Ham Radio Universal Prototyping System

Now i mostly work in SMD and design board for things I would like to test. But i do have a lot of through hole parts still that are sitting there pretty much doing nothing, so I started thinking of ways I can use them up and I think I have a solution. Anyway, I have a whole bunch of ideas I would like to try, different circuits to built, test and assemble into working transceivers. Back in the day, which day, ummm, ye olden day LOL, hams would breadboard circuits using actual breadboards. My idea here borrows on that concept and brings it into the modern age.

Starting with the baseboard, rather than mums old chopping board we have a PCB that has 2 power rails for 12 and 5v, a bunch of bypass caps, a DC barrel jack for power input and a 5V regulator. Lets face it, most of what we do only has 2 power rails and those are the most common. Along the baseboard we have 2 rows of dual 10pin headers for our plugin modules to slot in and out of. Each header has 2 power, 2 ground and 6 unused pins for moving signals between the plugin board. Making for neat and tidy wiring.

 

The prototyping module boards connect to the baseboard with right angle header pins. Either dual or single row header pins can be used, I used single row so i can easily wire stages to the header pins for routing between board on the baseboard.

The tops of each board can be locked together using brass standoffs. This makes for a modular system you can plug and play, mix and match different circuits for testing and characterization.

The backside of each module board contains grounds top and bottom as well as power buses on each side to make veroboard type prototyping nice and simple. This system should allow for quite interesting builds to be achieved  one stage at a time.

DOWNLOAD: Baseboard_gerber

DOWNLOAD: ProtoBoard_gerber

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Soldering Pro Tip

Lots of people say they have a hard time soldering. Well, I wear reading glasses because my eyes are not what they used to be and my hands are fucked with arthritis, i have only 55% use of my right hand and 70% in my left hand. It is what it is and they are only going to get worse over time, so no use bitching and moaning about it, i just get on with living as much as I can.

So, soldering, here is the tip and only the tip mind you (AVE HAHA) bright white light so you can see, and extra magnification. Even as a handycapped I am working with SMD components, I just magnify things enough and use the right tools. And the tools being different shaped tweezers and a nice thick 3mm chisel tip on the soldering iron. Yes, that big chunky tip is the key to things, you want to hold as much heat in the iron as you can. Use thin solder, 0.6mm or thinner because a little dab will do ya (AVE) and with heat in the tip, you are not spending time heating things up, just dab and go, dab and go. Tack one side of the part, lay the solder over the other pad or pads and dab the iron and its done.

The parts I use go down to 0.2mm pin pitch, SOT23 and 0802 in passives. I stay away from BGA and other leadless parts, they just suck, but everything else is pretty much good to go. So don’t be afraid, just illuminate and magnify, if you can see it, you can solder it. OH and flux the fuck out of it HAHAHA, flux will make you a winner.

 

 

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Antenna Tuner, It Works

Well, the saying goes, 3rd time lucky. In my case it is 4th time, well 4th version of the design and 3rd time I have had boards made for this. The good thing is, it works this time. There are not masses of strays floating about anymore. They are just about all eliminated. You can see by the gain plot that its nice and linear with 0.5db loss from 1 to 30mhz. That is good enough for me. The losses are actually a little less than that, because i did not calibrate out the cable losses, but lets call it good enough for the kinds of girls I go out with.

Now its just a matter of rewriting the software to account for the changes I made and then putting it to use. Next version will have the capacitace switchable from low Z to high Z and there will be an SWR bridge and probably auto tuning. For now, i will finish this off and put it to use with some other home brew bits I have here.

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It Did Not Work

 

I was bored yesterday so i thought i would try building an amp from these transistors I have sitting in the box. Ummm yeah I smoked it pretty hard before I even got any significant power out. I think the main thing is that I could not drive it hard enough to get it into the linear region and I might have had a bit to much bias happening. I will try again, but from what I was reading online, these transistors have a habit of wanting to detonate.

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Antenna Tuner Update

 

Looks pretty dont it LOL. Well it does not work. Why you may ask, well, the IO expander which was meant to be able to output 5V and 20ma per pin, could not raise the skin off a custard. 1.2V out into an open load is all i could get out of it. I do not know why, schematic is correct, the voltage is correct and the reset line is pulled high, I can read and write to the IC over I2C and turn the pins on and off, they just never get anywhere near being 5V out. Anyway, I have redesigned the board using only the pins on the micro to control the relays, having bodged some wires into it to make sure it would work.

I also have another iteration in the pipeline, were I have added some switching of the capacitance to either the input or output sides for low z and high z loads and have also added swr meter circuitry. It might be months before i have that totally ready, I am going to spend a lot more time on the layout to get it right.

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Air Variable Caps Part 2

Air variable cap parts arrived a couple of weeks ago now. Have had this sitting on the bench for over a week, thought i should post about it. These are the panels, i separated them by cutting the tabs off on the bandsaw. If i ever make a second iteration, I will add in some drillings to make the tabs break off.

6 plates top and bottom give a minimum capacitance of 20pf.

Fully meshed they give a maximum capacitance of 133pf. Using the parts on hand, I have enough plates to build 2 capacitors that are 60 to 400pf or there about’s, being 15 plates top and bottom. Its just a matter of spending the time assembling them. There are some changes i would make if I was to do them again, like make the rod 5mm rather than 4mm, this would make it easier to mount a knob on and things like that. There is a spring front and rear to apply resistance to the movable plates so they hold their position. Other than that, it works.

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New Country, St Lucia

This is a turn of events for my blog, I actually did some operating today. In fact it is even worse than that, I turned on the 2m fm rig and put it in scan mode and sat listening to a club net for a good 30mins while i did stuff for work. Shocking I know, but, you know what? It was not all that bad, at least the conversation was not about the weather, medical conditions or tomatoes.

So that got me excited enough to fire up the Icom and do a little FT8. A bit on 20m, a bit on 40m and I managed to work a new one for me on 40m. I did hear this station on 20m and pskreporter said he was hearing me, but never did see a CQ, so im thinking he might have taken a break from it. Anyway, got him on 40m and that is good enough for me.

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Yet Another 5w Amp

I have had the parts and boards for this sitting here for quite some time. After posting all the schematics and board files for everything i had working, i took a few weeks off to chill and regroup. Actually I have been racing F3 in Iracing and having a really good time. So anyway, today i got keen and thought i would assemble this board to see how i went. Other than leaving the DC blocking caps off and having to bodge them in, the board actually worked well. It has been sitting on the bench running for the last 30 mins and its barely gotten warm. Talk about some efficiency in these modern transistors. Signal source is an SI5351a and so square wave in and square wave out. This thing will chooch 5w all day without a problem. I was not sure it would work well, the fets are speced for UHF and I am using them at HF. I have the big brother to this fet and it will do 20w, so when i get brave I will have to see if i can make more power.

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The Filter That Never Was

One upon a time in a land far far away, LOL. Well, this is one of those stories and it reads like a horror story. I have spent all day on this, pulling my hair out and trouble shooting and wondering what the fuck is going on here. Is it me, was it my design, was elsie screwing me with stupid values. Well, hold onto your hat Batman, this is going to be a bumpy ride 🙂

It all starts here. Designing a filter in elsie. Bandpass filter, 7.150mhz center frequency, 400khz bandwidth, chebychev response with 0.001 ripple. All good, simple even. I do not like the inductor values it spits out, i rescale the network to use 500nH. And begin to wind up the coil forms.

Everything goes to plan, i wind up 9 500nH coil forms, LCR meter says I am a genius and I agree with it, not only am i super smart and know everything, I am also good looking and a legend. 😉 That was this morning. Now let me rewind things back 4 weeks ago when this plan started to evolve. This should not be the problem.

After having elsie tell me what to do, I laid out this schematic in Diptrace and proceeded to produce a pcb to use. Schematic looks fine to me, looks the same as what elsie says i should do. This should not be the problem.

This is a small screen shot of the PCB layout, if you close your eyes and squint you can see the series capacitance and the shut capacitance and the inductance are all in the right places electrically. This should not be the problem.

Elsie gave this plot as an idea of what the filter should look like. Looks fine.

Never to take the word of a machine seriously, I checked the design in LTspice, just for sanity sake. Looks fine.

Then i built the filter, just one mind you, there are 4 on the board, but i have learned the lesson many time not to jump ahead of myself, because as the Mythbusters would say, failure is always an option. Becides, things going to shit are the norm around here. Today was no exception, bloody abortion of a filter was on 14mhz. Its like 1/2 my inductance and capacitance just vanished into thin air and left me with a pile of shit. And i had no idea why.

Being the clever idiot that I am, i did say i am a legend right, I began by melting the plastic cases on the relays, I mean pulling all the caps off the board and measuring them. Frequency went up, so that means less capacitance and less inductance. I am the boss of making strays of everything on my boards, so i usually have more than i need. Caps turned out to be correct.

So i rechecked the value of the inductors.  Actually i wound the slugs all the way in and as expected the frequency shifted lower. LCR meter says that i had 600nH. More than i needed but I was still on 14mhz, not 7.

Then after much wailing and gnashing of teeth, I grabbed out an inductor of a known value and measured it. It was wrong. Not just a little bit wrong, but a lot bloody wrong. I calibrated the LCR meter and checked the known value again and BOOM right on value. Checked the other coils i wound and they were 160nH not 500. Well there is your problem. I screwed up royally. I did not calibrate my crap and thus made a huge pile of it and wasted half a day on what should have been a 3 hour tour, a 3 hour tour.

So there you have it. That has been my day, fun, entertaining and well, i learned a valuable lesson. Never trust your meter not to lie to you. And with that, i am off to have a shower and cook dinner. The filter board can wait now for another day. I am done 🙂

Oh one last picture, i put some 500nH crappy inductors in the circuit and yeah its in band. Now i need to rewind my nice coil forms and make some filters that do not suck as bad as this nano vna plot looks.

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