VHF, UHF and Microwave Record Table - the latest table of records is available from the VHF SA Record page. Click here to get a copy. Compiled and updated by Paul, ZS6NK - latest version 31 October 2019. Updates to zssixnk@gmail.com
Focus on VHF and Above 17 November 2019
Audio version
During December a new VHF beacon will be installed on a hill overlooking Bethlehem in the Freestate.
This is a very important beacon for the SARL Beacon Project. It will have two 8 element Yagi antenna connected to it with one pointing in the direction of Gauteng and the second antenna will be able to be pointed in various directions depending on what tests need to be done.
Why is this beacon important?
We have all heard about the fantastic tropoducting that takes place along the West Coast and across the South Atlantic to St Helena Island. There are also every now and then good opportunities along the South East Coast as well and these conditions can extend as far as Reunion Island and possibly Mauritius. The conditions are however a little more challenging along the South East Coast.
Tropoducting has been very well studied over the oceans and these conditions can be predicted with reasonably accuracy by software like the Hepburn Charts developed by William Hepburn. There are at least two other amateurs who have also been developing software to try and predict tropoducting, but again this is only over the oceans. The weather patterns are also dynamic and always changing and the predictions are not accurate, but an indication that there could be a possibility for tropoducting.
There is currently no way of predicting tropoducting over the landmasses.
We are starting to get an idea of what atmospheric conditions may result in tropospheric ducting, but again it is very difficult to predict and at the end of the day there is still a tremendous amount of work that needs to be done to understand tropospheric propagation.
The next best way to figure out if tropospheric propagation is favourable is to monitor VHF and UHF beacons. There are various types beacons around, but the most common beacons transmit a CW message that identifies the beacon and it’s grid square. The beacon will send out a signal every 30 seconds continuously, 24/7, 365 days in the year, regardless of the weather conditions.
There are a number of beacons operational through out the country that are regularly listened to. For example, Carl ZS6CBQ and Rickus ZS4A, two of the most active VHF and above enthusiasts will listen every morning and evening for certain beacons and depending on how well they hear the beacon they know whether there will be a chance of some long distance VHF or UHF communications. If they find that there is an opening then they will let the folk who are all part of the 46 Group on WhatsApp know about the opening. Openings also do not necessarily only occur in the mornings or evenings and the times may change as well depending on the weather conditions and we all know how predicable the weather is.
The problem is however that as with a large part of the amateur community they still need to work to put bread on the table and cannot spend all their time in front of the radio.
All of us also know how annoying WhatsApp groups can be where everything other than what is meant to be posted on the group is posted and eventually we mute the group and then we do not know what is happening.
A relatively simple monitoring station can be deployed anywhere to listen for the beacons and automatically decode and report on the beacons being heard. This system is called a reverse beacon network. The only catch here is that in order for software to decode the CW received, the signal needs to be of good quality with accurate timing of the dots and dashes as well as the spacing between characters and words.
This beacon going up at Bethlehem has been specifically designed to be able to be accurately decoded by software such as FLDigi, CW Skimmer and other similar programs.
At the same time Tom ZR6TG has written an application that runs on Telegram, known as a bot. This bot allows the user to register with his callsign and grid locator and then when a beacon is heard, the user tells the bot that he wants to report a beacon. The bot will then display a list of beacons from which to make a selection, ask for a RST report and once confirmed, will send out a message to all users registered on a Telegram group that the beacon was heard and at which grid locator. This is a closed group and only the bot can post propagation reports on it.
This bot will be demonstrated at the next Workshop on 23 November at the National Amateur Radio Centre.
Work can also now start on an automated reverse beacon network to monitor, decode and report when the beacon is heard, 24/7, 365 days of the year.
We will eventually be able to know when the beacons were heard and when VHF openings take place and slowly be able to build a record of openings that will aid in the study of VHF propagation.
The Bethlehem beacon will also be the test bed for the next beacon that will be developed to be placed somewhere in the Northern Cape to allow for monitoring propagation paths between Gauteng and the Western Cape and possible other paths as well.
Now for some other VHF and above news.
John Worsnop G4BAO has made available the details of his 23cm 45W amplifier that was published in RadCom in June 2009.
John announced on Twitter that he will no longer be stocking these kits and the design is now in the public domain under an MIT licence.
He's included a copy of the original article, Eagle board and schematic files, plus Gerber files for the PCB. You can find more information on his Twitter account https://twitter.com/g4bao/status/1194228652323549184
Also have a look at the 23cm-45W-PA on GitHub at https://github.com/g4bao/23cm-45W-PA
In the US the proceedings of the Microwave Update 2019 that was held on 3-5 October 2019 has been published. Take a look at it at http://ntms.org/files/MUD2019/MUD_Proceedings_2019.pdf
There is also a GNU Workshop Notebook available that tells you all about how to get started with the GNU Radio software that can be used alongside your SDR project. Take a look at http://ntms.org/files/MUD2019/MUD_GNR.pdf
The North Texas Microwave Society website http://ntms.org/ has lots of interesting documents from other meetings as well.
How about telling us about that VHF or UHF project you are working on!
Please send your news snippets and information about activities on VHF and Above to vhfnews@sarl.org.za.
Focus on VHF and Above 3 November 2019
Audio version
There are some exiting projects being done in the VHF and above bands.
Let us firstly look at NPR or New Packet Radio that is being developed by Guillaume F4HDK.
What is packet radio? Packet radio was very popular in the ‘80’s and 90’s and used the AX.25 Amateur Packet-Radio Link Layer protocol. The older radio amateurs will remember the packet bulletins boards that were around those years and used to send out messages far and wide. This was prior to everyone having emails. AX.25 is also still used with APRS or Automated Position Reporting System which a lot of local guys are playing with today, mainly as trackers in their vehicles, but it can also be used for reporting weather data. The important thing to note is that it is a low data rate protocol.
Around 2009 the use of the AX.25 protocol and packet radio fell by the wayside and some Polish radio amateurs developed a new protocol called NBP which comes from the Polish phrase "Ne-Brezhibni Protokol" (NBP) meaning Non-Flawless Protocol.
When Guillaume was looking at NBP, he decided that there must be a way of creating an even better protocol with a modern design that would be easier to use and inexpensive to physically implement. The result after six years of work was New Packet Radio.
NPR supports IPv4 and allows data to be transmitted at up to 500 kilobits per second on the popular 70-centimeter UHF ham radio band. 500 kb/s is not as fast as the European Hamnet or U.S. AREDN, which use Gigahertz
frequencies like those of Wi-Fi, but it is still faster than the 1.2 kb/s normally used by AX.25 links, and the 70-cm band permits long-distance links even when obstructions prevent line-of-sight transmissions.
Guillaume uses a ISM Si4463 radio module. To this he adds a DMR amplifier giving around 30W output to achieve longer distances. The radio module is controlled by an Mbed Nucleo STM32 L432KC controller connected to an Ethernet interface. Any connected PC or network sees the radio link as just another IPv4 connection with no need to install specific NPR software. The NPR modem can be configured over this link or via a USB connection.
For more information about this project and to find more information that will allow you to build your own system, take a look at his Hackaday project page at https://hackaday.io/project/164092-npr-new-packet-radio. This is an active project and continually being updated.
Now for something on a much higher frequency.
Neil G4DBN has released details of his latest project on the popular Hackaday site. A set of feedhorns, reference horns and flange couplers for use with the SiliconRadar TRA_120_002 chipset on the 122 GHz amateur radio band.
Building on the designs from Andrew Anderson VK3CV using a duplexer cavity fitted over the 5x5mm TRA_120_002 radar chip,
https://siliconradar.com/products/single-product/120-ghz-transceiver-tra_120_002/ but using threaded adjustment for best match.
Niel says, “I'm working on a range of alternative fittings including UG-387/U anti-cocking flanges, reference horns, feedhorns and Chaparral-style choked horns. I'll extend the range of fittings to include WR-08 rectangular waveguide transitions and tapered sections to 1.8mm or smaller round guides as demand arises.”
The 122 GHz band presents extreme challenges to long distance communication because of atmospheric resonances (2nd harmonic of the 60GHz Oxygen resonance) and water vapour absorption. Losses are in excess of 1dB per km. The world record distance for this band is around 60 km.
Further details of Niel’s antenna and feeds can be found at
https://hackaday.io/project/168231-122-ghz-antennas-and-feeds.
More information about the 122GHz project of Andrew Anderson VK3CV can be found at https://groups.io/g/The122GProject.
The innovation displayed by fellow amateurs is simply remarkable.
Hopefully these projects will stimulate some of you to try your hand at constructing or venturing into the higher bands.
How about letting me know what projects you are working on at vhfnews@sarl.org.za.
And now for some local contest news.
Carl ZS6CBQ has posted the following two reminders on the 46 Long Distance VHF/UHF WhatsApp group.
The second leg of the SARL VHF/UHF Analogue contest will be on the air from 10:00 UTC on Saturday 9 November to 10:00 UTC on Sunday 10 November 2019 with SSB, FM and CW contacts on 6, 4 and 2 m, 70 and 23 cm and higher. All QSOs must be two-way point to point and the exchange is a RS or RST report and your location - either a six-digit Maidenhead locator, or latitude and longitude.
Please consult page 48 of the 2019 Blue Book for all the information about the contest - multipliers and scoring, etc. Your log sheet must be sent to contest@sarl.org.za by Monday 2 December 2019.
Let’s hope that conditions are good next weekend.
The Contest team is busy working on the 2020 SARL Blue Book and requests Clubs hosting contests to submit any changes they would like to make as well as confirm e-mail addresses for log submissions. Members are requested to submit requests for new contests as well. Please send requests, suggestions and changes to contest@sarl.org.za by Wednesday 20 November 2019.
Carl says, “We are allowed and have made changes in the past to the rules of the VHF/UHF contest.
I think there is room for improvement ... specifically the Digital contest.
Please send me your ideas and suggestions as soon as possible. Read the rules very carefully and do not try and change the whole contest. We can have live discussions on the air as well. So this is YOUR chance to have a say. So no more talking about THEY or complaining next year when we use the rules. My email address is minnecd@absamail.co.za”
Thanks Carl for these reminders.
The VHF Work Group reports that the installation of the new VHF beacon in Bethlehem will take place on Saturday 7 December.
Well that’s all for this week.
Please send your news snippets and information about activities on VHF and Above to vhfnews@sarl.org.za.
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