Home Brew Straight Key. Update

So I got excited and rather than waiting on all the bits from China i ordered to polish the crap out of this, I decided just to put it into service. I am still waiting for the right sized lower springs to arrive from China, these ones i cut out of ones i bought from Bunnnings (hardware store in VK) and they do not sit correct. But, the key works, its nice and smooth and even though its not polished to within an inch of its life, i am very happy with how this turned out. I learned a lot and if i do another one, I know i can make it better than this one by a long shot.

 

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Home Brew Straight Key

All the bits have finally arrived and I can get onto making a key. Not your average crap key made from a paper clip or a couple of bananas and a peg, but something that is going to be solid and last a lifetime. Well, as part of my plan to home brew an entire station from key to antenna and everything in between, I have taken a break from the receiver project while i wait on some parts and will focus on building a key for a while.

Parts are 100x10mm aluminum, 30x10mm aluminum, 10mm delrin, knurnled nuts M4, M4 threaded rod, M4 copper rivets and some spring-a-ma-things.

The plan is to made a not very pretty but very functional straight key. Its going to be no Begali or Kent even, but I think it should work ok.

So i have made a start on it and cut out the base plate, yes I using aluminum for the base and not wood, the 2 pivot blocks and what will eventually become the arm. I have hit an impasse tonight and cannot cut the arm out until morning when i can open the garage door and get access to the vice. Onward and upward.

Day 2: Its starting to take shape.

So much sanding. LOL. Yeah its probably going to take 10 hours of sanding to get things perfect.

And the sanding continues LOL

Its coming along nicely.

Added some random springs for a temporary test and it seems to work quite fine. Actually when i make it properly adjustable and put a knob on it, it should be a pretty good unit all round. Waiting on springs to come from china. So not much doing now for 3 weeks.

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Rob’s Receiver Part 3: IF Amp and Xtal Filter

First IF amp and the Xtal filter is build. IF amp is perfect and works exactly as designed. The Xtal filter is a bit rough as you can see from the plots below. It needs to be a bit narrower, closer to 500hz would be nice. Its a bit ripply which is probably due to imperfect terminations and because the xtals are not very well matched, being more like + or – 300hz not 50hz. I have a better frequency counter and a couple hundred more xtals coming slow boat from China, so I should be able to improve things quite a lot when I can measure down to 10’s of hz.

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Metal Bending and Chassis Building

I made a few minor mods to the homebrew bending brake and have improved the quality of the bends, with corner radius much tighter and improved the accuracy and repeatability of the bends. All in all its a much better unit now. I have added a set of sheet metal bending pliers and should now be able to make much more intricate boxes for my projects. The pictures below are something i knocked up rather quick and rough. Its 80x60x30mm and turned out ok. Nice tight fits.

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Red Pitaya VNA

I got new toys. A VNA addon for the red pitaya. More on this as I work out how the hell it works LOL πŸ˜‰

Well i managed to get it connected and working and I ran a test on my 40m dipole. Seems to be working now i need to learn how to use it for serious things. Not just checking swr on antenna πŸ™‚

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Rob’s Receiver Part 2: Band Pass Filter

Bandpass filter as designed in Elsie. In practice was a little low in frequency when built. I changed the end caps to to make them a little lower to bring the frequency up. The bandpass is rather ripply and if i remember latter I will Bode Plot it on the red pitaya.

Here is the schematic. It works but does not have the smoothest bandpass. I will see how it goes for now and if its not good enough, redesign it.

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Robs Receiver Build: RF Amp

So i have started to build the actual project now rather than build and test different blocks. Its about time that I actually built something from beginning to end. So lets start with the schematic.

A blank canvas all ready to go.

The first stage built, but not working in this photo. The J310’s i have, have a different pinout to the data sheet and i put a cap where a resistor should be πŸ™‚

Got things fixed and working in this photo.

Maximum gain from the dual gate rf amp.

Minimum gain from the RF Amp.

So far things are going swimmingly and next job is to wind an output transformer for this stage and then start on the bandpass filter.

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