)
   Call Dsp_freq
   Locate 1 , 1 : Lcd ” “

End Sub

‘*******************************************************************************
‘ Store PLL
‘*******************************************************************************
Sub Store_pll

   If Sfreq <> Freq Then
      Efreq = Freq
      Sfreq = Efreq
   End If

   Locate 1 , 1 : Lcd Chr(1)
   Waitms 50
End Sub

‘*******************************************************************************
‘ Display PLL
‘*******************************************************************************
Sub Dsp_freq

   Dfreq = Freq – 8000
   Sdfreq = Str(dfreq)
   Sdfreq = Format(sdfreq , “0.000”)
   Locate 1 , 8 : Lcd Sdfreq
   Waitms 50

End Sub

 ‘*******************************************************************************
‘ Send Command
‘*******************************************************************************
Sub Send_command(byval Pmode As Word , Byval Value As Word)

   Set Cen
   Waitus 20

‘   Shiftout Dat , Clk , Cmode , 3 , 24 , 10

‘bit 0 to 13 (N value)
   For I = 0 To 13
      If Value.i = 1 Then
         Set Dat
      Else
         Reset Dat
      End If
      Waitus 10

      Set Clk
      Waitus 10
      Reset Clk
      Waitus 10
   Next I

‘bit 14-23 (mode)
   For I = 0 To 9
      If Pmode.i = 1 Then
         Set Dat
      Else
         Reset Dat
      End If
      Waitus 10

      Set Clk
      Waitus 10
      Reset Clk
      Waitus 10
   Next I

   Waitus 20
   Reset Cen

End Sub

Datasheet Link

LM7001
ATMega8
74HC04