----- Original Message -----
Sent: Sunday, May 19, 2002 10:40 PM
Subject: LF: Re: pegelmesser
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.
Hello Bob
Look for a pegelmesser with phased locked
loop oscillators, synthisized etc the same as mine and you will find they make
a great LF receiver, especially the models with the 20 hz filters.
Even the free running osc type are useful if
kept switched on all the time and inside the house with a fairly constant
temperature and not outside in the bicycle shed!!
I do not have any trouble resolving and
keeping signals within the 20 hz bandwidth for hours at a time. I especially
like the W&G SPM-12, with the 10 khz IF output. I built an external
product det, audio stage and it works extremely well, very sensitive and
the filters are well suited to LF work.
73 de Mal/G3KEV
Bob ZL2CA
