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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Boned In China

It was bound to happen eventually, anyone who buys parts off ebay gets stung and it was my turn. Looks like i got a packet of floor sweepings and rejects. Out of 120 xtals, 50% failed to even oscillate and the ones that did ranged in frequency from 11,996,000 to 11,999,600 with 4 being higher than 12mhz. Anyway, it is what it is and I will not be using that seller ever again and I will lodge for a refund. The 3 weeks wait has been the killer I wanted to get cracking on with filters for the receiver. ATM i do not have enough xtals the same frequency to even start. So, i just ordered some genuine parts from RS Components and will have them here within a couple of days and then I can move on.

That is the pile of dead or Q so poor that the amplitude of the sine wave was less than 1vpp compared to 4vpp on ones that were ok.

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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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