|
Mal,
Things have moved on a bit
You can use a class E/D amp
in linear , with envelope restoration , that
maintains the efficiency , s/n imd
is about 35 dB .
The Op structure allows for up to 50% loss of
signal randomly along the time line , ie
first 50% , last 50% or randomly distributed
Problem with short burst is the 'average energy' level ,
like a radar , huge KW peak powers but only
watts average power .....and yes , wide bandwidth
..
Detecting a carrier is one thing .. to
recover data is a much more difficult thing and requires
a higher level of energy
G..
Sent: Wednesday, September 12, 2012 3:59 PM
Subject: LF: Fw: LOST TRACK
----- Original Message -----
Sent: Wednesday, September 12, 2012 2:57 PM
Subject: LOST TRACK
LF/MF
I think most have now lost track of who is actually
available to work or listen at any one time on LF or MF with such a variety of
modes talked about and in use.
A new comer has no chance, would not know where to start
or what to listen for or what frequency.
In the days of CW or QRSS DXing, the procedure
seemed orderly then the scene became fragmented with the different DATA modes
being introduced and just as easly ended.
For simplicity and efficiency sake I would
suggest sticking to CW, QRSS and OPERA using class D or E type amplifiers at 90%
efficiency.
and avoid modes that might appear efficient but are not
when you consider they need Linear amps that are only 40%
efficient.
Slow slow modes are not the best when hit by QRN or QSB
that removes large chunks of the data stream.
in fact Short Burst transmissions would probably had an
advantage, anyone thought of that approach ie several repeative short bursts of
information sent periodically, of course more bandwidth is
required.
de mal/g3kev
| 