You still need a stable reference oscillator somewhere. You only cancel
the drift of the first L.O. If the reference oscillator drifts by a
ppm, your overall frequency calibration drifts by a ppm.
73 Martin AA6E
wa3fiy@radioadv.com wrote:
> What about the Wadley Loop? It is my understanding that it provided a
> high degree of stability using a tunable (read drifty) VHF oscillator and a 1
> Mhz crystal oscillator rich in harmonics along with a unique mixing scheme.
> Several commercial receiver designs took advantage of the Wadley Loop
> design including the Yaesu FRG-7, Drake SSR-1 and some RACAL
> receivers.
>
> Here is what Wikipedia has to say:
>
> "Of the three principal methods of such control, the Wadley Loop seeks to
> cancel any tendency for the oscillator's frequency to drift. It does this by
> mixing the received frequency up to a high IF frequency (more than 10
> MHz) and then uses the same oscillator to generate a lower frequency.
> These signals are then remixed to generate the second IF frequency."
>
>
...
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