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Old 18th Jun 2012, 2:42 pm   #3
AlanC
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Join Date: Jul 2006
Location: Sheffield, South Yorkshire, UK.
Posts: 312
Default Re: NAAFI receiver problem

Malcolm,

When you say the local oscillator is running at the right frequency, where did you set the tuning to measure this? Assuming you're on medium wave, the LO will be running at 465kHz above the signal, so 530 + 465 = 995kHz at the LF end, to 1600 + 465 = 2065 kHz at the HF end. 930 sounds a bit low to me. It's just worth checking this again with the tuning set to 300 metres. This is 1000 kHz and the LO should pop up on another set at 1465kHz or about 204 metres on the dial.

What happens of you inject the modulated IF signal at the mixer anode, via a small isolating capacitor? ... it should be a lot more sensitive than your reading at the detector. In fact, just touching the mixer anode pin with a screwdriver blade should probably result in crackling and/or a 'hash' being received.

Cheers
Alan
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