Monday, 24 August 2015

Data modes - 3. Modes and software

This is the third of three postings about data modes.

You can find others at:-
Data Modes - 1. Getting Started. Find it here.
Date Modes - 2. CAT etc. Find it here.
Data Modes - 3. Software and modes. You are here.
and a related posting:-
Flex 1500 and data modes. Find it here.

This posting is about Windows. I do use other OS as well myself, but I am not very knowledgeable about them.

I think I need to deal with modes in three categories (one of which is divided in two!).

First are "beacon" modes, where you do not have a QSO,
Second are "formula" modes, which allow you to exchange the minimum information and not much else - subdivided into "fast" and "slow", and:
Thirdly "free form" modes, where you can send whatever message you want.

There are hundreds of modes around. I cannot deal with the less popular ones, mostly because I do not use more than a few. Just because I leave a mode out, it does not mean that I do not think it is good. There are just too many to consider them all.

In many cases popular modes have been superseded, in other words replaced by something which the author thinks is better. However, many amateurs are used to dealing with the old mode and do not change to the new one.

Beacon Modes
1) WSPR - this is one of the best known beacon modes. You can use it to listen to WSPR beacons worldwide, or if you can transmit you can create your own beacon. The bit rate is very low, but as a result the possible signal to noise result at a distant receiver is surprisingly high. WSPR software collects the callsign and locator data it receives, organises it and allows you to see a list of the times and stations received. The list includes signal strength, locator, frequency., etc, so that you can see, for example, how propagation changes over time. You find all this here, and at other parts of the WSPRnet site.

2) OPERA - appears similar to WSPR but instead of frequency shift keying (FSK - transmitting a signal of varying keying) as WSPR does, OPERA uses on/off keying, rather like a CW operator would. On the face of it, this should produce a simpler system which requires less stability. However, WSPR is the established mode. Even though Opera may be technically superior (opinions differ on that point) WSPR is the more popular.

Formula modes - SLOW.
3) JT65 - this mode only offers very basic options for sending information. Unlike WSPR, stations exchange signal reports and acknowledge receipt of these, making each completed contact a QSO. The messages consist of short exchanges, usually
CQ (your callsign) and locator
(your callsign) (dx callsign and their locator) - other station calls you
(dx callsign) (your callsign) Signal report - you give other station a report
(your callsign) (dx callsign) R Signal Report - other station sends roger and your report
(dx callsign) (your callsign) RRR - you send acknowledgement
(your callsign) (dx callsign) 73 73 73  - not strictly necessary and then you can call CQ again.
There is scope to personalise the messages but only to the extent of 14 characters.  Sometimes I might send a greeting or some station details, but most stations just stick to the above.

JT65 is a "slow" mode as it works best in stable conditions without too much fading (QSB). You can also use it for earth-moon-earth communication (EME). JT65 has been adopted as a very popular HF mode.

4) JT9. JT9 is an ultra-narrow successor to JT65. It is less popular, even though it offers better performance.

Formula Modes - FAST
5) JT6M - this mode is frequently used for 6m meteor scatter (and also for tropo scatter and iono scatter). On 6m the meteor trails are of longer duration than at higher frequencies, so a slower mode can work quite well. However, this is still a "formula" mode and you usually only get to exchange the basic QSO details.

6) ISCAT - this outperforms JT6M and you might think that most 6m enthusiasts would have changed over to it, but it is still quite unusual to see it in use. Even it is now challenged by a new version of JT9  - called "Fast JT9" or the version many in Europe use - JT9H.

7) FSK441 - this is an even faster mode than JT6M. As you get higher in frequency the meteor bursts are shorter and you need a mode that sends the messages in a shorter time frame. "FSK" as it is usually known (though "FSK" means frequency shift keying which is a name that could cover most of these modes except Opera) tends to be used above 50MHz - though at 70MHz there is some debate about whether ISCAT is better. FSK does not seem to work very well with a stable signal strength, it works much better with short bursts of signal.

8) JTMS offers advantages over FSK441, but not many people have changed over.

Free form modes
9) RTTY - this is an amateur radio version of the two-tone signalling system used for commercial radio versions of the land-line based teletype network. Hard to imagine now, but there used to be a hard-wired international teletype network, with its own telephone-type exchanges. For military and other purposes the hard switching was converted in modems to tones and transmitted over dedicated radio links. When the whole teletype network was destroyed by the invention of the FAX machine, the old teletype machines were snapped up by amateurs and mated to amateur type modems. Now of course the tones are generated in computers. This mode is seriously outdated, slow, wide, power-sapping, inefficient and a lot of other dire things, but it is very popular. RTTY was the first data mode amateur really adopted.

10) PSK - a truly amateur designed and operated mode with many advantages over RTTY. Like RTTY you can send any message you like, have a rag-chew, etc., which can make it slow to use. PSK31 is the commonly used one, but there are faster versions for contest use etc.

11) SSTV - slow scan TV is a bit like a FAX machine for radio, and now exists in various digital forms too. The general idea is that a still photo  is scanned and transmitted by two tones.

Other modes are too numerous to mention.

The basic idea is the same. Once you have got your rig receiving and you can work the PTT, you can  work most of these modes. As they involve sending tones to the rig, changing the mode means changing the frequency of the tones and/or the speed with which the tones are changed. However, broadly the same computer and rig set-ups can be used for most of them.

This similarity means that you can download "suites" of software containing many modes. FLdigi is one of these and it is free  to download and use. Ham Radio Deluxe (HRD)  was formerly free but is now paid-for. Joe Taylor and others make his "JT" modes available for free.

With one suite, like HRD,  you can use many modes, such as PSK, RTTY, and many rather less well known ones like Hell and Contestia. If you have two suites you can switch between a wide range of modes suited to different types of communications.

Why do we need all these modes and why switch between them? Well, HRD covers much of HF operation within its modes. But WSJT-X, for example, extends this to JT65 and JT9 (useful HF modes), ISCAT and JT9H for 6m meteor scatter, and WSPR. So you can start with one mode, and then move on to others.

Got HRD and play with PSK on HF? Very good. Thought about meteor scatter - well anyone with a 100W rig covering 6m and a simple antenna can try meteor scatter with JT6M.

You see, once you have one mode, the door is open to try more.

I will give more details of Ham Radio Deluxe later.



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