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[Ham-80211] OT??? High power 2.4 GHz rules change

Tim Gorman ab0wr at ab0wr.net
Sun May 21 14:34:54 UTC 2006


Bogus? Hardly.

Look at what you are talking about here. Use of SS only for point-to-point 
links ala "fixed carriers". 

Yes, these fixed carriers can all run different coding sequences to avoid 
interfering with each other. But such a paradigm has several severe limiting 
factors built in as far as popularity of the mode is concerned. 

1. What are these "fixed carrier" links supposed to be carrying? 
  a. Traffic from Joe Blow to John Doe so they can type at each other every 
night? Just how popular is this ever going to be? How will this ever move SS 
into being a popular mode for amateurs to use? It might be useful for 
experimentation but as I've already asked several times, how many of these 
links require high power?
  b. Traffic between emergency agencies such as county EOC's and first 
responder agencies? The term "carrier" suits this perfectly - as in "common 
carrier". This is something that should be anathema to amateurs. Instead of 
having the FCC taking away our spectrum we would be "giving" it away as a 
free replacement for services that *should* be provided by common carriers. 
Again, how popular is this going to be anyway? Does anyone truly expect this 
to make spread spectrum a popular mode on the ham bands? Is this related to 
"experimentation" in any way, shape, or form? And why would it require the 
use of continuous high power since most links would see less than than a 20 
mile radio horizon?
  c. Are they going to be for "free" internet access links? Once again, this 
smacks of amateurs using "free" spectrum to bypass legitimate common carriers 
and ISPs. With the current move of so many cities putting in cheap, 
ubiquitous wireless access via Part 15, the marginal utility of amateurs 
doing the same becomes very, very small - i.e. it does nothing for making the 
mode popular with large numbers of users. And, again, just how would this 
contribute to experimentation in any way? Why would it require the use of 
continuous high power?

If SS is to ever become popular, even minimally, people have to be able to use 
it to set up more than point-to-point links as psuedo-common carriers. This 
fact alone prevents using a multiplicity of SS coding schemes - because then 
all you would have is a Tower of Babel with no one able to talk to anyone.

Once you have to settle on the use of few standard coding sequences in order 
to facilitate intercommunications between stations you then run into 
determining how the stations will have to operate in order to make the 
communications possible. Everyone running high power and interfering with 
each other is NOT the way to go. It is exactly 180deg from where you should 
go. 

I pull the Red Cross into this because I already know personally of one 
instance where a Red Cross wireless intranet was interfered with -  by a 
wireless intranet next door! They both happened to just use the same default 
channel on the equipment that was installed. Now, what do you suppose would 
happen if a high powered amateur link just also happened to be using that 
same channel? You say that the amateurs would shut down but how would they 
know to shut down? Do you suppose the Red Cross (or whoever) would have the 
capability to RDF the amateur links and could then find out who the control 
operators are? The problem is that the black eye would have already been 
received long before the problem could be alleviated. 

The mere fact that you don't want to face up to this kind of problem and just 
want to pooh-pooh it away tells me that you have no real rebuttal to offer. 
Just vague hand-waving and the statement that the problem will be handled. 
That's the same kind of magic the ARRL is asking us to believe when it states 
that the control operator of an SS link can tell better during a transmission 
what power level to use than a built-in feedback loop in the equipment.

And I would suggest that you go back and study the current FCC regulations on 
SS. I find nothing that limits what coding sequences or even coding types can 
be used. I believe you will find that the FCC lifted those requirements way 
back in the nineties. You are putting forth arguments that are no longer 
relevant. 

I am not against high power being used on SS. I *am* against it being used 
indiscriminately. APC should not hinder experimentation in any way. That is 
actually a very feeble excuse. Yes, it might increase complexity slightly but 
so what? Single Sideband increased complexity over AM. That didn't seem to 
hinder its development much. And the actual fact is that 1watt signals should 
more than suffice for most uses. 

While you didn't put it forth I have seen the argument that APC can't be used 
with point-to-multipoint or multipoint-to-point operations. Nothing is 
further from the truth. The FCC rules only say that power has to be limited 
to that required for communication. There is nothing to keep any 
implementation from using a leaky bucket type of measurement to determine 
what power level is needed when multi-point operation is involved. That is 
just another non sequitur put forth by those who just want to hang bricks on 
their transmitting chains to make up for other inadequacies in the design.

tim ab0wr


On Saturday 20 May 2006 23:14, hal wrote:
> Tim Gorman wrot
>
> > Those multiple stations have to be able to communicate or they are
> > worthless. The higher power they run the more they interfere with each
> > other. It's why the cell phone people don't just increase their cell site
> > power in order to increase capacity (i.e. they can reach further
> > distances and cover more people). They actually lower the cell site power
> > and put more cell sites in.
>
> You seem have a pretty strong opinion on high power spread spectrum so I
> am amazed you have not
> heard of the overlay concept that was the original reason the FCC
> authorized Part 97 use of spread
> spectrum in the first place. If I choose to experiment with a multipoint
> frequency hopping system on 2.4Ghz and pick the power, dwell time and
> channel spread, modulation type, etc .correctly there will be little
> interference to other fixed carriers in minimal.  The analogy with cell
> phones is bogus and led to the introduction of APC to start with..  I
> spoke up against inclusion of APC when it was proposed but it was
> politics, not experimental evidence or experience with Part 97 SS
> systems that championed into the rules.
> There was no experimental experience, then or now, that this feature in
> any way
> promotes experimentation, enhances innovation or is required to
> safeguards shared users.
>  The attempt to pull the Red Cross emergency
> communications in this argument is shameful.  Hams have always shut down
> their systems when it
> in anyway had the potential to interfere with an emergency operation.
> Its amazing how little people
> have learned.  I thought these arguments were put to rest when the FCC
> first authorized
> spread spectrum use in Part 97. Certainly we hams are our own worst
> enemies in this respect.
> You only needed to look at the reply comments, filed by hams
> themselves,  arguing against letting hams have any spread spectrum
> authorization at all.  And its not that we are grossly under-regulated.
> The authorized
> code sequences we received after a lot of behind the scenes back and
> forth are so limited as to be pathetic.
> The FCC essentially shutdown all planned experimentation with advanced
> code sequences, one of the most
> promising and fruitful areas of spread spectrum research.  A few weeks
> after this debacle they authorized practically  any sequence for
> commercial users.   Hams themselves killed  Part 97 spread spectrum  off
> 2meters because of imagined fears of interference. After reading the
> reply comments the Commission imagined all kind of complaints from the
> repeater operators who where themselves unaware of spread spectrum
> testing right on top of their allocation when it actually happened.
>  There continues to be a profound misunderstanding within amateur
> circles on spread spectrum.  Correctly
> chosen system parameters will produce a spread spectrum system that will
> be difficult to even detect
> without specialized equipment.  As an argument against high power 802.11
> that uses spread spectrum
> (as opposed to OFDM or other modulation techniques) it is full of holes.
> All this is argued even when it is a  known fact that there are very few
> such experimental spread
> spectrum amateur systems anywhere in the US.  APC does nothing to
> safeguard 802.11 users who have
> valid concerns over badly engineered high powered 802.11 systems.  Maybe
> thats where the APC  belongs,
> not as part of the spread spectrum rules.
>  In short, APC is a bad idea for Part 97 spread spectrum,  it adds
> complexity without purpose, it stifles innovation and doesn't protect
> anyone in an already overly regulated Amateur service.
>
> BTW has anyone really checked if the spread spectrum code sequences used
> by some 802.11 in amateur operation are Part 97 legal?
> Maybe not -- STA anyone?
>
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