Embedded Files
WD8DSB homebrew version of the W7IUV broadband preamp shown below.
W7IUV preamp commercially available at http://www.mtmscientific.com/preamp.html
In my builds I used the following component values
C1, C2, C3, C7 = 1 ufd (used 1 ufd for good low frequency performance)
C4 = 0.1 ufd
C5 = 1 ufd
C6 = 4.7 ufd Tantalum
R1 = 1000 ohm
R2 = 680 ohm
R3 = 3300 ohm plus 470 ohms in my first W7IUV preamp and 3300 ohms plus 680 ohms in my second W7IUV preamp (I added the 470 ohm resistor and in series with R3 to adjust the collector current to 75 mA per the Test and Performance Verification section of the Revision 5 document shown on page 13 and did the same with the 680 ohm resistor in my second preamp)
R4 = 6.8 ohm
R5 = 12 ohm
Q1 = 2N5109 (I use authentic 2N5109 transistors, not ones from Asia that have the Motorola emblem)
Measured Preamp Gain 100KHz to 30 MHz (50 ohm load, 12 Vdc)
Gain at 1.8 MHz measures approximately 20.6 dB
LTSpice model frequency response of W7IUV preamp using 1uf coupling and bypass capacitors.
Source = 0.1uV peak with internal resistance = 50 ohm.
At 1.8 mhz the input delivered to amplifier using this source = 0.0481 uV peak, and output across 50 ohm load = 0.585uV peak.
Output amplitude in dB relative to 1 volt peak at 1.8 Mhz : 20 log (0.585uV / 1V) = -124.66 dB as shown below in the frequency response curve.
Gain = 20 log (0.585uV / 0.048 uV) = 21.70 dB
Note : The Ferrite toroid core material was not taken into account, and it was modeled as if it were air.
Page updated
Google Sites
Report abuse