Solar Panels for Homebrew Projects.

I have been playing with some solar panels i got off ebay, they are 6v 1w. Its winter here currently and the sun is not as intense as it can be, so its a good time to see just what these panels can do and how close to their ratings they come. Surprisingly, pretty close to specs.

Started with a single panel checking voltage and ampers. Voltage looks good, 7v on an open circuit, and close enough to 6 under load.

Single panel was peaking about about 130ma, near enough is good enough.

Put a single panel on some very dead NiZn 1.6v per cell, cells i had laying about, and in a few hours all were reading 1.5v per cell, which was nice because I will use those cells with 2 panels in parallel to keep them charged for an Arduino Weather Station im currently building.

Next i paralleled all the panels up, not facing the sun in an ideal way or anything, voltage was close enough to 7v.

The for panels in parallel gave a nice 0.5a of current, so i got to thinking about series and parellel up 8 of these and make a nice 0.5a panel for the HB1B YouKits cw transmitter.

Series up 2 panels. 13v, perfect.

130ma, peaking 150ma in winter sun, 8 panels should give a nice 0.5a and keep the 7ah deep cycle well and truly topped up all day.

40m Band pass Filter

So i came across this schematic on Ebay for a 40m dc receiver kit, the front end looked nice so i copied it for my own project.

I am assuming that the band pass is transforming impedance also 50 ohm in and 1500 ohm out into the 612 mixer. I built mine for 50 in and out, by replacing the 270 and 18pf caps with 220 and 56pf.

Using my scope and signal gen i tuned the filter for max amplitude on 7.100mhz, and then did a sweep of the filter from 5 to 9 mhz and plotted its response on the graph above. Looked better than I expected.

Here is the filter as built on the board. Followed by a mess of failures where I was trying to add in a preamp that just kept loading up and not doing anything. Such is life.

SMD Soldering, Easy Mode!

Smd soldering is not always the easiest thing to do. I am certainly no fan of doing smd with a solder iron, sure some of the PRO guys can solder even the tiniest components with an iron, I am certainly not one of them.

So I bought myself as fancy smd reflow solder station to do some smd boards i have with past and hot air. And let me assure you, it was money well spend as it was just so easy.

The process is very simple, add the tiniest amount of solder paste to the pads, then place the component onto the pads, the paste will hold them in place, add hot air and watch the magic happen.

As the flux burns away, the solder coalesces and wicks to the pads and the component tabs, surface tension then pulls the components into alignment and down onto the boards pads. 9 times out of 10, leaving a perfectly solders part. See C4 and 5 in the above images.

All those other things you are scared of like tiny smd transistors become cake and nothing to be feared any more. I certainly won’t be bothered with kits and projects that contain smd anymore, even ones with multi pin devices should be super easy now with hot air and solder paste.

The above is a 10w CW transmitter kit from ebay. The schematic can be found here on my blog: http://robs-blog.net/2016/04/11/10w-radio-shortware-cw-telegraph-transmitter-7-023mhz-kits-hf-power-amplifier/

So we got it built, connected it up to an swr power meter and dummy load, as well as hooking the scope up to the output also and keying it up for the first time we get a nice 23.25 V RMS output, or 10w, I did not expect that it would deliver to the specifications, but it does, and that is kind of amazing for a cheap Chinese kit off ebay. This is in xtal mode, I still need to try it in VFO mode and see how much drive is needed to get the 10w out. But for now, I am pretty happy with how this thing works.

80m VXO

So today i thought i might be fun to whack together a VXO for 80m and see just where i landed me. Now i know that pulling crystals very far is not an easy thing to actually do, especially when they are on the lower end of the spectrum. So with this in mind, i set my initial goal as 1khz pull. I figure if i can get that, its kind of usable in other projects.

First job is to get on google and find a simple schematic, with that out of the way, I can get to putting the ugly back into ugly style home brewing and slap something together on some scrap board.

And slapping together is just what I did, a pair of 3.6864 xtals, with 10uH series inductance and 170pF of capacitance in the polyvaricon.

Give it some power and connect up the scope and freq counter and am greeted with this ugly waveform, harmonics, bias, its a mix of everything that is wrong in the world. So let see how far we can pull these bad boys.

High freq is 3.6867

Low freq is 3.6863 HAHA we managed a whole 400hz agility, as good as useless, but it was rock stable, pun intended. So i did a but of goggle foo and found that I can get much better pulling power with more inductance, 10uH is orders of magnitude not enough, so i added another 200uH in series and got a total pulling power of 2khz. 2khz is not much in the scheme of things, but, for a cw 80m rig, 2khz is a nice slice of spectrum to be frequency agile on.

So, whats next? rip out the xtals and drop in a ceramic resonator and adjust the series inductance to suit. Should see a good pull range with that.

Arduino Logger Update

Got back into a little development on the Arduino Logger. I have now transfered over from using a Uno/Nano to now using a MEGA as i needed that little bit more overhead in Sram. So i have it all zipped up in a box now, and am slowly working on adding to the code to make it more usable. As you can see in the picture, there is now Operator and Station Calls in keeping with how the WWFF program wants the data formatted in CVS format.