A company I used to work for manufactured a frequency hopper spread
spectrum unit.

It was a 'slow' hopper, with Ack/noack for packets so it would retransmit
a missed data packet which covered the case when a particular channel was
occupied.

The acquisition method would also work for a pretty fast frequency hopper
too. It used a master unit that sent a sync signal burst every time it
jumped to a new channel. The remote that was looking for the master would
jump in a duplicate pattern, but at a slower jump rate until it heard the
sync signal from the master. the remote would then start hopping at the
correct rate, and follow the master as it hopped.

Acquisition might be a bit slow, but it did work nicely, and it allowed
other remotes to be turned on at any time and acquire the network.

==============

I have never tinkered with an amateur radio version, but it seems to me
that the ARRL has a book on spread spectrum and there are some FCC mandated
requirements for the PN code, or the hopping pattern for freq hoppers, to
allow the FCC to be able to listen in.

The FCC also limited which frequency ranges Spread Spectrum can be used
on, so I'd do a bit of digging before trying to build hardware......



Jim Pennell
N6BIU

(Timothy C Holtom) wrote in message . com...
Can anyone out there tell me a good source of practical information
(schematics and the like) for building SS transmitters and receivers.
I'm particularly interested in how I'd design the part of the receiver
that acquires then tracks the synchronisation signal from the
transmitter (correlation etc)

How to synchronize to direct-sequence spread spectrum
should be obvious (think Costas Loop).

A sliding-window correlator is a common approach, other-
wise. Three correlators in parallel. One runs a little
ahead, one is on time, the third runs a little behind.
The LO free-runs (deliberately) a little slow or fast.
When the locally-generated PN sequence lines up with
the received sequence, the outputs from the early/late
correlators track the LO, while the on-time correlator
provides the output.

Look in back issues of Wireless World from 1993 for a
fully worked-out example.

Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte

(Timothy C Holtom) wrote in message . com...
Can anyone out there tell me a good source of practical information
(schematics and the like) for building SS transmitters and receivers.
I'm particularly interested in how I'd design the part of the receiver
that acquires then tracks the synchronisation signal from the
transmitter (correlation etc)

How to synchronize to direct-sequence spread spectrum
should be obvious (think Costas Loop).

A sliding-window correlator is a common approach, other-
wise. Three correlators in parallel. One runs a little
ahead, one is on time, the third runs a little behind.
The LO free-runs (deliberately) a little slow or fast.
When the locally-generated PN sequence lines up with
the received sequence, the outputs from the early/late
correlators track the LO, while the on-time correlator
provides the output.

Look in back issues of Wireless World from 1993 for a
fully worked-out example.

Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte

(Timothy C Holtom) wrote in message . com...
Can anyone out there tell me a good source of practical information
(schematics and the like) for building SS transmitters and receivers.
I'm particularly interested in how I'd design the part of the receiver
that acquires then tracks the synchronisation signal from the
transmitter (correlation etc)

I did an initial scout around on the net but the only stuff I could
come up with was TAPR but there's seemed to have been cancelled.

I'm into experimenting, and not afraid of math (an electronic engineer
from a long time ago...)


Can anyone help me here...


Tim

Hi Tim,
this wont be the answer you want but the usual method is to horribly
overdrive your ssb transmitter/linear and that way you are all over
the band! (a joke, OK?)

Miss Smarty Pants (aka Laura Halliday) in her usual inimatble(sp)
style has answered as well, I dont have a PHD so havent a clue what
she is talking about. But she says it should be obvious, maybe you can
figure it out and tell the rest of us uneducated slobs...

73 de VK3BFA Andrew

(Timothy C Holtom) wrote in message . com...
Can anyone out there tell me a good source of practical information
(schematics and the like) for building SS transmitters and receivers.
I'm particularly interested in how I'd design the part of the receiver
that acquires then tracks the synchronisation signal from the
transmitter (correlation etc)

I did an initial scout around on the net but the only stuff I could
come up with was TAPR but there's seemed to have been cancelled.

I'm into experimenting, and not afraid of math (an electronic engineer
from a long time ago...)


Can anyone help me here...


Tim

Hi Tim,
this wont be the answer you want but the usual method is to horribly
overdrive your ssb transmitter/linear and that way you are all over
the band! (a joke, OK?)

Miss Smarty Pants (aka Laura Halliday) in her usual inimatble(sp)
style has answered as well, I dont have a PHD so havent a clue what
she is talking about. But she says it should be obvious, maybe you can
figure it out and tell the rest of us uneducated slobs...

73 de VK3BFA Andrew

(Andrew VK3BFA) wrote in message . com...

Hi Tim,
this wont be the answer you want but the usual method is to horribly
overdrive your ssb transmitter/linear and that way you are all over
the band! (a joke, OK?)

Miss Smarty Pants (aka Laura Halliday) in her usual inimatble(sp)
style has answered as well, I dont have a PHD so havent a clue what
she is talking about. But she says it should be obvious, maybe you can
figure it out and tell the rest of us uneducated slobs...

What's with the personal abuse? Her answer made perfect
sense to me.

A direct sequence signal is spread by BPSK modulation at the
chip rate. Double the frequency and the 0/180 phase shifts
become 0/360, removing the spreading.

- Jack

(Andrew VK3BFA) wrote in message . com...

Hi Tim,
this wont be the answer you want but the usual method is to horribly
overdrive your ssb transmitter/linear and that way you are all over
the band! (a joke, OK?)

Miss Smarty Pants (aka Laura Halliday) in her usual inimatble(sp)
style has answered as well, I dont have a PHD so havent a clue what
she is talking about. But she says it should be obvious, maybe you can
figure it out and tell the rest of us uneducated slobs...

What's with the personal abuse? Her answer made perfect
sense to me.

A direct sequence signal is spread by BPSK modulation at the
chip rate. Double the frequency and the 0/180 phase shifts
become 0/360, removing the spreading.

- Jack

----- Original Message -----
From: "Laura Halliday"
Newsgroups: rec.radio.amateur.homebrew
Sent: Tuesday, March 30, 2004 8:32 PM
Subject: QUESTION: Homebrew Spread spectrum


How to synchronize to direct-sequence spread
spectrum should be obvious (think Costas Loop).

A sliding-window correlator is a common approach,
otherwise. Three correlators in parallel. One runs
a little ahead, one is on time, the third runs a
little behind.

The LO free-runs (deliberately) a little slow or
fast. When the locally-generated PN sequence lines
up with the received sequence, the outputs from the
early/late correlators track the LO, while the
on-time correlator provides the output.



Thanks for the info, Laura. I never did any work with a Direct sequence
system, but this makes a lot of sense.


Jim Pennell
N6BIU

----- Original Message -----
From: "Laura Halliday"
Newsgroups: rec.radio.amateur.homebrew
Sent: Tuesday, March 30, 2004 8:32 PM
Subject: QUESTION: Homebrew Spread spectrum


How to synchronize to direct-sequence spread
spectrum should be obvious (think Costas Loop).

A sliding-window correlator is a common approach,
otherwise. Three correlators in parallel. One runs
a little ahead, one is on time, the third runs a
little behind.

The LO free-runs (deliberately) a little slow or
fast. When the locally-generated PN sequence lines
up with the received sequence, the outputs from the
early/late correlators track the LO, while the
on-time correlator provides the output.



Thanks for the info, Laura. I never did any work with a Direct sequence
system, but this makes a lot of sense.


Jim Pennell
N6BIU

(Jack Gibson) wrote in message . com...
(Andrew VK3BFA) wrote in message . com...

Hi Tim,
this wont be the answer you want but the usual method is to horribly
overdrive your ssb transmitter/linear and that way you are all over
the band! (a joke, OK?)

Miss Smarty Pants (aka Laura Halliday) in her usual inimatble(sp)
style has answered as well, I dont have a PHD so havent a clue what
she is talking about. But she says it should be obvious, maybe you can
figure it out and tell the rest of us uneducated slobs...

What's with the personal abuse? Her answer made perfect
sense to me.

A direct sequence signal is spread by BPSK modulation at the
chip rate. Double the frequency and the 0/180 phase shifts
become 0/360, removing the spreading.

- Jack

Hi Jack,
it wasnt meant as abuse - merely that I didnt understand Lauras
references. If you think being called a smarty pants is abuse, then
you have had a VERY sheltered life - or perhaps its cultural, - BTW -
I went to her site and read the papers she has there - the writing is
clear, succinct and on a level that I can understand. Maybe it was
asking a bit much for Laura to "dumb down" her reply, and I have no
right to expect her to do this. But I rely on these groups as
tutorials on the wide variety of things I dont understand - I am a
mere technician who spends his working life trying to figure out what
the design engineer was trying to do and why it failed after only a
few months in service.

Hope this clears this up

de VK3BFA Andrew