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

jeff at aerodata.net jeff at aerodata.net
Sun May 21 03:59:25 UTC 2006


Are you the same Tim Gorman who is or was on the ISP-Wireless mailing list?

Just curious, I used to subscribe to it as well.

> See my comments below.
>
> On Saturday 20 May 2006 16:35, doc wrote:
>>  > Tim Gorman wrote:
>> >
>> > Point 2: 1 watt at 2.4Ghz is plenty of power to work all the way to
>> the
>> > radio horizon for most installations. Raising power levels to blast
>> > through obstructions is NOT a good way of doing things, it shows poor
>> > engineering judgment. Finding better paths and setting up mesh
>> networks
>> > that will allow routing around obstructions is a much better answer
>> for
>> > almost all system metrics - initial cost, operating cost, spectrum
>> > pollution, etc.
>>
>> I have to question the assumption underlying this
>> statement.
>>
>> Much higher power than 1W will be necessary to maintain
>> solid communications for the following circumstances:
>>
>> 1.  Airborne obstructions, e.g. rain, snow, hail, sleet,
>> smoke, heavy mist, windblown dust, windblown pollen, etc.
>> (your airborne nuisance will depend on your QTH -- expect
>> more if you deploy in disaster-impacted locales)
>
> Why do you think higher power will be needed? Exactly what radio horizon
> distances do you think you will be trying to cover with typical
> installations? Especially in disaster-impacted locales? Most of the links
> you
> will find in disaster-impacted locales will be local networks or
> point-to-point links - neither of which require high power *ESPECIALLY* on
> the amateur bands.
>
> If you think you will be setting up a 2.4Ghz SS hub with an
> omnidirectional
> pattern covering a radio horizon of 25-40 miles then I can understand the
> statement that you will need higher power - but so will all the stations
> trying to connect to you. That means they will interfere with each other
> AND
> with you and will just make an unholy mess of the spectrum being used. Its
> an
> issue you just can't get away from - its the nature of the beast.
>
> And while you are doing all this just how many people are you going to
> piss
> off that are running Part 15 networks? That's all the amateur radio
> community
> needs - a big black eye, especially if it occurs during an emergency.
>
>>
>> 2.  Antenna inefficiencies, e.g. snow or ice on the antenna,
>> the impact of various environmental sources such as acid
>> rain, soot, salt-containing rain or mist, etc., slight
>> misalignment due to unusual winds, etc.
>
> Would anyone like to put forth the word that applies here? Hint: begins
> with
> the letter "r".
>
> If you are using antennas that become misaligned enough to cause a problem
> with a link due to unusual winds then that tells me you are using
> high-gain
> antennas to begin with - which don't need the high power during regular
> operation. So when you are saying you don't want to have to run APC you
> are
> also saying that you will just run the link ALL THE TIME at the power
> level
> needed to overcome any possible impairment - whether the impairment exists
> or
> not.
>
> This is an even worse engineering practice than raising power levels to
> blast
> through an existing obstruction - you are just going to blast the signal
> out
> whether you need to or not.
>
>
>>
>> 3.  Seasonal changes, e.g. leaves not there when tests
>> were conducted show up in Spring, or new growth as a result
>> of taller bushes/trees, etc.
>
> I've been there when system designers haven't considered all the
> environmental
> conditions, especially with 11Ghz systems. Again, just blasting away with
> higher power is a poor engineering fix.
>
>>
>> Yes, there are reasons for the availability of higher-
>> than-1W power levels and they may be more rather than
>> less frequent.
>
> I'll repeat, use of high power with spread spectrum is self-defeating in
> the
> extreme, especially when the spectrum space is limited. If all you ever
> expect to have is one or two stations in any 25 mile radius using SS under
> Part 97 then have at it with your high power. If you ever expect to grow
> past
> that point, i.e. three or more stations, then you need to understand what
> use
> of more than the absolute minimum power needed does to the spectrum
> capacity.
>
>>
>> One key question goes to the mission-critical nature
>> of making and holding the link and the capacity to
>> locate multiple versus one-to-one sites.
>
> 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.
>
>
>>
>> IMHO, when one absolutely positively has to make and
>> hold the contact and cannot count on multiple link
>> sites then one needs QRO.  The regs nor the spectrum
>> planning cannot preclude QRO or it makes the band
>> unreliable for mission critical apps.
>
> The regulations don't preclude QRO, especially for emergency situations.
> But
> whoever is running that QRO also needs to understand all the ramifications
> -
> such as the liklihood of interfering with the local Part 15 network the
> American Red Cross has set up in their shelter to link PC's doing H&W work
> or
> inventory work, etc.
>
> tim ab0wr
>
>
>
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