robert casey wrote:
wrote:
"Acting on the premise that the amateur bands must flexibly and
comfortably accommodate present and future operating modes and
technologies over the long haul,

What about spread spectrum modes? Supposedly such a
mode could use the entire data subband of a HF band
but have only minimal QRM to other users?

Doesn't work that way. It's more like "QRM to almost all other users".

There was a clear discussion of this by KE3Z (IIRC) here some years
back. The interference potential of SS on HF was clearly demonstrated.
I can google it for you if you want.

Here's a quick synopsis:

Suppose I'm listening on 3825 with a 2.5 kHz wide receiver. A local
fires up right on frequency with a signal that's 2.5 kHz wide. He's S9
+ 20 dB, so unless I'm listening to someone even stronger than that,
there's harmful interference.

Now the local switches to an SS mode that is 250 kHz wide. To make the
math easy we'll assume the transmitted energy is evenly distributed
over the 250 kHz.

The transmitted energy that was formerly packed into 2.5 kHz is now
evenly spread over 100 times that spectrum, so the energy that gets
into my receiver is 1/100th of what it was before. The S9+20 local's
signal drops 20 dB - to S9. Only now he's S9 on 250 kHz of the band,
rather than just a few kHz.

Even if he drops his power 18 dB at the same time he goes SS, he's
still S6 (assuming 6 dB per S unit).

If a station runs 100 W to a dipole at a decent height, and the band is
in good shape, that station will be S9 + 20 over a pretty wide area on
80/75.

73 de Jim, N2EY

The transmitted energy that was formerly packed into 2.5 kHz is now
evenly spread over 100 times that spectrum, so the energy that gets
into my receiver is 1/100th of what it was before. The S9+20 local's
signal drops 20 dB - to S9. Only now he's S9 on 250 kHz of the band,
rather than just a few kHz.

Even if he drops his power 18 dB at the same time he goes SS, he's
still S6 (assuming 6 dB per S unit).

If a station runs 100 W to a dipole at a decent height, and the band is
in good shape, that station will be S9 + 20 over a pretty wide area on
80/75.


So much for SS then. Another problem might be what QSB might
do to that signal anyway....

wrote:
robert casey wrote:
wrote:
"Acting on the premise that the amateur bands must flexibly and
comfortably accommodate present and future operating modes and
technologies over the long haul,

What about spread spectrum modes? Supposedly such a
mode could use the entire data subband of a HF band
but have only minimal QRM to other users?

Doesn't work that way. It's more like "QRM to almost all other
users".

There was a clear discussion of this by KE3Z (IIRC) here some years
back. The interference potential of SS on HF was clearly
demonstrated.
I can google it for you if you want.

How does that compare to BPL? BPL is allowed on the ham bands.