In the recent VLF transmissions it was shown that it is most useful to
have a temp drift and offset compensated soundcard.
Within SpecLab, this function is included and makes it easy to "lock" a
soundcard to a reference MSK transmitter such as GQZ or GBZ... Just in
this time, GQZ is OFF, maybe due to maintenance or whatever. All the
MSKs have less than 100 % availability. I have observed that GQZ has one
of the highest availability which makes it preferred to use for drift
But if people wants to make the system as perfect as possible
(especially the VLF TX stations who won't be able to receive GQZ during
a own transmission!), there is a relatively cheep solution for this.
In ebay, there is a GPS module available which provodes a GPS locked 10
kHz output signal. This signal can easily be injected in the VLF audio
stream (i am using a 2.2 nF C for coupling) and SpecLab can lock on this
signal. It works quasi perfect and independent of the availability of a
This is the module which is not really expensive:
It is also available on german or french or finnish ..... websites i assume.
The module needs a 5 V power supply. This can be taken from a PCs USB
without problems. This module is running on my grabber since some months
and a second one was used in my transmission of the 8th experiment. Now
temperature drifts of my DDS VFO is history!
Just a hint for the upcoming VLF TX stations... :-)