For some time I have been thinking of setting up a remote receiver
in a quite location linked back to a more conveniently located
transmitter location. This would be an interesting extension. There
are however some licensing issues.
The obvious first stage would be to use a radio link, but that would
require licensing. Unfortunately the obvious band to use would be
70cms (quiet, low occupancy, reasonable range cheap equipment)
but it will be very difficult to get a permit, and then on top of that
an NoV will be required to relay the signals.
The alternative would be to use the Internet or the telephone, but
ironically our administration which is ostensibly promoting the linking
of amateur radio and the Internet has just changed our license to
require government approval to connect our stations to an public
network.
One approach that we could take is to record the sampled signals
for a long period with GPS timing markers, and post analyse. There
may be some stuff we can borrow from the SETI folks here.
One further thought. Perhaps we could use one of the powerful
signals in or near the band as our reference, synchronising to
their modulation. There would be a phase error, but we should be
able to compensate for that.
73
Stewart G3YSX
Andre' Kesteloot wrote:
Klaus von der Heide wrote:
> [...]
> 2. The symbol rate is exactly 1 bit/s. Starting every minute,
> a constant random pattern of 60 bits is sent out.
> Appropriate matched filters must be used at both ends.
That seems like a good idea. But just to start with, what about :
a) a transmitter keyed "on" for 1 minute, then "off" for 1 minute for
instance.
b) using a GPS based frequency reference (described in QST , and
mentioned again recently on this reflector)
c) if the "on" period is 60 seconds long, even if our timing is off by a
few nanoseconds that should not matter, since the error, if derived from
GPS, should not be cumulative
c) we could also add those into an accumulator, etc. and wait as many
days (months ?) as required.
After some preliminary success we could then go for more intricate
schemes.
> As I mentioned some weeks ago, phased array antennas
> at both ends would increase the signal by many dBs.
Should we consider several receiving stations, physically separated to
insure diversity reception, all listening to the same frequency, and
polling their resources afterwards?
73
Andre' N4ICK
|
