I have not had much luck with the inductance setting on LCR meters. Most of them are crap, inaccurate and just plane useless. I think this is the 5th cheapish meter I have tried and I have finally hit on one that works and works well. In the picture below is a 1.8uH slug tuned variable inductor. So yes, it works and is accurate and with 3 decimal places its going to be nice to use for getting those hand wound toriod inductors right. The test frequency is a bit low, it would be nice if it was in the MHZ range rather than KHZ, but for that you need to spend up big on high end gear, not $70 on ebay.
Ok, with my arduino woes out of the way, i can now focus on the transmitter part of the 3 band CW rig project. Cannot rush these things and i might even get this rig working before i die, well we all have goals to shot for. LOL.
So what do I need and how are we going to go about it. For a start I am a paddle guy, single lever paddle to be precise so I need some form of built in electronic keying. A fixed speed is all i need, say 15wpm, most of the people I work from parks are slower cw types so 15wpm is a nice speed. Memory keying would be nice as I will be using the rig mostly for WWFF or SOTA a basic CQ macro and CQ Sota and CQ WWFF are all i need build in. It needs to provide the sidetone and finally this needs to be able to key the transmitter on and off as well.
As far as arduino keyers go, the Arduino CW Keyer by K3NG is probably the duck nuts. Fully feature rich and does everything other than be the other half of your contact. I looked at it, tested it and its bloody awesome, but i really do not need all that complexity so I have decided to roll my own.
So i assembled some bits and bobs and started to write some code. I have it sending nice perfect 15wpm code already using the Piezo as the speaker. I probably will not release this code. I think if you want a full fledged keyer use the one by K3NG and if you are like me and just need a simple keyer for your project, then its time to man up and write some code. It is really not that difficult at all.
A Tale Of Woe
So i got this brain wave that it would be nice to use bare IC’s in my projects rather than Uno or Nano board supported on headers. It all seems rather simple don’t it. Buy some IC’s with the bootloader already installed, drop them into your socketed Uno board with its on board AVR programmer and Bobs the uncle who touches you inappropriately at family gatherings.
But Oh No No No No, things cannot be that simple can they. Firstly, ebay is a minefield and while you are probably getting top quality IC’s and not chinesium grade floor sweepings, the term with bootloader can be somewhat vague. Yes the IC will take a bootloader, yes the IC may or may not come with a bootloader, but what bootloader is anyone’s guess.
So armed with what look like a pile of bricks and armed with your google foo, you start to look for answers on the world wide interwebs because the pixies are not going where they are meant to or doing what you want. And here armed with your vague error codes from the arduino compiler you find 100’s of people who have no idea how to fix the problem let alone what the actual case of the problem is telling you all sorts of bullshit. From the IC is bricked and cannot be fixed, from edit this file, edit that file, use a capacitor, use this method of wiring, that method of wiring, this programmer, that programmer.
Well I tried them all and guess what, none of these bullshit explanations made any fucking difference to shit. It all comes down to the stupid who is connecting things together. After trying 6 or so different ways of burning a bootloader i finally got one of the 4 different programmers to actually work, it sent the bootloader to my so called bricked IC’s like a pro and then went on to program some software on the IC as well and made an LED blink.
Oh and don’t ask me how i got it working, i really do not know, this programmer did not work the first 3 times i tried it and today for god knows what reason it worked. Thats arduino for you. I giant pain in the arse when things do not want to happen and a joy to behold when things go well. Your Mileage May Vary.
After 2 years and 100 odd activations, I somehow managed to break the sotabeams linked dipole. Its been used, abused and not treated very nicely and its never let me down. Even once i noticed it was broken it was fixed with some electrical tape and we kept on trucking. Sotabeams, value for money thats for sure. Now to work out how I am going to fix it.
So its been a busy day here in the workshop. Caps arrived today and we set about to making low pass filters for the transmitter. I started by sticking in the caps and then in turn winding the inductors for each of the 3 filters, 80, 40 and 20m bands and giving them a test by feeding in a square wave from my it makes nice distortion signal generator.
80m Low Pass Filter Under Test
The output was fed into the spectrum analyzer on the Red Potato. The spurs either side of the fundamental are crud from my signal gen, it does that when you start to turn up the output. This was a 10 volt peak 3.6mhz square wave being fed into filter and I through up a few cursors to get some levels, first harmonic is -60dBm down on the fundamental. That should be more than good enough.
I did the same for the 40m and 20m filter, again -60db down on the first harmonic, the above image being for the 40m band.
Something I was worried about was isolation on the relays. These are no uber doober premium rf relays, no no no, they are 10 for $1 Chinesium Grade floor sweepings and seconds off Ebay. So we stick the signal in the in port and connected the 100meg Hantek scope up to the other end and turned the volts per division down to the noise floor and looked for signal leakage. Nothing, maybe a couple of microvolts but that might have been an aberration. Either way, good enough for the kinds of girls i go out with.
Final board all together and soldered up.
A bit of an idea of how its all going to go together as a stack. I think things might actually work ok after all. Touch wood. Tomorrows job is to program an ATMEGA IC to work as an iambic keyer, add in some switching and buffering to get the transmitter up and working. Not sure if i am going to have an external PA yet, or just use a couple of BD139’s and get 3 or 4 watts out. Will see how we go.
I watch a bit of blacksmithing on youtube and something these guys often say when they are building something is Need A Tool, Make A Tool. Its a good way to think about life, why run to the store when you can make something now and do the job you are trying to do now.
So, with my breadboard setup, I am wanting to monitor the current demands of everything I am hanging off the one micro as it will eventually be running off solar and batteries and I need to make sure i have a few days of battery supply and enough solar to charge everything up within a days daylight. Don’t want my things turning off and losing precious data.
So i grabbed an Oled display i could not get working out of the box and got it chooching, a voltage and current sensor that i had doing nothing and made them all talk together with some software and she is skookum as frig. So all i gotta do now is wire it up with a nano stick it in a tiny box with some banana sockets and put it in between my power supply and my breadboard and I will always know how much current we are drawing.
So when i designed the filter boards one thing i took into consideration was that often you need to use multiple caps to get close to the value required. Now when i first started home brewing, i used to obsess about values, oh i dont have this value, oh i dont have that value, but now i really do not give a crap, as long as its in the ball park she’ll be right mate, mostly the values are not super critical as long as they are ball park.
I mean does it really matter if the corner frequency of a LPF is shifted up or down a few 10’s of Hz, or Khz for that matter because your cap values are 5% off ideal? I am using 10% caps as it is, so there can be a bloody lot of variation here. But I did manage to get pretty close to the numbers using the one range of MLCC caps that minikits.com.au most of which are also NP0 types also. So below are the schematics for the filters.