JT65-HF : A New Hope

Back in late 2007 I wrote about what I thought was the impending demise of the JT65A mode on HF. I'm happy to report that I was wrong thanks in large part to W4CQZ (formerly W6CQZ) who developed several key components for this mode; a reverse-beacon system, a web-based chat/sked page which displays reverse-beacon data in near real-time, and an application (appropriately named JT65-HF) which improves upon the original WSJT application written by K1JT.

Each component is interesting by itself, but combined together they have generated a lot of interest and attracted a whole new breed of very active JT65-HF users; with more coming on the air every day. In 2007 interest in the mode was primarily from the US and Japan. Contrast that with this morning when my reverse-beacon logged nine European stations; including two new ones which I happily logged. Looking at global activity via the PSKReporter map it's clear that Europe is actually more active on JT65-HF than any other regions. South Africa, a rarity in 2007, has become an almost daily presence in the reverse-beacon display. I spoke yesterday with a ham friend in Egypt and hope to see North Africa in my log very soon.

None of this comes without a price, of course. There are some vociferous contingents in the HF digital world who have appointed themselves arbiters of the band-plan and created a lot of conflicts by publishing "official" bandplans which direct multiple (and often incompatible) modes to the same sub-band as part of a strategy to protect "their" channels. The group in question is skilled in search-engine optimization which means that when looking for information about digital modes you're likely to find their info first and take it for granted that this is "the law". Unfortunately this has led to a lot of people directing criticism at the JT65-HF users and (bizarrely) at people like W4CQZ for "promoting inappropriate use". Factoid for any EmComm dorks HFLINK/ALE folks reading this; W4CQZ's application, reverse-beacon system, etc are frequency agnostic. They don't "promote" anything. Choice of frequency is up to the user.

JT65A-HF, we hardly knew ye...

A while back I wrote about JT65A, the amateur radio weak signal digital mode being used on HF bands. My best contact was just before Field Day 2007 when I logged ZS6WN in South Africa; over 10,500 miles using 50 watts and an antenna made of speaker wire at the bottom of the sunspot cycle. It was a very interesting and powerful mode. And yet I haven't heard anyone on the bands in over a month. Which leaves me to ponder; why?

WSJT (the software for JT65A) was originally written for weak signal paths such as Earth-Moon-Earth. As with most weak signal modes, a trade-off is made where the amount of information transmitted is intentionally limited in order to pull weak signals up out of the noise floor. In JT65A, the total transmission cycle was one minute (actually, about 48 seconds plus 12 seconds for the recipient to react and respond) and in this minute only 13 ASCII characters could be sent. Not exactly a rag-chewing mode. So once I'd worked a station and logged them, I was basically done. I'd see someone calling CQ, note that I'd already logged them, and so wouldn't respond. And once I'd worked ZS6WN in South Africa, working non-DX contacts was (to be blunt) boring.

So my theory on the premature demise of JT65A on HF is this; everyone worked everyone and once they were done there was no point in continuing. Radio amateurs like to rag-chew, talk about stuff, brag about their rigs and such. Hard to do at 13 characters per minute. And without a conversation, it's hard to make friends. Sure, you could always get to know folks by hanging out in the Ping Jockey web chat, and there's certainly a core group of people who do just that, but if you're going to chat in a chat room then why bother with a radio? So I think JT65A on HF has turned into the one-hit-wonder of amateur radio.

Amateur Radio: 5,200 miles on 50 watts and a $2 antenna

Lately I have been getting prepared for the annual ARRL Field Day, which is an annual operating exercise and public showcase event for the amateur radio world. Amateurs all over North America will set up in campgrounds, parking lots, and fields and attempt to make as many contacts as possible using various "modes"; everything from Morse Code and "phone" (what normal people would call voice, talking into a microphone) to exotic digital setups which use computers connected to radios. My club (the Northern California Cactus Radio Association) will operate as K6SRA from a campground in Henry Coe State Park, near Morgan Hill CA.

I'll be running the digital station this year, and plan to use (in addition to the usual PSK31 and RTTY setup) a very new mode called JT65A-HF. JT65A isn't new to amateur radio as it's been used for a while for "moon bounce"; and yes, I mean literally for bouncing signals off the moon. Earlier in 2006, a few people decided to transmit JT65A signals over the HF bands; primarily 20 meters (14.076 MHz) and 40 meters (7.076 MHz). In only a few months this new mode has exploded in popularity, primarily due to the very high sensitivity afforded by a Reed-Solomon forward error-correction algorithm implemented this mode. It's mathematically provable that JT65A signals can be detected with 100% certainty even if the received signal is -22 dB under the noise floor.

In preparing for working JT65A-HF on Field Day I've been learning to use an application called WSJT which is used mostly by the moon bounce and meteor-scatter folks but now also HF enthusiasts. I've made some amazing contacts this way; just tonight I logged a contact with a guy in Australia using only 50 watts of power and a homemade antenna I built with $2 worth of parts I had lying around my garage. This is the equivalent of someone being able to see a 50 watt light bulb from space at a distance four times that of the International Space Station, or of someone talking from San Jose CA to San Diego CA on a CB radio. I expect we'll be seeing a lot more of JT65A in the HF bands, especially as radio amateurs suffer through the poor radio propogation conditions created by the current solar minima.

Update (15 June 2007) : I just beat my Australia record with a solid contact to ZS6WN in South Africa. 10,526 miles, same power, same antenna!

Update (24 Sept 2007) : WA3LTB has created a video demo of WSJT and posted it to YouTube.