A screenshot of a JT9 QSO with GWØTKX in Wales, UK. W4GAL was running 5 watts into a vertical in North Florida
|
An unbelievable mode A quick conversation with someone far, far away (something like a contest QSO), and running minimal power, with an antenna in the attic… if that sounds like your type of fun, JT9 is the perfect mode. It’s unbelievable. When you hear the description of how it works with very weak stations, it doesn't sound possible to copy another station that is below the noise level. Ham radio to me with bouncing signals off the ionosphere is next to miraculous anyway, and this is the cat's meow. I have an HOA restricted antenna farm which means two S9 monoband verticals for 40 and 20 that are based on a concept discussed by Robert Glorioso, W1IS in August 2011 QST. They are painted with Ace Hardware camouflage-brown and are nearly invisible from the street. I get out quite well, but I’ve had a lot of experience with CW and PSK. I was introduced to JT9 a few months ago by Keith Hunt, WC4U. I had heard of JT65 but didn’t know anything about it, and I had never heard of JT9. I did know about Joe Taylor, K1JT because of his Arecibo moon-bounce fame, and other accomplishments. I downloaded the WSJT-X software and Meinberg NTP timing program to sync the computer clock, downloaded a display program called pskreporter, I already had the SignaLink USB and I was in business. First QSO, W1UU, second one was W6NT, and the third (he was calling CQ) was K1JT. Gee. Who hears you when you call CQ? When I started into ham radio as a Novice in January, 1955, I can remember wondering frequently if anyone was hearing me. The answer was usually no because I didn't understand what I was doing, I was using a terrible antenna, and I was producing pages of logged CQs and no answers. Compare that to today with JT9. As an example, I had a JT9 QSO with Brendon Tadgell, VK4HIA in Australia. Brendon was running 1 watt and I was running 5 watts. According to the WSJT-X display on my computer, that was a 9081 mile trip. I then checked the www.pskreporter.info/pskmap.html website to see who else “heard” my signal. Lots of folks. I am having great success running somewhere between one and five watts, and I frequently look to see what stations, in other continents, have reported copying my signal. Fun! Power One to five watt transmitter output works well because each transmission of 13 characters is 50 seconds in length and the computer analyzes the signal according to the complex structure created by Joe, K1JT and friends. Power is not needed and is not appropriate for this mode. Too much power can be detrimental and may even cause other stations to be unable to decode the signal. Weak signal reception was originally developed for UHF and VHF moon-bounce transmissions. Now JT9 is for HF and MF. What a pleasure to work very weak QRP stations thousands of miles away. Amazing. Results Back to the pskreporter.info program. I did a test to make an example: I was using 1 watt power output from my TS-590S into about 70 feet of RG8x to my vertical antenna in North Florida. How much power arrived at the antenna? I don’t know, but it had to be less than 1 watt. I waited about 15 minutes to PrintScreen because it takes a little while for the reporting stations to populate the map created by www.pskreporter.info. Where was my transmission heard? Look at Illustration 1. Holy smoke! … with one watt output. My test was at about 5:30 PM EDT.  Illustration 1: JT9 - 20 meters - 1 watt output - Vertical Antenna in North Florida Equipment You need a transceiver running 20 watts or less power, a computer, a sound-card interface to connect the two, and some free software. You can find what you need to know with instructions on the WSJT-X website: http://physics.princeton.edu/pulsar/K1JT/WSJT-X_Users_Guide.pdf. Read the User’s Guide first; don’t wait until you have problems! And, you can get help at http://groups.yahoo.com/group/wsjtgroup/messages. My goal is to tell you how cool this mode is when you have a little-pistol station. Even if you have a big-gun station, see what you can do with 1 watt. Problems When first starting, it can be a little tricky getting your computer to sync with WWV or another time standard. If you can’t get your computer to within ½ second of correct WWV time, the WSJT-X program may not decode anyone. The User’s Guide can help. A second common problem is over-driving the audio. More is not better. I have found that if I set the audio drive at a point half way to where the ALC starts working, I have a clean signal. To get 1 watt, I can set my rig at the 5 watt minimum point and dial down the SignaLink to 1 watt on the antenna tuner meter. Discouraging? When operating low power, calling stations and getting no responses or being covered up with QRM, it can get discouraging. On JT9 when running 1 watt and you’re not getting answered by the station you are calling, but you can see that you were “heard” on pskreporter by 15 others, it’s not discouraging, it’s exciting! This is a new mode for me and I’m loving every part of it. What do you do when there is no sound to listen to? I play music. Don’t worry about your little-pistol station, be happy, get on JT9 and work the world. Thanks, Joe. |
