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<blockquote data-quote="spiney" data-source="post: 172693" data-attributes="member: 192438"><p>...... a bit more about the Micromatic.</p><p></p><p>The just above link</p><p></p><p>(again:<a href="http://hometown.aol.co.uk/peteroberts007/microradio/micro.htm" target="_blank"> http://hometown.aol.co.uk/peteroberts007/microradio/micro.htm</a> )</p><p></p><p>suggests it wasn't very sensitve. Not true!</p><p></p><p>If you look at the picture of it with back removed (great pics!), the black round component exactly in the middle is an inductor. You were supposed to bend this downwards - with your thumb - closer to the transistor, until howlround occurred on the strongest received signal, then "back off" slightly, which was the condition for max regenerative feedback and highest sensitivity. But, I suppose people who bought the ready made one wouldn't have known about that!</p><p></p><p>With such howlround, you were actually transmitting on the AM MW band, somewhat illegal!</p><p></p><p>The Micromatic's worst feature was using a trimmer as the tuning capacitor. This made the small size possible, but trimmer caps aren't supposed to be constantly adjusted, hence are fragile, and with much use the copper strip tended to snap off. I resoldered mine back on, several times, and eventually replaced the entire cap.</p><p></p><p>If you look at 2 Micromatic "clones" (ie, ripoffs!):</p><p></p><p><a href="http://hometown.aol.co.uk/peteroberts007/microradio/microindex.htm" target="_blank">http://hometown.aol.co.uk/peteroberts007/microradio/microindex.htm</a> .</p><p></p><p>it's noticable that the trimmer has been replaced by a "real" tuning capacitor. With good reason!</p><p></p><p>(the other tiny radios shown are more complicated, and may perform better, but don't retain the Micromatic's elegant simplicity).</p><p></p><p>Added: Sinclair was famous for cutting costs, often at expense of reliability! The project 60 pre-amp used entirely trimmers - instead of real potentiometers - which were "open", and very quickly became dirty and noisy. After a while, just changing the volume might possibly blow the power amp output trannies or damage a speaker! On mine, I replaced all the trimpots with proper ones.</p><p></p><p>Those 'orrible trimmer type pots easily visible in this picture:</p><p></p><p><a href="http://www.nvg.ntnu.no/sinclair/audio/gallery/project60_range.jpg" target="_blank">www.nvg.ntnu.no/sinclair/audio/gallery/project60_range.jpg</a> .</p></blockquote><p></p>
[QUOTE="spiney, post: 172693, member: 192438"] ...... a bit more about the Micromatic. The just above link (again:[URL="http://hometown.aol.co.uk/peteroberts007/microradio/micro.htm"] http://hometown.aol.co.uk/peteroberts007/microradio/micro.htm[/URL] ) suggests it wasn't very sensitve. Not true! If you look at the picture of it with back removed (great pics!), the black round component exactly in the middle is an inductor. You were supposed to bend this downwards - with your thumb - closer to the transistor, until howlround occurred on the strongest received signal, then "back off" slightly, which was the condition for max regenerative feedback and highest sensitivity. But, I suppose people who bought the ready made one wouldn't have known about that! With such howlround, you were actually transmitting on the AM MW band, somewhat illegal! The Micromatic's worst feature was using a trimmer as the tuning capacitor. This made the small size possible, but trimmer caps aren't supposed to be constantly adjusted, hence are fragile, and with much use the copper strip tended to snap off. I resoldered mine back on, several times, and eventually replaced the entire cap. If you look at 2 Micromatic "clones" (ie, ripoffs!): [URL="http://hometown.aol.co.uk/peteroberts007/microradio/microindex.htm"]http://hometown.aol.co.uk/peteroberts007/microradio/microindex.htm[/URL] . it's noticable that the trimmer has been replaced by a "real" tuning capacitor. With good reason! (the other tiny radios shown are more complicated, and may perform better, but don't retain the Micromatic's elegant simplicity). Added: Sinclair was famous for cutting costs, often at expense of reliability! The project 60 pre-amp used entirely trimmers - instead of real potentiometers - which were "open", and very quickly became dirty and noisy. After a while, just changing the volume might possibly blow the power amp output trannies or damage a speaker! On mine, I replaced all the trimpots with proper ones. Those 'orrible trimmer type pots easily visible in this picture: [URL="http://www.nvg.ntnu.no/sinclair/audio/gallery/project60_range.jpg"]www.nvg.ntnu.no/sinclair/audio/gallery/project60_range.jpg[/URL] . [/QUOTE]
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