Thursday, February 11, 2010
BF981 VHF preamp - 2
Another day, another test.
I decided to let the airband receiver stay with the same schematic. An BF981 preamplifier then the NE602 mixer and a TCA440 455Khz IF. Reason is I had to put another preamplifier after the SBL-1 to cope with the losses in the mixer.
With all this experiments I broke an BF981 that was replaced by an BF961.
Here the last schematic tested. Don't expect to much from a simple amplifier like this one unless it is placed close to the antenna. You can connect an hf radio right after the sbl-1 decoupling capacitor. Anyhow this also proved the the Si570 can be connected to the sbl-1 with good results, I already knew about the NE602. Amplification starts when G2 is around 2v, not much improvement if is goes bigger than 4v.