RF and Computer Matters

By Andy Cook G4PIQ (Written 2004)

Even with the best location in the world, in the rarest country, with a huge antenna farm, and a team of crack operators, no group will make a winning contest score without putting a lot of thought into what happens inside the shack. A full bore effort in the multi-multi section of CQWW requires you to have as a minimum six high-power stations capable of simultaneous operation, and preferably several more which are equipped to go in search of multipliers in tandem with the run positions. The stations need to be able to operate independently of one another, with as little mutual interference as possible, and need to operate reliably for the whole 48 hour period. And to complement the stations, a reliable computer network for logging all the QSOs and exchanging information between the operating is an essential feature of efficient modern contesting.

Building this sort of station in a permanent installation at home is an interesting challenge, but it’s much more exciting to be doing it from scratch every year, with a new set of problems, 4000 miles from home and with only whatever kit that you’ve got there! Some people may think that staying indoors to move a few boxes about, and plug a few wires together is the easy option, but it usually gets every bit as stressful as running around on the roof in the baking sun with lumps of aluminium!


The first ‘indoor’ decision that needs to be made when we get to site is exactly how to arrange the stations in the room or rooms available for the operating position. The best shack that we’ve ever had was at XT2DX where the hotel had a conference room on the top floor, large enough to arrange all 7 stations in an oval so that everyone could see what everyone else was doing and where they were operating. With good eyesight this can be an even more effective way of obtaining the operating frequency of one of the other stations to whom you want to pass a needed multiplier than any solution that only relies on the computer network. However – it’s more typical to have to split the operating positions into at least 2 rooms, usually for LF & HF.

Getting the Lights on

Once the team has agreed on the best way to arrange the operating positions and the hotel has been persuaded to remove beds, and rustle up (sometimes seemingly from the four corners of the earth) enough sturdy tables and chairs, we can go about getting power to the stations. To run six one-kilowatt stations simultaneously needs around 50-60A of 230V power to keep them fed. In the developed world, this is usually pretty straightforward, but you can never be so sure in Africa! Some of the larger more modern hotels in West Africa – especially in the francophone countries – seem to have had their electricity distribution systems built along European lines with modern good quality circuit breakers and sensible thick wiring. Getting enough power in this situation may be as straightforward as just plugging into the wall outlets, or perhaps breaking into the feed to a couple of water heaters. On the other hand there are some hideous arrangements in other places where the entire wiring system seems to be made of bell wire and something more enterprising needs to be done to get the required juice to the station. In these cases, it’s usually a matter of finding the right maintenance person who’s willing to hook your long length of high current cable into their main distribution outlet – hopefully via some fuses or breakers! I have been offered the opportunity to just hook our cable direct into the 3 phase 100A main breaker in the past – I was far too chicken to do that without any additional breakers – I could just see our big fat mains cable going up in flames like distributed flame thrower!

Keeping The Lights On

In the developed world, we take the availability of a good reliable mains supply for granted, but it’s not like that in Africa! Power cuts here are commonplace and unpredictable. For just that reason, finding a hotel with a generator has always been something that we’ve tried to do, but things are sometimes not all that they seem…. When we visited Elmina in Ghana for the first time in 1999 as 9G5AA the hotel had promised us that they had a generator. This was good news – especially since when we got there we found this relatively rural hotel had a really iffy power supply where lights turned to shades of orange on regular occasions – this did not bode well for running 6 full stations! As we wandered around the hotel grounds, we found the shed where the generator was located – complete with its removed covers and some discarded tools. A conversation with the maintenance staff said that it would all be fixed soon – you understand after a while that’s a West Africa euphemism for ‘maybe’! It got to Friday and the generator was still firmly in little pieces and we were getting anxious.

Six hours before the start of the contest we heard the sounds of a truck arriving – and what should be on the back of that truck but a very big orange generator! We duly hooked this up and all was well. Once the contest started, things went fine for a few hours, but then the generator started to cough and splutter every so often, and when it spluttered the amplifiers would drop out. As this spluttering got more frequent we decided that, bad as the mains was, it was better than this generator, so we stopped running for a while, whipped the cable out of the generator and back into the hotel mains supply.

This was just fine till mid Saturday morning, when all the lights went out, so it was a rapid scurry back to the generator. The lights stayed off for most of the day, and we just carried on through the busy QSO-runs of a Saturday afternoon putting up with the generator tripping the amplifiers every so often. After the lights came back on and the mains supply was clearly restored, we carried on with the generator for a while – thinking that the occasional outage was hurting our score less than a 10 minute outage to swap supplies over – thank goodness for batteries in the laptops! However, our patience eventually got tried enough to go and swap the cables back yet again to the hotel supply and as soon as we did this, we suddenly found that the supply was far better than we had seen since we had been there. At that point it was clear that the power outage that day had been the local power company coming along and improving the power supply for the hotel. Now, that did seem like a result – how long do you have to negotiate and cajole to get the electricity company in the developed world to come out and upgrade your supply?


So – once the power and tables are all in place, it’s time to start building the stations. All the kit which is stored in Africa is carefully packed away at the end of the contest each year into boxes and bags, but some of these containers take better to storage than others – and some seem to grow a little every year. Before opening the cardboard boxes I usually make a little bet with myself on just how many cockroaches will scuttle out, and how large the biggest one will be! I swear that I’ve seen them as big as 4 inches leg to leg – but not for long – they run away so fast!

The only thing hardier than the cockroaches however have been our amplifiers. We use the solid old Alpha 76 & 78 PAs. These astonish me by starting up first time every time after a year sitting in an African warehouse or shed, or having travelled many hundreds of miles in the back of a bus over some of the bumpiest roads that you can imagine. Some of the amplifiers look like they have done the miles with corroded front panels and a few dents, but, although there have been a few faults, they have proved remarkably hardy. I always make sure that I have a few spares to hand however: rectifier diodes, filter capacitors, vacuum relays, bleeder resistors, plate blocking / decoupling caps, spare tubes and of course fuses. Over the years, we’ve had a couple of tubes fail with a classic grid-cathode short – usually on first turn on which implies that they’ve been damaged in transit – these expensive tubes really need to be treated carefully, and I don’t think the problem is unique to the 8874 – I’ve seen the same thing with the much bigger and uglier 3CX1200.

Rude Awakening

One big lesson I have learnt is that – if you hear an odd ticking noise every few minutes – be afraid. I thought it was just the air conditioner, but at XT2DX in 2001, G4BWP got a very rude awakening on a rather quiet Sunday morning on 80m as one of the filter capacitors in an amplifier exploded and smoke streamed from the air exhaust! Some of the bleeder resistors had failed open circuit and over stressed one of the capacitors! A quick substitution of the 160m PA into the 80m position enabled us to run through to dawn, and I then took some time during the late afternoon in my off period to connect the spare AL811-H amplifier into the 160m position. Unfortunately, there had been some problems with the parasitic suppressors overheating in that amplifier and, while I’d replaced them with the bits I had to hand and tamed the amp on the high bands, I found that with an antenna connected on 160 it hooted like a banshee. Whipping the covers off and adding extra turns to the parasitic suppressor got the amp tame on 160. Since it was dark by now and I wanted to nurse the amp for a bit – I really wasn’t sure how the little amp was going to take to the abuse of hard duty cycle contesting – I took over my traditional (and slow but enjoyable) Sunday evening 160m position. The first QSO with this standby bodge was a double mult with 3B8/LA7MFA, followed shortly by JA5BJC for what was apparently a world first JA-XT2 contact on 160! This 5 hour session to the end of the contest with my bodged up amp delivered more than half our total QSOs on 160 for that contest and 40% of the multipliers. A real lesson that you should never quit!

The Stations

I always think that the particular radio that you use in contests is not the really big factor which is going to make the difference between success and failure. That said, some radios are definitely better than others, and often in subtle ways like the way that the AGC time-constants and thresholds are set making big pile-ups turn into mush. For multi-multi contesting there are a few additional requirements to the standard ones of good selectivity, low phase noise & high dynamic range. Issues such as broadband transmitter noise and the ability to operate with very large out-of-band signals also become key. Reliability is also of course really important.

To help with the handling of big out-of-band signals (the other stations), we use bandpass filters between the rigs and the amplifiers. These really help eliminate receiver overload (and importantly, torched front-ends) along with broadband transmitter noise. In addition to these, we then use coaxial stub filters on the outputs of the amplifiers – mostly to help with harmonic rejection. It’s not a perfect solution but provided you don’t operate too close to another station’s harmonic it’s pretty effective and we really suffer very little inter-station interference given that the antennas can usually be only a few tens of feet from one another.

All these bits and pieces which get inserted into the RF lines mean that we end up using a good number of RF adapters. Normally these are well behaved bits of metal, but just sometimes you can get a bad one – probably corroded or wet inside, and – at high power – once they start to fail they can fail catastrophically as the insulator turns to carbon dust! I recall vividly being called over to the 10m station by the operator saying – the grid current has gone high…. It was immediately obvious that there was no antenna connected anymore. I went to grab the antenna connection to see what was wrong and as I leapt in the air I knew I’d found the source of the problem – the back to back SO239 was almost red hot!

Which Radios?

Over the years we’ve used many of the common contest grade radios. We used to be almost exclusively a TS930 shop, with several stored out in Africa. Although a great CW radio, the 930 is really getting a bit long in the tooth now, and has a number of well known faults. One 930 has even left home working but been dead on arrival in Africa twice now! On the other hand, the better ones do just seem to keep going.

Unfortunately in 2001 some of the equipment got a little damp – there was a bit of a clue when the boxes had almost disintegrated, each box had its own cockroach family and the rig cases were rusty! This gave us a certain level of panic as we turned on the kit and found that two of the rigs were completely dead. We always try to have at least one spare of everything with us but with 2 dead radios we were one station down before we even started. Grabbing bits and pieces from both dead radios and building it into one got us to having something closer to one working, but both digital boards were dead. I retired to my room, fired up my PC and went in search of data on TS930 faults on the WWW. After a little while I ran across the W6NL fixes and some other data, and was ready to do battle. After a long late night with matchsticks propping my eyes open, localising the faults on the digital board with just a DVM and then re-making most of the plate-through holes in that area we had a working radio. This was a great relief – and it’s still working two further contests on, although I always worry when I turn that one on!

We’ve also used FT1000MP, IC756, TS850, FT990 in recent years, and all of these work fine in the contest. However – to varying degrees they are all big and heavy and once in a suitcase there’s nothing left of a 20kg baggage allowance to bring clean clothes with you. As the airlines have got much stricter on excess baggage in recent years we become very wary of this – at 1% of the 1st class fare per kg, excess weight gets expensive very quickly! Small lightweight radios like the IC706 and FT100 are not great contest radios but – there seems to be a new saviour on the block – the Elecraft K2/100. This kit-form radio is only a little larger than the size of an IC706 but its performance stacks up well against the top class radios and it plus a switching PSU weigh in at well under 5 kg. We’ve used one or two during 2002 & 03 but several of us have been busy with our soldering irons and we’ll have more in 2004! Standardising on one transceiver-model of course makes sense in a multi-multi environment – operators become skilled at driving it and any maintenance problems are common.


Getting the computers to talk to one another is the next thing to worry about. There are a whole bunch of different options for logging packages open to contesters, but we’ve stuck with the original CT by K1EA. This is certainly one of the better options for multi-multi contesting, with good facilities for passing multipliers and information between the stations and a user interface that we’re all familiar with. This may not be the most progressive approach to logging but it does what it needs to do and runs on a wide variety of computers. We all bring our own laptops with us and these now range from 33 MHz 80486 machines running DOS 6, to 2.5 GHz Pentium 4M machines running Windows XP. The fact that CT will run perfectly well on all of this huge range of machines is really important.

Everyone bringing their own laptop is great but sometimes when a team member has to drop out at the last minute it can leave you scrabbling around a bit. We’ve borrowed computers from the hotel in the past (the reception computer was sitting unused – no-one seemed to know how to use it!), and even gone round all the businesses which we could think may use computers in a small town in Ghana in search of someone who would hire us a PC for the weekend! With a long drawn out African style decision-making process someone eventually agreed and we were sorted! One year we even had to use a 286 PC with a corrupt hard disk for one of the stations – you had to boot from a floppy disk to make that work – thankfully the hard disk was intact enough to install CT on it (although it had to be an old version and there wasn’t enough memory to see all the QSOs on that machine!)

I’ve been especially pleased to see just how well the Windows version of CT – CTWIN works. It seems to perform just like the DOS version – interworking in a loop serial network & even keying perfectly well out of the parallel port – something that other Windows based packages seem to cough on. The ability of CT to cope with this huge variety of machines which have never been integrated together is a real strength.

Finding Keying Interfaces in a Fishing Village

Having CT automatically send its messages rather than manually keying every QSO is a really important factor in keeping operator fatigue under control, and in minimising sending errors – these ultimately damage rate. However, you do need the interfaces between the computers and the radios available to make this happen. For some reason when we unpacked all the kit at 9G5AA in 1999 we were short of a few keying interfaces. The site we used in Ghana was not in the capital Accra but close to the small fishing town of Elmina. This was not a promising location to find the bits and pieces needed to put more keying interfaces together. Nevertheless, Roger G3SXW enlisted the help of a local who I asked just to try and find some resistors between 1K and 10K and NPN transistors. They went off and, sure enough, a couple of hours later returned with a small brown bag containing some TV Line Output Transistors and 2W resistors! Jeff, 9H1EL put these together, wrapped the metal can transistors up in insulating tape, and we stuck and taped wires directly into the parallel port on the PC! This was a keying interface that looked like it could key the 25A supply to the radio rather than just the feeble little key jack!


It’s really important that all the computers are connected together so that everyone can see the complete log, understand which multipliers are needed on the other bands, and pass messages between the operating positions. So far we’ve always networked the machines together using the –loop serial option in CT, where the machines are all daisy-chained together out of a single serial port on each computer. This is usually a nightmare to get working and keep working but from experience it is easier (and a good bit cheaper) than trying to get additional PCMCIA serial port cards to work on this wide variety of laptops. You have to build a loop network a bit at a time and make sure that all those machines are talking both ways before installing another machine. The big killer about a loop network however is that if a machine goes down or if one particular segment of the network is getting RF into it then large portions of the network loose lots of QSOs and the logs on the computers end up out of synchronisation. This means that no one is really quite sure which multipliers are needed on other bands and can really hit the score.

Getting RF out of the network can be a real challenge. I now always take along a selection of ferrite beads, clamps & cores, chokes and capacitors with which I’ll attempt to keep RF out of a network. One of the jobs for the antenna folks who have had enough of the sun is to sit at the stations sending dots at different power levels while I run between the computers sending test messages and seeing whether a ferrite here, a ground here, or a capacitor there has made the immunity better or worse!

Headaches from the Antennas

Inevitably, the sorts of locations that we are using don’t usually allow us to locate the antennas a long way from the stations – they’re usually as little as 20ft over the top of you – and this can lead to lots of RF in the shack. At least we don’t have to operate on SSB though with all the RF feedback problems that can bring!

If you’ve made a really bad choice about antenna location it can be almost impossible to get RF out of the shack. In our first year as XT2DX, the 40m yagi was on a short tower section above the lift shaft of a multi-storey hotel, directly above the operating position. This looked an ideal location for this antenna – the highest spot of the lot, about 90ft over the ground. The antenna seemed to work really well in that folks heard us well enough but the interaction with the building was very clear as the SWR would rise from 1:1 to well over 2:1 as the antenna was rotated. With short tower sections on 40m some degree of interaction is inevitable above a steel re-inforced concrete building but this was wild. Sitting on top of the lift shaft it was also too precarious to try and extend the tower so we had to live with what we had. Unfortunately, the effect was that on many beam headings so much RF coupled into that steel in the building that the shack was absolutely hopping with RF and the network simply fell to pieces whenever 40m was operating. On our return the following year we placed the 40m antenna elsewhere on the roof and all was well!

Next year we’ll have a crack at running an Ethernet network using K1TTT’s NETTSR between all the PCs. This has worked very well at other multi-multis I’ve put together (M6T etc.) and will prevent all PCs getting out of sync when one goes down. However – getting all those PCMCIA Ethernet adapters talking happily with whatever PCs and operating systems we end up with on the day is going to be a bit nerve-wracking! I will have the rats-nest of serial cables (complete with my carefully packed grounding and decoupling arrangement from this year – all held together with Duck tape) as a backup! Moving to Ethernet will have the double advantage of enabling us to have computer control onto those radios which have the facility (everything but the old TS930s – we’re not using PIEXX boards). This will be a great help since as 5U5Z we have the LF and HF shacks in adjacent rooms and being sure that you know the frequency of a radio in the other room is so important for confident multiplier passing.

Packet Spotting

Having a feed of spots from the Packet Cluster is now an essential component of putting a competitive score into the multi-multi sections of CQWW – the days of being able to be competitive by doing all your own spotting are long gone. Expeditions now routinely log almost as many multipliers on the bands as the well established, but less rare, fixed stations.

One piece of technology which is firmly embedded in the less developed world is the Internet. Internet Cafés are everywhere and the internet is a much easier way to get access to the cluster than putting up an RF packet link to a node on the WARC bands. Of course, you really need your own dedicated internet connection rather than an Internet Café but arranging this has usually proved remarkably simple. Most West African countries have two or more ISPs and it’s always just been a case of turn up at the ISP, hand over some money and when you get back to the hotel it’s all working. The connection speed will probably not be what the developed world is accustomed to – but you don’t need all that much for a cluster feed! If you’re out of the capital city the phone lines can be quite poor – we even had to have one brought into the hotel specially at 9G5AA and call charges can be expensive. But the cluster is worth a lot of points.

Unfortunately, in 2003 at 5U5Z our run of good luck ended. We did some research before travelling and found that there was just a single ISP in Niger, run by the telephone company (PTT). This seemed pretty straightforward so after we’d started to get the antennas under control Lee, G0MTN & I went in search of the ISP. Actually, this didn’t turn out to be so simple and we ended up wandering around the PTT headquarters trying to ask, in our best schoolboy French, where we could sign up for an ISP account. After a lot of blank stares we eventually were directed to another building down the road but couldn’t find what we were looking for amongst the street stalls. They were selling some particularly unappetising meat which was just sitting out in the sun, but would be cooked on demand if you fancied some. So we retreated to our hotel defeated. I’d definitely found the limit of my language skills!

The obvious solution was to try and ask at the Internet Café at the Hotel gate where you could get ISP service. Several of us tried to do this but eventually Fred, G4BWP got a sensible answer and we set off again in search of the elusive building. Finally we found where we were looking for and were ushered into an office where it became clear that, in Niger, if you didn’t have your own phone you couldn’t have an internet account. This was a bit of a blow and on returning to the hotel we couldn’t make any headway at having them sign up for us. So, we were stuck. This is a fabulous example of why you mustn’t take anything for granted and should always plan ahead in great detail – things don’t work the same way in every country – especially in Africa!

Our score was really badly hit by a lack of packet – we were over 100 multipliers short of what we should have achieved. On Sunday we did think about stationing someone in the Internet Café logged into the cluster with a 2m handheld talking spots back to someone at the station who would enter the QSOs. Unfortunately, the Internet Café closed on a Sunday – but it was a nice idea!

For 2004, we’ll be desperately trying to get packet – whether we manage to negotiate an ISP connection, or whether we have to go through the pain of an HF data connection remains to be seen! An HF packet connection would at least give Mike, KC7V, a good reason for putting up the WARC band beam – he’s a man who never wants to stop putting more antennas in the air!