Originally Published in Radio and Electronics World in August 1982
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This converter will allow the reception of any four 4MHz (2MHz with a 144-146MHz IF) bands in the range 26 to 75MHz using a two meter receiver! tranceiver as the IF. This range includes the 10, 6 and 4m amateur bands, citizens band, European and American public service bands and band 1 television. These can make interesting listening and provide useful propagation data. Table 1 gives details of some of the services present in this part of the radio spectrum.
There is about 8dB conversion loss in the converter which, given a sensitive two meter receiver, provides adequate performance for most purposes. Despite the simplicity of the input filter, it is effective in reducing the level of IF breakthrough and other spuril to an acceptable level. The inclusion of a tuned preamplifier, such as that described in reference 2, increases the sensitivity and the immunity to out of band signals considerably. Most two meter receivers, however, suffer from severe intermodulation and adjacent channel interference if the preamplifier is included in a system for receiving citizens band. This should not be a problem above 28MHz where the band occupancy and signal strengths are generally lower. The frequency range of the original design was 26 to 60MHz. It was thought that the harmonic relationship of the local oscillator, input and IF frequencies would be the cause of spurious responses if this range was increased. In fact, despite the compromise of a 75MHz input filter cut off and the 120MHz LPF for the local oscillator, the performance remained acceptable. It is advisable, to use a tuned preamplifier above 50MHz to improve the selectivity and to reduce the oscillator radiation. The converter may be used with one to four oscillators without circuit changes. These oscillators are DC switched and may be remotely controlled.
|Original Article in .jpg form (80kb to 450kb
Page 1 Introduction, construction & test
Page 2 Filter responses & test
Page 3 Circuit, description & results
Page 4 Layout & parts list (300dpi)
Page 5 Component Overlay & references
|We reget that no support is available in connection with this article. This information is supplied in good faith and no liability is accepted for any errors or ommissions.
|Printed Circuit Board ArtworkThis should print 1:1 if printed at 300dpi. Toko components may be obtained from BEC Distribution in the UK. For other components, try some of the distributors listed here
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© 1982 G. Leighton © 2006 radioshop.co.uk