WWFF Park Activations

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

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Receiver Boards

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.

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Arduino Weather Station

Another project i have had going on for sometime an arduino weather station. Got some of it now working on the breadboard and still have some modules to go including RF transmission of data back to an indoors station monitor. More on this to come. Right now, I am just making sure that the libraries are all working and integrating the code together into the one program.

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5w Class C Amp

I was reminded by a video by VK3YE about a PA chain he is working on using BD139’s that I had sometime ago thought about using them in a class c amp. I had seen something similar in a schematic for a circuit by Diz at Kits and parts. When you can get a good 5w from a pair of transistors that cost 20 cents and a couple tv baluns, why settle for less in your qrp rigs.

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Negative Voltage

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.

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S-Meter

On ebay there are these audio meter kits for like a buck delivered. I plan on using one of these as an S-Meter in receiver I working on. I know its hard to see in the image, but the 5th LED from the left is lit, the 10 turn pot makes adjusting the signal range a rather trivial matter. Just trim for the max audio voltage from the AF stage and it will be in the ball park. Its certainly no calibrated S-Meter, but it should give a fair indication of the strength. I am just feeding it with a few volts 600hz sinewave from my signal gen.

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