electronic tuning - Electronic Circuits Projects Diagrams Free

soxido · 29th August 2003, 07:18 AM

how would you implement electronic tuning from a standard superheterodyne reciever that uses a tuning knob?

**kinjalgp** · 29th August 2003, 09:02 AM

You can not implement it in a standard superheterodyne reciever. There are special radio receiver ICs available for the tuning stage.

stevez · 29th August 2003, 11:22 AM

A friend of mine and I are giving this idea some thought too. In some simple receivers a varactor (or common one too) diode is used to shift the oscillator frequency with a dc voltage. I know in some remote tuning applications a varactor is used in parallel with other capacitors to provide some adjustment to a loop antenna. I don't think the range is that broad but it's apparently a useful alternative to other methods. Implementing this in multiple circuits in multi-stage receivers might be tough.

Roff · 29th August 2003, 03:44 PM

Take a look at TDA1072. This is a superhet receiver chip, and on p.18 they show a schematic which has electronic tuning. Getting the local oscillator to track the antenna tuning seems like an alignment nightmare, but I'm no expert on radio receivers.
I believe this chip is designed so that it could be used without tracking RF tuning. It would require very steep skirts on the IF filter. If there are any hams reading this, they may know whether this is true or not.

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29th August 2003, 07:18 AM	(permalink)
soxido	electronic tuning how would you implement electronic tuning from a standard superheterodyne reciever that uses a tuning knob? __________________ intelligence is mesured by the ability of the brain to hold tow conflicting ideas and stil come up with a reseanable solution.

29th August 2003, 09:02 AM	(permalink)
kinjalgp	You can not implement it in a standard superheterodyne reciever. There are special radio receiver ICs available for the tuning stage. __________________ "There is no way to peace, peace is the way!"

29th August 2003, 11:22 AM	(permalink)
stevez	A friend of mine and I are giving this idea some thought too. In some simple receivers a varactor (or common one too) diode is used to shift the oscillator frequency with a dc voltage. I know in some remote tuning applications a varactor is used in parallel with other capacitors to provide some adjustment to a loop antenna. I don't think the range is that broad but it's apparently a useful alternative to other methods. Implementing this in multiple circuits in multi-stage receivers might be tough. __________________ stevez

29th August 2003, 03:44 PM	(permalink)
Roff	Take a look at TDA1072. This is a superhet receiver chip, and on p.18 they show a schematic which has electronic tuning. Getting the local oscillator to track the antenna tuning seems like an alignment nightmare, but I'm no expert on radio receivers. I believe this chip is designed so that it could be used without tracking RF tuning. It would require very steep skirts on the IF filter. If there are any hams reading this, they may know whether this is true or not.