I plan to be activating the following parks over the Easter holidays. There might be another couple added to the list on the Saturday. Just depends on time.
Fri, 14 Apr 2017 Afternoon (WWFF) VK4FFAB on 7.030 CW in (VKFF-1517) Cooloothin Conservation Park 7.144 also will self spot
Fri, 14 Apr 2017 Evening (WWFF) VK4FFAB on 7.030 CW in (VKFF-1554) Harry Spring Conservation Park 7.144 also will self spot
Sat, 15 Apr 2017 Morning (WWFF) VK4FFAB on 7.030 CW in (VKFF-1551) Great Sandy Conservation Park 7.144 also will self spot
Sat, 15 Apr 2017 Afternoon (WWFF) VK4FFAB on 7.030 CW in (VKFF-1667) Tuchekoi Conservation Park 7.144 also will self spot
Sun, 16 Apr 2017 Morning (WWFF) VK4FFAB on 7.030 CW in (VKFF-1645) Six Mile Creek Conservation Park 7.144 also will self spot
So i have been busy laying out some boards for my receiver project. Bandpass and Lowpass filter boards, DDS and AF Amp board and a shield board for stacking these things together with other bits of circuits. Got them sent off the the fabricobblers in China and will have them back in a few days and will start to assembling them
3 Band Filter Board
DDS VFO and Audio Amp board with TX and RX switching.
A shield board that stacks under the DDS board.
So i was looking for a way to make a negative voltage. Did a bunch of google and came up with a number of different ways. One that was kind of catchy was to use a 555 timer as an arsetable vibrator with a couple of caps and diodes to invert a signal voltage.
So in the above schematic, everything on the right of the 555 timer just sets up the chip to make a square wave which is then fed into C3. C3 and D1 invert the signal and D2 and C4 act as a filter.
So i built this on the breadboard as it gets very little love in this house. The cap on the right is the input and the output is taken from the junction of D2 and C2.
Using my signal generator rather than a 555 timer, I fed an 8v 50khz signal into the circuit. Yes my RedPotato scope has loss from the input protection diodes on its input and i am not using any compensation. So the yellow trace in the scope output is the input signal and the 2nd probe was used to measure the output voltage, 8v in -7v out, which is about right accounting for all the diode losses on the scope input and in the circuit under test. All in all i learned something out of this, which i am happy about and now actually understand what its doing and how it works.