Excellent Lucien! Thanks for sending this. I know what you mean about a project that doesn't work. It is rewarding and educational to figure out where you went wrong. I knew a guy who would ask, at a hamfest, "Does this rig work?" If the the seller admitted that it didn't, he'd reply, "Good, I pay extra for that!" He liked the challenge of fixing it. Of course, there are limits to this, and sometimes these challenges will make you wish you had taken up stamp collecting.
Hi Bill and Pete,
For me too, it's a happy day - I got the Mighty Mite working! Thank you so much for the inspiration to get into homebrewing...
I'm just licensed for a year now and this was my very first project (except for 2 basic kits that I build) and it really was a great learning experience. The best part: Since it didn't work out "plug'n play", I had to debug the thing and actually start thinking - so I put 2 caps in parallel instead of the wrong one I had used (I found them in a little box some guys at a hamfest gave me for free - never thought I would ever use something from it...). And I had to use the voltmeter to look for a short circuit. Basic stuff, but for me, this was a breakthrough!
Here are some more things I learned during this first project (don't laugh):
Where the heck do I plug stuff that's supposed to go to "ground" in? Now I know: usually to the negative pole!
When 2 lines cross in a schematic, that doesn't mean there's a connection!
How do these ready-made breadboards actually work? Had to try out...
It's important to think about the actual layout beforehand!
When debugging, trial and error doesn't help.
There's yet another crazy foreign unit called "gauge"! (I used smaller magnet wire than recommended, it still seems to work...)
9V-blocks get VERY hot when shorted for a minute or so!
Attached is an image of my ugly prototype, now I want to give it a better "home"... And here is a little video, demonstrating that it works, inspired by IZ1KSW:
I love this video. Colin finished his BITX a week or so ago and has been waiting for an opportunity to test it. Over the weekend he braved the winter of Northern England and, with his son, set up his new rig out in his snow-covered garden. Appropriately for a first contact with scratch-built rig, the circuitry was unencumbered by any kind of case or box. That's the way it should be done! Well done Colin! You are well and truly a member of the International Brotherhood of Electronic Wizards, and the diagnosis of "The Knack" has been confirmed (a severe case, it appears).
Hi Pete and Bill,
It's been a lovely fine day here in West Yorkshire, so I took a table out into the garden and set up my BITX circuit on it. I set up my SOTA dipole on a 9m fishing pole.
I heard a strong German station calling CQ, so I gave him a call and hoped for the best!
How amazing to contact someone in another country using a rig and mic you've made yourself! Do I qualify as a REAL radio ham now? Do I have a confirmed case of the knack? :-)
Although I may appear underwhelmed in the video, (besides the air punches!), I did really get a kick out of the QSO.
73 and huge thanks to both of you for the encouragement and support.
Thomas KK6AHT is the intrepid radio amateur from France who moved to California and successfully built a Minima as his first homebrew project. Yesterday we got additional evidence that Thomas definitely has THE KNACK. It seems that he has been looking through really old radio magazines (clearly a symptom). He sent us this add from 1942. Yikes! Imagine getting your ship sunk because your Local Oscillator is not quite local enough!
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Hey!
I thought you would get a kick out of this 1942 ad. Sounds like those guys had a some good reasons to fight QRM ... Who knew the important role played by the FCC during the war?
Now tell me: why were the receivers so noisy at the beginning of the war? What did they change? Happy new year to you both! May the gods of radio (and digital) bring you much fun on the air.
73, Thomas
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Good to hear from you Thomas. Long time no hear -- I was beginning to fear that you had grown disillusioned with homebrewing and had switched to stamp collecting or something else less frustrating.
As for the ship radios, two things come to mind. Some of them may still have been using regens at the start of the war. If so, that was kind of suicidal -- regens radiate! The detector moves in and out of oscillation (sometimes staying in oscillation) at the receive freq. The Germans were quite good at detecting and direction-finding these signals, on land and at sea. So the regens would have to go.
Superhets are not quite as bad, but they too can radiate. My Bitx spills out a bit of signal at 23 MHz (VFO) and at 5 MHz (BFO). Without adequate shielding, these sigs could also be detected and triangulated. Looks like the radio in the picture had lots of shielding.
We watched a French movie last night: The French Minister. A comedy about life in the French Foreign Ministry. It was kind of fun.
What are you working on? I am listening to 17 meters using an OLD superhet in which I have replaced the VFO with an Arduino/DDS generator. Works great but the display is making lots of noise.
73 Bill
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Hi Thomas,
Well Thomas, I will dip my toe into some very deep water and attempt an answer for you which also is an important clue about QRP operations.
Today we have many many signals co-existing in the radio spectrum. During the war there was much less radio garbage and the military lit up the ether with transmissions very sparingly. But that is on the transmit side. That said the local oscillators (much like you have with the Si-570 on your Minima) used in receivers also produce RF that unless is minimized in some fashion is passed right through to the antenna and can be detected. Regenerative receivers are especially prone to this. Yes some military equipment used regenerative receivers. In fact the famous Paraset had to be constantly moved so it would not be detected.
This receiver generated RF into the antenna was addressed by companies like Scott by shielding everything. That receiver in the photo probably weighed about a 100 pounds or more. Much attention was paid to RF bypassing and grounding. The cheap table top radios were RF generators par excellence.
There was another approach developed in WWII to solve that problem and forms the basis of what makes work that little device sitting in your pocket. The odd part it was invented by a famous movie star. Look up Heddy Lamar in wikipedia. She and a co-inventor came up with the concept of frequency hopping and spread spectrum technology. By jumping frequencies it would be hard to pinpoint a transmitting station. That concept forms the backbone of our cellphone system
Now the QRP part – if the RF output from a receiver local oscillator (milliwatts) can be detected from afar – then it follows QRP works!
Bob LeDoux sent us a link to a really amazing site about the Hellschreiber system. The site is filled with great videos, pictures, and animations like the one above. Lots of radio history too. Check it out: http://www.nonstopsystems.com/radio/hellschreiber-function-operation.htm This is all the work of F. Dorenberg, N4SPP. Thanks OM!
Bob writes: I'm working on a microcontroller based reader for this mode. For old fossils, like us, this mode looks perfect. It can be sent using simple CW equipment and it appears to be a great replacement for those who are tiring of Morse code. Its perfect for Knack victims. We can even build mechanical printers. Thanks Bob!
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