Thursday, January 20, 2011

Just the messenger(s)

Last night I was privileged to pick up a real 3rd party message, as opposed to one of the “bulk” messages that we get on the traffic nets.  I received it from someone that I have not worked with much before, who is a very good op, but who made mistakes when trying to key slowly enough for me.  The message also had errors already in it, as well as a couple of unusual names & an usual handling code.  Also, the station of origin was in a different state, the opposite corner of the coterminous U.S. in fact, from the place of origin (where the 3rd party lives, in this case), which raised a red flag with me.  To add to the trouble, RF propagation conditions were okay, quite readable, but not great.  I thought there were hyphens in the preamble, but since a hyphen is not a character I usually encounter, I wasn’t quite sure if they were hyphens or the sender “crossing out” something that was sent wrong.  I did finally get it all, but even then, I admit I sort of had my fingers crossed.  The transfer took between 15 & 20 minutes.  It was a long 20 minutes.
                The message was inconsequential, just family greetings and “HERE IS A RADIO MESSAGE USING MORSE CODE FROM US TO YOU” etc.
                But I was ecstatic to find that the telephone number checked out (on whitepages.com) to the right name & address!  So today I called the party up & delivered the message.  They were happy to get it & might even have known (with the wonders of modern technology) that it was coming.  “So it works, wow!”        
I don’t know if it was a curious anachronism to them, an oddball type of greeting, or a family test to see if contact could be made in an emergency.  No way to know how they managed to know a ham on the complete other corner of the nation to originate the message.  We never get to know that stuff.  We just send it (or deliver it) like we get it.
                One reason I thought it might be a test of some sort was that the handling code was HXDE.  I even had to look up the D, never having encountered it before.  It calls for each station in the relay chain to service the message, leaving a paper trail across the country where it can be seen who got the message when.  Well, in this case the system worked & not especially slowly.  No time of origin was given, but the transit time was probably less than a day.  Then I had to wait for a civilized hour to call.
                I helped the recipients compose a short reply & waited while they dug up the necessary address & telephone number needed for the ham on the other end to make the delivery.
                Sent the reply message out on the RN6 net this evening.  It was also a tough transfer.  The other station had a so-so signal, but I could copy him.  He said, though, that I was fading in & out (QSB – which is cause by, of course, the ionosphere).  With all the requests for repeats, I kept slowing down more & more & turning up my power.  That session took almost 30 minutes, for my two messages (the reply & the service message).
                I take these difficult sessions as training, feeling that I will have an easier time of it next time, having stuck with it.  On last night’s session, though, I was sort of at a wall.  This is where you have to say to yourself, once piece at a time.  You missed the address figures, ask or them again.  I think there was something in the text before “HELLO”, ask for “WB HELLO”.  Etc.  Eventually I have it all pieced together, one piece at a time.  On a slow net, I may actually have the option of walking away from it, but not on the Region net.  It’s good for me not to succumb to frustration, or quit because it’s hard.

Monday, January 17, 2011

E E

Last year, an on-line newsletter K9YA Telegraph (a very worthy publication) printed an article by Bob Dillon WB9LTN (February 2010, “The Shortest NTS Message Ever Sent”), which struck me as very funny, in my warped traffic-handler sort of way.
It all goes back to the “shave and a haircut – two bits” thing where people are compelled to add “dit dit” at the end of everything, whether it sounds like “shave and a haircut” or not.  Whenever someone tries to end a CW ragchew, they send the other guy’s call sign, then theirs & SK, or “out”.  End, I’m done.  E.g. KJ6HWL DE K6HTN SK E E.  The other op either does the same or else thinks of something else to say & the whole closing ritual has to be started all over again.
Apparently, and I will paraphrase – some ops got into a joking mode of interjecting “dit dit” many minutes later into a round-robin ragchew that they had supposedly signed out of already.  It became a competition of sorts for the “last word”, or last “dit dit” in this case, with longer & longer time delays.  Over time, the exchange degraded into single a single “dit”, which in Morse is an E.
Mr. Dillon got tired of this & went silent, but still got – not quite – the last word, by sending his final E in a radiogram, over the NTS traffic nets.  The entire text was just “E”.
As quoted in the article, here it is, the shortest NTS message (mostly “overhead”) ever sent:
NR 201 R WB9LTN 1 HUNTINGTON IN AUG 17 BT WB9KTR BT E BT BOB WB9LTN AR N
                Of course, there was a reply radiogram & I’m sure you can guess what it said.
                Wonderful article.

You can subscribe to K9YA Telegraph for free, at http://www.k9ya.org/.  It’s worth every penny & more.

Pile-up !!!



On Saturday I had another first in my short time in ham radio – a pile-up!
                I belong to a fine organization called the Straight Key Century Club, or SKCC.  One of the many on-air events that they have is a “special event station” called K3Y (key, get it?), which lasts the entire month of January.  Members can sign up for time slots & operate the special event station during that time – by calling CQ CQ DE K3Y/6 – in my case, since I’m in the 6th calling area (Sixland, pretty much equivalent to crazy California).  Every half hour or so, I have to interject a brief announcement about the special event, then DE K6HTN K6HTN NR 5405.  (My SKCC number is 5405.)
                Since there is a rush to make a “sweep” by contacting all twelve of the K3Y stations (calling areas 0 through 9, plus KH6 & KL7, Hawaii & Alaska, which are “DX”), bunches of people start answering your call, all at once.  This is called a pile-up.  Somehow, in all the clatter, I have to extract at least one call sign & acknowledge it.
                Often the one I catch is the last one & I only get the tail end.  So I send back “NEC AGN PSE” (station ending NEC, come again please).  With luck, everyone else stops & NEC sends back “DE KI4NEC TU UR 459 459 KY KY HERB HERB NR 6415 6415 AR BK” (this is KI4NEC, thank you, you are – your signal is – 459 (not very good) – I am in Kentucky, my name is Herb & my SKCC number is 6415).
                 AR and BK are characters for which there is no equivalent in English - AR means “end of message” & BK means “over” – back to you.
                 Because the signals are weak in this case, everything is sent twice because the ionosphere may fade out briefly.  If I miss part of his message completely, I’ll ask him for a repeat.
                Then I answer “KI4NEC (so he knows I have his call right) DE K3Y/6 QSL QSL TU UR 559 559 CA CA KATE KATE NR 5405 5405 AR TU ES 73 73 E E”.  QSL means I’ve copied all his message, 73 E E is a bit of shorthand – 73 means “best wishes” & the E E is something added to make it sound a little musical.  If I were just ragchewing & no one else was waiting, I’d extend it out to GE ES 73 DE K6HTN SK E E, where ES means “and”, GE means “good evening” & SK means “out”. 
                (Whoever says Morse code is an alphabet & not a language is nuts!  And there is a funny story about those E E’s, which I will save for another posting.)
                KI4NEC comes back with “K3Y/6 DE KI4NEC E E”.  With the pile-up waiting, I don’t even have to call CQ again.  I just wait a few seconds & the pile-up starts again.  Pick one & do it all over again, meanwhile taking notes.
                Later on in the evening, when there was no pile-up, I spent more & more time calling CQ & my hand got tired!  For this event, since it’s for the SKCC, I have to use a straight key.  This is the old type of telegraph key that you would see in the Western movies, famous among telegraphers for causing repetitive motion syndrome, known as “glass arm” in those days.  Many improvements have been invented, including a mechanical speed key called a “bug” & a modern electronic “iambic” keyer.  For the traffic nets, I always use a keyer.  A bug is allowed by SKCC rules, but it is very difficult to learn & I’m not there yet.  Bottom line:  I’m not very good with a straight key, maybe because I’m not straight, but most likely because I don’t practice enough.  My wrist extensors are always a bit sore after an SKCC event.
                My last duty, after I shut down the radio, was to enter all my notes into the logging program, create a .adif output file & email it to the /6 coordinator.  Anyone who claims a contact with me for their “sweep” will have their log checked against a compilation of all the K3Y operator logs.  They will get a fine QSL card (above) from the K3Y event & if they send me one of theirs, they’ll get mine, too.
                Most ops would enter the data into the logging program as they went along.  But I still don’t headcopy my code, meaning that I have to write every character down as it comes in.  So I don’t have time to also use the logging program.  It’s one of those cases of “just take good notes.”
                So that’s my pile-up story.
                The ability to work a pile-up is a good thing to have.  You can do much better in contests, where the object is to make as many contacts in a given period of time as possible.  You may also one day want to participate in a DXpedition.  This is a vacation to some remote part of the world where there aren’t many hams, only to spend your entire vacation setting up antennas & operating the radio.  Many hams “collect countries” & depend on DXpeditions to contact the rarest ones.
                Learning to work a pile-up generally sharpens ones ears.  It's all a learning experience.
                

Monday, January 10, 2011

What the heck is going on up there?

Geek alert!!!  If you are aware that there are a few ionized layers in our upper atmosphere, which are created by radiation from the Sun & which affect our ability to communicate over HF (short wave) radio, read on.  If not, most of this entry may be in your “skip zone”; go to the last paragraph.

I’m still obsessing about understanding what I hear on the local & area 80-meter traffic nets, related to readability & propagation.  After asking several experienced hams about it, I decided that I would get nowhere without some data, so I started collecting some.  Along with trying my hardest to copy the net transactions, the traffic list & the traffic, I started also trying to estimate the readability of each station.  This would be the R of RST, basically clarity of copy on a scale of 1 to 5; 0 would be nothing heard at all.  

Our nets are SCN (local stations only) at 6:30 pm, RN6/1 (all of California) at 7:45 pm & RN6/2 at 9:30 pm.  All of these are after sunset; solar radiation is not generating any new ions & those that are there already are steadily recombining.

Here are my data.  



foF2 rules the quality of HF propagation.  It is a frequency, the critical frequency for the ordinary wave in the F layer of the ionosphere.  If you send a radio wave straight upward, if its frequency is higher than the critical frequency, it will go through the ionosphere & off into space.  If its frequency is lower than the critical frequency, it will bounce back at you.  You won’t hear it, because you are still transmitting, but your buddies on the local traffic nets will.  The MUF or maximum usable frequency (where you just get the signal back), is just about equal to the critical frequency.

The foF2 “now-diction” (a mathematical model, found on the internet at http://www.spacew.com/www/fof2.html) is a median value.  In other words, half the time reality will be higher than the model & half the time it will be lower.  If foF2 is listed as 3.5 MHz (80-meter CW band), then other local stations should not be heard in 50% of net sessions (assume vertical incidence – close).  If foF2 is listed as 3.0 MHz (about 15% - the lower decile - below 3.5 MHz), then 90% of them should similarly fail.



NC stations should always be heard.  A glancing hit on the ionosphere is more likely to reflect than flat-on vertical hit – you can’t skip a stone by just dropping it in the water, you have to arrange a glancing impact.  For a distance between stations of 600 km & F2 layer height of 300 km, the incidence angle is 45 deg, the MUF = foF2/cos(45 deg) = foF2/0.707 (assuming the Flat Earth Society rules!).  foF2 = 3.5 MHz leads to MUF = 4.95 MHz.  foF2 = 2.8 MHz leads to MUF = 3.96 MHz.  (Just a little trig here.)
This is the way I understood it, that was causing me such grief.  It’s not what we see.  Nets work much more often than this analysis predicts.

Further digging (in Radio Amateur’s Guide to the Ionosphere by Leo F. McNamara), however, yields that:

MUF for vertical incidence is really the critical frequency of the extraordinary wave(fxF2).  Since the ionosphere is a plasma in a magnetic field, it is birefringent (like calcite crystals are with light).  A radio wave that enters the ionosphere splits into two waves, the ordinary wave & the extraordinary wave, that see different refractive indices.  The critical frequencies, where the wave comes back, are not the same.  We have linearly (horizontally) polarized antennas, so each of these circularly polarized waves should get about half the energy?  I’m not sure ….

fxF2 = foF2 + ½ gyrofrequency.  Gyrofrequency is the frequency that free electrons naturally spiral around the Earth’s magnetic field; it depends on the local magnetic field & appears to be about 1.35 MHz in our area, so fxF2 = MUF for vertical incidence foF2 + 0.7.

So our median (50% fail) point should be when foF2 is listed as 2.8 MHz.  2.8 MHz is about the lowest I’ve seen it listed; most days are better.  But I do see 9 instances of readability = 1 or 2 (more or less “fail”, to copy the traffic, at least), out of 40 check-ins.  This is, as they say in physics, “in the right ball park”.

The extraordinary wave does NOT explain:
·         Why is SCN at 6:30 pm so often worse than RN6/1 at 7:45 pm?  Some of the good sessions have been with the lowest sunspot numbers, even more odd.  Could the D layer still be too active?   6:30 pm is about an hour after sunset.  (I don’t know if the D layer explanation holds much water, though – in the summer, SCN is reliably good & that can be before sunset.)
·         Why RN6/2 (9:30 pm) can be better than RN6/1 (7:45 pm)?  Among the local ops who checked into both the same evening, I have 3 instances when RN6/2 was better than RN6/1,  5 when it was worse & 3 when it was the same.  My copy of Northern Cal stations shows about the same record.

The books & articles that I have looked at speak of “unexplained” day-to-day & hour-to-hour variations in the ionosphere, clouds of ions floating on the wind, so to speak.  They don’t know what causes those, but they might account for some of these variations.

So basically, I feel that I understand the trends, but the variations that are covered up by statistics, who knows?

Maybe it’s true what people in the radio club say: HF propagation is at least 50% governed by magic.