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This is a sample map for 04 April 2012

One of the big differences is the RAE; radio amateur’s examination; forty years ago it was a two [...]]]> This year is something of a milestone; it is 40 years since I was first licensed as G8FRA. A lot has changed and it is easy to become nostalgic and bang on about ‘the good old days’.

One of the big differences is the RAE; radio amateur’s examination; forty years ago it was a two part three hour City and Guilds exam. The questions required much more detailed technical knowledge than the modern test. Even though I was working in electronics at the time I well remember spending many hours revising and learning the license regulations.

In the 1960s and 70s the hobby was still ‘technical’ in the sense that you had to understand what you were doing in order to get a working station together. There was no quick fix or cheque book shack available to the ordinary op. It is now much easier to a get a license and get on the air with the minimum of technical knowledge. I really do feel this has diluted the hobby and taken away its very reason for being.

Years ago achievement was measured by a) getting on the air b) working somebody and c) knowing that it had taken time and trouble to do a) and b). Now you can get a license after a weekend course, buy a rig and off you go. If amateur radio is no longer a hobby that requires an understanding of the technicalities of radio communication for ‘self-training’ then what is it?

The ‘prize’ is not from working a station on homebrew equipment that has taken 6 months to build it is from winning. Winning contests, working exotic DX/DXepditions and gaining points at every opportunity. It no longer requires learning about the technology but is about finding ways to get points, break through pileups and generally get one over your fellow op who is trying to do the same. This results in selfish operating practices and during contests, the complete disregard for anybody else who gets in the way. Harsh words maybe and I know it is a generalisation but it is a big problem that is slowly eroding the very basis of why we are here.

The way forward is not to continue encouraging people to take a foundation license by the shortest, quickest route but to re-engage with the technicalities of radio communication. I feel that if somebody is not really interested in the technical side then they should think about another hobby.

It could not be a better time to start rebranding the hobby with the upsurge in interest in ‘hacking’ electronics, i.e. making commercial stuff do things it was not designed for. From various news reports over recent months there is a definite increase in interest in electronic hacking with new clubs and groups springing up.

Recently there have been many TV programmes making astronomy and physics more accessible. Media reports say that applications for physics courses at university are up and some institutions are reopening departments to take in new students. There are also exciting developments in micro-satellites with some hacking groups saying they want to build and launch their own.

As a community we need to act NOW and regenerate ham radio as an exciting, dynamic technical past time. There are enough interested young people out there; we just need to find a way to engage them that goes further than getting them on repeaters with hand helds! So will the RSGB take up this challenge? Or will it be just more of the same? Time will tell!

Today is a cold, wet [...]]]> A few months back I bought a VNWA from SDR-Kits. Now this was a big purchase, equal to a new rig or well on the way to one. So what can it do? The answer to that is that I am still finding out and learning how to use it.

Today is a cold, wet and windy Thursday afternoon just after Christmas, exactly the time to make some BPF’s, band pass filters, for yet another home brew project. The new rig is using the R2Pro direct conversion RX modules with a Tayloe mixer. Originally it was designed to use a ring diode mixer with discrete LNAs, low noise amplifiers, for each band. I say each band but I think this was originally intended to be a single band RX.

The original LNA design was well filtered to stop local oscillator radiation as well as giving some selectivity. Using a Tayloe mixer means that the LO is running at four times the signal frequency i.e. at around 40-41 MHz for the 30m band. This means that a simple low pass filter should stop any of the LO sig from going up the antenna so the need for extra filtering in the RX front end is eliminated.

I want to make a three band transceiver covering 40m, 30m and 20m. It will be mostly for /P use so needs to be small and light. There will be one RF amp with separate BPFs for each band. The last project used some very good toroid based. They were far from small and light so this time I wanted a different approach and decided to use canned coils from Spectrum Communications.

The photographs belows show the first tests of a simple BPF taken from a PDF information sheet from the GQRP club. The sheet shows the values of capacitor to use for TOKO coils which provided a close enough starting point to get instant success. In most cases all that was needed was to go the next value down for the resonating capacitors (C1 & C3.)

Getting back to the VNWA. It was really very easy to tune the coils. For the first time I could actually see what was happening and get figures for both forward and return loss and VSWR. This makes life much easier and produces a better filter response than is possible by tuning for maximum signal. The next step is to cascade 3 or 4 coils to try and improve the bandwidth although only operating at the CW end of the band means that I do not want full band coverage on 40 and 30. More fun on a wet Thursday afternoon!

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The [...]]]> I have always liked using DC, direct conversion receivers. Their sheer simplicity makes them attractive but the drawbacks can be irritating. They often suffer from breakthrough from broadcast, BC, stations and rarely have very good selectivity. I have heard of designs for high quality receivers but have been sceptical of the claims, until now!

The July/August edition of QEX included an article by AAoZZ which described a programmable phase locked loop, PPLL, VFO using the Si570. The VFO was used to drive a Tayloe mixer with several variations of receiver from a simple I Q output for use with PC programs to a full blown RX using an analogue audio board.

The article grabbed my attention because I had used a similar PPLL VFO for the last project. The other interesting part was using an analogue AF section to make a high quality DC receiver – the R2Pro project of a few years back; kits are still available from Kanga US

Yesterday the mixer was built on RF matrix board. I had already ordered the AF board, AF amp and 30m LNA and had a PA0KLT PPLL VFO built from a kit supplied by SDR_Kits. In the article Craig Johnson, AA0ZZ described building his version of the mixer ugly style. It was impossible to obtain DIL chips and all I could get were SOIC versions. Luckily the GQRP Club have some conversion boards from QRPme.

Initial tests involved feeding the I & Q outputs into the PC soundcard. This worked well but tests with headphones were better. The circuit as shown in the photographs will drive a pair of hifi ‘phones well enough for me to be able to copy CW sigs from about 2m away.

The RX performance is amazing, the background is VERY quiet, without an antenna attached there is just no noise. Sensitivity is good and overall this is easily the best DC receiver I have heard. Listening on 30M last night there was no BC breakthrough.

The next thing to build will be the analogue AF section, filters and the AF amp. I want the RX to be dual band, 30m and 20m, so will add an LNA for 20M.

The article also included a very simple TX strip so with some TX/RX switching this could be a useful, small transceiver.

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