Lightning scatter is one of those exotic propagation modes that sometimes get a mention in books and articles but there seems to be very few examples. I think most people would expect this mode to be perhaps seen in the VHF part of the spectrum so it was a surprise to read that VK7MO and VK3MAP in Australia claimed to have made an lightning scatter contact on 1296 MHz!
They report that on the 13th of February 2024, there was a severe lightning storm between them and they attempted to make contact on 1296 MHz using the MSK144 mode.
They write... "The distance between us is 505 km and we ran 33 & 36 element single yagis with power levels of 120 and 50 watts. We were surprised that at this distance it was also possible to receive MSK144 decodes on aircraft scatter. However, we found it was possible, by replaying the files and examining the MSK144, Fast Graph window, to clearly identify the difference between both types of propagation. While at the time we completed three QSOs on 1296 MHz using MSK144, examination of the files shows that only one QSO was completely on lightning scatter and the other two were partly on aircraft scatter. Still, we can report the completion of a QSO using lightning scatter on 1296 MHz."
After their tests, they came to the following conclusions...
We are confident that we achieved 50 lightning scatter decodes and one QSO at 1296 MHz.
We used 15 second periods and auto sequencing to respond quickly enough.
If aircraft are present, it will be difficult to confirm that a QSO is completely via lightning scatter until files are subsequently decoded.
The durations of lightning pings between 0.1 and 0.3 seconds are ideally suited to MSK144.
We are somewhat surprised that no corresponding pings were detected on 2 metres but conclude that 1296 MHz is a better band. Even if lightning pings can be detected on 2 metres it will be difficult to discern them from meteor pings.
We think 1296 MHz is probably the optimum band for lightning scatter.
Stations in the tropics should have a much better chance of seeing such events.
Commentary: Aircraft scatter is a very common mode of propagation and its effects are often seen on signals in the VHF, UHF & Microwave bands.
At 10kms above the ground, an aircraft has a visible horizon of about 400kms (800km circle).
Looking at an airplane pilots forum, cloud to cloud lightning is most common at about 3kms above the ground. This means the visible horizon from that height is about 200kms (400km circle).
Doing a quick check, it seems that the lightning would need to be at least 4.5kms above the ground for it to be visible to both stations for a 500km path.
It would be interesting to see if others could replicate these results? Some locations in the Mediterranean or the SE of the United States are possible locations during the summer months?
I'd expect it won't be easy to stations to pick out any possible lightning scatter signals from the many aircraft scatter reflections and tropo-scatter signals present.
If you would like to read the article from VK7MO and VK3MAP, then click on this LINK
Addendum: In this video, VK7MO talks about the contact and some of the background information.
In the video, VK7MO makes the valid point that at lower frequencies like 144 MHz, the RF noise from the lightning discharge may actually interfere with the actual MSK144 signal that is being propagated.
With the development of GPS and other radio navigation satellite systems, the part of the radio spectrum above 1 GHz has become very attractive and this has put pressure on the 23cms / 1.3 GHz amateur radio band. For the last few years, it looked as if the decades old allocation might be lost altogether.
The International Amateur Radio Union (IARU) are now reporting that an agreement has been reached for a recommendation for 23cm band amateur operations to be allowed on a non-interference basis alongside the co-frequency radio navigation satellite service (RNSS). The recommendation from the the ITU‑R Radio Assembly (RA) will form a component of the WRC-23 discussions which are ongoing until December 15th. (see update below)
While the threat to the 23cms band hasn't been removed completely, it is significant that a technical sub group has reached an agreement and hopefully it will be approved at the main conference.
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Update - 8th Dec 2023:23cm band outcome approved at the 7th Plenary meeting of WRC-23
The following was posted today on the IARU web site: During the WRC-23 deliberations, strong positions were expressed by all the parties involved. The result is a well-supported compromise for a footnote in the Radio Regulations regarding amateur and amateur satellite service operation in the 1240 – 1300 MHz range. The footnote reminds administrations and amateurs of the need to protect the primary RNSS from interference and provides guidance to administrations to allow both services to continue to operate in this portion of the spectrum. The compromise was formally adopted by the Conference Plenary on December 8 and is not subject to further consideration during the final week of the WRC. The IARU team continues its work on other WRC issues including the development of agendas for future conferences.
IARU President Tim Ellam, VE6SH, noted “This is a very good result for the amateur services. The decision reached at WRC-23 on this agenda item makes no change to the table of allocations nor incorporates by reference M.2164 into the Radio Regulations. The addition of a footnote that provides guidance to administrations in the event of interference to the RNSS is a good regulatory outcome for amateurs and the primary users of this band.”
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The image above from the IARU gives a good overview of what is going to happen to the 23cms amateur radio band.
1)Parts of the band restricted to just milliwatts... The current band is 60 MHz wide going from 1240 MHz to 1300 MHz. There will be a severe power restriction for large segments of the band that might overlap the radio navigation satellite signals.
Example...The section of 1240 to 1255.76 MHz overlaps the Russian Glonass system, Here, just 1.26-milliwatts in a 150 kHz wide signal is allowed. Note that this is effective radiated power so it includes any antenna gain. In simple terms, this prevents any amateur use of these segments of the band.
2)Protecting the DATV segment... The key target for the IARU has been to protect the main centres of activity and one of these is the Digital Amateur TV segment around 1260 MHz. The frequencies below are from the current IARU Region 1 band plan...
There will be power restrictions in terms of EIRP (combined power and antenna gain) and the IARU gave these examples...
1255.76 to 1256.52 MHz (760 kHz) = 250W eirp... 4W into typical beam antenna (18dBi) or 60W into 6dBi mobile ant.
1256.52 to 1258 MHz (1.48 MHz) = 125W eirp...2W into typical beam antenna (18dBi) or 30W into 6dBi mobile ant.
3) Protecting the narrowband segment... The other important part of the band from an amateur radio point of view is the segment for narrowband modes from 1296 to 1300 MHz (e.g. CW, SSB, FM, FT8). Here, the plan is for a simpler power output restriction rather than taking the antenna gain into account as well.
1296 – 1298 MHz = 50W pep into antenna & 1298 – 1300 MHz = 150W pep into antenna
There is a higher power limit for moon bounce operation as long as the antenna has more than 30dBi gain and is pointing more than 15 degrees above the horizon.
4) Amateur Radio Satellites... There is a complex set of power restrictions covering narrowband operation in the amateur satellite band from 1260 – 1262 MHz. These range from very low power at low elevation angles to higher power levels at high angles (−3 dBW for 0° to 15° / 17 dBW for 15° to 55° / 26.8 dBW for 55° to 90°).
I'm not aware of any amateur satellites using these frequencies or if any licensing authority will be keen in the future to give permission to any potential new satellites considering the contested nature of the band.
23cms / 1296 MHz... Why does it matter??? AMSAT UK sums it up nicely... "The 1240 – 1300 MHz band is important for the amateur radio service, being the lowest allocation for radio amateurs on which typical microwave propagation can be experienced. Access to these frequencies is facilitated by commercially available equipment and provides a ‘bridge’ building motivation to become involved in more specialized higher frequency microwave and millimeter wave operations providing the self-training which is at the heart of amateur radio."
In conclusion... As the IARU notes..."The final recommendation represents the culmination of more than 4 years of work by the IARU team within the ITU‑R study groups to ensure the best outcome for amateur radio in the face of intense regulatory, political and commercial pressure."
Some people may be disappointed with some of the proposed changes but there really isn't another alternative. The choice here is pretty simple... either the amateur radio service can co-exist with radio navigation satellite systems in the 23cms band on a non-interference basis or have no amateur allocation there at all.
If the plan is agreed at the conference as expected then it offers some certainty to radio amateurs who want to use the band, They can buy or make equipment safe in the knowledge that the band won't be gone in a few years time.
It also allows the radio amateur service some protection in that we can hide under the protection of these radio navigation satellites. It's highly likely that the various governments would have serious objections to any commercial interests trying to get access to the 23cms band in the future.
Further reading... You can find more information at the links below...
Addendum...After I put up this post, the RSGB released this related video which was made in October 2023 (1h 42m in length)...
1. Barry Lewis, G4SJH talks about "Amateur/RNSS coexistence in the 23cm band" 2. John Worsnop, G4BAO considers "How will the possible RNSS changes affect narrow band DX operation and EME?" 3. Dave Crump, G8GKQ looks at "The future of ATV in 23cms"
On the 30th of December 2022, the Dutch amateur radio station PI9CAM carried out a series of tests by bouncing Slow Scan TV (SSTV) signals off the moon at 1296 MHz. PI9CAM is the callsign of the special station at the Dwingeloo Radio Observatory in the north-east of the Netherands.
PI9CAM used the 25-metre dish at the site which was originally built in 1956 and was once the largest radio telescope in the world. As far as I know, they were using 100-watts for the SSTV tests.
One of those monitoring these tests was Rob, M0DTS in the NE of England. Listening on a frequency of 1296.120 MHz USB, Ron managed to get these images.
While the images have a lot of noise in them, it should be remembered that these 23cms SSTV signals on 23cms were bounced off the moon.
SSTV is an old analogue technology where signals well above the noise floor are usually required for a good decode and picture. It's not some sort of modern digital technology which decodes signals buried in the noise.
This short video clip shows what the slow scan tv signal from the moon sounded like...
Back in the first half of 2022, I was following the progress of what was termed the 'ICOM SHF Project'. ICOM first announced this in December of 2021 and it suggested that they were developing a transceiver for the 2.4 GHz and 5.6 GHz microwave bands. See my earlier post HERE.
The blog post got a good deal of traffic and it was obvious that a lot of people were interested in this product even if was supposed to be for only two microwave bands.
I don't think many people had an idea earlier in the year just what ICOM had in the pipeline and it turned out to be pretty amazing.
In this post, I'll look at the new IC-905 in two parts. The first part is a summary and if anyone wants to look at the finer detail, that will be in the second half of this post further down.
In a future post, I'll look at the 10 GHz system.
Part 1 - The ICOM IC-905 in summary
The ICOM IC-905
At the Tokyo Hamfair in August of 2022, ICOM announced their new IC-905 radio which covers the following bands... 144 MHz (2m) 432 MHz (70cms) 1296 MHz (23cms) 2.4 GHz (13cms) 5.6 GHz (6cms)
They also have an optional transverter for 10 GHz (3cms).
As you can see from the photo above, it does have a similar appearance to the current IC-705 model which covers all of the HF, 6m, 2m & 70cms bands.
Note however that there is no RF in this part of the IC-905, it's just the control unit. The radio itself or at least the RF part of it is in the head unit which goes up next to the antenna.
This is part of the concept of putting the control unit indoors where the user is and putting the radio (RF) section up at the antenna. The 'LAN Cable' connecting the two will use PoE (Power over Ethernet) which will carry power and control signals up to the RF module as well as transferring the signals from the radio back down to the controller.
The main point here is to eliminate losses from coaxial cables running from the radio shack to the antenna. These can be really high at UHF and Microwave frequencies.
Some features of the IC-905 system...
1) The power output is 10-watts on 144 MHz, 432 MHz and 1296 MHz from a single N-Type connector. There is a separate SMA type connector for 2.4 GHz and 5.6 GHz and the power on those bands is 2-watts.
2) The controller has a 4.3 inch (11cm) colour display and as you might expect, a real time spectrum scope and waterfall display.
3) All the usual analogue modes like FM, SSB & CW as well as the D-Star digital mode which is standard for an ICOM radio.
4) One nice feature is ATV (Amateur TV) in FM mode.
5) One feature of huge importance is that the RF module will be frequency locked by GPS. This is a major shortcoming in several of the existing ICOM rigs on the market in that frequency drift on some digital modes on the UHF bands is a major problem. The GPS locking should help resolve this.
Price & Availability...
As of November 2022, ICOM have not announced a price for the IC-905. I suspect it will be in the $2000-$2800 price range but we'll have to wait and see.
As for availability, they haven't announced it. I suspect it will be the second half of 2023 before we see any units for sale.
Game Changer...
When ICOM released their IC-705 radio, there was huge interest in it despite it being a low power 10-watt radio. One of the key selling points is that it was a 'shack in a box' with all of the bands from 1.8 MHz to 432 MHz in one unit.
In a similar vein, the new IC-905 is very much a 'shack in a box' for the VHF bands and above. If ICOM had announced a new VHF/UHF radio with just 144 MHz, 432 MHz & 1296 MHz, there would be a lot of interest in it. The fact the IC-905 has 2.4 GHz and 5.6 GHz as well is pretty amazing.
I suspect the biggest change will be to the 1296 MHz or 23cms band. There is a serious lack of radios available for this microwave band and getting a separate radio for just one band is prohibitive.
Close up of the base of the Diamond X6000A
I can see a LOT of people buying Tri-Band type verticals made by the like of Diamond and Comet and using them with the new IC-905. I think it's going to generate a lot of activity on the 23cms band in urban areas in many parts of the world.
The thing about a radio like this is that it is really versatile. People may come up with new ways of using it that we haven't considered at the moment.
I can really see this radio being a game changer for the UHF and low microwave bands IF the price isn't too high.
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Part 2 - The ICOM IC-905 in more detail
IC-905 Controller... Let's have a look at this is a bit more detail.
The image above shows the front of the IC-905 and you get some idea of the depth as well.
The photo above is of the front of the controller from the Toyko Hamfair last August.
The photo above shows the rear of the controller and again, you get some idea of the depth.
As you can see from the photo above, there is very little on the rear of the controller other than two heatsinks.
While the IC-905 uses a 12-volt supply, it seems likely that there is a much higher voltage going up the Power over Ethernet cable to the RF unit. It's likely that there is some type of switch mode power supply in the controller to generate this higher voltage and a reasonable heatsink is required for that. There are of course all of the low voltage supplies to all of the electronics in the controller as well and again, a heat sink aids in keeping things cool.
The image above shows the right hand side of the controller.
The image above shows the right hand side in more detail. The port with the Green LED and the cable in it is the Power over Ethernet cable that goes to the RF module.
The image above shows the left side of the controller with the various ports.
The photo above is an actual photo of the left side of the controller.
And now onto the RF module. This image above gives an overview of the underside of the RF module. From left to right...
a) The cable on the left is Power over Ethernet LAN cable from the controller unit.
b) The BNC socket has an RF output at 10 MHz which is controlled by a GPS unit inside the RF module. The 10 MHz signal reference from here is fed to the optional 10-GHz transverter and provides that unit with a stable frequency reference.
c) The connector on the right is for the CX-10G which is the optional 10 GHz transverter.
This image above is another view of the underside of the RF module.
The image above is the top side of the RF module. All 2m, 70cms & 23cms signals are fed out via one N-type socket. Both the 2.4 GHz and 5.6 GHz bands have their own individual SMA socket. There is also a SMA socket for a small whip antenna for to receive GPS signals.
The image above gives another view of the top side of the RF module.
The image above shows the top side with the GPS antenna connected.
The image above is an actual photo of the RF module on display at the Tokyo Hamfair.
If we consider that a N-type connector is about 2cms in diameter then the dimensions of the RF module above is about 18cms across and 26cms in height. The depth is perhaps in the region of 8cms.
In terms of operation, the new IC-905 is basically the same as the popular IC-705.
This image above is a screenshot from the controller showing it operating on the 5.6 GHz band with a selection of modes.
The image above is a screenshot of the 11cm display showing a selection of menu items.
One amazing feature of this radio is it's ability to use ATV (Amateur TeleVision). In the above image, you can see a received ATV signal inset in the screen.
And this is the received signal on full screen.
ICOM also intend to sell omni-directional antennas for both the 2.4 GHz and 5.6 GHz bands.
I suspect third party antennas for these bands will be a lot cheaper.
Video... and finally, this is the promotional video from ICOM for the IC-905
That's it. I've done my best to collate all of the information available and put it in one spot. We'll just have to wait now until ICOM announce a release date and price.
Addendum 25th Dec 2022... At a recent presentation, ICOM had this slide which showed the frequency stability of the new IC-905 versus the old IC-9700.
The IC-9700 which was released in 2019 and is a VHF/UHF transceiver covering 2m, 70cms and 23cms. It is not frequency disciplined by an external source and as can be seen from the chart on the left, it can drift hundreds of Hz with a change in temperature on the 23cms band.
This isn't an issue on say FM, D-Star, SSB or CW but it is on the very weak signal modes like FT8 or WSPR where a high level of frequency stability is required. This has led to some third party providers providing frequency stability solutions.
The chart on the right by contrast is that of the IC-905 at roughly four times the RF frequency. The IC-905 which is frequency stabilised by GPS only drifts a few Hz with changes in temperature.
This really is a game changer for all the VHF, UHF and SHF bands as frequency stability is now essential for very weal signal modes.
It was interesting to see that a contact on 1296 MHz was made between EA5TT in Spain and SV8CS in Greece on the 2nd of January 2022. The distance was around 1850kms.
Manolo, EA5TT reports working SV8CS on 1296.174 MHz on FT8 after working him on 144 MHz and 432 MHz earlier. EA5TT was using just 10 watts with a 35-element Yagi antenna.
As for the mode of propagation, it looks like it was a tropo duct over the Mediterranean Sea. This is the tropo forecast from Pascal, F5LEN...
I'm not sure what the record is for tropo in the Mediterranean but it looks like there is a 3300km sea path between the SW of Spain and Israel. Is it possible on 23cms?
VK3DXE in Australia recently posted this article on his Facebook page and it is republished here with his kind permission to reach a wider audience. In it, he outlines what attracted him to the VHF bands.
I've been a member of a number of VHF/UHF Ham pages for a while, and keep seeing a lot of misconceptions and myths being picked up and quoted over and over by newcomers, and sadly a lot of not-so-newcomers who’ve brought their HF Game with them to the higher bands.
I first became fascinated with VHF tropo propagation as a young kid living in the country, where we only had 2 TV channels, but occasionally we’d get the channels from the city suddenly appear when the conditions were right. You can imagine the excitement for a young kid way back then who's suddenly discovered some new TV channels! We had a neighbour up the hill who happened to be a Ham, and he explained to me how tropo worked. I was hooked, and from then on, whenever the weather forecast maps looked promising, and we got the right conditions, summer or winter, I’d start looking for the telltales that the city channels were going to pick up.
Fast forward 7 or 8 years, and I eventually got my Australian Novice license, quickly upgrading to the Advanced Call within a year when I was about 15 or 16. We were near the top of the sunspot cycle at the time, so I went nuts on HF for the next few years. But as the sunspots waned, I was drawn to the higher bands…..
As a youngster it was sometimes tough putting up a decent 2m yagi, but I always found a way of getting something in the air, and making the most of what I had available, even when living in rental housing. I just had to be creative, and sometimes a bit cheeky. The good thing about a 2m yagi though, was that even if anybody noticed it, they'd just figure it was a TV antenna.....
You can build a small yagi like this in an afternoon with some simple tools.
I learned about aircraft enhancement in the days before we had all the funky tools we have today, before the widespread coming of the Internet. We managed to regularly make 2m SSB contacts of up to 700km (400+ miles) with smallish yagis and relatively low power - one path of 740km was quite good even with my portable station, with just a little 4 element yagi and Yaesu FT-290R II running only 2.5 watts!
Living in inner city urban areas, I really began to appreciate low noise antenna designs (DL6WU & K1FO were the early leaders) and radio frontends that didn't collapse in the presence of strong out of band signals. I learned about GaAsFET LNAs (Low Noise Amplifiers, or preamps) too, and the importance of what was in front of the radio on RX. You have to think of your station as a system.
In the early 1990’s the Bible of VHF+ was published. The VHF/UHF DX Book very quickly became the must-have tome in every serious VHFer’s library. Although some of the chapters are now a bit dated, especially those relating to equipment, I strongly suggest everybody with even a fleeting interest in the higher bands downloads a copy and reads it. Hopefully it’ll help to undo some of the myths about VHF+ that have persisted in the hobby for far too long, things like the belief that troppo is only a summertime thing, and that troppo is the only worthwhile propagation mode on VHF+. Download it here: http://www.trpub.net/assets/applets/VHF-UHF_DX_Book.pdf
As the Internet came along and people developed all sorts of new tools, and we learnt about Forums, email reflectors, and then FaceBook pages, the opportunities to learn and collaborate grew amazingly.
Then the WSJT suite of software changed things overnight. All of a sudden, the little guys running just 100w to a 10 element yagi could successfully work stations on the other side of the world on 2m and above via EME, or Earth-Moon-Earth. I worked a dozen countries with just a single yagi and less than 200w at the antenna.
Just last weekend, I was listening to HB9Q in Switzerland on 23cm for hours here in my /P shack while we're living in temporary accommodation, with a beautiful steady signal, often quite audible in the speaker, all on a tiny 60cm x 90cm gridpack antenna.
Eventually, once I get my 2.4m dish in the air and find a suitable amplifier, I hope to be able to work him on 23cm SSB at home.... JT65 and Q65 will be an absolute walk in the park.
Lots of signals on 23cm with the gridpack.
In Australia, where we don’t have the population of Europe or North America, the Ham fraternity have embraced WSPR on 2m, and have demonstrated VHF paths of sometimes thousands of kilometres that no amount of listening to white noise for beacons or a coincidentally-timed CQ would find with the naked ear. Those paths are now being exploited regularly on digital modes, with people moving to SSB when conditions become strong enough. I've been around the hobby for a long time, but so too have the "old farts", some of whom vociferously decry the use of digital modes, but our experience here in Australia has really demonstrated how digital modes can be exploited to help get those SSB contacts that very probably would never have taken place otherwise. WSPR has been so successful that there are now WSPR beacons on Hawaii (often heard on West Coast USA), and in New Zealand, with a fantastic signal into East Coast Australia during the summer tropo season.
A little 4 element Cushcraft yagi. Even this is enough to decode some of the Big Guns off the Moon. I had many WSPR 2-ways with this one, out to 700km with Aircraft Enhancement
Next time you're asked by anybody (PARTICULARLY CHILDREN AND YOUNG PEOPLE) about the hobby, instead of trying to excite them with boring stories of talking on HF or FM repeaters, which they tend to equate with the equivalent of dialing random numbers on their cellphone to talk to old farts with bad combover hairstyles about their hemorrhoids, try telling them about stuff like all the space comms stuff we have access to, and can actively participate in, like using the repeater on the ISS, and all the other satellites we have access to. Tell them about Moonbounce, and how you can actually demonstrate the speed of light in action - you know exactly when the station on the other end has stopped transmitting, but can still see and hear his signal coming back at you for those additional 2 or 3 seconds it takes to travel all the way to the Moon and back. THAT gets young people more excited than listening to old farts! Try talking to them about meteor scatter, and how the military has used it for communication systems to counter the effects of comms satellites being wiped out in a conflict, or a dirty big EMP bomb wiping out HF. Tell them about aircraft enhancement, which is really bistatic radar, and how some clever dude worked out a way of using it to detect stealth aircraft by using commercial broadcasters behind enemy lines to illuminate the target. Tell them about all the really funky atmospheric and weather science they can learn just by playing with weak signals on VHF+. Tell them about the funky networking knowledge they can gain from modes like D-Star, IRLP, Echolink, etc.
The /P shack while I'm away from home
Anyways, I've written this piece in response to a recent influx of newcomers and not-so-newcomers to the higher bands, possibly on the back of purchasing themselves a brand new IC-9700. I fully appreciate that everybody starts their learning journey from different places and has different interests, but some of the myths and misunderstandings I see are staggering. Unfortunately, so much of the Ham narrative has become very HF-centric, and that mindset often pervades discussions, and the marketing of the hobby, so this is just my little bit to try to counter some of that. Remember to download the VHF/UHF DX Book from the link above, and jump onto some of the more technical pages and start learning.
I'll be doing a bit of a write up soon on the importance of frequency accuracy and STABILITY on VHF+. Watch this space.
