[digitalradio] A closer look at ROS]]

[Tom Azlin N4ZPT]

Looks like that statement simply mirrors what is in Part 97: (8) SS.
Spread-spectrum emissions using bandwidth-expansion modulation emissions
having designators with A, C, D, F, G, H, J or R as the first symbol; X
as the second symbol; X as the third symbol. Or did the FCC just mirror
the language used by AMRAD in getting the rules changed to allow SS.

Nothing in part 97 about using data independent spreading codes to
reduce power/hz such that only a receiver that knows the spreading code
and can sync up will be able to copy. Also was interesting that on the
AMRAD page one of the issues was whether or not the FCC could geolocate
an SS transmitter. Answer appears to be yes.

Would think that simply expanding the bandwidth with a non-data derived
code to reduce narrow band power density could be argued as different,
i.e. SS, than using the data itself to generate massive error correction
which is then sent out on one or more carriers modulated at 300
symbols/second or less.

Or perhaps much ado over nothing?

73, Tom n4zpt

On 2/23/2010 2:51 AM, Per-Tore Aasestrand wrote:
> Amrad itself has a loose 'definition' of SS:
> 
> "Spread spectrum is a technique to reduce the power density of a radio
> transmission by spreading its signal over a wide band of frequencies, at
> least 10 times the information rate and usually much higher."
> 
> 
> Per-Tore / LA7NO
> 
> On 22 February 2010 23:45, Mike O'Dell <mo at ccr.org> wrote:
> 
>> the mere addition of redundancy isn't sufficient to make it
>> spread-spectrum. anyone have his copy of Dixon handy? i'm sure
>> there's probably a useful definition in there and that would more
>> than likely be the one in everyone's mind "back when".
>>
>> doing forward error correction certainly adds redundancy but
>> even the most obstreperous pedant would have trouble making
>> a convincing argument that it constituted
>> "spread-spectrum" if it was still contained within the
>> bandwidth of a "communications-grade voice channel."
>>
>> I would require a definition of Spread-spectrum to include
>> the notion that the final signal is many multiples of the
>> bandwidth of a "communications-grade voice channel".
>>
>>        -mo
>>
>>
>> On 2/22/10 4:17 PM, Tom Azlin N4ZPT wrote:
>>
>>> Hi Andre,
>>>
>>> Still does not answer my question. What was the concern at the time
>>> AMRAD was working SS approvals.  If a signal were inside a 3KHz voice
>>> grade bandwidth would those original fears be applicable?
>>>
>>> I certainly accept that there is no free lunch. that is my favorite
>>> systems trade comment.
>>>
>>> 73, Tom n4zpt
>>>
>>> On 2/22/2010 1:54 PM, Andre Kesteloot wrote:
>>>
>>>>
>>>>
>>>> Sent from my iPhone (apparent spelling errors are due mainly to the
>>>> thickness of my index and the size of the iPhone keyboard).
>>>>
>>>>
>>>> On Feb 22, 2010, at 11:31, Tom Azlin N4ZPT<n4zpt at cox.net>  wrote:
>>>>
>>>>
>>>>
>>>>> Spreading is adding known redundancy otherwise you would not get
>>>>> spreading gain.
>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>> Alas, there is no such thing as a free lunch.
>>>> You only get spreading "gain" because you first introduced spreading
>>>> losses.
>>>> 73
>>>> André N4ICK
>>>>
>>>>
>>>>  _______________________________________________
>>> Tacos mailing list
>>> Tacos at amrad.org
>>> http://www.amrad.org/mailman/listinfo/tacos
>>>
>>
>> --
>> "Of course it's hard!
>> If it was easy, we'd be buying it from somebody else!"
>>
>> _______________________________________________
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>>
> 
> 
> 
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