04-05-2011, 05:43 PM
Adding to the noise 
A while back on a different forum someone posted a very good, albeit lengthy, tutorial about how to sneak by without springing for $20-30 on a signal generator. Like Nash indicates, the first step is to get the IF to the correct frequency or else you're just shooting in the dark. The tutorial explained how to tune in a station and then listen on a second radio to observe if the local oscillator signal could be heard 455 kc higher on radio #2. If you understand the fundamentals of a superhet you can see how this can work but its probably bad advice to a first-timer. 
Its easier to spring for a signal generator. Nowadays with digital radios available for next to nothing a fellow can take a cheapo hobby generator and calibrate it well with a few pencil marks on the dial! Probably better calibration than the old radiomen had at their disposal.
And...the nature of the old beasts is that some of them (the cheap home radios) don't track that well anymore and I sometimes wonder if they ever did? BTW, the term " tracking" refers to the relationship between the RF section and local oscillator section...not just where the signal appears on the dial. Sometimes its a compromise.
A while back on a different forum someone posted a very good, albeit lengthy, tutorial about how to sneak by without springing for $20-30 on a signal generator. Like Nash indicates, the first step is to get the IF to the correct frequency or else you're just shooting in the dark. The tutorial explained how to tune in a station and then listen on a second radio to observe if the local oscillator signal could be heard 455 kc higher on radio #2. If you understand the fundamentals of a superhet you can see how this can work but its probably bad advice to a first-timer. Its easier to spring for a signal generator. Nowadays with digital radios available for next to nothing a fellow can take a cheapo hobby generator and calibrate it well with a few pencil marks on the dial! Probably better calibration than the old radiomen had at their disposal.
And...the nature of the old beasts is that some of them (the cheap home radios) don't track that well anymore and I sometimes wonder if they ever did? BTW, the term " tracking" refers to the relationship between the RF section and local oscillator section...not just where the signal appears on the dial. Sometimes its a compromise.
