Homebrew


I made a post to the 147_120 Projects group on Yahoo encouraging all to check out the mbed.com web site.

It’s been a long time since I posted to this blog, I guess it’s time that I got things going again. Now that we’re planning on restarting the long awaited Tech Parties, it will be good to have some things to post here.

Take a look at mbed.com, join the 147_120 Projects group on Yahoo, and stay tuned for where the new Tech Parties will be held.

I look forward to seeing you there!
Tracy N4LGH

This is going to be a good one. It will focus on the Stellaris and will provide a Stellaris Launchpad along with a Kentec LCD Display.

The $29 cost is a little over half what you would pay for the board and display plus you get hands on training that is invaluable. If you attend, their lunches are ‘Stellar’ ;]

You can get to all of the course material online and register at these links –
Register Here
Workshop Page (Pay attention to the many links! There is a huge amount of info here including 8 hrs of video!)

The training event will be held at the Avnet office at
2501 Discovery Dr #150
Orlando FL 32826

These people do things right! TI and Avnet have put on awsome presentations in the past, I have no doubt this will be one of them!
Tracy N4LGH

Recently I found this toroid in a piece of telco equipment. It was in the ‘junque’ box for parts so I have no clue what the equipment was used for, although the majority of things going in that box are ring generators and various other kinds of power supplies.

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It looks like a wound toroid inside a wound toroid with *some* windings common to both. Possibly a current sensing configuration with provisions for power control.

I don’t have a high res photo for you close uppers. Click on the image to get a little bit bigger version.

Does this spark your imagination for a radio project? Regen? I just thought it was cool.

Tracy N4LGH

I love ‘Deadbug’ and ‘Manhattan’ construction. Look ’em up, neat way to build a radio.

Lots of people think Deadbug is for ‘quick down and dirty’ construction, and for many it is. But it also produces circuits with an excellent ground and many times better performance because of it. And frankly, Deadbug and Manhattan projects just Look Cool.

So my friend Corey is getting on Six Meters and broke out his old transverter that converts an all mode two meter rig to an all mode six meter rig. Neat. Way back then I had started a similar project that I never completed; a six meter to two meter transverter. Just the opposite of his because at the time I had a six meter rig but not a two meter rig and he had a two meter rig but not a six meter rig …

I decided to go ahead and complete some of the wiring I had left out and realized this booger got dirty over the years. I cleaned it with flux cleaner (alcohol) and it took most of the dust and surface junk and a bit of the old flux, but the copper is still ‘ugly.’

So now I’m in a quest for a chemical, I guess. I tried a fine ‘brush’ on the flux cleaner but I just can’t get between the parts. It would look awful if I did anyway. What I really want is something I can run over the board to clean it a little better than it is but something that won’t hurt those caps …

Here’s some pictures I took from the bench cam at work. You can click on them for a little closer look. They really don’t do the little booger justice, it just looks cool.

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Last night on the net I spoke a little about the Android operating system. It’s gaining a lot of popularity and is hugely supported, and it’s FREE.

We should consider this for a myriad of reasons, I’ll just mention a few that hit me.

1) It’s designed for communication systems. What do we do? ;]
2) It’s open source and accommodates free software and development quite nicely
3) There is a huge support community for writing ‘apps’ on Android
4) There are a number of hardware accessories that are coming on the market to facilitate talking to homebrew hardware or commercial equipment.

Here is a link to the development platform. Again, it’s free, and there is a huge pile of data to sift through
http://developer.android.com
The ‘Get the SDK’ link is at the bottom.

These little devices should be available soon. Some are now.
There are others, these got my attention
https://www.sparkfun.com/products/10748?
http://www.adafruit.com/products/885

Here are some projects people have done with the IOIO
http://pinterest.com/ytaibt/ioio/

I think an informed conversation on the Android platform would make for a great net. Read a little about it and perhaps even download and install the SDK. Got the Hello World app running on your phone or tablet? Tell us about it! Failure? Lets try to solve it.

I see a great application of Android and homebrew radio with the proliferation of inexpensive Tablet PC’s coming on the market. Also, there are devices like the Mini6410 and other project type embededed devices that are capable of running Android and have LOTS of IO built onto them. Do a little creative searching and see what other similar hardware you can find and what projects may be out there that interest you.

Keep in mind you can still develop for older versions of Android. Why? Lesser capable hardware for one, as well as devices that are not intended to run a display with all the fancy graphics and touch screens.

Perked a little interest? I hope so. If so, bring yourself to the next Tech Net and lets talk Android for Ham Radio!

Tracy N4LGH

..

The Penguin! This was the happiest thing I've seen from and embedded linux project since I started chasing the NGW100. I haven't given up on the NGW, but for just over $100, this kit can't be ignored

I FINALLY HAVE an embedded linux kit working with a touch screen. Mind you, I have not yet installed or set up any of the tools for Linux, Windows or QT development on this board yet, but it looks so far to have a lot of support and CURRENT information!
 
I haven’t done anything but turn it on and click a bunch of icons. One thing I did notice, once a program starts it runs until you stop it, even if you reboot. I still haven’t found how to stop a running process, but I’m sure I’ll find it soon.
 
For instance, there is a nice little program that illustrates the 4 LEDs on the board – one function counts from 0-15 in Binary. Guess what? This little thing is counting it’s ass off all the time, even though I told the app to quit lol. I’m sure there are some inconsistencies on this distro ;]
 
What a nice, COMPLETE kit!!
At first glance this sure looks like a complete kit – as far as the hardware goes anyway! There is every cable you will need, a power supply (wall wart) and even a ‘JTAG’ programmer. I’m sure this JTAG is just for the mini2440, but it’s the only kit I’ve ever seen come with one. This is a necessary tool if you ever hose the ‘bootloader’ in a board like this. Also, if you choose to bypass using an ‘OS’ and just write native code for the processor, you will need this to program it.

A complete hardware solution including the MINI2440 board, a 3.5 inch touch screen, every cable you need, the wall wort supply, and even a JTAG programmer for programming the FLASH.


The CD is packed with example code and supposedly all the tools you need to build Linux, Windows or uCos2. The only drawback I found to programming, and this is only from one post I found on the web, is that it appears you need the full PRO version of Visual Studio, not the ‘Express’ edition. I found it in this post.

Looks like a PDA example to me! For some reason they have a kind of 'background image' behind the apps - note on the title bar those lines aren't there ... at first when I saw this I thought it was the display - but on other pictures, and te video, these lines do not appear.I'd certainly remove these if I recompile.


There is a lot of work already done for any interface you ever want to build. With all the work done on PDA’s and Smart-phones, you will not want for example code for displays whether you use Linux or Windows to develop. Keep in mind my motivation is to be able to control modern day RF chips with this controller – I want to have it be the display, the hardware controller and the audio interface.
 
I was impressed with the manufacturers site although it isn’t really mature, there is good information on it and they’ve gone through the trouble to put up a Forumboard and monitor it. I’ve perused the posts and responses and while there doesn’t seem to be the resident gurus like there are on AVRFreaks forums, a lot of the questions get answered.
 
The company’s Download Section is pretty good; they have datasheets for every part on the board and information on every aspect of the board. Most are links to other locations but are good quality material.

This 'World Clock' is remarkably like a Greyline Propagation Map


My Motivation with this board is to make a modern radio controller. There are already hundreds of apps for amateurs that manipulate audio. key rigs, keep logs, etc, that will be nice toys on a ham radio transceiver. The big rigs put stuff like the world maps, etc. I’ve been staring at this ‘World Clock’ for a while, it remarkably resembles a greyline propagation map!
 
There are 34 ‘GPIO’ lines that can be used to control any line you want, and a serial control line that I don’t yet understand that can address many 2 line serial devices. There’s input for a camera, audio in and out, 6 user buttons and 4 user LED’s. Opie, Android, WinCE, all are ready to control a digital radio!
 
In the coming weeks as I get this thing going I intend to document everything I do – failures and successes. The NGW100 board was a great find, but we let it ‘mature’ and is now difficult to support. PLUS, if you put all the functionality into the ‘NGW that this board has you’ll spend nearly $300 …
 
The only thing I haven’t found on this board that the Mediama add on for the NGW supplies is a LiPo battery charger. I got one from Sparkfun and would love to apply it to this little marvel. Actually, I got the beefy three cell version … Think it will run a transceiver for a bit? ;] It would be very interesting if this charger would be able to interface with the USB on the board? Or something that would interface with the GPIO would be even better.
 
Here are a few more pictures. This sure is a neat toy – I’ll report more this week!

A nice looking little JTAG programmer

The board - you can find many better pictures on the Manufacturers website

We need to recompile this - message says please waiting ?? lol I love Chinglish!


 

 
 

Last Wednesdays tech net was a raving success! Although there were only a handful of us there we finalized the defeat of our shortcomings with the Bitx20 VFO. What’s best, is that we used the tools that WE BUILT to test it! woo hoo!!
 

lower frequency

Lower Frequency

Upper Frequency

Upper Frequency

Verns VFO
is the first working properly. With the caps that Dave got from Mouser Electronics (Part # 23PW156; Film capacitors; styrene 50V 560pF) and the replacement variable cap, this puppy is dead on and unbelievably stable! The poor little am radio cap just wasn’t happy; it was shorted or possibly corroded, either way it was ‘jumpy’ every time we tried to do anything with it and we just couldn’t figure out the little trimmers on the back.
 
Replaced the Capacitor
The original was a little rusty or something

nice open air capacitor

reduction and variable capacitor

I had picked up a small ‘offcenter’ variable cap off ebay some time ago. The value is the same as the one in the kit so I was confident it would plug right in. I had built a small reduction on a 6:1 vernier giving a total of 30:1. Yup, it takes 15 turns of the knob to go from one end of the band to the other – 10 KHz per turn at the bottom end, and 20 KHz per turn at the top. Not bad!!

We used the FLL frequency counter kit we had built a couple months ago to test the VFO. It turned out to be a nice little tool for tuning the circuits in the BItx20. Verns ended up having a coverage of apx 3.998 to 4.352 – again very nice! Verns price for the reduction? He has to make the transceiver look really good ;]
 
The Perfect Setup?
Good enough for Nate!

In Operation

In Operation

The test was done on top of Nates neat setup he is building for his breadboard. He found a ‘briefcase’ type box at Skycraft and attached his breadboards on top of it, leaving room inside for all his accessories. In this test we used the power buses to make hookup much easier. Below is a view from another angle. Note the power supply showing the unit drawing 90 mA at 12v – backlight and all! Of course just the VFO and Frequency Counter are powered right now.

The Setup

The Tech Party BItx20 Setup!

We really did have a lot of fun with this one. Vern had to rewind his toroid several times, finally finding a smaller diameter wire in order to put his final 54 turns on the core. It is spec’d at 50 turns, but it ended up being too high in frequency. When he tried to go over 50, it was not in a single layer winding with the wire provided to the inductance was way off. The final verdict – 54 turns with #32 wire on the core provided. Yay!

hot glue

Fastening the toroid with Hot Glue. Once on, simply press the core against the board before the glue sets and this little circuit is good n' stable!

Vern really likes hot glue. Every time he wound a core he’d glue it down for testing. We finally convinced him to just glue the final result down. When dealing with things like this, like the inductor in an oscillator, physical stability is very important. Gluing the core down will keep it from moving and causing minute ‘microphonics.’ Good job Vern.
 

Fine Tune arrangement

Fine Tune Control

The Fine Tune Control gives almost a perfect 3 KHz shift – a little over 1.5 KHz each side of center. That’s extremely nice as all you have to do is tune ’em in so you can hear ’em with the main tune, and then adjust ’em so you can understand ’em with the fine tune. As designed and described!

So we were able to conquer the VFO – now on to the next stage. There are several builders going on to the audio stage next, a couple into the mixers. Next week we’ll discuss who is where and what new challenges we may face.
 
 
The Meeting Was A Smash
and we had a good time, too!

All in all we had a great tech experience, a great tech net, and a great result from the evening! I hope to see you next week at the tech party or at least check you in to the Wednesday Night Tech Net.

TECH ON!!

We have been having a difficulty with the VFO section of our BiTX20’s … I’m scratching my head and wondering why we’re off frequency but with the right spread. Enter Mario …

DUH, I never checked the values; we had discussed that there were no 560 PF NP0 caps in the kit, but I totally forgot. Mario asked, ‘where did you get the caps?’ Well, the builders had used the 56pf caps in the kit and it makes sense why none of them were on frequency.

We are making an order for 560 pf caps, but they will not be NP0. They will be very close, but we can’t find NP0 caps. It’s fine tho, the ones we are looking at have less than a decimal of a PF over a huge temperature range.

If you’d like to get in on that buy please contact Dave KC4ZVW or myself in the next few days and we’ll get you in on the pile.

I feel stupid, sorry I didn’t look at that, but at least we know where to get replacements.

Tracy N4LGH

This weeks Solder Social was a great learning experience!

Yeah, I’ve started calling our BiTX20 building group the Sewing Circle with Soldering Irons. A Soldering Circle! What’s the difference? A bunch of old bitties sitting ’round gossiping and trying to make ourselves sound important to one another. It’s a hoot!

We saw firsthand what a couple of picofarads can do to / for a filter. The BiTX20 transceiver front end has a nice bandpass filter that doubles as the front end filter for the receiver and the driver filter to the 5W PA. It’s a fairly important part of the circuit because if it’s not tuned well, performance will suffer on both receive and transmit.

First off, the documentation is a little contradictory to the markings on the board. In the photos of the board layout, the filter capacitors are marked 68pf. They are also 68pf in the supplied schematic. BUT, on the board itself, and in the written text, it calls for 33pf. In the text it states one could use either a 33 or 47 pf. We figured it was because of the tuning range of the inductors.

Some of us had already built the filter with 39 pf caps that appear to have been substituted for unavailable 33’s or 47’s. Maybe it was in the middle of the range?

Contemplating the filter

Dave KC4ZVW had his Filter / Amp assembly ready first so we applied power and checked voltages per the instructions – everything was within tenths of volts, fantastic!

Next we went about setting up the Tracking Generator and Spectrum Analyzer. Thanks to Tom KD4WOV for helping us get that set up. I’ve never done that on a filter before.

Wow, what a mess! It had huge insertion loss and a lousy pattern. But after fiddling with the caps a bit Dave found a nice compromise between pattern and insertion loss.

At last, a decent pattern with low insertion loss!

Mario KU5E had used 33pf capacitors and came up with completely different results. He ended up removing the 33’s and putting in the 39’s. What a difference! We spent quite some time fiddling with the pattern and insertion loss with the 33’s and were never able to get less than 15dB of pure wasted signal.

As usual, Vern Ki4SDY was an excellent host and generously provided some caffeinated beverages, although I’m not sure this group really needed any stimulants ;]

Best we could get with the 33pf caps!

Now this is a good pattern!

Once I finally figured out how to take a picture of the spectrum analyzer screen these shots came out pretty well. Next week I’m going to bring my desktop tripod so that I don’t have so many blurry shots. These screens sure tell the story. We were able to get these tuned to with a dB or so insertion loss.

Overall the filter looks like it has better than 20 dB overall rejection, with less than 3dB insertion loss in about a 100 kHz passband. We don’t think we have this filter optimized – I will likely try several values there. Perhaps a variable?

a higher resolution shot of the pattern

Everyone is invited to our weekly Solder Social at Verns barber shop in Longwood, near the intersection of Ronald Regan Blvd and Church Street. Vern is the second door east on Church.

Hope to see you all there next week!

Last nights build meeting was great! We’re officially batting 1000 on the FLL kits! Jims took some rework on the solder connections to the chip socket, but we were all functional before we left.

We were amazed at the accuracy of these little buggers. One of the units was within 3 Hz at 10 MHz! We were able to accurately read frequencies up to 60 MHz. It was fairly sensitive from 20 MHz and down but we needed to pump up the output of the signal generator as we went up in frequency. But it was very accurate right up to the point where it couldn’t lock any longer.

Cool!!

The next part of the build is the bandpass filter and amplifier for the receiver. Some of us have elected to start on the Power Supply section of the PA so that we have a source of 12v for testing. Since there are provisions on the PA board for ac operation most of us are taking advantage of that.

Anyone is welcome at the build party! We have a couple extra ‘seats’ and truly enjoy sharing at this meeting. I would have to say we’ve had the most pleasant and productive build sessions I’ve been to in decades.

Each week we share sources of parts, play ‘show n tell’ with ‘stuff’ we’ve acquired, and generally just chat away in between questions comments and statements about the project. We discuss the circuit, the nuances of the mechanical construction and even ponder programming code.

All in all, it’s a great meeting and I can’t wait ’till the next one. See you all then!!

Tracy N4LGH

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