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I am trying to understand how exactly to tune the Superhet receiver. In my simulations, I have attached to the initial frequency mixer---> A local oscillator and an AC signal source to model the incoming frequency.

enter image description here

Now my question is how will this wanted frequency reach the mixer from the antenna ( Since antenna is exposed to all frequencies ) ?

Do i need to add an additional tuning circuit or will this be sufficient ?

If an additional tuning circuit is needed, how will I co-ordinate the oscillators attached to them ( since both of them will require different frequency).

I believe gang capacitors come into this play ( not sure) but I have only this piece available ( nothing else) :

http://www.petervis.com/electronics/tuning-capacitor/tuning-capacitor.html

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What you have drawn is a demodulator (it can also be used as a modulator and therefore acts as a mixer). Before the demodulator is usually an intermediate frequency (I.F.) circuit that is tuned to a fixed frequency and has several stages of band pass filtering in order to reject out-of-band (unwanted) signals.

Before the IF strip is usually the mixer - this mixes the broad array of signals from your antenna (loosely band-limited) to the intermediate frequency for filtering by the IF strip.

Tuning is done mainly on the IF strip and setting it up is usually an iterative process.

BTW - using 1N4007 diodes will not yield great results because of their slow response - try a BAS16 or 1N4148 - they are much quicker and if you want to run your mixer at beyond 1 GHz, there are others you can choose.

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  • \$\begingroup\$ By usage, this looks much more like the mixer which would produce the IF than the demodulator which would follow. \$\endgroup\$ – Chris Stratton Aug 2 '14 at 14:06
  • \$\begingroup\$ @ChrisStratton I've used a demodulator exactly the same as the one above (on a quadrature FM receiver) but I did also suggest that in my 1st paragraph. \$\endgroup\$ – Andy aka Aug 2 '14 at 15:01
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The main feature of the superheterodyne is that tuning is done at the IF stage, not at the carrier frequency stage.

The output of your frequency mixer should go into a bandpass filter. To tune the receiver, you simply change the local oscillator -- the bandpass filter remains fixed.

Wikipedia has a great article on the superheterodyne receiver. Consulting the block diagram would have answered your question.

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