Posts Tagged ‘ROS’

Operatic debut

Nothing to do with Verdi or Rossini, nor the web browser of the same name. OPERA is a new weak signal digital mode that has been developed for use on the amateur LF (500kHz) and VLF (136kHz) bands.

Information about it seems to be a bit hard to come by, but there is an OPERA Yahoo group from where I presume you can download the latest version of the software. I managed to find a copy and was surprised at the sophistication of the program. It already has working CAT support for many transceivers including my Elecraft K2 and K3. It also has a built-in chat system showing reported signals from other users.

Although the new mode is apparently the invention of Graham, G0NBD, the program has been written by Jose Alberto Ros, EA5HVK, author of the ROS digital mode, and there are clear similarities in the user interface. The program supports all amateur bands from VLF to 6m but currently you can only select the frequencies 136kHz and 500kHz.

There are actually two OPERA modes, one of which is claimed to be even better (i.e. work with even weaker signals) than the WSPR mode. What is particularly interesting about OPERA though is that it does not need to use a sound card to send a transmission. Although the sound card is an option – and a convenient one for users already set up for data modes – OPERA actually (if I understand correctly) uses on/off keying, in other words CW (though not Morse code.) This offers the potential for long distance contacts to be made using ultra-simple QRPP (very low power) transmitters designed for QRP CW use – though I imagine that success depends on use of a very narrow bandwidth so you might need to pay more attention to transmitter stability than you would need for Morse code.) If the digital encoding scheme is published then it would also be simple to build microcontroller based beacon transmitters.

As I am not equipped to operate on the 500kHz or 136kHz bands I have been unable to try OPERA out on the air myself. But it certainly looks an interesting mode, especially if it is opened up to allow use on the HF bands where it could be used as an alternative to WSPR and QRSS CW modes.

Jam tomorrow

I have not been keeping up with the development of the controversial ROS digital mode as for reasons given in earlier posts I decided it was not something I wanted to use. However a recent post in the Yahoo digital modes group brought to my attention a development that seems rather alarming. The ROS software has recently included an anti-jamming switch the purpose of which is described as “improves rejection against strong CW and Beacons interferences.”

Polite usage of the amateur bands require that you check the frequency is in use before making a call so no-one should be jamming anybody. Furthermore, no-one should be using ROS in the CW or beacon sub bands. So what exactly is the purpose of this switch and why should anyone need it?

Perhaps an inkling of what may be going to happen can be drawn from some of the comments relating to the performance of the anti-jam switch, for example:

  • “The New ROS/2000 passed the test successfully during the CW Contest last weekend.”
  • “More test with the New ROS/2000 in other hostile environment. This time during a PSK63 Contest on Sunday.”

As I said all along (indeed, this was my original objection to the use of this mode) ROS is just too wide for use in the narrow digital allocations of the HF bands. There just isn’t the space for it, unless it remains a niche, occasionally used mode, which clearly its developer and supporters don’t intend it to be. As another comment in the ROS forum states: “The bands will fill up once people realize how good this mode is.”

The development of anti-jam techniques suggest that ROS is being readied to engage in war with users of other modes. When users can’t find a clear frequency they will just operate on top of other modes. The principal claimed advantage of the wide ROS mode is that it enables contacts to be made under similar weak signal conditions to JT65A but that it permits keyboard chats to take place rather than the basic exchange of signal reports and locators. So it appears that a vast swathe of spectrum space is going to be made unusable for other modes simply so that people can exchange brag files.

We need strict regulation of digital modes on the amateur bands. The days of gentlemen’s agreements are over. There are too many modes competing for limited spectrum space, and too many hams who aren’t gentlemen.

Narrow minded

Due to having been banned from using the software I have not been keeping up with what is going on in the development of the ROS digital mode. However there have been a few interesting postings about it. In the digitalradio Yahoo group Skip KH6TY has posted the results of some tests conducted with ROS on 432MHz which appear to show that it suffers badly from the effect of doppler shift and flutter experienced at those frequencies, failing to decode over paths where Olivia was successful and even SSB was readable.

This has prompted a rebuttal from the ROS author, which however seems to overlook the problem of doppler distortion encountered by Skip. He has posted a series of comparisons between ROS 2250/8 and Olivia 32/1000 which purport to show that ROS holds up while Olivia prints garbage. He concludes: “The difference between both systems is about 5dbs (3.16 in natural units). This means that ROS8 need 3.16 times less power than OLIVIA 32/1000 to establish a QSO to 150 characters/minute.”

Assuming that this is true, I nevertheless feel that a tradeoff of bandwidth for power or speed is inappropriate in the context of the narrow HF band allocations for digital modes. Most amateur QSOs do not need to go at 150 characters/minute (most people can’t type that fast). On the other hand the 2250Hz wide ROS transmission blocks three channels that could be used for Olivia 32/1000, and even more channels that could be used for a narrower mode. The use of 2250Hz ROS effectively limits the number of people who can simultaneously hold a digital QSO.

Even if it is true that Olivia needs 3 times the power than ROS to get through, Olivia is still a better choice of mode in the real world, because it is easier to increase the power 3 times or to switch to a slower mode than to find extra space within the HF allocations to accommodate the use of such a wide mode.

ROS would be less of a problem if people used it only in circumstances where it would not be possible to communicate using a narrower mode. Unfortunately that discipline does not exist among today’s radio amateurs. People are using ROS to make contacts with others whose signals are strong enough that 30Hz wide PSK31 could be used. This is just selfish, and it is the reason why I feel that such a wide digital mode should not be permitted on HF at all.

The village green

Suppose you were a member of a village football team that had practised and played on the village green for years. And suppose that one day you turned up for a game and found a new rugby team using your pitch. You’d be pretty annoyed, wouldn’t you? Even though the village green is common land and so legally there for all to use, the football team would not expect its use of the football pitch established over many years to be usurped in this way. So it isn’t all that surprising that when it is, there’s a punch-up.

Turn now to the amateur bands and this is precisely what has happened to users of the Olivia data mode. Someone has turned up with a new game called ROS that requires a much larger pitch and it is interfering with the Olivia users’ ability to play Olivia.

OK, you say, but surely no-one could object to the rugby team using the football pitch when the football team isn’t using it? It’s a fair point, although as the football team uses the pitch off and on throughout the day they wouldn’t be happy about it. But here the analogy starts to fall down, because not only do the football team (Olivia) and the rugby team (ROS) not speak the same language, but they are also blind so they can’t see each other to ask even if they were able to.

The only way for the two teams to both play on the village green without falling over each other or resorting to fisticuffs is for each of them to have their own, separate pitches. Now could someone please translate this into Spanish and show it to the coach of the rugby team?

ROS not legal after all

I’d sworn I wasn’t going to post any more about the ROS digital mode, or even mention it by name again, but the latest bizarre twist in the tale is too much to resist. Here’s the story.

On March 3, Dave AA6YQ called the FCC to confirm whether the statement that ROS was now legal for use in the US which had been posted on the ROS website and which I wrote about on Tuesday was true. The FCC advised that the information (which has since been removed) was not true, and that the matter was still under review. Dave was told that the ARRL was involved and would publicize the outcome. This they have now done, and the outcome is that ROS remains illegal for use in the USA on frequencies below 222MHz.

ROS may still be legal in the rest of the world but I have to ask whether amateurs in Europe and elsewhere really want to be using a mode developed by someone who posts false information and rude remarks on his website and issues threats to any amateurs (including myself) who dare to make any statement against his mode. This is not mature, responsible conduct nor is it in the spirit of amateur radio. We don’t need this sort of behaviour which has come close to bringing the hobby into disrepute. It might be for the best if everyone stopped using ROS altogether. It isn’t as if there aren’t already plenty of other digital modes. And be honest, a mode that offers no chance of working any North American DX is not as interesting as one that can, is it?

What is a contact?

As someone who has quite often used WSPR, I have often said that it would be nice to be able to exchange reports with other stations and confirm the “contact”. I felt this simply because the WSPR network is a friendly community and it feels right somehow to be able to do that, just as you would confirm an enjoyable contact on another mode.

Modes like the little used WSPR QSO mode and JT65A on HF offer the chance to make two way QSOs using similar power levels to WSPR. But my recent experience using JT65A on HF, and more recently watching a station in Iceland take half an hour to try to exchange a signal report and confirmation with a station in Brazil using a certain other weak signal mode led me to wonder if in trying to make it possible to make “contacts” using the least possible power we have thrown the baby out with the bath water.

Communicating via moonbounce (EME) on VHF has always been about exchanging the barest minimum of information, because even doing that is a major achievement. But on HF it is always possible to have a proper contact, even if it means using a bit more power or waiting until propagation is a bit better. So why are we endeavouring to use modes designed for EME on the HF bands? What is actually being achieved? Someone’s computer is able to pick a few characters of information out of my barely audible signal, with the help of heavy error correction and the fact that the message format is known. My computer is able to do the same with his. Is this actually a contact?

Yesterday I tried for the first time in several years to use the Olivia digital mode. Before I did, I Googled up some information about it, and came across a Yahoo group containing a post by Waldis, VK1WJ. He wrote: “Yesterday I had a sked with DJ2UK on 20m in JT65A. Bert came in with around -17dB but he couldn’t decode my signal. After a while I saw in SPECJT that he had switched to Olivia 8/125. So I did the same, and we had quite a long error-free QSO. Olivia 8/125 is not exactly fast, but it still beats JT65A hands down. May be we could entice our JT65A friends to try Olivia instead?”

According to Waldis, instead of exchanging a couple of numbers using JT65A, you could have an actual (if slow) conversation using the 8/125 variant of Olivia. But the JT modes are currently in vogue, whereas Olivia – being developed in 2003 – is yesterday’s news. People are raving about the capabilities of a certain other mode that is making a lot of news recently. Have all these people actually tried some of the forgotten modes? Because I think if they did they might wonder what all the fuss was about and whether the newcomer really justifies its use of bandwidth.

What was I saying about reinventing the wheel?

Letter to RadCom

Dear Sirs.

I understand that the trend in amateur radio these days is towards self regulation. However, recent events in the digital sub-bands lead me to believe that this is just a recipe for chaos. I refer to the recent appearance of ROS, a 2.2kHz wide digital mode apparently developed for weak signal work.

Soon after the ROS software was made generally available, chaos ensued with ROS users causing interference to IBP beacons, established APRS and ALE networks and Olivia users, not to mention other ROS users. Any chances of making DX low-power contacts were dashed by the number of people trying to use a limited number of frequencies to make short range QSOs that could have been accomplished using PSK31 and one twentieth of the bandwidth.

The band plans do not set aside specific sections of the digital sub-band for different modes. I am told that this is so as not to hinder experimentation. However, many popular modes such as PSK31, WSPR, Olivia etc. have established their presence on various parts of the bands and this is normally honoured by “gentleman’s agreement.” This all goes out the window when someone posts on the net that a new mode is available and hundreds of people download software and go mad with their new “toy” without any authoritative guidance as to where to operate.

The experience with ROS throws into question whether different digital modes can co-exist in the same band space. Many digital users seem to treat signals in another mode as QRM to be transmitted over rather than somebody else’s contact. The problem in the case of ROS is exacerbated by the fact that the transmission of this mode is 2.2kHz wide, which makes it harder to avoid causing interference to somebody. I think we should also be asking if there ought to be a limit on the width of digital modes that can be used on the HF bands, because there just isn’t enough space in the digital sub band for many people to each have a clear 2.2kHz wide channel.

I am not against experimentation, and would suggest that a small part of each band be set aside for experimental modes, experiments being conducted by the developer and a few chosen testers. However, before a mode can be made available for general use it should be approved by an international committee which would take into consideration the benefits of the mode, the amount of bandwidth it occupies and what frequencies it may be used on.

Julian, G4ILO

CC: Andy Talbot, G4JNT, Data Modes columnist


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