Push-pull 2x GALI-74+ Pre-Amp (LNA) for HF Receivers Built & Tested PCB Module
2 x GALI-74+ in push-pull for great IMD2 & IMD3 performance
IN/OUT (Pass-Through) Relay
DC through coax (Bias-Tee)
10 KHZ - 60 MHZ suggested frequency range
Steve, AA7U, was kind enough to point out that my photo with the voltage regulator bolted on the PCB is misleading. Actually the voltage
regulator runs hot and needs either a small heatsink or removed from the PCB and attached on a box wall or any metal surface.
For some buyers asking me to place this preamp inside a box, I fix it just under the PCB, under its silkscreen position.
He also noticed the input impedance was not correct. In the schematic diagram first released I swapped the transformers winding
information of my other project "DXer's LNA" with 4x GALi74+ preamp. The schematic is now corrected. Steve, also measured
second and third order output intercept point (OIP2 and OIP3) and together he measured NF at 10 MHz with the HP 8970B
noise figure meter: +24.59 dB gain, NF 3.36 dB
IMD results for this preamp, using my two-tone IMD test set:
SV1AFN dual GALI-74 preamp, 12.5V, 230 mA. 3/4 Mc test tones, set for 0 dBm at output of preamp:
1Mc +70.6 dBm OIP2
7Mc +69.3 dBm OIP2
2Mc +40.5 dBm OIP3
5Mc +40.7 dBm OIP3
ATTENTION: The current draw from a 12V DC supply is around 220mA. If you leave the voltage regulator as is on the PCB it will run very hot! You can use a small heatsink or relocate the voltage regulator on a box wall for nice and cool operation.
The input transformer is wound with 4 turns for the primary winding and 6 turns for the secondary.
The output transformer's primary has 4 bifilar turns (or 8 turns center tapped) and the secondary 6 turns.
The two inductors are identical and are wound with 18 turns.