Topband: Fwd: Spot Light Effects... Beacon netwrork

[Steve Dove <dsp@hifidelity.com>(by way of Bill Tippett<btippett@alum.mit.edu>)]

------- Start of forwarded message -------
From: topband-owner@contesting.com
To: dsp@hifidelity.com
Subject: Fwd: Spot Light Effects...  Beacon netwrork
Date: 01/03/05 20:35:29



  From:        Steve Dove <dsp@hifidelity.com>

  To:          Topband@contesting.com
  Date:        Mon, 03 Jan 2005 20:32:35 -0000
  Organization:d s p
  Subject:     Spot Light Effects... Beacon netwrork

  Hi Ford,

  Your description, with minor differences, of a multi-station beaconing
   network
  parallels an 'ad hoc' system presently in use in the 136kHz amateur band and
   at
  'Lowfer' frequencies, particularly at 185.3kHz.  The tools in the form of
   logging
  software etc. are ready to hand, and time-tested.

  The beacons at LF have *extremely* low ERPs, but are readily sensed and are
  measurable using PC-based FFT programs at levels many tens of dB below
  normal CW bandwidth ear-hole levels, and certainly well below measurable S-
  meter strengths.  They are considerably below the noise floor as 
perceived by
   a
  normal receiver.

  A principle implication of this on a similar scheme for 160m is that the
   beacon
  signals do not have to be anywhere near as potent as a normal
  'communications' level signal:  A key factor often missing in discussions
   about
  beacon networks is the high degree of involvement and hardware usage on
  behalf of the beacon-keeper;  that essentially as long as he has the beacon
  running, he is out a radio, a big antenna, and as a consequence use of the
  band.  Reducing the ERP to enough to still allow ultra-narrowband sensing
  means that the transmitter need not even be a radio (!) and the antenna need

  not be very efficient nor full-sized;  with judicious filtering, the 
beacon's
   presence
  need not preclude normal topband operation, either.

  This reduction in scale and resources reduces disincentives and could allow
   far
  more beacons to be constantly available, which would obviously be far more
  useful.

  Without getting too involved in possible operational details, a quick look
   at how
  the system works at LF may be of interest as an initial model:  the beacons,
  rather than time-share, 'stake-out' their 'own' known frequencies, but all
   within a
  fairly tight cluster a few Hertz wide, and ID repeatedly at a very low
   symbol rate
  commensurate to the very narrow measuring bandwidths (30 or 60 seconds per
  dit CW are common).  As a departure from this for a predominantly 
propagation

  beacon network, a better approach may be a simple continuous carrier,
  interrupted every few minutes by a say 10wpm legal ID;  the FFTs would
  essentially ignore the wide-spectrum ID;  knowledge of which beacon was
  which would be from their frequencies within the window.

  A couple of years ago there was a minor storm-in-a-teacup here over low
   power
  beaconing on 160m, which was resolved by an informal 'ghetto' being created
  for such in the top kHz (i.e. 1999-2000kHz);  indeed a few such low-power
   low-
  rate tests showed promise, with one-Watt and even tenth-Watt ERP signals
  being usefully detectable country-wide. N2XE's tests show that even such
  power levels could be leaning to the profligate, although 1 Watt ERP would
  make for an easy 'standard'.

  Might I humbly point to:

  http://www.w3eee.com

  where a number of real-time FFT LF beacon monitors are running;  indeed one
  has been keeping continuous track of a German data station at 138.83kHz for
   a
  number of years now.  I will gladly provide a template for 'SpectrumLab' (a
  program by DL4YHF) which will facilitate the data-logging and plotting of
   multiple
  simultaneous beacons/carriers, to you or to whomever might become the 'point

  man' on such a system on 160m.

          73

                  Steve

_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband