The JT Modes
Waterfall Display Showing JT65 Signals
(Notice the alternating TX/RX sequence from top to bottom.)
(Notice the alternating TX/RX sequence from top to bottom.)
So here we are now in 2016. It has been a while since I submitted an article to the “Digital Modes Meanderings”. In previous sections I talked about a few of the digital modes available to the digital mode operator. At that time a couple of newer modes were just starting to become popular, JT65 and JT9. At first I was a bit cool to these modes, not in favor, nor against them. I will explain my initial reaction in more detail later. A short history on the JT modes is needed before I say any more.
JT digital modes are the creation of a very smart man named Joe Taylor (K1JT). When I say smart, I mean smart like Nobel Prize smart, of which Joe Taylor is a recipient. Joe is a scientist who studies astronomical objects which helps explain how and why he became interested in weak signal work. The JT type modes were created to aid in making EME (earth-moon-earth) contacts, also known as “moon bounce”. JT65 was so successful in EME work that eventually it was used in modified form for meteor scatter and then HF communications. It is the HF work using JT65 and JT9 that I will be discussing. By now I guess you have figured out that the “JT” in JT65 and JT9 are from Joe’s callsign, K1JT, which incorporate his initials.
JT65 is a MFSK type mode utilizing a 1270.5 Hz synchronizing tone and 64 additional tones. These tones give JT65 a musical and melodic sound. It is also a bit hypnotic if not downright boring at first. This is one of the reasons that I was not overly interested in JT65 at first. It was kind of like watching paint dry. But you will soon get over this part after a few QSOs. JT modes utilize a very structured QSO format of alternating one minute transmit and receive sequences. Timing and frequency synchronization are fairly critical but not overly hard to achieve. Most, if not all, modern commercial transceivers have good frequency stability so that should not be an issue. Timing is another matter however. All computers have clocks that drift which makes the timing an issue for JT modes. There are a couple of ways to overcome this problem. The simplest and easiest is to just update the time setting in the computer by listening to WWV. You can do this right before your JT modes session and it will stay accurate enough for several hours or even the entire day. Of course, this needs to be done each and every time to ensure good timing synchronization but this technique is free (Ah, the ham operator’s magic word, FREE!).
All JT mode software have a DT (delta or deviation time) readout so you can monitor the difference in timing between your signals and the other stations. If the DT starts to get up to around 1.5 seconds it is time to reset the computer’s clock. Be aware that even if your clock timing is perfect the other station’s timing may be way off. So look at the average DT of several transmissions from other stations to get an idea if it is your timing that is off or the other operator. If it is the other station that is off in timing there is nothing you can do about that. Fortunately, even though the timing is critical, I have seen successful decoding with times off by as much as 3 to 4 seconds. But I don’t advocate attempting to do this on a regular basis. It seems that the particular software you use has something to do with the timing tolerance. I use WSJT-X software by K1JT and it is excellent it this area. But I have used another JT software program and it was not very tolerant of wide timing deviations. Signal strength is a factor also. The stronger the signal the better the possibility of a correct copy or decode.
A typical JT65 QSO begins with either you or the other station calling CQ just as it does with any mode. Let’s assume you are listening and hear a CQ call and answer it. Here is how the QSO will transpire.
Minute 1: CQ DE W2XXX FN20 Other station calls CQ
Minute 2: W2XXX DE K5ZZZ EM12 You answer the CQ
Minute 3: K5ZZZ DE W2XXX -15 Other station gives your report (reports are S/N in dB)
Minute 4: W2XXX DE K5ZZZ R-10 You confirm receipt of the report and give his report (R stands for roger)
Minute 5: K5ZZZ DE W2XXX RRR Other station confirms receipt of your report (RRR stands for roger roger roger)
Minute 6: W2XXX DE K5ZZZ 73 You say 73
Minute 7: K5ZZZ DE W2XXX 73 Other station says 73
Let me explain a couple of things about this QSO. All of these exchanges are already in the software. Each exchange is like a small pre-programmed macro. The pertinent details like the callsigns, grid square and reports are the only variables and those are filled in automatically by the program. When the CQ message (CQ DE W2XXX FN20) comes up in the “Band Activity” window in the software, you will use your cursor to click on it. The next message that needs to be sent, your response to the CQ (W2XXX DE K5ZZZ EM12), will be sent automatically by the program. This is not a robotic hands-off type QSO as it might first seem to be. You are most definitely part of the process.
If you don’t click the correct response to be sent things can get really fouled up quick. After a message is received by you in any minute (actually reception uses just the first 48 seconds and decoding takes about 2 seconds) you have 10 seconds to click the proper response (“Quick! What are you going do hotshot?”). If you don’t react correctly or in time the wrong message will be sent and you have no way to correct it. Your only options after the wrong message has been initiated are to either let it go or abort the message. Either way you may confuse the other station (and cause him to have a low opinion of you operating skills). Don’t let anyone tell you that using the JT modes is a no brain usage mode. There are definitely skills involved in successful JT mode operations, especially when working DX. Time management is only one of these skills. Oh BTW, mistakes WILL happen regardless of your experience level. Trust me. A wise ole Elmer (mentor) once told me, “If you ain’t making mistakes, you ain’t doing nothing”. A very true statement. Just try to keep the mistakes to a minimum.
The above QSO sequence is the standard QSO exchange. However, as you can see it takes 7 minutes to complete this minimum information exchange. So operators are always looking for ways to shorten the process. Many times there will be no RRR exchange sent, just a 73 DE W2XXX. Technically this is not a complete QSO as there is no confirmation of report reception, but it is a common occurrence. If you wish to shorten things a bit you should use something like this, RR 73 W2XXX. That way you include the confirmation with the salutation and shorten the exchange process.
Since the exchanges are preprogrammed in the software, how do you send a nonstandard message like RR 73 W2XXX? Good question. Incorporated in the software is an option to send what is called a “free message” or “freehand text”. Essentially it is a blank macro that you can write whatever you choose to send instead of a “canned” message. But there is a caveat. You can write anything you want as long as it only uses 13 letters! Folks get quite creative at times trying to convey as much information as possible.
Except for the actual transmitted signal structure, JT9 operates just like JT65 with the same messages and QSO process. JT9 is a much smaller transmitted signal. It uses less than 25 Hz of bandwidth whereas JT65 uses around 175 Hz. Because of the smaller bandwidth and different software processing JT9 is about 2 dB better in digging out weak signals. It is not as popular as JT65 for some reason. But its usage has been on a steady increase lately.
As you can infer, the JT modes are NOT ragchew (conversation) modes. That was another reason I was less than enamored with the modes at first. I am definitely a ragchewer first which is why I love Olivia type modes. But ragchewing aside, the JT modes do get the job done of making long distance contacts under poor conditions and with less than stellar radio station setups. Only Olivia mode does this better (and you can actually talk to someone!). Enjoy the JT modes but still try other digital modes for variety. JT modes are only one of many ways to get the most out of your digital modes experience.
JT digital modes are the creation of a very smart man named Joe Taylor (K1JT). When I say smart, I mean smart like Nobel Prize smart, of which Joe Taylor is a recipient. Joe is a scientist who studies astronomical objects which helps explain how and why he became interested in weak signal work. The JT type modes were created to aid in making EME (earth-moon-earth) contacts, also known as “moon bounce”. JT65 was so successful in EME work that eventually it was used in modified form for meteor scatter and then HF communications. It is the HF work using JT65 and JT9 that I will be discussing. By now I guess you have figured out that the “JT” in JT65 and JT9 are from Joe’s callsign, K1JT, which incorporate his initials.
JT65 is a MFSK type mode utilizing a 1270.5 Hz synchronizing tone and 64 additional tones. These tones give JT65 a musical and melodic sound. It is also a bit hypnotic if not downright boring at first. This is one of the reasons that I was not overly interested in JT65 at first. It was kind of like watching paint dry. But you will soon get over this part after a few QSOs. JT modes utilize a very structured QSO format of alternating one minute transmit and receive sequences. Timing and frequency synchronization are fairly critical but not overly hard to achieve. Most, if not all, modern commercial transceivers have good frequency stability so that should not be an issue. Timing is another matter however. All computers have clocks that drift which makes the timing an issue for JT modes. There are a couple of ways to overcome this problem. The simplest and easiest is to just update the time setting in the computer by listening to WWV. You can do this right before your JT modes session and it will stay accurate enough for several hours or even the entire day. Of course, this needs to be done each and every time to ensure good timing synchronization but this technique is free (Ah, the ham operator’s magic word, FREE!).
All JT mode software have a DT (delta or deviation time) readout so you can monitor the difference in timing between your signals and the other stations. If the DT starts to get up to around 1.5 seconds it is time to reset the computer’s clock. Be aware that even if your clock timing is perfect the other station’s timing may be way off. So look at the average DT of several transmissions from other stations to get an idea if it is your timing that is off or the other operator. If it is the other station that is off in timing there is nothing you can do about that. Fortunately, even though the timing is critical, I have seen successful decoding with times off by as much as 3 to 4 seconds. But I don’t advocate attempting to do this on a regular basis. It seems that the particular software you use has something to do with the timing tolerance. I use WSJT-X software by K1JT and it is excellent it this area. But I have used another JT software program and it was not very tolerant of wide timing deviations. Signal strength is a factor also. The stronger the signal the better the possibility of a correct copy or decode.
A typical JT65 QSO begins with either you or the other station calling CQ just as it does with any mode. Let’s assume you are listening and hear a CQ call and answer it. Here is how the QSO will transpire.
Minute 1: CQ DE W2XXX FN20 Other station calls CQ
Minute 2: W2XXX DE K5ZZZ EM12 You answer the CQ
Minute 3: K5ZZZ DE W2XXX -15 Other station gives your report (reports are S/N in dB)
Minute 4: W2XXX DE K5ZZZ R-10 You confirm receipt of the report and give his report (R stands for roger)
Minute 5: K5ZZZ DE W2XXX RRR Other station confirms receipt of your report (RRR stands for roger roger roger)
Minute 6: W2XXX DE K5ZZZ 73 You say 73
Minute 7: K5ZZZ DE W2XXX 73 Other station says 73
Let me explain a couple of things about this QSO. All of these exchanges are already in the software. Each exchange is like a small pre-programmed macro. The pertinent details like the callsigns, grid square and reports are the only variables and those are filled in automatically by the program. When the CQ message (CQ DE W2XXX FN20) comes up in the “Band Activity” window in the software, you will use your cursor to click on it. The next message that needs to be sent, your response to the CQ (W2XXX DE K5ZZZ EM12), will be sent automatically by the program. This is not a robotic hands-off type QSO as it might first seem to be. You are most definitely part of the process.
If you don’t click the correct response to be sent things can get really fouled up quick. After a message is received by you in any minute (actually reception uses just the first 48 seconds and decoding takes about 2 seconds) you have 10 seconds to click the proper response (“Quick! What are you going do hotshot?”). If you don’t react correctly or in time the wrong message will be sent and you have no way to correct it. Your only options after the wrong message has been initiated are to either let it go or abort the message. Either way you may confuse the other station (and cause him to have a low opinion of you operating skills). Don’t let anyone tell you that using the JT modes is a no brain usage mode. There are definitely skills involved in successful JT mode operations, especially when working DX. Time management is only one of these skills. Oh BTW, mistakes WILL happen regardless of your experience level. Trust me. A wise ole Elmer (mentor) once told me, “If you ain’t making mistakes, you ain’t doing nothing”. A very true statement. Just try to keep the mistakes to a minimum.
The above QSO sequence is the standard QSO exchange. However, as you can see it takes 7 minutes to complete this minimum information exchange. So operators are always looking for ways to shorten the process. Many times there will be no RRR exchange sent, just a 73 DE W2XXX. Technically this is not a complete QSO as there is no confirmation of report reception, but it is a common occurrence. If you wish to shorten things a bit you should use something like this, RR 73 W2XXX. That way you include the confirmation with the salutation and shorten the exchange process.
Since the exchanges are preprogrammed in the software, how do you send a nonstandard message like RR 73 W2XXX? Good question. Incorporated in the software is an option to send what is called a “free message” or “freehand text”. Essentially it is a blank macro that you can write whatever you choose to send instead of a “canned” message. But there is a caveat. You can write anything you want as long as it only uses 13 letters! Folks get quite creative at times trying to convey as much information as possible.
Except for the actual transmitted signal structure, JT9 operates just like JT65 with the same messages and QSO process. JT9 is a much smaller transmitted signal. It uses less than 25 Hz of bandwidth whereas JT65 uses around 175 Hz. Because of the smaller bandwidth and different software processing JT9 is about 2 dB better in digging out weak signals. It is not as popular as JT65 for some reason. But its usage has been on a steady increase lately.
As you can infer, the JT modes are NOT ragchew (conversation) modes. That was another reason I was less than enamored with the modes at first. I am definitely a ragchewer first which is why I love Olivia type modes. But ragchewing aside, the JT modes do get the job done of making long distance contacts under poor conditions and with less than stellar radio station setups. Only Olivia mode does this better (and you can actually talk to someone!). Enjoy the JT modes but still try other digital modes for variety. JT modes are only one of many ways to get the most out of your digital modes experience.
73 and keep on “digitaling”!
(I just made that word up, but it sounds good, doesn’t it?!)
(I just made that word up, but it sounds good, doesn’t it?!)