30W Digital RF Power Meter AD8307 + Atmega8


Eksperimen dengan RF (Radio Frequency) tidak lepas dari instrument pengukur daya. Baik untuk sekedar mengukur daya pancar, kuat penerimaan (RSSI) atau bahkan pengaturan daya osilator lokal untuk diumpankan ke mixer.

Uraian berikut saya share eksperiment dalam membuat sendiri alat ukur daya RF yang saya kumpulkan informasi dan rangkaiannya dari berbagai sumber di internet. Rangkaian yang digunakan adalah umum dipakai untuk mengukur daya RF berintikan sebuah IC AD8307,  yang saya kombinasikan dengan  IC microcontroller Atmega8.  Rangkaian pengukur ini di desain untuk dapat mengukur daya RF hingga 30 watt.

Sekilas Tentang AD8307
IC AD8307 adalah sebuah logarithmic amplifier yang mampu bekerja dengan baik hingga pada frekwensi 500MHz.
Perhatikan gambar berikut.

AD8307 basic

Masukan daya RF -75dBm hingga +16dBm memberikan keluaran slope (25mV/dB) yang linier dari kira-kira 0.5Vdc hingga 2.5vdc. Pada penerapan kali ini saya batasi hanya di -70dBm s/d +10dBm (0.1nW s/d 10mW).

Aplikasi AD8307
Karena input ADC pada microkontroller menggunakan internal reference sebesar 2.56V pada skala maksimum maka diperlukan attenuator berupa resistor ladder terhadap masukan daya rf sebelum diumpankan kedalam ADC, bila kita ingin membaca daya RF yang lebih besar dari 10mW.  Perhatikan gambar berikut:

30W scale conversion

Sebuah rangkaian ladder dari beberapa resistor membentuk pembagi tegangan dari aktual tegangan pada dummy load (50 Ohm = 30buah 1K5 Ohm di parallel). Dengan mengasumsikan bahwa daya 30Watt akan memberikan keluaran 2.5V pada keluaran IC AD8307 maka diperlukan kombinasi nilai resistor seperti diatas (lihat juga tabel perhitungan berikut)

equation

Dengan menggunakan formula diatas berhasil di buat table map untuk membantu perhitungan ADC di dalam mikrokontroler (lihat map pada source code).  Untuk rangkaian LCD bisa menggunakan rangkaian standard (bisa mengikuti pin config pada source code atau di sesuaikan, hanya pada program masukan ADC digunakan pin ADC 5.

AD8307 + Dummy Load (30x1K5)

RF Power Meter

RF Power Meter

RF Power Meter PCB

Dummy Load at PCB

Source Code

‘*******************************************************************************
‘ ATMega8
‘ 16×2 LCD
‘*******************************************************************************
$regfile = “m8def.dat”
$crystal = 8000000

$swstack = 64
$hwstack = 48
$framesize = 64

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

Config Lcdmode = Port
Config Lcdpin = Pin , Db4 = Portd.4 , Db5 = Portd.5 , Db6 = Portd.6 , Db7 = Portd.7 , E = Portb.7 , Rs = Portb.6
Config Lcd = 16 * 2

Config Adc = Single , Prescaler = Auto , Reference = Internal

‘*******************************************************************************
‘ constant
‘*******************************************************************************

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

Dim Vadc As Word
Dim Dbm As Single
Dim Watt As Single
Dim Sdbm As String * 6
Dim Swatt As String * 6
Dim B As Byte
Dim I As Integer
Dim W As Word

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

Init:
   Cls : Cursor Off
   Locate 1 , 1 : Lcd ” RF Power Meter “
   Locate 2 , 1 : Lcd ” jalapindai.com “

   Waitms 1000

   Cls
   Locate 1 , 1 : Lcd “dBm :        dBm”
   Locate 2 , 1 : Lcd “Watt:         mW”

   Enable Adc
   Start Adc

   Do
      Vadc = Getadc(5)
      If Vadc < 200 Then
         Locate 1 , 6 : Lcd “<-35.23”
         Locate 2 , 6 : Lcd “<0.00030”
      End If

      If Vadc > 1000 Then
         Locate 1 , 6 : Lcd “>44.77”
         Locate 2 , 6 : Lcd “<30000”
      End If

      If Vadc >= 200 And Vadc <= 1000 Then
         Vadc = Vadc – 200
         Dbm = Lookup(vadc , Logdata)
         Sdbm = Str(dbm)
         Locate 1 , 6 : Lcd Mid(sdbm , 1 , 7)
         Dbm = Dbm / 10
         Watt = 10 ^ Dbm
         Swatt = Str(watt)
         Locate 2 , 6 : Lcd Mid(swatt , 1 , 7)
      End If

      Waitms 500
   Loop

End

Logdata:
data -35.23!,-35.13!,-35.03!,-34.93!,-34.83!,-34.73!,-34.63!,-34.53!,-34.43!,-34.33!,
data -34.23!,-34.13!,-34.03!,-33.93!,-33.83!,-33.73!,-33.63!,-33.53!,-33.43!,-33.33!,
data -33.23!,-33.13!,-33.03!,-32.93!,-32.83!,-32.73!,-32.63!,-32.53!,-32.43!,-32.33!,
data -32.23!,-32.13!,-32.03!,-31.93!,-31.83!,-31.73!,-31.63!,-31.53!,-31.43!,-31.33!,
data -31.23!,-31.13!,-31.03!,-30.93!,-30.83!,-30.73!,-30.63!,-30.53!,-30.43!,-30.33!,
data -30.23!,-30.13!,-30.03!,-29.93!,-29.83!,-29.73!,-29.63!,-29.53!,-29.43!,-29.33!,
data -29.23!,-29.13!,-29.03!,-28.93!,-28.83!,-28.73!,-28.63!,-28.53!,-28.43!,-28.33!,
data -28.23!,-28.13!,-28.03!,-27.93!,-27.83!,-27.73!,-27.63!,-27.53!,-27.43!,-27.33!,
data -27.23!,-27.13!,-27.03!,-26.93!,-26.83!,-26.73!,-26.63!,-26.53!,-26.43!,-26.33!,
data -26.23!,-26.13!,-26.03!,-25.93!,-25.83!,-25.73!,-25.63!,-25.53!,-25.43!,-25.33!,
data -25.23!,-25.13!,-25.03!,-24.93!,-24.83!,-24.73!,-24.63!,-24.53!,-24.43!,-24.33!,
data -24.23!,-24.13!,-24.03!,-23.93!,-23.83!,-23.73!,-23.63!,-23.53!,-23.43!,-23.33!,
data -23.23!,-23.13!,-23.03!,-22.93!,-22.83!,-22.73!,-22.63!,-22.53!,-22.43!,-22.33!,
data -22.23!,-22.13!,-22.03!,-21.93!,-21.83!,-21.73!,-21.63!,-21.53!,-21.43!,-21.33!,
data -21.23!,-21.13!,-21.03!,-20.93!,-20.83!,-20.73!,-20.63!,-20.53!,-20.43!,-20.33!,
data -20.23!,-20.13!,-20.03!,-19.93!,-19.83!,-19.73!,-19.63!,-19.53!,-19.43!,-19.33!,
data -19.23!,-19.13!,-19.03!,-18.93!,-18.83!,-18.73!,-18.63!,-18.53!,-18.43!,-18.33!,
data -18.23!,-18.13!,-18.03!,-17.93!,-17.83!,-17.73!,-17.63!,-17.53!,-17.43!,-17.33!,
data -17.23!,-17.13!,-17.03!,-16.93!,-16.83!,-16.73!,-16.63!,-16.53!,-16.43!,-16.33!,
data -16.23!,-16.13!,-16.03!,-15.93!,-15.83!,-15.73!,-15.63!,-15.53!,-15.43!,-15.33!,
data -15.23!,-15.13!,-15.03!,-14.93!,-14.83!,-14.73!,-14.63!,-14.53!,-14.43!,-14.33!,
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data -13.23!,-13.13!,-13.03!,-12.93!,-12.83!,-12.73!,-12.63!,-12.53!,-12.43!,-12.33!,
data -12.23!,-12.13!,-12.03!,-11.93!,-11.83!,-11.73!,-11.63!,-11.53!,-11.43!,-11.33!,
data -11.23!,-11.13!,-11.03!,-10.93!,-10.83!,-10.73!,-10.63!,-10.53!,-10.43!,-10.33!,
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data -9.13!,-9.03!,-8.93!,-8.83!,-8.73!,-8.63!,-8.53!,-8.43!,-8.33!,-8.23!,
data -8.13!,-8.03!,-7.93!,-7.83!,-7.73!,-7.63!,-7.53!,-7.43!,-7.33!,-7.23!,
data -7.13!,-7.03!,-6.93!,-6.83!,-6.73!,-6.63!,-6.53!,-6.43!,-6.33!,-6.23!,
data -6.13!,-6.03!,-5.93!,-5.83!,-5.73!,-5.63!,-5.53!,-5.43!,-5.33!,-5.23!,
data -5.13!,-5.03!,-4.93!,-4.83!,-4.73!,-4.63!,-4.53!,-4.43!,-4.33!,-4.23!,
data -4.13!,-4.03!,-3.93!,-3.83!,-3.73!,-3.63!,-3.53!,-3.43!,-3.33!,-3.23!,
data -3.13!,-3.03!,-2.93!,-2.83!,-2.73!,-2.63!,-2.53!,-2.43!,-2.33!,-2.23!,
data -2.13!,-2.03!,-1.93!,-1.83!,-1.73!,-1.63!,-1.53!,-1.43!,-1.33!,-1.23!,
data -1.13!,-1.03!,-0.93!,-0.83!,-0.73!,-0.63!,-0.53!,-0.43!,-0.33!,-0.23!,
data -0.13!,-0.03!,0.07!,0.17!,0.27!,0.37!,0.47!,0.57!,0.67!,0.77!,
data 0.87!,0.97!,1.07!,1.17!,1.27!,1.37!,1.47!,1.57!,1.67!,1.77!,
data 1.87!,1.97!,2.07!,2.17!,2.27!,2.37!,2.47!,2.57!,2.67!,2.77!,
data 2.87!,2.97!,3.07!,3.17!,3.27!,3.37!,3.47!,3.57!,3.67!,3.77!,
data 3.87!,3.97!,4.07!,4.17!,4.27!,4.37!,4.47!,4.57!,4.67!,4.77!,
data 4.87!,4.97!,5.07!,5.17!,5.27!,5.37!,5.47!,5.57!,5.67!,5.77!,
data 5.87!,5.97!,6.07!,6.17!,6.27!,6.37!,6.47!,6.57!,6.67!,6.77!,
data 6.87!,6.97!,7.07!,7.17!,7.27!,7.37!,7.47!,7.57!,7.67!,7.77!,
data 7.87!,7.97!,8.07!,8.17!,8.27!,8.37!,8.47!,8.57!,8.67!,8.77!,
data 8.87!,8.97!,9.07!,9.17!,9.27!,9.37!,9.47!,9.57!,9.67!,9.77!,
data 9.87!,9.97!,10.07!,10.17!,10.27!,10.37!,10.47!,10.57!,10.67!,10.77!,
data 10.87!,10.97!,11.07!,11.17!,11.27!,11.37!,11.47!,11.57!,11.67!,11.77!,
data 11.87!,11.97!,12.07!,12.17!,12.27!,12.37!,12.47!,12.57!,12.67!,12.77!,
data 12.87!,12.97!,13.07!,13.17!,13.27!,13.37!,13.47!,13.57!,13.67!,13.77!,
data 13.87!,13.97!,14.07!,14.17!,14.27!,14.37!,14.47!,14.57!,14.67!,14.77!,
data 14.87!,14.97!,15.07!,15.17!,15.27!,15.37!,15.47!,15.57!,15.67!,15.77!,
data 15.87!,15.97!,16.07!,16.17!,16.27!,16.37!,16.47!,16.57!,16.67!,16.77!,
data 16.87!,16.97!,17.07!,17.17!,17.27!,17.37!,17.47!,17.57!,17.67!,17.77!,
data 17.87!,17.97!,18.07!,18.17!,18.27!,18.37!,18.47!,18.57!,18.67!,18.77!,
data 18.87!,18.97!,19.07!,19.17!,19.27!,19.37!,19.47!,19.57!,19.67!,19.77!,
data 19.87!,19.97!,20.07!,20.17!,20.27!,20.37!,20.47!,20.57!,20.67!,20.77!,
data 20.87!,20.97!,21.07!,21.17!,21.27!,21.37!,21.47!,21.57!,21.67!,21.77!,
data 21.87!,21.97!,22.07!,22.17!,22.27!,22.37!,22.47!,22.57!,22.67!,22.77!,
data 22.87!,22.97!,23.07!,23.17!,23.27!,23.37!,23.47!,23.57!,23.67!,23.77!,
data 23.87!,23.97!,24.07!,24.17!,24.27!,24.37!,24.47!,24.57!,24.67!,24.77!,
data 24.87!,24.97!,25.07!,25.17!,25.27!,25.37!,25.47!,25.57!,25.67!,25.77!,
data 25.87!,25.97!,26.07!,26.17!,26.27!,26.37!,26.47!,26.57!,26.67!,26.77!,
data 26.87!,26.97!,27.07!,27.17!,27.27!,27.37!,27.47!,27.57!,27.67!,27.77!,
data 27.87!,27.97!,28.07!,28.17!,28.27!,28.37!,28.47!,28.57!,28.67!,28.77!,
data 28.87!,28.97!,29.07!,29.17!,29.27!,29.37!,29.47!,29.57!,29.67!,29.77!,
data 29.87!,29.97!,30.07!,30.17!,30.27!,30.37!,30.47!,30.57!,30.67!,30.77!,
data 30.87!,30.97!,31.07!,31.17!,31.27!,31.37!,31.47!,31.57!,31.67!,31.77!,
data 31.87!,31.97!,32.07!,32.17!,32.27!,32.37!,32.47!,32.57!,32.67!,32.77!,
data 32.87!,32.97!,33.07!,33.17!,33.27!,33.37!,33.47!,33.57!,33.67!,33.77!,
data 33.87!,33.97!,34.07!,34.17!,34.27!,34.37!,34.47!,34.57!,34.67!,34.77!,
data 34.87!,34.97!,35.07!,35.17!,35.27!,35.37!,35.47!,35.57!,35.67!,35.77!,
data 35.87!,35.97!,36.07!,36.17!,36.27!,36.37!,36.47!,36.57!,36.67!,36.77!,
data 36.87!,36.97!,37.07!,37.17!,37.27!,37.37!,37.47!,37.57!,37.67!,37.77!,
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data 38.87!,38.97!,39.07!,39.17!,39.27!,39.37!,39.47!,39.57!,39.67!,39.77!,
data 39.87!,39.97!,40.07!,40.17!,40.27!,40.37!,40.47!,40.57!,40.67!,40.77!,
data 40.87!,40.97!,41.07!,41.17!,41.27!,41.37!,41.47!,41.57!,41.67!,41.77!,
data 41.87!,41.97!,42.07!,42.17!,42.27!,42.37!,42.47!,42.57!,42.67!,42.77!,
data 42.87!,42.97!,43.07!,43.17!,43.27!,43.37!,43.47!,43.57!,43.67!,43.77!,
data 43.87!,43.97!,44.07!,44.17!,44.27!,44.37!,44.47!,44.57!,44.67!,44.77!

referensi:  http://www.radiolocman.com/shem/schematics.html?di=55369
http://hem.passagen.se/communication/watt2.html

semoga bermanfaat
Dian Kurniawan

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12 thoughts on “30W Digital RF Power Meter AD8307 + Atmega8

  1. Pa Dian, kalo Power Meter ini bisa dijadiin Strength Meter bagian receiver di HT IC-2N ga ya?
    Supaya kaya RIG/HT jaman sekarang, bisa mantau kekuatan signal orang lain keterima berapa di kita.

    Kalo bisa, dipasang di titik2 mana aja ya?
    Email ke sini ya NiksenH@gmail.com
    Thanks…

    • prinsipnya bisa, tapi mungkin agak terlalu mewah, utk strength meter di HT IC-2N bisa di tap pada IC MC3357 pin 5, lalu diperkuat dgn transisto atau bisa dipakai rangkaian VUmeter amplifier yang banyak di jual dipasaran

  2. pak kalau dibuat bisa nampil 1000watt bisa ngk? kalau skema fwd.rfl,temp,volt,ampere yang pakai lcd ada ngk?

    • Pada prinsipnya bisa, tinggal disesuaikan pembagi daya pada masukan, untuk volt dan ampere bisa gunakan port ADC (analog to digital converter) yg belum terpakai (atmega8 kemasan SMD memiliki 8 buah port ADC, sedangkan kemasan DIP ada 6 buah port ADC), lalu sesuaikan firmwarenya.

  3. selamat pagi bapak

    salam kenal
    bapak punya artikel atau rangkaian power supply 6A yang bisa di atur arus dan tegangannya?

    terimakasih sebelumnya

  4. mas, kalo input AD8307 dapatnya dari mana ya? apa dari modul receivernya?kalo iya, modul apa yang dipake pada proyek ini? makasih mas

  5. mas dian, ada ga skema transceiver fm < 88mhz yg pake pll dg ic tc9122 tc5081 dan tc5082 seperti pada ht ic2n, dg step 10khz ato lbh kecil…. klo ada share dong mas, buat belajar…

  6. Pak, kitnya diproduksi gak atau saya bisa pesan?

  7. beli komponen IC AD8307-nya dimana?? sudah cari2 ditoko elektronik online dan offline tidak ada

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