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Saturday, November 29, 2014
Colorburst Explained
http://en.wikipedia.org/wiki/Colorburst
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Labels:
Michigan Mighty Mite,
minimalist radio
Friday, November 28, 2014
Bill's Dominican Mighty Mite (1993)
If you look closely, just in front of my keyboard you can see the Michigan Mighty Mite that I rebuilt this morning (scroll down to see the previous post). Looks like I was using a polivaricon as the capacitor. Other than the cap, all the parts used in this 2014 version were from the 1993 effort. Here is how it is described in "SolderSmoke -- Global Adventures in Wirless Electronics":
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
I decided to start off slow, with small
projects that seemed likely to succeed.
The secretary in our office in the Embassy, Mady Bullen, had an interest
in ham radio that had been sparked by service in far-off places where
short-wave was the only way to talk to home.
She would pass me old issues of CQ magazine.
It was in the March 1992 issue that I found the Michigan Mighty Mite.
It was originated by Ed Knoll, W3FQJ and developed by Tom
Jurgens, KY8I. It is
about as simple as you can get in a radio transmitter: just one stage, a
crystal controlled oscillator.
An oscillator is basically an amplifier in which some of the output signal is fed back
into the input. If you provide enough
feedback in the right way, the amplifier will “take
off” and begin generating a signal. The
howl you hear when the microphone of public address system gets too close to
the speaker is this kind of signal. The
speaker (the output) is sending energy back to the input (the microphone) and
what was an amplifier turns (annoyingly) into an oscillator. In this case it is an audio frequency
oscillator because all the filters and tuned circuits in the PA system are
built for the audible frequencies. But
the same thing will happen at radio frequencies. That’s what the Michigan Mighty Mite is all about.
I put the thing together using parts obtained from the Santo Domingo
Radio Shack store. The resonant circuit used a coil that was just some wire wound
around a discarded plastic 35mm film container.
Homebrew radio projects rarely work the first time you power them
up. I had to fidget with this thing
quite a bit—obviously there wasn’t enough feedback. I had my Drake 2-B on and tuned to the crystal’s frequency. As I poked around on the little circuit
board, I suddenly heard a little chirp from the 2-B.
There it was! The little device
that I had put together was producing radio frequency energy on the 40 meter
band. Hooray! The joy of oscillation!
Now I felt like I was truly in league with Faraday and Marconi, with Shep, Stan and Bollis, and
with Serge! Hilmar would have been proud of me (but he still would have been
horrified by my sloppy wiring).
I never was able to talk to anyone with that little device—the power
output was very low, and my antenna for the 40 meter band was very poor. But it didn’t really matter. I had had my first real success at
homebrewing a piece of ham radio gear.
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Bill's Re-Born 1993 ColorBurst Michigan Mighty Mite
So far we've sent out 9 of these color burst 3.579 MHz crystals. It occurred to me that I should make sure these particular rocks work with the Michigan Mighty Mite design we've been advocating. So today -- still in something of a turkey-induced haze -- I pulled out the surviving remnants of the MMM that I built back in 1993. That one had been for 40, so I rewound the coil for 80 using the data from this MMM site: http://www.qsl.net/wb5ude/kc6wdk/transmitter.html
I was hoping that this rig might oscillate even without the variable capacitor, but mine did not. Once the cap was placed in the circuit, the oscillations began. It sounds pretty good on my Drake 2B.
I have not yet wound the secondary (antenna) coil but (as I suspected) the oscillator works fine without it.
So, no excuses folks. These cheap junk box crystals work. Time to build one of these things and join the ranks of hams who have homebrewed a transmitter (and, of course, The ColorBurst Liberation Army).
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Labels:
Michigan Mighty Mite,
minimalist radio
Wednesday, November 26, 2014
Colin's BITX is Receiving!
Wow, quite a bit of progress at M1BUU since our last look (see below). I must admit, that Arduino DDS board looks quite nice sitting there in the VFO territory. In his original BITX20 article Farhan recommends a pause before the construction of the final portions of the transmitter -- the builder is advised to sit back and enjoy the receiver that has just been created. Colin is at that point! Congratulations Colin. He has noted that his board is a bit(x) smaller than mine. Maybe he should stick with Farhan's recommendation and build the PA and driver on a separate board. This will also help prevent the dreaded oscillations -- no need to tempt fate or anger the radio gods!
Hi Pete,
Another great SolderSmoke episode this weekend, I really like the humour between you and Bill! I listened to SS whilst melting solder on my BITX project.
I'm so pleased to have got so far, and I'm very pleased with the build. That big copper clad board doesn't look so big now, but I think I have room for the TX/RX switch, BPF, RF driver, RF PA and LPF which I still need to add.
Thanks for the encouragement and advice so far, I doubt I'd be feeling so elated at this point without it!
This is going to be a really cool rig!
73, Colin M1BUU
Hi Colin,
Two words come to mind: Absolutely Superb! Wow that is such a work of art. I may never show another one of my projects as you have set the standard and benchmark.
You also have demonstrated building from the back end which we discussed in SS168. Now what you have built is a part of the test system.
Really outstanding. Be sure and video your 1st qso and share on You Tube.
Bravo!
73’s
Pete
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Labels:
Arduino,
BITX20,
Farhan,
Juliano -- Pete,
UK
Tuesday, November 25, 2014
Pete Builds a Michigan Mighty Mite
We have been distributing quite a few 3.579 MHz crystals, but until today we hadn't seen a single new Michigan Mighty Mite. I commented on this in the last podcast. Pete came to the rescue and built one:
Hi Bill,
The MMM was built – took me a long time (about 30 Minutes so it was kind of slapped together). The most time was consumed drawing squares on the sheet metal. I used a pill bottle cut down for the coil.
Used a piece of Home Depot sheet metal for the based. I highly recommend a .01 Ufd from the 27 Ohm to ground –key clicks are awful.
BTW the circuit can be modified so that the tuning cap is soldered to one side of the coil and the other side to ground –essentially the tank tuning cap is in series with the 0.05 bypass cap and is effectively across the coil. Tribal Knowledge
The CLA lives on!
Pete
VIVA EL EJERCITO DE LA LIBERACION DEL COLORBURST! VIVA EL CLA!
Pete's Michigan Mighty Mite Manhattan MePad Noodle
New recruits have been signing up for the Color Burst Liberation Army. We have been sending out many more 3.579 MHz crystals. Pete Juliano was doing some noodling and came up with this plan for Manhattan pads or Me(Maine)Pads. All you need is some copper clad board, a pair of Home Depot tin shears and some super glue. Cut out the pads, glue them down, add components and get the Mighty Mite percolating.
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
FINALLY! A Computer Made with Discrete Transistors!
http://hackaday.com/2014/11/22/a-4-bit-computer-from-discrete-transistors/
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Saturday, November 22, 2014
SolderSmoke Podcast #168 Software Inefficiencies! DSB Blues! Schematic Errors! QRO Confessions!
SolderSmoke Podcast #168 is available.
22 November 2014
http://soldersmoke.com/soldersmoke168.mp3
The benefits of software inefficiency.
Don't throw a wet blanket on computer baby steps.
DDS-ing Pete's old boatanchors and Bill's BITX.
Bill's DSB amplifier woes: a JBOT unfairly scorned.
Getting ready for solar-powered beach DSB.
Michigan Mighty Mite Crystal Offer -- FREE ROCKS!
Tribal knowledge: Beware of mistakes in published schematics!
QRO update: Working Japan on 17 meters.
Happy Thanksgiving!
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
22 November 2014
http://soldersmoke.com/soldersmoke168.mp3
The benefits of software inefficiency.
Don't throw a wet blanket on computer baby steps.
DDS-ing Pete's old boatanchors and Bill's BITX.
Bill's DSB amplifier woes: a JBOT unfairly scorned.
Getting ready for solar-powered beach DSB.
Michigan Mighty Mite Crystal Offer -- FREE ROCKS!
Tribal knowledge: Beware of mistakes in published schematics!
QRO update: Working Japan on 17 meters.
Happy Thanksgiving!
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Labels:
DSB,
JBOT,
Juliano -- Pete,
SolderSmoke Podcast
Friday, November 21, 2014
Tube Transmitter in a Cuban Cigar Box
Beautiful use of a cigar box by Ben, KK6FUT. Ben is working in close proximity to Pete N6QW and has obviously fallen under the influence of Pete's "Build Something With Tubes" field.
Watch out for the high voltage Ben. You aren't in Arduino-land anymore! One hand behind the back OM!
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Labels:
Cuba,
Juliano -- Pete,
Tubes
Thursday, November 20, 2014
Impedance Matching Transformers -- Pete's Magic Decoder Ring!
We got some questions on this and Pete was kind enough to write up some notes on the topic. We may talk more about this during the next podcast (Saturday):
Broad Band
Impedance Matching Transformers.
Broad Band impedance matching transformers are designed to transfer power
over a wide frequency range. More basic you have an amplifier that has an output
impedance of 200 Ohms and you want to match that to a 50 Ohm load.
So what is the magic decoder ring so that you get a 4:1 match, ie going
from 200 Ohms to 50 Ohms. Getting technical for a moment the maximum power
transfer theorem says maximum power is developed when the source is matched to
the load. The Broad Band Matching
transformer enables that to happen over a wide frequency range.
So how do we get from 200 Ohms (the source) to 50 Ohms (the load)? Just as there are many
airlines that fly from LA to NY so it is with the matching approach. We will
cover several.
First a short discussion about broadband cores themselves. One of the most
common cores for HF work is the type 43 core which is good up to about 50 MHz.
For transformers up to 200 MHz then the type 61 are a better choice. Typically
at HF the FT -37-43 is one of the more common ones see (3/8 inch in diameter),
as is the FT-50-43 which is ½ inch in diameter. The iron powder cores are not the 1st choice
for broad band matching.
#1 Way:
Build a transformer that has a
primary of x number of turns (and since it is large, 200 Ohms will have
more turns) and the secondary will have y number of turns ( and since it is
smaller, 50 Ohms, will have fewer turns.) The transformer action is based on
the ratio of the Primary turns Squared to the Secondary Turns squared. Our
transformation is 4:1.
Thus if we divide the primary turns squared and divide it by the secondary
turns squared the result is 4. Here are some example: if we had a primary of 8
turns ( 64) and a secondary of 4 turns (16) – 64/16 = 4. So that is our transformer a primary of 8 turns and a secondary of 4 turns. When building
these transformers use two different colors of wire as that makes it much
easier to identify the windings. Observe the phasing, meaning the end you
connect to the collector of your output transistor is the start end. That same
start end for the secondary winding is the output “hot” side of the secondary.
#2 Way.
The same ratio holds in going from 200 to 50 Ohms. But this time we will
use a single winding of 8 turns and at 4 turns we will have a tap for the 50
Ohm point. Since that tap will very likely have Dc on it connect a 100 NF cap
at the 4th turn winding and this is the output. What you have just done is
create an auto transformer.
#3 Way.
At time one may have an oddball transformation and you can cascade
transformers and multiply their individual turns ratios. At one time I needed a
9:1 transformation. I built a 2.5 transformer and then hooked that to a 4:1 and
the result was a 9:1 transformer.
The attached table has “worked out” some common matches that are often needed
like matching a 50 Ohm amplifier to a 500 Ohm Crystal Filter which is a 10: 1
match. This is easily done with a 6 turn primary (50 ohms 6^2 = 36) and the
secondary has 19 turns ( 500 Oms 19^2 = 361). 361/36 = 10.03:1. Close enough for ham radio! The 1st way is probably more preferable for this
application.
Pete N6QW
11/2014
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
Labels:
Juliano -- Pete
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