I will be closing my blog down for sometime. I am soon to be without an income, or a very reduced income for quite sometime, so I am taking this opportunity to make backups of my blog and to hand the server back. I have to do everything I can now to survive and this is certainly a non essential item.
The server will remain up until payment is due and then I will turn it off. I may bring it back up from home off my broadband service, but that would be a rather slow option. Things are what they are, and we all have to do the best we can right now.
Good luck everyone and Gods speed. What i will probably do once i have some normality and get back into homebrewing is do my videos, youtube costs nothing.
Corona virus, whats it mean to me and my home brewing? That is an interesting question and one i am asking myself daily. Sure it looks like I might have more time on my hands with the chance of being locked down growing daily. So that is the positive. The negative is I am also watching the economy tanking and along with it my income. I am a contractor, our clients are all pulling work so that means I will not be earning much at all. This is ok, I have some savings and will survive, but it means that I will lock down my budget to essentials and so I cannot see me starting any new projects for quite sometime.
However, I do have 4 or 5 projects already going on at various levels of progress, so i have plenty to do for now and I have a lot of parts so that is not going to be an issue. I think what will happen is that once i have worked through the projects in the cue, I will end up going back to doing manhattan builds with through hole parts. I have a lot of board and parts, so I am good for a couple years at least. About all it will really mean is that I wont be buying any fancy PCBs at all.
Oh and I have a lot of kits here also, so I can bring them out when things get desperate and have something to build. All in all, i will be ok, but if things get really tight, I might have to shut down my blog, or move back to cheaper VPS hosting rather than having dedicated server hosting. One stupid flu and the world is turning to shit.
I dont remember ordering these transistors, but they are cheap, i have 100 of them and so i mounted one up on a test fixture to see what it could do. To my delight, I was seeing 1.5w out and I am thinking I hit the jackpot. I can push pull these as a predriver stage and its not going to cost much for a good amount of power.
A couple hours later, I noticed the scope probe was on 1x and the scope on 10x. My super awesome power just vanished out the window. Its still a good transistor, reasonable gain for small signal stuff, good enough bandwidth to be useful for most the HF bands of interest. Its just now a power house HAHA.
I am building something where I needed some IO expanders. I have these modules sitting in my box of arduino crap and figured i could desolder the headers and reverse them and then plug these into my pcb board.
I got to starting on that when I realised, there is no annular ring on the top side of the board. There is no way to really solder the headers in the other way. Bloody stupid board designers doing stupid things like this.
So I pulled everything off the shelf to give this a test. Its working. What I have done in the pictures below was to use an DDS vfo as the incoming 7mhz signal. It run into as much attentuator as I have here, giving a final signal out of about -95dbm or there abouts according to the spec-an. This number is rather uncertain because that is right on the noise floor of the device and by my calculations, the actual signal is closer to -100dbm. Now I am still hearing a signal out of the speaker at that level. So its not an Icom, but its not totally deaf either. I do think i could use a little more gain in the audio stages. But, we will see how things pan out with some loudish signals on 40m this afternoon.
WOOP i have tamed the beast. Its actually reasonably linear now and not busting into oscillation just because it can. I will try and hook up the rest of the crap to it later today and see if we can hear some signals.
For whatever reason, the MMIC amps in the receiver are super unstable. They have 2 states, oscillating wildly or not working at all. This is a real head scratcher, because the exact same circuit using though hole parts was super stable. The other thing is, if i stick my finger on the input cable, it becomes stable again. Go figure.
OK I got it sorted out and now its stable. The issue was the limiting resistor R9 was to low a value. I am not sure why the through hole version was happy with 60ohms and the SMD version wanted 150ohms. But, either way, I learned a valuable lesson here with MMICS, if they are going bonkers and oscillating wildly, cut their current back by increasing their limiting resistor.
Its still not working, but it is getting there. All be it, slowly. So i fixed the oscillation in the PA, replaced the fet and now at least the PA is all working as it should be. Now I am still not getting anything out of the Mic. Not sure what is going on there, but there is power and it worked when i bread-boarded it. Obviously something is not right, but I will work that out soon enough.
A few days back I slapped together an superhet, it kind of works, certainly nothing to rave home about that is for sure. A few take outs from it, using MMICs as IF amps is not a clever option as you really cannot control the gain all that easily. And the other thing is audio. You really gotta make sure you use an audio amp with sufficient enough power rating to drive a speaker.
After playing around with things, I did notice that I had some rather obvious distortion. After changing out the audio amp for something sturdier and testing the audio stages by themselves, I came to the conclusion that the distortion was coming from the IF amps. I will see if i can tame the gain in them somewhat and see if i can get this working better.
I am still not sure about the audio sound, the SSB filter is somewhat thin and the audio AGC is really not AGCing. I am not sure what is going on there. But I have an AGC ic here on a board that i might try and see if that works better than the discrete version that I built.
I configured the superhet with both CW and SSB IF filters. Not sure how good my filters really are, but once i sort out the distortion, it should be able to see how the filters perform.