Sunday, September 9, 2007

New Antenna!!


My wife spent the day visiting a friend, and took the girls with her, which left me about 12 blissful hours on a weekend to do whatever I wanted to do. I'd be intending to install a new HF antenna for some time, so this was the best and obvious time to do this.

I put out a call asking my amateur radio friends to come by and help. Bojan agreed, which was great. He's a bright guy, very creative when it comes to technology. If you're ever looking for someone who can turn ideas into reality, give him a call.

The antenna I chose was a Comet CHA250B. This particular antenna is unique in that despite being vertically-polarized it has no ground radials, and it will also tune all bands from 80m to 6m. The coax feeds into a large black cylinder which acts as a matching network. This particular antenna has been alternately praised and vilified on review sites like eHam. People are either giving it a 0/5 or a 5/5. There doesn't seem to be a lot of rhyme or reason to this; although it's interesting to note that people giving it a 0/5 tend to compare it to a dipole which might be unfair.

For me, I was willing to try it out. Considering that my comparison point was my aforementioned $2 "Speaker-wire Special" I suppose anything would seem better. The real challenge in the antenna install was not so much the outside work, it was deciding how to get the coax up to the roof from my shack. Doing so entailed slithering around in my attic, which is a complete mess after a roof replacement earlier this year. There were also a few setbacks, such as a broken lag bolt and a too-small bracket on another antenna (my HDTV antenna) which is now needs to be adapted to the new larger mast.

In the end we got the Comet installed, and two extra runs of coax. I fudged up a temporary VHF/UHF antenna (until I can get a replacement lag bolt and the new mast installed) by slapping a magnetic mount down onto a metal attic vent. I may also sell the VHF/UHF antenna I had on Craigslist and get something else because it's a 6m/2m/75cm tribander and the Comet now covers 6m.

As expected the Comet performs better than the homebrew. I'm getting signals where there were no signals before, I don't have RF-in-the-shack problems like I did before, and the antenna is clearly quieter (lower noise floor) than the homebrew. It tunes a lot of bands, so all in all I'm happy with it. I'm not quiet sure why some people have panned it so hard on eHam. I suspect that it may have to do with unfair comparisons to dipoles, but also it might be the install makes a difference. The Comet's instructions call for it to be installed 32 feet off the ground. Perhaps if it's not installed at that height the matching network doesn't work?

Wednesday, September 5, 2007

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.

Tuesday, August 14, 2007

Echolink Follies


One of the developments we're seeing in amateur radio over recent years is the proliferation of VOIP and digital voice technologies. Examples of this are things like D-Star, IRLP, and EchoLink. The latter is sometimes a contentious technology, in that some amateurs don't consider it "real" radio because the audio/control interface is PC-based. Once while on a visit to San Diego I was having a pleasant conversation with a local repeater operator which turned very sour at the mere mention of the word "EchoLink" as he went into a tirade about the evils of the system. Normally hams reserve this sort of loathing for CB radio and BPL companies, so I was a bit surprised.

Since then I've encountered a few more instances of "EchoLink Enmity". My personal opinion is that there's little difference between controlling a radio/repeater with EchoLink versus using Ham Radio Deluxe plus Skype to control a rig remotely. The question of whether EchoLink users are higher or lower on the amateur food-chain is best left to the philosophers. I will concede however that there's an annoying element to EchoLink, but it's the fault of the developers and not so much the users themselves.

Allow me to explain: Most if not all EchoLink users are unaware that when they connect to a repeater or simplex link the server software by default transmits an announcement over the air which says "Connecting to EchoLink [callsign] -- Connected". Since a lot of EchoLink users are looking for QSOs (amateur-speak for conversations) they tend to hop from repeater to repeater looking for traffic. If a repeater's quiet, they tend to silently disconnect and go looking elsewhere. And again the server software by default transmits an announcement which says "[callsign] -- Disconnected". To the locals on the repeater, this can seem a bit rude. If the EchoLink user was looking for a QSO, then why didn't he transmit and ask if anyone was interested/available to chat? So throughout the day you hear a lot of Connect-Disconnect, Connect-Disconnect...over and over again. After a while, you might start to think that maybe EchoLink users really are bozos.

However I think the users are largely not to blame for this. The connection announcements are not played back to the EchoLink client's inbound audio, so users don't know about them unless they're listening to the repeater in question. Most EchoLink users connect to remote repeaters or links in other parts of the country or even around the world, so they often don't ever hear what goes out over the radio. I once sent a detailed email to the EchoLink developer team explaining all this. I was told that a repeater/link admin can turn off the announcements, but they're on by default. Most admins clearly don't bother to turn announcements off, and the users are unaware of them. I suggested to the EchoLink developers that they might want to add a note to the EchoLink FAQ/guide explaining all this, but they didn't. And so EchoLink users will continue to unwittingly annoy repeater users, and apparently the developers think this is OK. I don't understand this, but whatever. Therefore, here are my How Not To Be An EchoLink Bozo tips:

  • Be aware that every time you connect/disconnect, your callsign is transmitted over the air.
  • Knowing the preceding it should be no surprise why when I further suggest: Don't repeatedly connect/disconnect to the same repeater. It is amazingly annoying to the locals when you do.
  • Try saying hello if it's quiet. You may be surprised at how many locals are listening and willing to come back and chat with you.
  • Be careful about "calling CQ" on a repeater. CQ is traditionally used for simplex contacts, and a repeater is not a simplex system. Some people won't care, but others will think that you're a bozo. If the EchoLink node ends in "-R" it's a repeater and I advise against calling CQ. If the node ends in "-L" (a link node) then CQ is probably OK.
  • Don't ask for a QSL card because you made a contact over EchoLink. People will think you're a bozo. For that matter; I will think you're a bozo. QSL cards are for commemorating simplex contacts. Would you send a QSL card to someone you chatted with over Skype?