The first question you may ask is, Why would I want to build my own Arduino UNO? Economically speaking it does not add up in your favor after you acquire the parts and consider the time it takes to put it all together. This is especially true when you consider that a Nano “clone” could be purchased for around $3! You might have a permanent use application that makes building one your best option? Maybe you just like to learn and do stuff just because you can!
The unit below is built on a prototype shield that has become the main board. For my keyer application I have no need of USB communications and I can keep the wiring down to only what is needed. The 5v regulator will soon have a small heatsink as it gets warmer than I would like.
Below is the other side of this board. I used #4-40 screws as “legs”.
On Saturday, January 28th the Nashua Area Radio Club (Nashua ARC) will be hosting a special event for Interested kids, parents, and friends in the community about the joy of amateur radio at MakeIt Labs in Nashua from 9:00 am – 3:00 pm. You may drop in at any time and stay as long as you like to participate! Among our activities, you can:
Get-On-The-Air Station (GOTA)
This is amateur radio at its best and what it’s known for! We invite you to get on the air and make a contact (we call them QSO’s — pronounced: cue-so) somewhere in the world! You might be able to make a new friend in Germany or even Japan! Making contacts sits at the heart of amateur radio and is an activity that brings people together. So don’t be shy, step up, and hit the push-to-talk button!
Satellite Station Display
The Radio Amateur Satellite Corporation (AMSAT) began in 1969 to foster amateur radio participation in space research and communication. Currently, AMSAT groups help advance the state of the art in space science, space education, and space technology. Come learn about what components go into constructing a station capable of contacting a satellite and what antennas, and smart phone apps, operators use to keep a pulse on the satellite location.
Digital Amateur Television (DATV)
Not only are amateur radio operators granted privileges to transmit speech, but we also can send fast-scan data such as TV signals! Many operators have experimented with how to homebrew their own fast-scan TV stations, and our club president Fred (AB1OC) and our member Skip (K1NKR) have chosen to use construct a station which uses a Raspberry Pi (RPi) with an Arduino shield to sit at the heart of the transceiver. The RPi is the brains of the TV which runs Linux and among other things is responsible for sequencing, transmit / receive control, automatic VSWR monitoring, and a touch-screen controlling interface to configure and operate the system. Learn about what it takes to build and operate one of these stations. We may even be able to make a contact! More information can be found at https://stationproject.wordpress.com/category/amateur-television/.
Kit Building with Nashua ARC
The Nashua ARC holds kit-building nights where both inexperienced and experienced members homebrew in a relaxed, learning environment. In the past we have built Pixie QRP (low-wattage) kits transmitting Morse Code on the 40m amateur band. But, on February 18 from 1 – 5pm, First Church in Nashua, Nauss Hall, we will build the digital oscilloscope kit DSO138 (shown to left). This kit comes with a clear acrylic case to protect it, build instructions, and among its specs has a 1 Msps sampling rate, 12 bit accuracy, 200 kHz bandwidth (good for audio signals), capable of freezing the waveform display, and comes with a 1Hz / 3.3V test source. We invite you to join us and will bring some kits with us. More info can be found on our website at http://n1fd.org/2016/03/27/inexpensive-diy-digital-oscilloscope-kit/.
We hope you will join us for our event! Please bring friends, family, but most importantly we want you to have fun and enjoy this hobby with us!!
The Nashua ARC has began teaching a Morse Code training class on Saturday July 16th 2016. The class was created in response to interest in learning Morse Code, expressed by several club members who are drawn to this unique mode of communication. While this unique skill-set is no longer a licensing requirement it continues to be a longstanding practice enjoyed by may radio amateurs worldwide. Numerous groups and organizations exit to encourage and promote the practice of communications using Morse code such as FISTS; North American QRP CW club (NAQCC); CW Operators Club (CWops); and the Straight Key Century Club (SKCC).
The use of Morse Code is one of the simplest ways of modulating a Continuous Wave (CW) RF carrier by generating characters composed of a series of “dits and dahs” to create a message. Most QRP (low power) operators favor CW operation because of its low circuit complexity, light weight (for portable operation) and extreme efficiency. A limited number of amateur radio operators find great satisfaction in operating using Morse Code aka CW as their only mode.
The Nashua ARC Code course employs the Chuck Adams – K7QO, training CD. Chuck’s course is available for download free of charge and is well-organized with over 500 audio MP3 files to help learn and improve your skill levels. Our class encourages following K7QO’s guidelines and instructions to develop good CW habits that avoid the later roadblocks to greater speed and proficiency. Our class has introduced a few variations to Chuck K7QO’s training plan with a couple of special CW practice quizzes that help keep the classroom fun and more interesting. The G4FON software trainer utility has added to the fun with background noise, QRM and QSB listening challenges, which adds a taste of real CW operation. Learning and gaining proficiency with Morse Code requires practice, practice, practice. The K7QO training MP3 files can be listened to with a PC, MP3 player or in many of the newer car CD players.
Our training class has provided an opportunity for many of the students to observe several different Morse Code keys. A couple of students have also brought in some innovative code practice keys that were constructed from some unique household items. Other students are building a small microcontroller based keyer that can be used with a straight key or a single or dual paddle key for training or use with a transmitter. The class will continue for a few more weeks and then many of the students will be ready to try their first on the air CW QSO. Each on the air QSO will help grow their CW skills and is ultimately the best form of practice, practice, practice.
This article discusses some work on designing matching network to make antennas match well (low VSWR) across the whole ham band. This will be a described in more detail at the September Tech Night.
Antennas have an impedance (or match) that varies with frequency. Transmitters want to see a matched antenna with an impedance of 50 ohms. The antenna has a best match at one frequency and the match gets worse as the operating frequency changes.
Some bands and antennas are more challenging to match than others. Shortened or loaded antennas have a narrow range of match frequencies. The 75/80 meter band has a wide bandwidth in term of percentage.
Here’s a plot of the SWR for my 40 Meter Dipole. It’s a good match at 7.000 MHz and degrades to about 2:1 at 7.100 MHz. Obviously this is not optimized.
Modern radios have built in automatically adaptive matching networks make the radios work over a wider bandwidth, but networks are lossy and reduce transmitted power.
A manual antenna tuner has a lot lower loss that the built in tuner, but it requires manual adjustment. In fact, the extra tuned circuits generally act to make the antenna have even less bandwidth.
The QUCS RF circuit simulation program has the ability to model SWR, bandwidth, matching networks based on data about antenna performance. The antenna data can come from either an antenna modeling program such as 4NEC2 or EZnec. Or the data can come from measurement made by a good antenna analyzer.
QUCS also has a built in optimizer. It has the ability to try hundreds of circuit values and home in on a optimal design.
The optimizer setup needs a definition of “optimal”. For the case of a broadband antenna, “The worst case SWR anywhere in the ham band shall be as low as possible”. In term that QUCS understands, “minimize the maximum SWR over the frequency range 7.00 to 7.35 MHz.
Here is the result from running the optimizer on the data for my mistuned 40M dipole. QUCS has designed a broadband matching network that can achieve less than 1.5:1 SWR over the whole band.
QUCS achieved this by varying the components of a filter network. I drew a generall filter network and let QUCS tune the component values. This network is designed with coaxial stubs.
The model of the antenna is stored as a file in the X1 file component. Line7 is a 30 meter coax feedline. The actual matching network consists of Line 1, 2, 3, 4. Each line is 50 Ohm coax. Line 1 and 3 are configured as open stubs. The line lengths predicted by the model are…
Line 1: 7.75 meters
LIne 2: 4.47 meters
Line 3: 8.49 meters
Line 5: 8.03 meters
Here’s another example. 160 meter antennas are often implemented as shortened loaded verticals. The loading makes the match very narrow-band. The red curve in the plot below shows a top loaded 160 meter vertical. It only covers a fraction of the band.
The blue curve shows the result of an optimization run that selected the values for a 7 component matching network. It achieves about 1.7:1 across the whole band. This network uses capacitors and inductors because coax stubs would be very long on 160 meters.
The component values for this network…
C1: 3450 pF
L1: 3.954 uH
C2: 3978 pF
L2: 6.951 uH
C3: 6156 pF
L3: 2.831 uH
C4: 4778 pF
I have not built any of these networks to see how they work in practice. The 160 meter network has some extreme values and it is probably very touchy to get right. Building that network to handle Tx power will require vacuum variable capacitors in parallel with high quality stable fixed value capacitors. But, the 160 network doesn’t really need 7 components. Put in one less stage of L-C and the ripple across the passband goes up a bit.
QUCS is a great RF circuit simulator. This shows that it can work with data from a antenna model or analyzer and can optimize matching networks to create a broadband antenna.