Crystal Frequency Tester

Need a tool, make a tool as they say. Well i need to sort these 100’s of xtals into groups of similar frequency for use in xtal filters for an upcoming homebrew receiver project I have started. I have like 200 12mhz to sort through, so i should be good for a few filters at least. Its just a matter now i sitting here for a few hours and sort them all. Not looking forward to that. 🙂

No rocket surgery here, just your basic oscillator and buffer circuit that can be found all over the internet. Its simple, it works and it is reliable.

Built it up Manhattan style on a scrap of copper clad pcb. Yeah i love MeSquares to all you MeSquare fan boys out there. LOL

The Joy Of Oscillation, it works. 3 xtals checked, 100’s left to go.

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Lab Power Supply Final Update

Just A Bunch Of PSU Modules?

All good projects need a name don’t they? Sadly I think just a bunch of modules has been taken by Pete Juliano for one of his many radio projects. Oh well, such is life. I was thinking Buck This or Well Switched or Ebay Wonder might also do. Anyway, i have now completed the project. It has its lid on and it works. Here are the final images, a couple of them are even hi-res using the SLR and not my mobile.

Here is one of those Tribal Knowledge moments that we often hear about. This is 6 core shielded computer cable, I used it to wire up the pots. It helps keep things nice and neat.

It worked out quite ok, next time I will spend some more time measuring then cutting just to the right size.

I do not like playing with mains voltage or anything that can kill you. It is why i went for a modular option, so that when I am done there is no exposed 240v anywhere inside the case that dummy hear can touch while doing da-finger-poken inside the case. Not that the lid will come off hardly every, i just am very cautious of anything that can kill me.

Here i have started to wire up the DC power side of things. I am not all that much of a neat freak like my friend Simon 6MSC, who can make toriod winding look like an art form, but I am trying to keep things somewhat tidy.

Now we are getting into the meat of it, things are all wired up and zippy tied all over the place.

All the power is done and dusted.    

An overhead shot of the whole guts of it.

Now i do not pretend to be a metal worker. I was really happy with the bottom half of the case. But, alas i turned the top half into an abortion. First off i folded the metal on the wrong side of the line and made it to narrow so that it would not fit properly. So I had to try and fold it flat and start again. Sure i could have scrapped it and started over, but hey, why waste such a large sheet of metal. So i folded it a 2nd time, this time it fit, but one side is 5mm short. I can live with that. I know that the next time i make a case, which will not be all that far away, will be much neater now that I know what I am doing. Thanks for reading, hope you enjoyed the project.

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Lab Power Supply Update

So i got in and did a bit more work on the lab power supply. Finished off marking out and drilling every hole for every component so i do not have to go back and make a mess inside when i start to wire things up. Other than 2 tie bars across the top, the lower half of the case was done in the image below.

 

Mounted the switch mode PSU into the case, its held in with 4 M5 bolts and is not going anywhere, the fused, switched power connector and EMI filter are also bolted in with M5 bolts. The earth wire will be bolted to the case also with M5 bolts as well as serrated washers, so it cannot go anywhere. Go over the top on safety is my motto.

 

Mounted all the front panel items. From here its now just a matter of wiring up the spaghetti and making it all work together. But that will be another day, i do not think i have any wire suitable for 240v ATM and will need to go and get a meter of 3 core to pull apart for the internal wiring.

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TSSOP Soldering

I just want to say that soldering TSSOP at home packages sucks big fat balls. What a pain in the arse this has been. I spent lots of tine chasing out solder bridges. But they are done now and I guess i can start to use them. Oh and if you want to know what it is, its a compander, to be used to make an audio compressor for the uBitx, Bitx and the receiver I am building, and maybe ALC as well.

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Active High Pass Filter

So for the receiver I am building I figured that some sort of filtering is going to be required in the audio stages. Not entirely sure yet on the final make up of things, but to start with I thought that I would design and evaluate a high pass filter to cut out the low frequencies as this is likely to be fixed weather i am receiving CW or SSB. Though for the low pass filter, i do want either variable bandwidth or select able widths. More on that later.

As with all filters more orders, more betters LOL. And so i jumped online to a calculator tool and quickly designed up a 3rd order Sallen-Key highpass with a cutoff of 350hz. The simulation looked reasonable so i then simulated it in LTSpice just to confirm things and check the OpAmp i had chosen was going to be ok.

Schematic of 3rd Order Sallen-Key Highpass Filter.

Simulation Bode Plot

Next the circuit was built on a solder-less breadboard, the OpAmp is an NE5532 and negative supply rail is an LM2662 Charge Pump. This gives the OpAmp plenty of room to swing when powered with + – 5v.

For the initial testing the OpAmp was fed with 1vpp 600hz sinewave.

 

Dumb people do dumb things and I spend 10mins wondering why I had 10x gain in a circuit that should have unity gain, then i noticed i had the scope probe on 1x not 10x where it usually lives. There is my 10x gain.

For final shits and gigles i busted out the bode plotter and swept the filter from 10hz to 5000hz to see just how it really looks, and other than a little noise down close to DC, which i think is just the frequency generator not liking being that low, the filter itself is pretty much as designed. -40db at 100hz should be good enough for the kinds of girls i go out with.

Next job will be to either add in a couple of low pass filters for typical CW and SSB filter widths or have a crack with switched capacitor lowpass filters and make it variable. Thats a job for another day.

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Audio Amp Again?

I have been slowly and by slowly I mean very slowly working on the audio amp stage for a receiver that I am building. Its a slow effort as i try things, fail things and then finally decide on an actual plan. So, I was looking at using a TDA2822 in bridge mode as i have a bunch of those in my parts box here, but after building it and blowing a few up I figured stuff it, its time for a different tack.

Then i saw these on ebay, I have used the PAM8403 boards before but in a different configuration with a dual gang pot on there, they are class E, uber efficient and sound nice, so i figured fuck it, lets stop trying to make the parts count high and lets just use something that works. And yes these things work.

So i busted out the digital calipers and took a few measurements and knocked up a component for Sprint Layout and can now get to the next stage in the audio stage plan, compression, filtering, pre-amp and AGC. That is, if i do not get distracted by something else shiny and play with it for a while. 🙂

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Antenna is Done

So i got the dipole up now in its final position. The coax is now clamped to the mast so there is no flapping about in the breeze. The ends are up at their finished height. All up we have 7.6m apex and about 3m at the ends. Seems to be working ok, rx is certainly up.

 

SWR is as good as it is going to get and much broader banded than the old shortened dipole.

Photo bombed by Buster the Boxer. This is some fancy engenerding going on here. There is a 6ft star dropper 2ft in the ground right up the masts clacker providing the main support, the 2nd star dropper is screwed to the retaining wall and some big automotive clamps tying the 2 together. No idea what the safe working limit on all these things are LOL, but it did not move much during the big storm we had go thought last night. So i think it should be ok.

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New Dipole and Mast

Today i pulled down the old antenna and mast and put up a new and improved version of each. The old shortened 40m dipole was only ever meant to be a temporary solution that stayed in place for 3 years. So it was time to bring her down and put it to rest.

I bought a flag pole cause it seemed like a quick and simple way of putting up a new dipole and a balun because i want to be one of those balun guys who has to tell you what kind of balun he is using even though its kind of not important to the conversation but the word balun gives the air of technical know how and ability especially when you say its a 9 to 1 balun which is really an unun or as I call them 9:1 onions, because endfails will make you cry, but I digress. <– this is called sarcasm to anyone who is going to get hurt feelings over their antenna of choice, don’t email me call your local politician and complain to them.

Erected the flagpole and hoisted up the balun and new dipole cut for 40m on the flag raising rope, saluting while humming the national anthem and got the ends up in a temporary fashion to check the long or short of it with the analyzer, when the wife gets home from work. She comes out the back, looks at the new flag pole and remarks, Oh great, its storm season and you go and erect a dirty great big lightning attracter. Chuckles to herself and leaves me to antennaring like i know what i am doing. And if my Pythagoras is correct, when i put the ends up about 4m in the air, i should have 50mm to spare. The joy of living on a postage stamp block in the city.

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2018 Major Project

I have been slowly clearing things off my bench either to the its complete pile or the it does not work look at it another day pile. And not that that is done, it is time to start on a major project that will take sometime to complete. I really wish I had the time to knock out  rig a week like Pete Juliano, but alas I am neither that skilled or that time free LOL. Anyway, so what am i going to build, well a receiver to start with that might eventually morph into a transceiver.

Starting initially as a direct conversion and later becoming a single conversion superhet, It will loosely follow the simple-ceiver, simple-ceiver plus builds by Pete, which can be read about on his blog HERE: and a few bits off the bitx hacks page which can be found HERE:

Mixers will be Mini Circuits ADE-1, oscillators will be SI5351a with an Arduino powering it, audio will have AGC and some kind of audio filtering for both CW and SSB, I am currently not sure if i will go passive or use a Teensyduino and DSP audio filtering, I have the bits for both so either or can be done quite easily, but filtering will not be part of the initial audio amp build, all the rf amps will be Pete’s J310 as dual gate mosfet amps, bandpass filters will probably be my own 3 band switched module.

So that is the rough details of what I am planning to do, now its a matter of starting to build it. With that in mind, I will be starting tonight on the audio amp stage, using the AGC from bitx hacks for the bitx 40, a 2n3904 preamp by Pete Juliano and a TDA2822m in bridge mode. I will be building each stage on its own scrap of board for testing in isolation using manhattan construction and Me Squares.

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