Tag: yagi antenna

26 January 2007

I-TASC expedition 2006/2007

Ambitious Elements
Today is the day Remmy and I got ambitious with the antenna building. We decided we were going to go and build a much stronger yagi antenna after being encouraged by the success of the first design. So we loaded up the yagi design program and designed an antenna with 8 elements which gives us 14 dBi gain. The first antenna we had was 7.9dBi and the one we made a few days ago was 12.2 dBi. So if this works, it’s going to be quite a significant improvement.

We decided to use an all-metal boom which changes the design a little bit. With 8 elements, the lengths we had to cut are as follows:

LENGTH		BOOM POSITION
144mm		120mm	
142mm		179mm
140mm		250mm
138mm		331mm
136mm		423mm
135mm		521mm
133mm		625mm
132mm		733mm

Additionally, we needed what is known as a ‘reflector’ which is 170mm long and placed at 30mm on the boom, and ‘radiating element’ which is 148mm and placed at 96mm on the boom. So Remmy worked on the elements (and reflector and radiator) and I worked on the boom.

All materials are recycled from the HF Radar at the back of the base. The boom was a little more tricky to drill holes in than the PVC and with less room for error but with a little hacking, we got it looking pretty good.

Then we inserted all the elements at and pop-riveted them to the boom.

Last to add was the ‘radiator’ as this needs to be insulated from the rest of the antenna. We searched around and within a few minutes I found a small piece of electrical cable which we stripped and it fitted perfectly over the radiator.

So, now we have a very robust antenna which should deal with the high winds pretty well. If it works (will be tested in the next few days), we will use the PVC antenna inside and the larger one we built today at the unit.

Advice from the bottom of a well, Part II : Coffee, Computers, Correspondence

Coffee
If you are on your way to Antarctica, one thing you will already know is that there aren’t many espresso cafes here. Worse than a continent without espresso is the coffee at the base. By the time you get to the base you are drinking the leftover packets of last year’s filtered coffee… eeek… so you need a solution for your caffeine addiction and here it is

This is a portable one cup espresso maker… you just unscrew the top, clean the filter, pour in the water, add the coffee, and plug it in. It takes about 3 minutes before you have excellent espresso. The important thing about this gadget is that it runs off electricity. You won’t get much of a chance to access the kitchen, so any ‘stove top’ espresso makers are out… a coffee press is also a good strategy but this one is better 😉

Computers
Ok, well the thing is, you need to come with as much software as possible as there is no chance to download software over a 1K connection… If you run Windows or Mac then you just need to try and think what you need in advance and download it before you come… If you are slightly geeky then you are in a better situation. The best idea is to install Debian as it’s super for portability. Once Debian is installed, you need to download all the CD sources from a Debian mirror and copy the contents of these disks to your computer. Then you can apt-get install any software you want straight off your hard disk without needing to download anything…

This is a _major_ advantage, and if you feel like going the Linux way then it would really be worth getting familiar with it before you go installing it and considering this strategy.

Correspondence
If you are coming here, there are a few things you should do before you leave:
* download all your email
* unsubscribe from any email lists you might be on
* set up an auto responder (you will be about 2 weeks on the boat without mail access)
* ask someone to read your email and forward only the necessary correspondence
* setup your auto responder email message to tell all your friends *NO ATTACHMENTS*
* make sure you have a SPAM filter working which is server-side not client-side

Email here is actually functioning quite well (if you use an smtp client… don’t try and use something like Mutt or webmail which requires a direct connection to the net). The above steps are really for managing the travel here so when you arrive you don’t have to download 2000 emails. Once here, you can operate pop-email more or less normally.

If you want to chat with someone in real-time, it’s not impossible over the 1K connection. You need to use ‘internet relay chat’ (IRC). It is a super lightweight system for text chat, and sends minimal data over the network. You can then chat away very easily in real-time, even over this slow connection. Forget Aim, Gaim, MS Chat (or whatever it is), Skype etc…they will not work. If you don’t know what IRC is, then please google it before you come, and train yourself and those you want to chat with before you come here. IRC has been excellent for me, I chat with my girlfriend Lotte a couple of times a week for some hours with occasional timeouts: this has been especially good, considering they only allow 2 calls a week for 10 minutes each (and these are mostly only to South Africa unless you are lucky).

24 January 2007

I-TASC expedition 2006/2007

Yesterday Amanda and Tom went to Gronehogna to test the home-made antenna we made the day before. I was a bit nervous because I wasn’t sure if it would work or not. Making an antenna out of PVC pipe and old HF Radar elements, with extra bits of gaffer tape to hold it together seemed unlikely to really do the business. Also, we didn’t know they were going until about an hour before they left, so we had no time to make any adjustments. The antenna had to go as is (although we made a quick mounting bracket and mounted the antenna to an old broom handle). First then posed for a picture with the antenna and newly acquired broom handle and tried to look tough 😉

They left in the Challengers which takes a few hours, so in the meantime, First and I prepared the other modems and the equipment he would take to Lorenzo Piggen. The idea was to do the tests in the same order as we had done them 4 days earlier, which was this:
1. SANAE – Gronehogna (yagi-to-yagi)
2. Lorenzo Piggen – Gronehogna (omni-to-yagi)
3. SANAE – Lorenzo Piggen – Gronehogna (yagi-to-omni-to-yagi)
4. Lorenzo Piggen – Gronehogna (yagi-to-yagi)

The home made yagi antenna would be at Gronehogna the whole time and would be the only one used at that site. With the earlier test with the manufactured antenna, we got about 15% signal, yagi-to-yagi between Lorenzo Piggen and Gronehogna, and no signal to speak of using the omnidirectional antenna at Lorenzopiggen.

So, off they went. We decided to do the tests at 1500, and change every ten minutes. We had to decide on this beforehand as they had no radio equipment at Gronehogna that would go the distance, so we had to hope that Tom and Amanda would be there in enough time and we would then do the tests ‘deaf’ (so to speak). When 1500 spun around, we tried the connection. I could talk to First Born at Lorenzo Piggen but we could not talk to Gronehogna, so we had to go with our instincts a bit. I was pretty disappointed that we got no signal on all tests. First and I then agreed we would hold on a little longer, as the new antenna (if it worked at all) would be more directional than the ones we used earlier, so it might take them a little longer to ‘find target’. So we waited an extra few minutes, and bingo – we had 50% signal. Amazing! I was very excited. Just to be sure, I shut down the systems at SANAE so we could tell that this was actually signal coming from Gronehogna and not from the equipment I was using at SANAE. I shut down the modem and First reported the signal was still strong. He then opened a browser (we had a computer connected to each modem) and he could see the web pages we had setup on the machine they took to Gronehogna. First said it loaded instantly! Great!

The trick was, however, that this connection was yagi-to-yagi which is not what we would use in the final setup so we had to quickly switch to omni-to-yagi, the omnidirectional antenna being at Lorenzo Piggen. So First had to change the antenna very quickly as we were afraid that if we disconnected from the yagi for too long, Tom and Amanda would not see signal and would assume we had stopped the tests. To do this he would have to hold the omnidirectional antenna as he would not have time to mount it on the pole. So it was a bit hacky, but it wasn’t worth the risk of Tom and Amanda thinking we had stopped the tests and packing up before we could confirm the final set-up could work.

So First switched the antenna in the cold in record breaking time, with just a few tens of seconds downtime (he asked Luta, one of the crew that went with him, to hold the antenna). I turned on the modem here and ….. 30% signal! Great! First loaded their web page again to confirm the connection and it seems that our homebrew antenna was really doing a great job.

It wasn’t till Tom and Amanda returned that we learnt they had real difficulties setting up in the snow there (there was a storm) and that they didn’t have difficulties ‘finding target’. They couldn’t get the system working for some time, which was why we got no signal through the tests, but as soon as they were set up and turned on the modem they got 50% signal immediately. The fact that they had bad weather there was bad for them but in terms of the signal tests, it was a better situation for the tests than the earlier one as the first test was a perfect day. If we get 50% signal with some snow around, then it’s a very good sign. Tom apparently had also logged onto the IRC (chat) running on my computer at SANAE which is even better! Great.

So we know now the radio systems will work. Additionally, we can build a stronger antenna than this one,  one that is also more robust. It shouldn’t take more than about 4 hours to do. So now we await the discussions between Tom and the SANAE management about whether they can get us to Gronehogna before we leave in 9 days….

22 January 2007

I-TASC expedition 2006/2007

Yesterday we decided we would like to try and improve the reception for a possible installation of the AWS in Gronehogna. We cant improve the transmitters, or the position of the base, so the next thing left to do is to try and improve the antenna. Tom and I mailed a few people to ask them to find a diagram online or some software for an antenna for the frequency we needed (900MHz). Marko responded by mailing an application that helps you design yagi antenna. So, not having done it before, we dived right in. Thankfully at hand was Remmy (my roommate) and he didn’t have much to do today so we went through the process of sourcing the materials we needed. At the bottom of the backyard here is a small radio orchard. It grows big HF antenna for measuring the depth of the earth’s atmosphere.

So naturally, Remmy and I figured this would be a wonderful place to start looking, so Remmy and I went down the back to see what we could find. Rumours have it that antenna elements have been known to ripen and fall off the big radio trees. Strongman Struan told us that he himself had been down to pick up some elements there just recently (Strongman Struan is a story in itself, the story would be longer but a few days ago he tied himself to a huge kite and the wind played unkind games leaving him with a broken leg and dislocated foot. He was lucky he had thought to tie the other end of the rope to the base, else he would have been blown over the cliff). We stopped by the first small grove to enjoy the sun and take some photos.

Then we pushed on to see if we could find anything interesting. It wasn’t long before we found a small antenna sprouting from the ice. That would have been good for what we needed but we decided it was best to let it grow in case the scientists found out that we had taken all the saplings and their measurements next year might not be as tasty.

Luckily it didn’t take long before we found an element or two lying about under the enormous electromagnetic branches, and most of them looked just about right. So we kept searching for what we could find, looking for the telltale long shadows they cast on the snow.

Remmy proved an expert at finding them and he quickly found many more than I did. I think in all he found about a dozen or so and I found one or two. I put this down to the fact that he has spent more time in this orchard than I and knew what to look for.

So we decided quite soon we had found enough and walked back slowly in the sun to home.

Next up was to cut and dice the found elements according to the pattern we had designed with the software. No problems. Remmy started in this while I went to look for something to use to mount the antenna. In the backroom above some stairs, there is a pile of unused junk. In the pile was a nice discarded piece of PVC pipe about the right length and width. I brought it back to Remmy and he was delighted, thinking it a very good find indeed.

Remmy measured and cut the elements we found and I marked the pipe with the right points that we would mount each element. We then went to drill holes in the pipe. Within an hour or so we had all the elements completed and the holes drilled.

Next up, we needed to start inserting the elements into the pipe at the right spots.

It meant we needed to file out the holes a little and by the time we had finished it was looking like a yagi antenna (but possibly not like the ones you buy in the shops).

We had to make the connection between the antenna and the cable which requires a ‘balun’ (short for ‘BALance UNbalance’).

So we taped the new antenna onto a bit of plastic pipe and Tom volunteered to run down to the airstrip on a Skidoo with one of the transmitters so we could test the antenna. Zama (cabin mate 2) was also on hand to give us his guru tech advice on the balun.

Within a few minutes, we could test it and it seemed to work! At first glance, it does appear to be quite a bit stronger than our original antenna but we will need to do some more comprehensive tests yet. Anyway, it was in interesting thing to do and means at the very least that we have now tried every possible thing to get the radio communications going the way we want them. Many thanks to Borja, Luta, Marko and Zama for their invaluable advice regarding building a yagi.

Any other news? I don’t think so… ah yes, there is a hippy living in a tent at the garden, but that’s not surprising I suppose since hippies like gardens.

Any other news? Not really…hmmm…I think the radio station round these parts sounds pretty good, you should tune in – 90FM i think…..no more news I think… oh yes, I have a beard (don’t worry Lotte, it will be gone before I get to NZ 😉

(Happy birthday Wayne!!!!)