General question regarding vintage (primitive?) signal generators-
I have an EICO 322 AM RF signal generator that I would like to use with some confidence to align a couple of tube FM tuners of the same vintage (both have ratio detectors ) and am looking for ideas on how to verify that the 10.7 mhz signal is accurate.
First idea was to measure the ratio detector voltage with the signal generated connected to the mixer tube, and slowly sweep the generator frequency for maximum voltage (similar to what you do when you align the IF, but in reverse). My thinking being that if the tuner was close to proper peaking, then the maximum voltage should be when the generator is at 10.7mhz, regardless of what the dial says. Obviously, accuracy would be dependent on the tuner being close.
Second idea was to set the tuner on my Philco 38-690 to 10.7 MHz (yes, it has a SW band that covers that frequency); again sweep the signal generator with a modulated signal- when the radio picks up the signal, the generator would be at 10.7 MHz, again regardless of where the dial was set.
Third was to verify a lower scale on the generator (as the higher bands are harmonics). MW were right on.
Well, results were mixed; the FM tuner method put the generator at about 10.8, the radio method at about 10.65 I averaged the setting and was able to align the Magnavox tuner with slight trimming. Sounds good and my multiplex decoder works on it, so it must be close.
Thoughts before I try it on another tuner?
I have an EICO 322 AM RF signal generator that I would like to use with some confidence to align a couple of tube FM tuners of the same vintage (both have ratio detectors ) and am looking for ideas on how to verify that the 10.7 mhz signal is accurate.
First idea was to measure the ratio detector voltage with the signal generated connected to the mixer tube, and slowly sweep the generator frequency for maximum voltage (similar to what you do when you align the IF, but in reverse). My thinking being that if the tuner was close to proper peaking, then the maximum voltage should be when the generator is at 10.7mhz, regardless of what the dial says. Obviously, accuracy would be dependent on the tuner being close.
Second idea was to set the tuner on my Philco 38-690 to 10.7 MHz (yes, it has a SW band that covers that frequency); again sweep the signal generator with a modulated signal- when the radio picks up the signal, the generator would be at 10.7 MHz, again regardless of where the dial was set.
Third was to verify a lower scale on the generator (as the higher bands are harmonics). MW were right on.
Well, results were mixed; the FM tuner method put the generator at about 10.8, the radio method at about 10.65 I averaged the setting and was able to align the Magnavox tuner with slight trimming. Sounds good and my multiplex decoder works on it, so it must be close.
Thoughts before I try it on another tuner?
