Dear Mike, LF group,

...I am writing a short chapter on using computers in amateur radio, for

the new edition of the RSGB's Radio Communication Handbook.

This is about construction and not operating, and I am interested in

what software is used by group members when designing building and

testing amateur radio equipment, including antennas and not just for

LF...

Spectrogram programmes, such as Spectrum Lab, are useful for very many things apart from LF reception, such as measuring distortion, intermodulation, noise, oscillator drift, modulation, and propagation study (see, for example, the CDG2000 transceiver articles from RadCom a while ago, the various LF propagation web pages). The performance of spectrogram software plus soundcard as an audio spectrum analyser is hard to beat, provided you don't mind supplying your own amplitude calibration.

There are quite a few NEC-based programmes around for antenna analysis, some available in free demo versions - see for example: http://www.cebik.com/model/nec.html

I suspect that amateur antenna designers have become a bit over-reliant on NEC, and tend to neglect the “real world” aspects of antenna behaviour as a result, but it certainly does provide a useful facility, all the same.

There are also many SPICE-based simulator programmes around - see http://www.terrypin.dial.pipex.com/ECADList.html , for example. Some of these are available as free demos (as rather large downloads), usually with restrictions on the free version. These things are very useful to see if or how a circuit "works", and can usually quite accurately predict performance (mostly for analogue circuits), although they do require substantial effort to learn to use effectively. I have used PSpice a lot when designing amateur radio circuits, mostly because I can “borrow” it from work. A circuit simulator won’t do the designing for you, but it does help a lot in finding out what is wrong with a design, and predicting what will happen before you actually build the circuit.

I would echo what people have already said about G4FGQ’s software utilities, and the AADE filter design software – these programmes have saved me a lot of time pushing buttons on a calculator in the past!

Cheers, Jim Moritz

73 de M0BMU