In this episode, I join Martin Butler M1MRB, Caryn Eve Murray KD2GUT, Edmund Spicer M0MNG, and Ed Durrant DD5LP to discuss the latest Amateur / Ham Radio news. We discussed the following:
As my ham radio journey takes me on a more formal study of electricity, my home laboratory grows. I remembering purchasing the Tektronix 2465 a few years back on a suggestion of a friend, not having a clue what I was doing with it. I just knew that real electronics enthusiasts had an oscilloscope.
Now that I am crawling my way through the Sedra/Smithβs Microelectronic Circuits tome, I have plenty of reasons to fire up my mushrooming pile of test equipment.
Letβs start with this circuit, the bridge rectifier.
The bridge rectifier is a fairly simple circuit to build, consisting of only four diodes (1N4001 in this case) and a load (10kβ¦ resistor). In the Multisim sketch above, the device on the left is a function generator producing a 5 volt peak-to-peak 60 Hz sine wave. On the positive half-wave of the signal cycle, the function generatorβs positive terminal feeds into node D1/D2 of the four diodes forming the bridge rectifier. This positive signal forward biases D2, allowing the signal to continue on toward the load R1. D1 and D4, however, are reverse biased, and the signal is only able to conduct through D2. On the negative half-wave of the sine signal cycle, the function generatorβs negative terminal now feeds a positive signal into node D3/D4. The signal now forward biases D4 and reverse biases D3 and D2. This half signal proceeds through the load R1 in the same direction as the positive half-wave portion of the signal did. All of the electricity conducting through the load in the same direction is considered direct current, as it does not have a component that flows in the reverse βbackwardβ direction (as the original imputted sine wave did). Therefore, the bridge rectifier has done its job of βrectifyingβ alternating current into direct current.
By placing oscilloscope leads across the load resistor, the desired output of the bridge rectifier can be seen, at least in theory. Below is the Multisim oscilloscope simulation result. The bolded reference line is at zero volts. You will note that this βfull-waveβ rectifier has produced a waveform that is more or less continuously greater than zero volts. As we will see, this is in contrast to the βhalf-waveβ rectifier, where there is no voltage seen when the originating sine wave enters its negative half.
In my home lab, I went ahead and set up a bridge rectifier on a breadboard, and set out to show its characteristics on my oscilloscope.
Part of the new fleet of test equipment are these two beauties, the Topward 8112 function generator producing a 60 Hz signal shown to be 5 volts peak-to-peak on the oscilloscope. And a Fluke 45 digital multimeter which will come in handy later.
After constructing the circuit exactly as shown in the schematic, I hooked up the oscilloscope across the resistor and found a trace that looked like a half-wave rectifier instead of a full-wave. This pretty much looks like a circuit consisting of an sinusoidal signal traversing through a signal forward-biased diode. There is no inversion of the negative portion of the sine wave, as seen with the full-wave rectifier, rather the negative portion of the wave just turns in to zero volts. In essence, unlike the full-wave rectifier, only half of the original sine wave is βrectifiedβ into direct current. This is NOT what this circuit should look like on the oscilloscope.
Based on some earlier work, I expected though that this is what the oscilloscope would show without a bit of careful consideration. It turns out that this oscilloscope trace is not the result of the circuit malfunctioning, but rather a poor testing design creating a false result.
Remember the circuit diagram. The signal generator produces a signal that enters into the bridge rectifier at two distinct nodes D1/D2 and D3/D4. The signal generator needs to be electrically isolated from the output of the bridge rectifier, which occurs through nodes D2/D4 and D1/D3. Instead, however, the oscilloscope and function generator share a single ground, the earth ground in my house when I plug the unit into the wall. This makes both node D3/D4 and D1/D3 grounded which in essence creates a short circuit across diode D3. Without D3, the circuit now functions as a half-wave rectifier.
The multimeter was used to prove that indeed the oscilloscope and function generator grounds were shared. Everything was unplugged from each device and the digital multimeter was set to resistance. Checking the resistance between the outer shields of the BNC connectors of the oscilloscope and function generator showed, none, indicating a short circuit, and proving that this was the cause of the bridge rectifierβs apparent malfunction.
In order to fix this issue, I checked to see if my new TekPower TP-3003D-3 power supply shared a common ground as well. It did not! There were several megaohms of resistance between the ground terminal of the supply and the generator. So, I connected the oscilloscope probe ground and the function generator ground to one of the negative terminals of the power supply and checked the output waveform. It was still not correct.
I had one last trick up my sleeve. I declared the function generators ground as the common reference ground of the circuit. I attached one oscilloscope probe to one side of the load resistor (the top trace) and the other oscilloscope probe to the other side of the load resistor (the bottom trace). I attached the oscilloscope probe ground leads to the function generator ground. The results are shown in the oscilloscope trace below.
In essence, I can see that the top trace is displaying a half-wave rectifier. The bottom wave is showing another half-wave rectifier out of phase with the top trace. In fact, this bottom trace has been inverted, and this waveform now appears upside-down with the humps going upward, when really they would be going downward with negative voltages.
However, the inversion of the second signal is important, because now I can do math with the oscilloscope. Take a look at the third row of controls on the scope below. First I want to βChopβ the displayed signal as this will allow us to see the waveforms better. I have already inverted the signal. Now I want to add the first (upright) and second (inverted) channels together, essentially performing a subtraction function.
Revisit the image of the oscilloscope display above, and you can see the middle trace is now showing a full-rectifier. The middle waveform in the mathematical operation of Ch1 β Ch2 as performed by the oscilloscope.
And sure enough, when you take a voltage reading with the multimeter across the load resistor, you can see a 1.8 V output of direct current. Woo hoo!
I used the new AI image feature on this WordPress site to prompt a proud scientist overlooking the display of a full wave rectifier on his oscilloscope. So darn goofy! My favorite part is the Hollywood vanity lights just like in a professional lab! It is also hard to tell exactly why he is so proud given those resultsβ¦
It is not surprising that I have a interest in test equipment. Learning the nuances, limitations, and intricacies of testing is paramount, or else you can make what I would refer to in my other life as iatrogenic errors. This little experiment is perfect for showing how something that works exactly as it should can be deemed malfunctioning due to misinterpretation of a lab test. While getting it wrong with this device in my little electronics laboratory is inconsequential, bad testing in the real world can be disastrous.
So the lesson here? Always look for that common ground.
Following this a number of girl guides posed questions which were very quickly answered as the ISS passed overhead.
Using my new Wouxun UV-980PL and simple end-fed vertical dipole I got a great signal from the ISS HAM radio station and was able to receive the ISS side of the conversation as the space station approached the N/W Coast of Spain until it eventually dropped below the horizon out of site nearing East Russia.
Below is a short video clip with audio showing the clarity of reception. The ISS peaked at an S9 signal, it was a perfect pass for the special event.
Iβm hoping to put up a better antenna for 2/4/6m & 70cm in the next few days so that I can start joining the local nets on these bands and perhaps get contacts through a few more of the FM Low Earth Orbit (LEO) satellites.
Iβll also be writing a full article on the Wouxun KG UV-980PL in the very near future, so if this radio is of interest to you then watch this space.
ARISS is planning a Slow Scan Television (SSTV) experiment from the International Space Station, scheduled to start on Tuesday, October 8, at 16:00 GMT and running until Monday, October 14, at 14:10 GMT.
There will be an interruption on Friday, October 11, for planned school contacts over Europe.
The SSTV transmissions will be made using the amateur radio station in the ISS Service Module. The transmission frequency will be 145.800 MHz FM, using SSTV mode PD120.
At 11:29 GMT on Saturday October 5, 2024, an Amateur Radio on the International Space Station (ARISS) radio contact between astronaut Sunita Williams KD2PLB aboard the International Space Station (ISS) and members of Girlguiding Surrey West County, took place at the Brooklands Museum and Brookland Innovation Academy, located in Weybridge, UK.
ARISS conducts 60-100 of these special Amateur Radio contacts each year between students around the globe and crew members with ham radio licenses aboard the ISS.
Girlguiding Surrey West is a charity organization for girls and young women. Girlguiding wants to inspire their members to learn skills in science, technology, engineering and math with fun guiding activities and science-based activities. The Brooklands Innovation Academy, established in 2022, creates inspirational STEM experiences for young people. The age range of the participants for this ARISS contact are 5 to 19 years old. By hosting this ARISS contact they are also demonstrating real-world application of STEM concepts (an important principle at Brooklands Museum) to space missions and are encouraging the girls to complete their space interest badge. The group is being supported by the Radio Society of Great Britain and the ARISS UK Team to establish the radio link.
Girlguiding patron, Her Royal Highness The Duchess of Edinburgh attended the contact to help in promoting the engagement and involvement of girls and young women in STEM. At the start of the contact she greeted Sunita Williams on board the ISS.
This was a direct contact via Amateur Radio allowing students to ask their questions of astronaut Sunita Williams, amateur radio call sign KD5PLB. The downlink frequency for this contact was 145.800 MHz and was heard by listeners within the ISS-footprint that also encompasses the relay ground station.
The amateur radio ground station for this contact is in Weybridge, UK. Amateur radio operators using call sign GB4GGB, operated the ground station to establish and maintain the ISS connection.
The Β Brownies, Guides and Rangers asked these questions:
1. Who or what inspired you to become an astronaut and what advice would you have for any of these girls here today who might want to become an astronaut?
2. Do you have any free time and if so what do you spend your time doing?
3. There are many international time zones so how does time work on the ISS?
4. If you were not an astronaut, what job would you like to have instead?
5. What things do you like to take with you to remind you of home?
6. What is the hardest part of your job?
7. How does the food and drinks do you have in space compare to foods on earth?
8. What do you miss about Earth?
9. How long have you been on the international space station?
10. What was your reaction when you found out you had been selected to fly to the ISS?
11. What stars or other things have you seen in space?
12. Is space hot or cold?
13. Does space smell of anything?
14. How do you sleep in space?
15. What is your favorite planet and why?
16. Have you done a spacewalk? If so, what was it like?
17. The spacesuits look very heavy, are they uncomfortable to wear?
18. What is it like floating in space? Have you ever lost anything from it floating away?
19. What things do you like to take with you to remind you of home?
About ARISS:
Amateur Radio on the International Space Station (ARISS) is a cooperative venture of international amateur radio societies and the space agencies that support the ISS. In the United States, sponsors are the American Radio Relay League (ARRL), Amateur Radio Digital Communications (ARDC), Radio Amateur Satellite Corporation (AMSAT), NASAβs Space Communications and Navigation program (SCaN) and the ISS National LabβSpace Station Explorers. The primary goal of ARISS is to promote exploration of science, technology, engineering, the arts, and mathematics topics. ARISS does this by organizing scheduled contacts via amateur radio between crew members aboard the ISS and students. Before and during these radio contacts, students, educators, parents, and communities take part in hands-on learning activities tied to space, space technologies, and amateur radio. For more information, see http://www.ariss.org/
Those satellite enthusiasts thinking of getting their UK Amateur Radio licence may like to know a Free online training courses are available at http://hamtrain.co.uk
AMSAT-UK is delighted to have been able to accept an opportunity to provide a FUNcube Lite payload, with a mode U/V FM transponder, for the exciting Jovian-1 satellite.
This 6U CubeSat is being designed and built by Space South Central which is the largest regional space cluster in the UK.
This is a partnership between industry and academia, designed to accelerate space business growth, grow the reputation
of the south central region of the UK and foster an environment of innovation.
A collaboration between the universities of Surrey, Portsmouth and Southampton, JUPITER β the Joint Universities Programme for In-Orbit Training, Education and Research β will equip participants with invaluable hands-on space industry experience and training for their future careers.
The FUNcube Lite payload from AMSAT-UK will collect and send telemetry from Jovian-1 sub-systems for educational outreach to schools and colleges, using the tried and tested FUNcube data format.
Telemetry will include data from the payloadβs own radiation sensor, along with GPS information gathered from the satelliteβs CAN bus.
These data can be used to map radiation throughout the orbit, identifying planetary radiation βhotspotsβ such as the polar regions and the South Atlantic Anomaly. It will also give an accurate measure of how much radiation reaches the sensitive electronics within the satellite.
While Jovian-1 and its ground station at Surrey University will use commercial S and X band for primary communication,
FUNcube Lite will use frequencies in the amateur UHF and VHF spectrum.
When not sending telemetry, the payload can be configured as a mode U/V FM voice transponder for amateurs to use for international communications.
More information will be provided during the AMSAT-UK Colloquium taking place during the weekend October 12/13th https://amsat-uk.org/colloquium/
Note: This was supposed to be published in the November issue of The SPARC, the Boston Amateur Radio Club newsletter, however, due to unforeseen circumstances, it was never published, so here it is for the first time in print!Β
It was a busy public service month for
me. First off was MassJam 2023, the multi-state scout jamboree that
is held every five years at the Cape Cod Fairgrounds in Falmouth.
While the communication staff was made
up of entirely of hams, the event did not use amateur radio for its
operation as obviously, while there are hams in Scouting, not
everyone is a ham and therefore, commercial band radio was a must for
the event. Using radios provided by DC Rentals (who seem to provide
the commercial radios for practically every large event in Boston)
MassJam got underway. Net control was a 24/7 operation with shifts
scheduled in blocks and food for the net controllers was cooked on
site. Despite some hiccups, the event itself was mostly successful,
including exodus from the campground was went really well and
finished practically on schedule.
After a week and a half off, it was
time for the next major public service event, the 2023 Head of the
Charles Regatta. I was stationed all 3 days at the Attager (which is
Regatta spelled backwards) Row First Aid tent. A hamβs job at the
regatta is to be the primary link for the first aid tents to net
control and from there to the eventβs roving bike teams on
commercial radio (again, provided by DC Rentals) and if needed to our
public safety partners such as the Massachusetts State Police (who
provide their command post for the weekend where a ham is stationed
as a link between net control and them), Boston EMS and Cambridge
Fire. Joined by a rotating motley crew of hams, including our very
own public service chair, Ethan KC1OIP, we made the best of it
despite pouring rain on Saturday and cold winds on Sunday.
All in all, a good month of public
service. I recommend the Regatta as a good place to start if youβre
interested in the public service side of this great hobby. Now to
look forward to next yearβs public service season with the Boston
Marathon!
Β Jim Fisher, AJ3DI passed away a few weeks ago. I met Jim at Winter Field Day in 2022 down in Pennsylvania. I followed him on Twitter. He was a real helpful ham, especially to my friends down in Philly who now miss his dearly.
I can't really say much more because I didn't Jim that well, but to measure his impact he had on the Philly ham scene, here's a few others posts and his obituary.
Ever since I started using Node-RED Iβve been using the standard node-red-dashboard set of user interface (UI) nodes to build my numerous dashboards to enhance my radio hobby and add new functionality to the operating of the station. The series of UI nodes are very simple to use and have served me well however, they are no longer being developed and are now deprecated in the overall Node-RED project.
To this end flowfuse.com have stepped up to the mark and developed Dashboard 2.0. This new series of UI nodes brings a new, more modern look and feel to the Node-RED dashboard along with some new functionality.
Iβve only just started investigating Dashboard 2.0 but, itβs proving to be fairly easy to use. The short video clip above shows an S-Meter display developed using Dashboard 2.0 for my FTDX10 transceiver.
Full instructions on how to install and configure Node-RED Dashboard 2.0 can be found on the flowfuse.com website.
Be aware though, Node-RED dashboards developed using Dashboard 1.0 will not work under Dashboard 2.0, you will have to import the old v1.0 flow(s) and manually go through them and change all the UI nodes to new Dashboard 2.0 nodes. Since some of the new nodes work differently to the old nodes youβll also find you will need to make code changes to get the same/similar functionality.
Iβm finding it easier not to import old flows but to recreate them afresh under Dashboard 2.0 using the old flow version for reference.
Overtime I will migrate my dashboards over to the new 2.0 version however, this is going to be a lot of work, especially in the case of my QO-100 Ground Station Dashboard as it contains a considerable number of UI nodes, and will take a fair amount of time to migrate.
Iβll document my findings as I go as Iβm sure there will be a few trials and tribulations along the way.
Thanks to Neil, G7UFO for pointing me to the new Dashboard 2.0 information.
Please join us this evening, from 7PM β 9PM at the Cumberland County EMA Bunker, located at 22 High Street, in Windham, ME, for our monthly Emergency Communications Team (ARES) meeting.
Tonight weβll be discussing the upcoming Simulated Emergency Test, which takes place Saturday, October 26th.
For those who wonβt be able to join us in person, please tune in to our ECT training net on the 449.225 (- / 103.5 Hz) WS1EC repeater at 7PM.
This month, we will also be testing Simplex coverage, after the net on the repeater, on 146.580.
Please join us this evening, from 7PM β 9PM at the Cumberland County EMA Bunker, located at 22 High Street, in Windham, ME, for our monthly Emergency Communications Team (ARES) meeting.
Tonight weβll be discussing the upcoming Simulated Emergency Test, which takes place Saturday, October 26th.
For those who wonβt be able to join us in person, please tune in to our ECT training net on the 449.225 (- / 103.5 Hz) WS1EC repeater at 7PM.
This month, we will also be testing Simplex coverage, after the net on the repeater, on 146.580.
In ham radio, we often use Handie-Talkie or HT to describe a compact, handheld transceiver. My first exposure to the term Handie-Talkie was when I first became a licensed radio amateur in 1977. While I was a student at Purdue University (W9YB), the absolute coolest VHF radio to have was the Motorola HT-220. Even a used one commanded a high Continue reading Handie-Talkie or Walkie-Talkie?β
Not clear on the concept. If you or someone you know has an HF station with a goal of DX communications in disaster situations, I have a question: What are you really trying to do? What is the need for very long distance communications in a SHTF scenario? Save for... Read more Β»
Over the weekend, KOTBTY and I got to spend more time moving the CW key relay inside Project TouCans and adding a power on/off latching relay. As you can hear and see in the video below, the latching relay is up and running! Thanks for Simon Willison for the Claude artifact that enabled me to easily package up the video below.
Ha, that's interesting! It's not so much a video packaging as a video thumbnail tool, which is of course what it said it was. Well, here's the video all bundled up into an iframe ready for your viewingβand listeningβpleasure. I'll have to work with the gang on a version of the tool that outputs iframes soon.
What you can see in the video: the Darlington array has two control leads coming into it from the PICO-Ws GPIO 17 and GPIO 18 pins, (the orange and red wires respectively.) Now that we're using a latching relay, we need one control wire to latch the power on and a second wire to latch the power off. Positive rely coil power is attached directly to the latching relay, but the circuit through each coil to ground is broken by the Darlington array. When the Pico-W signals to the Darlington array to conduct for a fraction of the second, the appropriate relay coil, (either power-on or power-off), is energized and then the connection is latched by the internal latching magnets of the relay.