Feature Articles
- Details
- Written by: Alex M0TOT
- Category: Feature Articles
- Hits: 499
Alex M0TOT has followed up on his uni-polar stepper motor project with some modifications and enhancements - it now uses a more powerful Bi-polar motor and a new driver. It's also now controlled by an Arduino Uno open-source microcontroller board. You can see the code ('Sketch' in Arduino terminology) below. It's quite easy to follow along and see how it works. Well done Alex.
This is what he had to report on his latest project. Thanks to Alex for his contributions as always.
I am not really into Arduino and Sketches but could not use the uni-polar motor P.C.B. from last time to run a bi-polar motor. It would have meant building two new 'H' Bridge PCBs.
The Arduino ‘Example Sketch’ gives all the ‘C’ Code lines for the motor:
// Example sketch to control a Stepper Motor with TB6600 Stepper Motor Driver.
// Reference: https://www.makerguides.com/tb6600-stepper-motor-driver-arduino-tutorial/
// and ‘Programming Arduino – Getting started with Sketches’ by Simon Monk (Second Edition).
//
// Compiler defines Stepper Motor connections and steps-per-revolution:
// Each step of 1.8 degrees is divided 8 x times = 0.225 degrees.
// 360 degrees is divided by 0.225 degrees = 1600 microsteps.
// Microsteps help to reduce the amount of vibration at slow speeds.
// In microsteps a phase is not fully 'ON' or fully 'OFF'.
// This may cause the motor to become warm/hot at low speeds.
int dirPin = 2;
int stepPin = 3;
int stepsPerRevolution = 1600;
void setup()
{
// Declare pins as OUTPUT:
pinMode(stepPin, OUTPUT);
pinMode(dirPin, OUTPUT);
}
void loop()
{
// Set the spinning direction CLOCKWISE:
// Spinning direction of the motor is set in
// the'dirPin', either HIGH or LOW.
digitalWrite(dirPin, HIGH);
// Spin the stepper motor one-revolution SLOWLY;
for (int i = 0; i <stepsPerRevolution; i++)
{
// These four-lines result in one-step:
// The speed of the motor is determined by the
// frequency of the pulses that are sent to the
// STEP pin. The higher the frequency the faster
// The motor runs. Pulses are changed in the
// 'delayMicroseconds()'.
digitalWrite(stepPin, HIGH);
delayMicroseconds(2000);
digitalWrite(stepPin, LOW);
delayMicroseconds(2000);
}
delay(1000);
// Set the spinning direction COUNTER-CLOCKWISE;
digitalWrite(dirPin, LOW);
// Spin the stepper motor one-revolution QUICKLY:
for (int i = 0; i <stepsPerRevolution; i++)
{
// These four-steps result in one-step:
digitalWrite(stepPin, HIGH);
delayMicroseconds(1000);
digitalWrite(stepPin, LOW);
delayMicroseconds(1000);
}
delay(1000);
// Set the spinning direction CLOCKWISE:
digitalWrite(dirPin, HIGH);
//Spin the stepper motor five-revolutions or 8,000 microsteps FAST:
for (int i = 0; i < 5 * stepsPerRevolution; i++)
{
// These four-steps result in one-step:
digitalWrite(stepPin, HIGH);
delayMicroseconds(500);
digitalWrite(stepPin, LOW);
delayMicroseconds(500);
}
delay(1000);
// Set the spinning direction COUNTER-CLOCKWISE:
digitalWrite(dirPin, LOW);
//Spin the stepper motor five-revolutions FAST:
for (int i = 0; i < 5 * stepsPerRevolution; i++)
{
// These four-steps result in one-step:
digitalWrite(stepPin, HIGH);
delayMicroseconds(500);
digitalWrite(stepPin, LOW);
delayMicroseconds(500);
}
delay(1000);
}
Bi-polar stepper motor specification:
NEMA 17 Bi-polar Stepper Motor, 4-Wires, 12 Volt, 0.4 Amp, 28 Ncm.
When the motor is running slowly it becomes warm/hot, so I had to attach some heatsinks. In fact the two together are still too small, but I did not have anything else at the time.
Alex M0TOT
- Details
- Written by: Maintenance Guy
- Category: Feature Articles
- Hits: 684
Our very own WebSDR
I think most members are aware that we now have a WebSDR available to us (a link to which is available at the bottom of the website homepage). What you may not realise is that it's temporarily installed at my home while we test out suitable antennas, and then look to get the whole shooting match installed either at the club shack, or if that proves problematic, at a secondary location which is both RF-quiet and has a good internet uplink.
I'll be posting three or four articles on how the whole project comes together to provide a useful addition to our shack, and I'll write them in the style of a retrospective guide for those that come after us and who are seeking guidance. The implementation has certainly proved to be popular with members so far, with all four available access slots filled up every weekday lunchtime. On several occasions, I have been unable to snag one for myself, and if that trend continues we do have the option of allowing eight concurrent users, though only two of those eight will get the full graphical 'waterfall' experience. The rest just get an audio interface.
For this first instalment, I'll detail the physical build so that you can get a feel for what it looks like in the raw. I'll also cover the initial setup process and explain some of the difficulties I encountered along the way. The next article will give an overview of the back-end software configuration so that you can see some of the flexibility we have in that regard.
Other articles may cover wideband antenna testing, and possibly one on how to actually use it once you've loaded the webpage into your browser. That last one may just end up being a talk at the club or over Zoom, and would be a very high-level walkthrough to enable everyone to have some fun with it, regardless of experience. Most of you will already be well beyond that, I suspect.
Hardware - What's in the Box?
I purchased the KiwiSDR in kit form from Mr Lynch. I'd have been happy to have sourced it from anywhere, but they happened to be by far the cheapest. I also picked up a 5V power supply while I was at it (1.5A, although owners in the know often recommend a modified 3A Raspberry Pi item). You can also get a really nice aluminium enclosure, but it's around £45, and is not in stock anywhere that I could find. Thankfully the kit comes with an adequate DIY acrylic case which turned out to be fine as long as you don't plan to throw it around too much.
The box contained nearly everything you need to get started, and contrary to the instructions, the two main parts (the little BeagleBone computer board, and the KiwiSDR radio board) were already mated together via a subset of the GPIO pins. I pulled them apart again for the photos below.
There is lots of information on the BeagleBone computers at beagleboard.org. They've made several variants of this developer-focused board over the years, but apparently all the KiwiSDR kits come with the later BeagleBone Green (BBG) which is good news as these all include 4GB eMMC flash memory. The Green board (Green, as in the colour of the screen-printed background) is actually a Seeed Studio collaboration - an evolution of the original BeagleBone Black, and made possible by the open-source hardware philosophy much loved by the maker community.
The 4GB of memory is important, because ultimately it'll give us an upgrade path to Debian 10.x (Buster) from Debian 8.x (Jessie) which is now unsupported and therefore effectively a burning platform.
In an attempt to avoid letting the magic smoke out, I read all the info on the maker's website which proved very useful albeit a little bit daunting for a complete newbie. I needn't have worried, as most of the scary situations that beginners seem to find themselves in are as a result of just diving in and not reading up on the basics first.
Turns out that as long as the two boards have been connected together correctly, you can pretty much just plug in the various cables and then watch it all power up.
The only pre-requisites for a successful first boot appear to be a reasonable internet connection and an existing DHCP server set up on your network. The Beagle will need the latter to establish an IP address for itself, as you can't easily set this up manually until after it has performed a software update. You can change it to a static IP address once it's up and running, which is what I did. I like to know where my flock are at all times.
I built and tested the device before attempting the enclosure assembly. This seemed sensible in case there were any issues encountered, and because although I read the instructions before starting, I'm only human, and the case is boring!
I'm going to suggest that a logical pre-power-on procedure would therefore go something like this:
1) DON'T INSERT THE SD CARD. There is an Micro-SD card included in the kit, and a corresponding slot on the BeagleBone. It's for emergency recovery only, and is not needed unless you really know what you're doing, or the support guru on the official forum suggests it's a good idea. I'm going to guess that the Micro-SD card contains the self-same v1.2 image that's already pre-loaded onto the device.
2) Connect some sort of reasonable HF antenna (via adaptors if necessary) to the RF ANT section of the KiwiSDR board. There is a standard screw-terminal block for a High-Z antenna wire and ground, but I did what most people will do and connected a 50Ω coax-fed antenna to the commonly-found SMA socket. No antenna is supplied in the box.
Make sure you pick the correct SMA socket though, because there are TWO on the Kiwi board. The other one is for a 3.3V GPS antenna. The silk-screen printing on the board and the manual clearly identify which is which.
3) Connect the above mentioned GPS antenna, if required. The kit comes with a neat little GPS antenna, so although the whole thing is going to live under my desk for the time being, I connected it up even though it has no possibility of seeing clear sky in this location. I wanted it to be detected during any automatic software update and to have its driver correctly installed. Its presence gets flagged for inclusion on the receiver list at kiwisdr.com as well as being used in actual TDOA directing-finding functionality. More on that another day.
4) Plug in an Ethernet cable. Thankfully there is no WiFi capability on-board. Good old-fashioned copper twisted-pair technology for solid reliability and bandwidth. Woe betide anyone who thinks it's a good idea to use a cheap WiFi bridge as a permanent solution. My experience of these is mixed to say the least. The other end of your cable is obviously going into your router, network switch or whatever. This isn't a networking tutorial, though it might turn into a bit of a networking anecdote later on. An Ethernet cable is not supplied either, though I'm sure you have a whole bunch of them in those otherwise empty boxes up in the loft.
Now before we reach 5) Connect power supply, get yourself ready for bed, or find something else to do which will keep you completely occupied for at least two hours. You are NOT going to want to interrupt the initial start-up process until it completes normally, and it's almost impossible to resist the temptation to power-cycle your new toy every five minutes if you're just sitting there staring at it.
5) Connect power supply. Yes, you can do it now, as long as you definitely read and understood 1) DON'T INSERT THE SD CARD
Most, if not all BeagleBones which come in the Kiwi kits are pre-loaded with a Debian-based operating system which is ready to go out of the box. I have a feeling that my retailer of choice had performed this step on my behalf. The initial startup process (assuming you have an active internet connection) will soon sniff out the latest version of the Beagle/Kiwi software on Github and go get it. It will then compile everything on your device and then reboot itself. As mentioned, the pre-loaded version is v1.2 but the latest version (at time of writing) is v1.544, and there is no comparison. Security issues alone mean you must upgrade, but functionality is massively improved too.
If everything has worked as it should have, your KiwiSDR is now available on your local network. You can probably find it at:
my.kiwisdr.com
or
kiwisdr.local:8073
...if you're lucky.
I just dipped into my router's admin pages and found it's DHCP IP address, and then added the port number :8073.
Your admin page can then be found at yourlanip:8073/admin
Relevant password information can be found at kiwisdr.com.
I'm not going to cover the dynamic DNS setup, because either you know how to do this already, or you're going to do some research online and work it out. The Kiwi group used to offer a reverse-proxy solution, but no longer. Fortunately though, there is a DUC (Dynamic Update Client) included in the (downloaded) software and accessible via the Kiwi admin panel. Unfortunately, it only allows configuration of services from no-ip.com (so you can select a yourname.ddns.net:8073 address). Annoyingly, no-ip nag you to death every 30 days on the free version, so I used my own script instead of the regular DUC so I can peacefully enjoy the free services offered by duckdns.org.
You're also going to need to do some port forwarding on your router. You probably know how that works. Just set up a virtual server, where you map an external port number to your newly-assigned static IP address (you don't have to go static, but it's much easier IMO) and internal port number, then tell it to use the TCP protocol.
You can find generic information on how to perform these last two steps all over the place, including the manual for your router hopefully.
Once you've got everything working, you can go back to the acrylic enclosure build. Instructions are included, and are generally OK, except that the position of the USB port printed on the acrylic base panel doesn't correspond to where it is on the BeagleBone (in my version at least) and the photos are lousy and lack detail. Top tip: the bottom acrylic sheet (and yes, you will need a hairdryer and some serious patience to get the protective film off) goes on the UNDERSIDE of the metal side panels and not INSIDE, or you simply won't have enough clearance to get the paired boards underneath the slide-in top sheet. You'll also have to separate the Beagle and Kiwi to bolt it all up and then get the enclosure push-pins in place which hold it all together (remarkably well). Be sure to push the GPIO pins fully home between the boards too, otherwise clearance will once again be an issue when assembling.
I've made all that sound like a bit of a nightmare, but in reality it's really straightforward and fun if you take your time - especially if you've done this kind of thing before.
Next Time...
What happens when all of this goes to hell in a handcart, how to fix it, and how to finally get yourself some much needed alone-time with your new KiwiSDR.
Berni M0XYF
- Details
- Written by: Alex M0TOT
- Category: Feature Articles
- Hits: 573
Alex Henderson M0TOT has got itchy fingers again, and this time he has decided that an upgrade to his BT master socket and router cabling is needed in an attempt to clean up his broadband DSL, and he has kindly documented the process should anyone else be considering a similar move.
It should go without saying that if you have any reservations about your confidence or competence in attempting such a swap-out, then you should call in a professional. Having said that, this is not a difficult job, and there is no mains electricity involved.
This is what Alex started with - the ubiquitous Openreach Mk3 split phone/DSL master socket:
So, the first step is to start unpicking the old socket:
Woah! Sorry, I meant to say that the first step is to buy all the stuff you need to do the work, including the best quality shielded and filtered S/FTP (Screened Fully shielded Twisted Pair) RJ11 cable you can find. This one happens to be from that great big emporium of everything online:
And you do need to get yourself one of the latest Openreach NTE5C master sockets. I do believe that Alex got his HERE.
Now you can transfer the wires over like for like.
BT Openreach's new NTE5C Installation Instructions are available to download below, as is the RSGB's guide to identifying VDSL inteference. Some of this may be of use to other members.
Good luck!
Openreach NTE5C Instructions
RSGB VDSL Interference Guide
- Details
- Written by: Richard G0LFF
- Category: Feature Articles
- Hits: 532
I have been interested in the 6m (50MHz) band from the time we were originally allocated the former Band 1 TV spectrum. To start with, only a maximum of one hundred ‘A’ licence holders would be permitted to use this new allocation, but eventually the band was made available to all ‘A’ licence holders and then subsequently released to all UK Radio Amateurs in 1986.
Harold Rose G4JLH played a major part in negotiations with the Radio Regulatory Division of the Home Office (at that time the licensing authority) on behalf of the Radio Society of Great Britain (RSGB) for a small number of permits that would allow two-way operation on the 6 metre band. A group had been formed with Harold as Chairman and Harold himself recommended that they call themselves The UK Six Metre Group - UKSMG.
The first AGM was held at the 1982 VHF convention, where the temporary committee resigned to allow the formal appointment of a full committee and officers.
At the time, there were no 100W 6m rigs on the market and very few with 6m added at 10W output. I had a Yaesu 726 at the time, which was a three module rig with a choice of 70cms, 2m, 6m or 10m modules. My antenna was an old Band One TV dipole, which produced amazing results with 10W during the sporadic E season. I then modified a 10m HB9CV that I had brought back from my stint in Cape Town, and that plus a newly acquired BNOS 100W solid state amp improved my 2 way contact rate considerably.
I am listed as being the first UK station to work Czechoslovakia, Italy & Romania. I was also the first ZB2, Gibraltar station to be worked on 6m by many EU stations.
I eventually put up a five element Tonna antenna, and worked all continents on the six metre band during the solar peak of 1989/90.
50MHz is still my favourite band, even though I only have indoor antennas these days, with a short boom 3el duo 4/6m Yagi fixed ESE in the loft with various delta loops for other directions. Last year during the sporadic E season I worked 80 DXCC on five continents with JR1LZK at 9567km being my furthest contact.
Looking at the list of past recipients of the trophy, quite a few were really ‘big guns’ with special research permits to run 32db (1632W) into very large antennas. I am very proud to have been added to that list as a ‘small pistol’ operator.
In 2011 I built a short boom 5el LFA Yagi and pointed it towards the setting moon. Within minutes I heard tones from the speaker even though I was at the far end of my garden talking to my neighbour. I rushed in and there was W7GJ working EU stations via the moon, WOW. I called Lance with my 90W and he came straight back to me and we completed a 2 way EME on 6m. The path loss at 6m is 265db so that was an incredible achievement. It goes to show that regular stations can achieve extraordinary contacts with patience and attention to detail.
The 2022 Sporadic E season is about to burst into life and all the numbers are looking good as we climb Solar Cycle 25. Here is hoping the Solar Peak is a strong one and this 'little pistol' can work some more rare DX on the magic band.
Dick G0LFF
- Details
- Written by: Maintenance Guy
- Category: Feature Articles
- Hits: 437
Yet more excellent project offerings from the workbench of Alex M0TOT, and this one's a cracker.
I'm very grateful to Alex for supplying me with his project documentation. If anyone else has anything to contribute in terms of self-constructed goodies, then please do get in touch.
This is what Alex has to say about this really interesting active antenna:
"This is an unusual project; it may not be everybody’s ‘cup of tea’. Essentially it is an antenna-amplifier for receiving only, for the HF and VHF/UHF bands.
There is provision for connecting a telescopic whip for AM/FM, long wire, UHF and dipole. I believe the original designer, Tony Van Roon-Werten VA3AVR is now a Silent Key. The transistors can be found on the Internet.
I have a few spare boards, if anybody is interested in assembling this unit.
In order to check whether the item worked alright across the bands, I connected the Active Antenna output to my radio and attached a frequency generator to the antenna input in place of an outside aerial. Shown attached is a screen capture of the response of a 50 MHz signal on the radio. Other bands responded in a similar fashion.
Alex M0TOT"
