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Mal,
The frequency stability of any selective
level meter with a VFO for a local oscillator makes them suspect for staying
tuned within a fraction of a Hz for long periods. The digital display on a
Siemens D2019 I have merely counts the VFO (with a constant 100 kHz offset to
give passband centre frequency) and numbers actually change with VFO
warmup. The display is to 10 Hz, so it can not be used for pre-setting to
a QRSS signal that is expected to be below the noise and therefore
impractical to try tuning by "ear". As well, the BFO is a free-running RC
oscillator so the recovered audio can have further drift of centre
frequency.
There are some selective level meters with master
oscillator arrangements for tuning and demodulation, and can have fractional Hz
stability.
In saying the obvious, selective level meters are
primarily intended for determining signal levels.
Bob ZL2CA
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