Decade Resistor Box

Just finished a new decade resistor box, it currently covers 10, 100, 1000, 10000 ohms, I did not have any 100K or 1M 1% resistors so i will have to go back and add them in at some stage, not that it is really important, none of the typical measurements that I will be doing will go anywhere near such big values of resistance.

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New Server Host

Well after being with the same host for 2 years, they decide to shutdown the actual rack I was on and leave me in the dark. Given 10 days to move hosts I think I have managed to bring my blog across to a new host and get things working again with minimal fuss. I am sure something will pop up thats not working, but for now it looks like i am back in business and can homebrew rather than play interweb server man.

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Youkits Tuner

So the HABIB (HB1B) got himself a matching tuner. I also have a Sotabeams 10m pole, so the plan is to run these 3 things together with a 1/4 wave 40m vertical with a couple of radials, using the tuner to match the impedance difference. Won’t be the greatest for locals, but should improve things with DX with a low angle take off of the vertical.

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Switch Mode PSU Noise

So a few weeks back I got making this nice looking lab power supply, but other than running my bench LED lights, its not been used. And thus begins my world of hurt, because the other day I had a project that needed some power and after connecting it up, things just were not doing what you would expect them to do.

 

A circuit that should give a nice sine wave looked a mess on the scope, a receiver I powered up had this god awful switch mode racket on just about everything. So get get the pixie wrangling gear out to take a look at what was going on and it was nice a pretty picture.

 

 

As you can see from the scope output, the 12v DC was not pretty and it was making my projects not happy. So i figure, It needs a filter and I do 30 seconds of math and figure 10 to 100uh of inductance with 100uf of capacitance should be close to enough to the business.

So I make a nice looking filter and connect it up to the power and yes it attenuated the noise and ripple but it really did nothing else, all the problems were still there.

 

When you know you are chasing your own tail, start talking to the smart people. In my case this is Brenton, and we got talking about all aspects of the design, what modules I used what SMPS i used and a bunch of other specifics.

My pretty Power Filter

Well it turns out, had a fundamental flaw in my PSU design, I had left the 0v DC floating and this is a trap for young players. Because in the words of someone smarter than me  “Without that connection the output is magnetically isolated and noise leaks out via capacitive coupling in the output transformer.” So after checking that 0v DC was not tied to Mains Earth, they were quickly coupled together and all my problems went away.

 

And as you can see from the first scope output above, the power is now rather clean, and in the 2nd scope output, is the DC after my new filter. The filter will be installed permanently in the next few days and will remain a permanent part of my lab power supply. And with that fixed, we can get onto building a receiver now for the 10w CW transmitter.

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Home Brew Straight Key

I am not much of a straight key user, but I am building one anyway to be a park of my novice station. The hinge is brass, the arm brass, the knob is a a button i found in the wifes sewing collection and the spring is one i picked up from the hardware store and the base is red gum.

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A little progress, using the cnc, routed down the board, retaining a plinth at the rear to mount the arm to. Need to drill out a recess to house the spring, and also another for the contacts at the front. I have some Copper rivets on the way to use as the contacts and some longer brass bolts for other side of the contact, with tapping the bar and a lock nut, the contact gap will be adjustable.

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CW: The Mode For Low Power Stations

So I was doing some log maintenance and uploading logs to all the essential services, LOTW, EQSL, Club Log and while i was looking at club log, I noticed that as far as the DX i work goes, it is predominately using CW. I figure that due to the inherent efficiency of the mode, those of us with low power stations and less than ideal antenna situations, have a better chance of working DX than if we are using Phone only.

And when i look over some of those Pacific Island DXpeditions that have taken place over the last month or so, I have not heard them on Phone and they have been weakish even on CW, but I have still managed to get in the log even when they have had substantial pileups going, just by listening and working out where the operators are listening to the pileup. In this instance, with CW skill over brute force wins every time. And in a phone pileup I get swamped, but in a CW pileup, i can spend 20 mins finding just the right frequency to call on and be heard over the bigger stations calling either side of it.

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