Saturday, June 10, 2017

Better Know a Mode: JT65 and JT9 Part 1/x

JT65 and JT9 are new modes made possible by computers. Back in the halcyon days of the late 90s, the preferred weak signal communication mode was CW. Now, the new JT modes are a popular way to get your Worked All States or at least build a healthy QSL card collection. What's better is that the mode works so well, it's possible to use compromise, HOA-friendly antennas and work the world. Next, if you're an introvert then you'll love this mode. There's nothing to talk about other than the bare basics.

WSJT-X waterfall and JTAlertX showing activity on 40 meters at 0102Z on May 6, 2017

There are compromises for any weak-signal mode, and the JT modes are no exception. They are slow. Transmission cycles run in 1 minute intervals. The messages you can send are limited as well. You're not going to be racking up major contest points using this mode, however for casual operation it is fantastic.

The JT modes were created by Joseph Hootoon Taylor, Jr., Ph.D. Joe is an astrophysicist by trade, and has used binary pulsars to make high-precision tests of general relativity, and has bagged a Nobel for his efforts. He's also an avid amateur radio operator, and created the JT modes as a means of facilitating Earth-Moon-Earth contacts. [1] With JT9 and JT65, you can now work these modes with a modest antenna [2] and patience.

It turns out that weak-signal work is good for traditional HF frequencies too. We'll talk about some of the intricacies o, followed by some details of how to use this fun mode.

The algorithm uses a small shifting tone, that is then used with a Hamming-tree to decode messages. There are many different versions of software out there, and I use WSJT-X. Looking at the source code, there's a lot of Fortran, it's written in C++ with the QT GUI subsystem. It's not easy to read code, either. There are various other versions of implementations of the modes, but these are almost all minor GUI tweaks.

Good Mode For:
  • Ham's who have young children, that cannot go for more than 30 seconds without some sort of interaction. The 1-minute intervals are enough time to change a diaper, make a sandwich, refill a juice box, extract a marble from a nose, etc.
  • Compromise antenna situations, such as a station in an HOA. I use a 350' Horizontal loop fed with an LDG-600 remote tuner, which I'll talk about in a later post.
  • Those who have a hard time figuring out what to talk to other ham's about.
  • Working the world on 5 watts and a mattress bed-spring
Not a Good Mode For:
  • Rag chewing
  • Making more than one contact in 4 minutes
  • Any message requiring more than 13 characters.
Future posts will include details on how QSOs work, what all the fiddly-bits of the GUI mean, and a general description of the software setup that works for me. I'll also delve into intricacies of getting the software working with the FlexRadio and Kenwood TS-590SG rigs.

[1] If you're not familiar with EME work, it involves sending a large and indecent amount of power at the moon, then listening for other nerds who are trying to do the same thing. In my day, EME was the coup-de-grat of the hobby. It often required massive antennas that made me wonder how many drug dealers were in our fine hobby.
[2] The joke is, "How do you know when your EME antenna isn't big enough? When it didn't blow down in the last wind storm."

Saturday, June 3, 2017

Flex Radio Systems: A Love Letter

FlexRadio Systems is the new belle of the ball in amateur radio. These simple black boxes, festively adorned with a power button, an LED, a headphone jack, and a CW keyer port, are nothing to display prominently. They are controlled almost exclusively with software that you need to run on a Windows PC (more about that later).
Figure 1: The stunning good looks of the Flex 6300

I'm here to tell you they are magical. If you want to know why, I present the following evidence for your consideration:

Figure 2: The entire 40 meter amateur radio band, complete with actual jibber-jabber!

This is a view of the entire 40 meter band. The whole thing. At about 7pm (-7 GMT) you can see that the band is open. On the left you can see a pile-o-CW operators. On the right you see the sideband portion of the band, where I happen to be currently tuned. If I were pre-disposed to contesting [1] this would be a godsend. My radio, the FlexRadio 6300 can handle two of these such views (slices) to monitor and work separate bands at the same time. It even has a transverter output on it, just in case you lose your mind and want to get on VHF/UHF/Microwave for some reason.

Flex has some sticky parts, but being able to pull signals out of the weeds is very helpful when your aspirations of stacked monobanders at 100 feet conflicts with a home owners association's sense of aesthetics [2].

Here are some issues I worked through:

  1. The software only works on Windows PCs, and it's a good idea to make sure you're running a beefy system. I run mine off of a Intel NUC 6i7KYK with a Razer Core external graphics card and a Radeon RX 580 and 32GB of ram. The on-board Intel video card could not keep up with what I wanted to do with it.
  2. The other platforms available are iPads and iPhones. This is awesome for operating from the hot tub, bedroom, or other places where you don't want to sit next to the radio. 
  3. Make sure that your bios, and OS patches are up to date. A lot of problems were resolved for me by updating to the latest software.
  4. The Flex series requires an actual hard-wired network connection. You'll have fewer problems if you don't try to use the software over 100M, 1Gig networks just work better.
  5. Throw away the stock microphone. I wish Flex would just leave this out and knock the 75 cents off of the device. You can get a USB microphone for your PC that is reported to work very well. I use a Heil PR-781 (Yaesu adaptor cable) and I'm happy to report that I still can't make an SSB contact to save my life.

Overall I'm extremely happy with the setup. I don't get much use out of standard radio interfaces, so the PC software makes for very comfortable operating. It helps that my first contact was all the way to Japan on my 350' Horizontal Loop antenna on 40 meters.

I have several half-written Linux implementations of the SmartSDR interface, but it's a complicated enough task that I haven't had a chance to flesh it out completely.

[1] I'm not into contesting. I am happy to say that I made my first official entry into the RTTY-roundup sometime earlier this year. I made one contact. Mostly I was just testing the Ham Radio Deluxe program's multiple call-book feature.
[2] My HOA does not like antennas that are required by the FCC's concessions to the TV/Radio broadcasting industry.

Better Know a Mode: JT65 and JT9 Part 1/x

JT65 and JT9 are new modes made possible by computers. Back in the halcyon days of the late 90s, the preferred weak signal communication mo...