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deviation_meter [2018/09/14 21:50] (current) vk3smb created |
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+ | Here is a deviation meter using the discriminator output of a scanner (any cheap scanner you want to hack into.....). If you search the internet for Discriminator taps you will find listings for nearly every available scanner. | ||
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+ | I came about this idea after reading on the internet about how they did it in the " | ||
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+ | All I have done here is use an op amp as a comparitor and compare a reference voltage to the discrim voltage and show the difference on a meter movement. This is similar to a TODF fox hunting antenna I was reading about (The comparitor bit...). | ||
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+ | Please excuse the rudimentary scribble I call a diagram. One day I will enter it into a drawing program and tidy it up | ||
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+ | {{ : | ||
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+ | * | ||
+ | * The meter movement is a 0 - 50uA meter, Jaycar P/N QP5012, with a 30kohm resistance. | ||
+ | * You need a very regulated and filtered 8V supply. I chose 8v to allow for 13.8V power supplies that arent really regulated. | ||
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+ | ===== Setting it up ===== | ||
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+ | - Set the switch to the offset position, transmitting a carrier on the centre frequency. | ||
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+ | - Flick the switch to Dev and you should see the needle sit on 0 with a carrier and move with audio. | ||
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+ | I have used this to adjust all my radio' | ||
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+ | I scanned in the meter movement background and re-wrote the numbers to reflect deviation. I also added the centre freq mark (its a little above centre on my scanner) to show freq error. I have been able to test other amateur' | ||