40m DC RX Continued

So i finished of wiring the receiver up and putting power and an antenna on it and having a tune about. Well it works, I was receiving the Manly Warringah radio club doing an open night for the cubs, where the cubs were sending their names back and forth using the phonetic alphabet. The kids were having fun and enjoying the radio. Also, a number of Japan and Indonesian stations were copied as well as some VK3 and 5 stations on CW. All in all, I am happy with the radio other than the finicky tuning system.

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This is how i had the receiver setup on the bench for its initial test.

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Did not plan the internal layout all that smartly, but it did fit in there eventually.

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And it looks all pretty with its nobs on.

40m DC Rx

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9mhz IF Filter

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What to do when bored? Experiment with some bits you have sitting about of course. Its been so long since i have experimented just for the sake of experimenting. So in many designs you see the 4 crystal ladder filter with various value capacitors of the same value. So i grabbed 4 9mhz crystals out the parts box and some 100pf capacitors and soldered them up in the ugly style. Connected up the signal generator and scope and began to plot out the shape of the filter.

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The basic setup.

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With 100pf caps a filter with about 900Hz -3Db width, not sure why the right hand side is not a smoother curve, i probably need to match impedance’s and use better quality caps.

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Next i changed the capacitor values to 50pf, and plotted out the filter shape again, this time converting millivolts to Db to see what sort level of attenuation is being achieved, and after some stuffing about to get my math right, this is what i ended up with, well 3rd times a charm, to get the math right HIHI. Kind of looks like a filter now and not a Mr Squiggle drawing.

 

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The test setup.

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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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Ted Powell Memorial DX Contest.

The Ted Powell Memorial DX Contest is a contest run by the Fishers Ghost Radio Club in memory of Ted Powell VK2AU now silent key, who was an avid DXer who worked 301 DXCC with 300 confirmed. The contest runs each calendar quarter with the object to for entrants to work the 5 rarest dxcc they possibly can.

I found the format to be interesting and decided to put in an entry just for the fun of it and was very surprised to receive a 3rd place for working 5 pacific island stations, Tuvalu, Solomon Islands, Norfolk Island, Niue and Marshall Islands.

A big thanks to club and those who run the contest, and if you would like to enter the contest yourself, here is a link to their website. http://www.vk2au.org/#Results

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40m DC Rx

So today we start on the next project in the series, a 40m direct conversion receiver to mate up with the 40m cw transmitter i built previously. I will update this post as I make progress.

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What we are starting with.

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Diodes in.

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Electrolytic capacitors in, kind of an upside down way of kit building, but i am looking to add in some landmarks because of the lack of silk screen on this kit.

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Without a silk screen it is a good idea to lay the components out on the board layout I think. HIHIimg_20161010_165811

Capacitors all in.

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There was some resistance, but i overcome it in the end.

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Most things now on the board. Next job is to wind the toriods and add wires where the power and speaker sockets go.

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