Winter 2001/2002 Newsletter

Welcome to the New Year!

AFS Contest

 "I haven’t had so much fun with radio for a long time" That was Chris’s (M5IMI) comment after he and Alex (M1EPR) had just operated a "run" frequency for 40 minutes and worked stations at an average rate of one per minute….

This comment summed up everyone’s feelings at the end of the AFS SSB contest held for 4 hours on Saturday Jan 19th. This year we had a full team of three stations, used the best available locations, Dave at the farm, Iain at the club and Chris and Alex operated from Dave’s QTH. We also used much better antenna systems. The antennas being inverted V dipoles.

The weekend before was used to set up the stations and antennas. All three stations were to use computer logging. Dave ran 400w with an amplifier, and the other stations ran 100w barefoot. Dave designed and made all three of the antennas.

With the contest only on the frequencies 3.6 to 3.75 a reasonable SWR could be obtained without the inconvenience of using an ATU.

Chris and Alex (who did not have much experience of HF contesting) started to S&P. About 40mins from the end they found an empty frequency and Alex decided to try a "run".  This generated a lot of interest, and they worked at a rate of 60 an hour for the last 40mins.  They ended up with a score of 129; again well over the 100-target set.

The good thing was that we all enjoyed it and all exceeded our individual targets.  

Our combined QSO count should be around 476, giving us a total points score of 4760. This would have put us in 12th position, based on last year’s scores. Results are usually published in RadCom around September/October.

Happy contesting, Dave G3UEG.

It’s Not a Wire It’s a Wave-Guide

At DC and low frequencies the current in a wire flows through the wire, as you’d expect.  As the frequency gets higher, like the 33 MHz of 100BaseT, the wire starts to radiate or act like an aerial, and the current only flows in the skin of the wire.  Some of the energy is actually travelling as radio waves along the length of the wire – and we become susceptible to Alien Crosstalk. At 75MHz, the frequency used for Gigabit Ethernet on UTP cabling, more of the energy is on the outside and the potential for Alien Crosstalk increases. But once we get to the 250MHz limit for Cat 6 the wire is acting just like a wave-guide.   Most of the electrical energy travels from one end to the other OUTSIDE the conductor as electromagnetic energy.   Quite a lot of it travels within the plastic of the insulation, so these are no longer just mechanical things for protecting and holding the wires together, they are now an integral part of the dielectric of the cable.   The sheath becomes a significant factor in the cable’s impedance make-up. At these frequencies, any kinking, crushing or elongation of the cable has a proportional effect on the impedance and a consequent knock on effect on transmission performance.        Extracted from an article in Cabling World, October 2001.

Dayton Hamfest Report - part II

In the previous article I described the lead up to the Hamfest and left you all as we sat in the hotel bar the night before the show.  I posed the question "would it be worth it?"  The answer is a '40 over 9' YES!

Chris and I met for breakfast at 07:00 and were out of the hotel at 07:45.   With so many visitors there needs to be some form of traffic and parking system - and they have this down to a fine art.  We used the free park and ride system from a local shopping mall.  We entered the Hamfest gates at 08:35, just over half an hour after the flea market (boot fair) opened and 25 mins before the main halls opened.

At this point it's worth trying to explain the magnitude of the show.   Inside there are 5 large halls, each several times the size of the Picketts Lock halls. These contain the major retailers and there were a total of 500 stands.   Yaesu, Icom, Kenwood, Alinco, Ten-Tec, HyGain, RF Parts, Ham Radio Outlet, MFJ, I could go on, they were all there in force.  Kenwood was supposed to release a new topband to 23 cms rig for less than $2000 - but they just had a mock-up in a perspex case and a very poor hand out. Apparently the design was not complete - embarrassing! (This has now appeared as the TS2000) Yaesu announced the FT1000 Mk V.  All of the major magazines had stands and I dropped by to chat to the RSGB - who unfortunately had the majority of their goods stuck in customs in Chicago.  The ARRL naturally had a big stand.

There was a large food hall for snacks and drinks - and from what I saw this tended to be a place of annual meetings between friends.  What impressed me was the friendliness of everyone - indeed I don't think I heard a raised voice or a moaning trader once!  I swear I did not stop at all of the stands inside - and it was only with the aid of the floor plan in the programme that I was able to navigate even after two days.

The weather plays an important part of Dayton.  The event used to be held in March, but everyone got fed up with being cold and/or wet, so they moved it to May.   We had just about ideal weather; on the Friday it was dull in the morning but sunny and hot in the afternoon.  Saturday was similar but not so sunny.  The important thing was it didn't rain - imagine all those outside traders in the rain.  However one veteran told me "if it rains the stuff outside gets mighty cheap".

Dayton is not just about the inside and outside traders, there is a comprehensive lecture stream that runs throughout the two and a half days.  Chris & I went to a lecture in the afternoon which was part of the antenna stream - about 150 people attended.   I looked in later and it was still full.  In addition, the ARRL were holding their Annual meeting at the show.

Being avid topbanders, Chris and I had organised to go to the Topband dinner on the Friday night.  This is a smallish annual affair which attracted about 40 of the US and world topband community.  It was amazing to meet people that are icons of the band and many who I have 'known' over the air or the Internet but never met.  While we were seated and waiting for the food, we each had to stand up and introduce ourselves to the group.  When we mentioned we had been GJ2D in the CQWW160 contest we got a warm round of applause - it was a new country for a great number of topbanders and obviously a juicy multiplier in the contest. At the end we had the short drive back to the hotel and a late night.  We could have gone into the town where the various DX Foundations host meetings - I understand this is a euphemism for a considerable amount of drinking well into the small hours.

On Saturday the flea market opens at 6am - we weren't there to see it.  We got to the show soon after 8am and spent the entire day walking the stands and the outside arena.  We had been advised that if we saw something we wanted, to make a note of its pitch - I did not always do this and there were 3 or 4 stands that I never did find again.   I was steadily collecting brochures and odd bits and pieces, my rucksack becoming uncomfortably heavy on both days - and I still had to lug this lot home.  We left the show a little earlier on the second day as we had booked to go to the Hamfest Dinner (they called it a Banquet but I think it lost something in the translation!).  This was held in another huge auditorium just across from our hotel.  We sat down to dinner at 6:30pm and by 7:30 the three course meal was finished and we were on to coffee.   Speeches, which naturally concentrated on the American scene, and awards in a somewhat 'Oscars' style continued for the next hour.  After a short break there was entertainment from an ageing US double act - which actually wasn't that bad.   Compared with the rest of the Hamfest this part was not very good value and I'm not sure I would bother to go to the 'banquet' next time.

We decided to have a lazy morning on Sunday and reflect on the two days.   Breakfast was a relaxed affair and then there was the job of sorting and packing the goodies for the flights home.  All the time we kept asking ourselves whether we should have gone back for one last look around.

So what will be the lasting memories of Dayton 2000?  The enormity of it, the car park full of trucks bristling with HF mobile antennas, the friendly atmosphere, meeting the topbanders, the wish that we had an amateur scene like that over here. Will I go again?  I met a number of Brits who now make it a regular trip - so who knows? If only there was an easy way to get the goodies back to the UK. One thing is for sure – I would strongly recommend that everyone should try to visit Dayton at least once during his or her Ham Radio lifetime.

     de Dave G3UEG

PS. Next year’s event is from May 17th – 19th.  (Not too early to start planning)

Bluetooth

Bluetooth is vying to become the industry standard for short-range, point to multi-point voice and data transfer using digital radio. It is designed to operate in the unlicensed ISM (Industrial, Scientific, Medical) band, 2.4000 GHz to 2.4835 GHz in Europe and America, where it uses spread spectrum, frequency-hopping techniques across 79 channels.  The specification includes air interface protocols to allow several Bluetooth devices to communicate simultaneously, and includes provision for handling interference from external sources like domestic microwave ovens. The short range referred to above is defined as up to 10 metres in normal operation although greater range/penetration can be achieved through higher output powers under some circumstances.

The home of the future might include a Bluetooth enabled computer which controls remote heating and ventilation devices, polls intelligent kitchen cupboards for inventory data, updates your personal organizer shopping list and fetches the email via your Bluetooth enabled mobile phone.  A place where you can sit in the garden and listen to your hi-fi, talk on the telephone or pick up messages from your computer all through a Bluetooth enabled headset.

Extracted from a White Paper by Intercai Mondiale Limited

Ever wanted to walk upside down?

Flies do it, spiders do it, even geckos do it…but humans are useless at walking on the ceiling. What do they have that we don't.

Gecko's feet are even more high tech. The fine hairs covering their feet appear to use something called 'van der Waals' forces - a weak attraction molecules have for each other when they are brought very close together. The combined force from the gecko's half a million hairs on each foot - plus the fringe of 1,000 sub-microscopic hairs branching from each hair - have a powerful effect. The gecko's little feet have an adhesive force theoretically capable of holding 90 pounds or 40 kilos. To move, the gecko releases each foot by peeling off the hairs, rather as one would adhesive tape. Scientists hope to use the same technology for upside down robots.

Isolated Computer to Radio Interface

This little interface came about after talking to other amateurs on GB3NL, about using PSK31.  One person was having trouble with a voltage difference between the PC and Radio so I suggested using an isolated interface between them. (From what I remember the fault was a bad earth in the PC’s mains cable) After looking at the price of the commercial interfaces I decided to build one from the junk box.

Circuit description.

Construction.

Set-up.

Both pots should be centred and adjusted to give the required audio drive for TX so as not to over drive the radio when using SSB, in RX the program will usually control this.

After building the interface I found as an added advantage I had less background noise on receive on the HF bands, the result of isolating the radio from the pc.

By Iain (G4YBN)