[CW] IF Intermediate Frequency

[Ed Tanton]

Actually, I think I answered the wrong question... it is called 
"Intermediate Frequency" because it is the frequency of the stage in a 
receiver (or transmitter) TO which the original frequency is changed in 
order to perform any bandwidth filtering, or other frequency-related changes.

These changes were more easily accomplished at lower frequencies, like the 
very common 455kHz. National was fond of using 50kHz as one of its IF 
frequencies (because they could use L-C filters [very effectively I might 
add]). Heathkit liked something in the 5 or 6 MHz range, and many other 
manufacturers came to like 9 MHz filters.

It's "Intermediate" because it's only a transition stage... meaning that 
you're going from, say, 7 MHz down to 455kHz, then further down to audio 
frequencies, as in a receiver. That is a single-stage superheterodyne 
receiver description. In a transmitter, making SSB its mode, the audio 
input is mixed/translated UP to 455kHz, and then UP to 7.2 MHz RF output. 
In all cases the stages correspond to the filter requirements-along with 
the obvious input and out parameters.



73 Ed Tanton N4XY <n4xy@earthlink.net>

Ed Tanton N4XY
189 Pioneer Trail
Marietta, GA 30068-3466

website: http://www.n4xy.com

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