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.

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.

IARU Contest

I did not try and make any contacts in the contest, but i did turn on the SDRplay and have a listen for a while. Not that i heard a great deal, but there was enough there to keep me interested for an hour or so. Anyway, mostly i played with settings and the like seeing if i could improve the reception. I was using an outboard bandpass filter for 40m. I know the filter is quite good because i have plotted it with the VNA, but when you are looking at 4Mhz of spectrum, and see the above image, it just reminds you of the job the filter is doing keeping stuff out of the front end. Lastly, take a look at that strong CW station, you can read the dots and dashes, who says morse is not visual HAHAHA.

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.

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.