pa0r

Since yesterday I can read my PSK mail using Evolution, or with the standard UNIX 'Mail' client (and of course with all mail readers that use the mbox file standard. Here is a pic...

There is a heated debate going on over which is the best digital mode. This debate gets fuzzier and louder every time a new mode is introduced. Those new modes always have more carriers, larger bandwidth and doubtful increases in performance.

This increase in performance is argued to be the very thin line between copy and no copy. The differences are measured in dB with reference to the noise floor, and for some the throughput speed of the system is the main cryterion. Meanwhile, the appliance operators (is your MixW version up to date?) cannot wait to apply the new mode and whine about not being able to tell them apart in their waterfall anymore. Yes, we are now turning the waterfall into some sort of TV where the 90% clueless can actually read with their own eyes that this is a PSK31 signal! I am amost certain I will witness the day when voice output will be added ("You are looking at a PSK31 signal, courtesy of the Microsoft Company"). (Sorry for that one, but I had to...)

Now you could argue about what is copy, and what not. And when have you last heard the noise floor in the digital portion of the band? In person-to-person communication we are used to signals with holes in them because of QSB or QRM. That's why we have learnt to repeat the most important information ("My name is Xilantriugharius, I spell X, i, l, ...). This has been practise since the advent of ham radio, and at least my generation thinks this is perfectly normal.

As soon as the machines (RTTY, TOR) took over the generation of the signal stream, and the operator did not get tired anymore when a long message had to be sent, as his brain did not have to do the de'coding', some clever people though that it might be advantageous to send everything twice, as a preventive measure. This marked the birth of FEC. FEC was used in one-tx-to-many-rx messages, the so-called bulletins. In station-to-station communication, however, not FEC was used but ARQ.

The difference between ARQ and FEC is simple. FEC allows to reduce the number of errors generated at the receiving end, and ARQ allows to kill them completely. For bulletins ARQ is not possible because you need 2 concrete entities for it, and bulletins have many receivers which would create chaos. The interesting thing about it is that when ARQ is used in a clever way it  has a lot less overhead than FEC, and wastes less power per symbol. Which is a nice contribution to ecology.

In other words, FEC is just a stop-gap which should be used in situations where ARQ is not possible.

Now, why is it that all these new fancy, qrm generating bandwidth eating modes are conceived? I think it is an outcome of the primitive way the male brain works. If more developers were women, you would have more emphasis on intelligent solutions than on 'wider, bigger, stronger', in other words the brute force method. I know that a lot of people are very much in favour of the bulldozer approach, but could we plase do it outside of ham radio?

OFDM modes work after the principle of: 'when you qrm one of my frequencies, I will transmit simultaneously on two frequencies'.  And 'when you qrm 8 of my frequencies' I will transmit on 8 more frequencies. 'And moreover, I will make sure I  transmit everything twice, 4 times or whatever I need to get the message through'. All this sounds very much like war to me. And frankly, some days I have the feeling I am already in the middle of one.

Now, as the free lunch (TM) is still 'pie in the sky', all these simultaneous carriers and send-twice-with-a-time-gap need lots of power (the larger the bandwidth and the length of the message, the more power), and all the unnecessary redundancy produces a lot of qrm on our crowded bands.

ARQ, however works more like the radio operator every large ship or airplane used to have - when they could still afford them. If some part of the message does not come through, it can ask for repeat of just that part... If my single carrier is knocked out for 10 seconds because of qsb, it will repeat just the part which was missing. And if my single carrier is suddenly disappearing because a bloating OFDM signal comes on top of me the ARQ system can wait until the brag tape is sent, and pick it up from there...

And now an easy puzzle: If it takes 20 Watts to produce an S9 signal with 1 carrier, how much power do you need for 16 carriers? Or 64?

Now let's see... if I am 5 carriers above the noise floor...

One of the things you can do with pskmail is search Google. Just open the webpage interface and enter:

http://www.google.com/search?q=searchphrase

where 'searchphrase'is anything you had always wanted to know', but never dared to ask....

Tnx Per, SM0RWO for this info!!

I am sure this will get us into the "Guinness Book Of Records" for supplying the slowest Google interface without using an internet connection.

Congratulations to Per, SM0RWO who decoded the callsign of the pregnant sea cow which has been haunting the 30 meters frequency where we carry out our pskmail and aprs experiments. It turned out to be one of the gateways on the APRS net on 30 meters...

Per, the beer (a famous Belgian Brand) is yours!!

Now, the transport problem...

I have just discovered the time leak effect. After the gas leak, the fresh water leak, the oil pipeline leak and the famous memory leak (what?? you still program in C++?) the time leak is one of the the biggest nuisances you can come across.  We have to fight it on a daily basis  here (we are still in Spain, and the sun is rewarding us for it every day now).

When I still had to work for someone else there was no such thing. You had your diary and your local time on the Palm, and except for the days when you were 'completely interrupt driven', you followed the path your secretary had written into your machine, and in the end your boss was happy, you were happy and your xyl was reasonably happy. Especially when you were away for a contest weekend. And you had the feeling time did not exist,it was just a figure (8 divided by 15) on the front page of your Palm (TM).

Now that I do my own planning there seems to be a constant lack of time. The xyl is of the opinion that my planning skills are not on par with what I try to achieve, but it must be something else. When we drove down to the South of Europe I had a todo list for tlf and for PSKmail. I also wanted to write a database program (in PERL of course) for the locations we can park the camper for a free overnight stay, so I can feed them into gpsdrive. It was a waste of time. The planning that is...

Until now I have spent all my time on testing pskmail. Writing additions and changing stuff so it works even better. This camp ground is an excellent test bed for the program. I am 2200 km from the server and the internet facility (4 old desktop computers with W98 of which 3 are constantly out of service because some virus has to be removed) is in use all the time. At least at the occasions when you could fit in into your planning.

The pskmail link to Stockholm works all day. From 8:00 UTC (no use getting out of bed early because the bread shop is not open before that time) until sometimes 22:00 UTC. During mail sessions I use 80 Watts and in between my APRS beacon roars along with 20 Watts input. If the computer is not in use for something else :)

Then we have to go shopping. There are 3 supermarkets in walking distance, so we tend to buy a lot of stuff which I have to carry back to the camper (a bottle of good wine weighs just short of 1 kilogram). Then we have to go walk on the fantastic beach, and watch the sand castle artist rebuild his castle which has been ruined by the dogs during the previous evening. Then we've got to have lunch, mostly sitting outside in the sun. With a glass of good cheap wine. After that we have to do the spanish lessons. We have 3 different courses on CD, DVD and accompanying books.

Then the weather is so fine that it would be a shame to go sit inside to write some software, so we sit outside in the sun and I do some reading in my favourite books (Programming PERL and PERL Cookbook). After that it is time for a drink and some nice food, and we go to the beach again. When we come back it is time to download the second email batch and start preparing dinner.

Somehow I have the feeling something is missing. The 4th dimension strikes back. Time has leaked away without any positive effect on mankind. Or has it?

I noticed this time leak thing has a positive effect on creativity. It tends to make your todo lists longer, thereby creating the need for more time. Which is not a circular reference; I am afraid it is a recursive function without a return condition...

One positive outcome has been a so-called crapmail filter for pskmail, which filters out all references to MIME stuff and advertizing and please unsubscribe this and that and our ADSL service is faster than yours...

This has already saved lots of time downloading the mail...