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.

Way to Encourage New Ops, Dude

I'm on 80m right now listening to a Cuban station (CO8LY) on CW. The guy is doing well, about 15 wpm with a 9 wpm Farnsworth rate; just my speed. He's got a good fist and is managing the pileup well.

Three times in the past half hour I've heard guys come back to him at well over 25 wpm. He's patiently trying to confirm their calls, sending bits with a question mark at the end. It's clear that his max rx speed is around 9 wpm. And yet; these clowns won't slow down for the guy! It's like they're insisting that he match their speed. Unbelievable.

Why do CW ops do this? Slow down. It's not a race, not a competition. He who dies with the fastest key doesn't win. Give the kid a chance to learn and maybe in a few years you can work him at 30 wpm if that's what gets you off.

Power Struggle

Recently I blogged about amateur radio's culture of exclusion; a post which generated a large amount of interest, new readers, and surprisingly little if any hate mail. Based on the blog post I doubt I'll be invited to join CWops or FOC, but the SOC has welcomed me with open arms and they're a fun bunch of folks.

One of the areas I touched on was how some modes such as RTTY tend to stay away from subbands used by older modes such as CW during contests. WW2PT pointed out a post by W2LJ which indicates that RTTY contester's self-enforced deference to CW may be ending.

It's clear that there is a schism within amateur radio's digital mode world between RTTY and basically everything else. Amateur radio's so-called digimodes (PSK31, Olivia MFSK, etc) are almost always run at 50 watts or less. Some modes such as JT65 and WSPR (developed by K1JT ) are run around 20 watts. And CW (which is technically a digimode) has a large following of QRP operators who run CW using 5 watts or less.

Reason for these low power levels is that modulating/demodulating a radio signal using a digital signal processor allows the use of error-correcting techniques which results in what's termed "Coding Gain". Coding gain usually adds (depending on the code used) about 2 - 6 dB to the system gain. This means that a signal which is transmitted 50 watts into a vertical antenna (unity gain) is seen effectively as 75 - 200 watts by the receiver. Coding gains higher than 6 dB are possible. So digimode practitioners don't run "big power" because in digimodes you don't need much power to work the world.

Stack this up against RTTY where "big gun" stations running kilowatt amps into high-gain antennas are not unusual. While it's true that RTTY doesn't offer any coding gain I think that a kilowatt of power is a bit overkill. If all RTTY operators remained within the usual subbands there wouldn't be many issues. But the problem comes up during contests where the contesters spread out across the band and the other digimodes simply get wiped out; this includes QRP CW ops.

Lately there has been a resurgence of interest in WSJT modes; probably due in part to the excellent work done by W6CQZ in providing a reverse-beacon system, chat/sked system, and building upon K1JT's original software to create a new and improved application. Yet with this new interest there have been a disturbing trend of late where people have been applying an RTTY approach to WSJT modes and wiping everyone out in the process. For example; there's one guy who's just across the valley from me that's creating all sorts of havoc by (1) running big power (his QRZ vanity photo clearly shows his amps), and (2) driving his system into ALC which heavily distorts his signal. And it's not just one guy; the other night I was getting overloaded by a guy in Colorado. How much power must he have been running to overload the front-end of my receiver from 1,000 miles away?

So why is this happening? Because many operators have forgotten a cardinal rule of amateur radio; use only as much power as you need to complete the contact. I've completed three JT65a QSOs to South Africa using 50 watts of power with no sunspots on a vertical antenna that most people consider mediocre at best. Big power in digimodes is simply not necessary. Running JT65a with a linear and a gain antenna is like shooting a mosquito with a bazooka.