An easy Sunday morning spent baking. LOL
I love CW, I am also rather crap at CW, but now and again i like to have a go just to see what happens, sometimes its good, sometimes its bad. This story is the latter HAHA.
Something i do now and again when bored, it drop the the bottom of the band and hit the auto keyer on the radio and just leave it call CQ for 10mins. Bottom parts of the bands are often dead, conditions have not been all that good for a while for anything other than FT8. But with the sun spots and solar flairs, other modes are looking up.
So last night after getting bored with FT8 I dropped down to CW on 15m tuned around and heard 1 station in the UK calling CQ, i worked him and then found a frequency to park on and call CQ. After 10mins of calling I was just about to call it a night and then out the blue someone came back to my call.
I was not prepared for this, no time time to pray to god, i was on my own. So, i copied the call quite ok, UA3DEQ, entered that into my log and proceeded to send him a report. This is where things went really really wrong.
I was making mistakes and making corrections and worst of all, he kept sending back NO NO NO UA3DEQ. This morning, in a moment of clarity realized that I was not sending Q dah dah di dah, I was sending L dah di dah dah. HAHAHA what a moron. I did send Igor an email and explained my predicament and he seemed understanding. I really need to work on my CW skills a lot more. With the sunspots improving and moving into the new solar cycle, I am going to have to spend a lot more time doing CW and much less time doing FT8.
I did get there in the end and sent Q a few times, survival, that was my great victory.
Don’t you love it when a plan comes together? Well, if you are going to copy the work of a master, you cannot go past copying the work of Wez Hayward. Having built this amp design before on some copper board with through hole parts and done a whole lot of measurements on it, I knew that it was a design that was not going to disappoint. What I was not ready for though, was just how much better it is when using somewhat better design principles, SMD parts and an average PCB layout.
Just how good is it? Well, flat gain from 1Mhz to 50Mhz, without using any fancy transistors, just plain old vanilla popcorn 2n3904’s.
The dip between 5 and 7Mhz is an artifact from the NanoVNA and is not actually there, i looked with the oscilloscope and function generator just to be sure. While the NanoVNA is good, its not perfect, but as AVE likes to tell us, its good enough for the kinds of girls I go out with. The gain, in dB is actually also not right.
The input is 100mV and the output is 1V, by my math that is 20dB gain, so its exactly as designed. All that is left is to populate the attenuators and I have an variable gain amp to use for testing purposes or a receiver front end, which is the ultimate end use for this.
I know I work a lot of FT8, mostly because that is where all the action is at. But I also like to dabble in a little CW. I am not much of of a CW op, but i know enough to be dangerous. So most times when I am doing some radio, I also drop down to the bottom of the band and call CQ for 5 to 10 minutes just to see whats going on. As you can see, I was being spotted in quite a number of places, some with with a signal strength strong enough to work quite comfortably. The problem is, there is no one listening on CW.
For a while now I have been thinking of receiver front ends. Yeah i know in many situations, home brew receivers do not need RF preamps, but hey, if i can build it, why not?
I have actually tried a number of times to make something that resembles variable gain, some kind of worked, others were a dismal failure. I think the best of of the ones off the internet was the dual gate mosfet front end with J310’s out of the simpleceiver. It worked well enough but was not really want I wanted and it did not have the bandwidth i desired.
So what do i actually want? Well, i kind of figure that I want a broadband amp to cover all of HF and maybe even all the way to 2 meters, with at least 20dB of gain and also -20dB of attenuation. After a lot of thought, I came up with the following solution.
What i did was take the TIA amp as designed by Wez Hayward, because its very broad banded, even with rubbish 2n3904’s I was getting flat gain from 80m to 6m. So with transistor with a better fT i should be able to get to 2m quite easy here. With a fixed gain of 20dB it has more than enough gain.
The amp is then followed by a series of 4 attenuators that can be switched in and out using RF relays suitable for use into the VHF bands. This means I have variable gain from -23dB to +20dB in 3dB steps. More than goof enough for the kinds of girls I go out with.
So I knocked up a test board to put it all to the test. Rather than using the expensive RF relays, I put in some DPDT switches I have here in a box. The boards are back from China and are with the post office for delivery tomorrow. I hope to build up a couple of these with different transistors I have here to see if it will do exactly what I want.
More to come on this.