Re: IF frequency

On Mon, 30 Jan 2006 13:34:33 +1100, "Phil Allison"
<philallison@xxxxxxxxxx> wrote:

>
>"John Fields"
> Peter Bennett
>>>
>>>I think I would put it another way around: The designer of the radio
>>>chose to use 29.05 MHz as the IF, and designed the IF amplifiers to
>>>pass that frequency. The frequency that the receiver will receive is
>>>that IF frequency plus (or minus) the local oscillator frequency.
>>
>> ---
>> I think he stated it rather succinctly since the IF _is_ the
>> difference between the carrier and the LO, regardless of the
>> location, spectrally, of either the carrier or the LO.
>>
>
>
>** That excludes those receivers where the IF is the sum of the received
>carrier and the LO.

---
Not so.

Notice that he asked:

"Does it come out by the difference between the incoming radio
signal and the Local oscillator frequency?"

If we choose an arbitry IF, say 10MHz, and we have a carrier of
100MHz, then the LO can be either 110 MHz, whereupon the IF will be
the difference between the 110MHz LO and the 100MHz carrier, or
90MHz, where the LO will be the difference between the 100MHz
carrier and the 90MHz LO.

--
John Fields
Professional Circuit Designer
.

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