[Fwd: LF: Transatlantic]
Fri, 28 Jan 2000 09:28:29 -0500
Klaus von der Heide wrote:
> Hello LF-Friends,
> the negative result of the recent transatlantic experiment only says
> that the usual ham methods for LF contacts are not adequate for a
> transatlantic distance. A weak signal never excludes information
> transmission, it only reduces the information bit rate. Why not try,
> as a first step, to get one single bit over the ocean?
> The communication theory says that BPSK is optimum, and a
> bandwidth considerably larger than the information bit rate is better
> than a small one.
> I therefore, propose the following experiment:
> 1. Both, transmitter and receiver, must be synchronized to an
> atomic clock, i.e. all oscillators that determine the carrier
> or the symbol rate. Especially the sampling frequency of
> a DSP (not the processor clock) must be synchronized.
> A soundcard normally cannot.
> 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.
> 3. At the receiving end, a DSP adds the 60 new values to
> 60 accumulators.
> 4. The contents of the accumulators is correlated with the
> known random bit pattern. After many hours or days
> (or years?) the correlation must become significant.
> 5. It is important to suppress the non-Gaussian noise as
> good as possible before the data are accumulated.
> As I mentioned some weeks ago, phased array antennas
> at both ends would increase the signal by many dBs.
> There isn't any dought that hams can cross information
> over the atlantic. The minimum information of a ham QSO
> is 50 bits in either direction. The open questions only is:
> Is the possible information bit rate 1 bit per day or is it
> 1 bit per 5 minutes or in other words: can a QSO run
> within 10 hours or can it definitely not.
> 73 de Klaus, DJ5HG