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June 19th 06, 12:58 AM posted to rec.radio.amateur.homebrew

On 18 Jun 2006 10:41:25 -0700, wrote:

All,

I've got a brother who works for a consulting firm whose main customer
is Homeland Secrity.

What the feds want to do is to be able to communicate mil-spec digital
packets over low power links in the middle of a disaster-hit area
between squads of Guards deployed across a destroyed city.

They cannot assume that hams and ham equipment will be available, and
they do not want to carry heavy equipment into a city. They want to be
able to use equipment that they can readily commandeer from stores such
as Radio Shack.

That pretty much means CB radios. I have heard of hams working DX
using 5 watts of PSK on 10 meters using poor antennas, so that gives me
the idea that Guard units could form medium range mobile networks using
5 watts of PSK on 11 meters using wires dropped off bridges.

Eventually the hams that do get on the scene could set up a CB to HF
gateway so that the packets could make it out from the Guards to the
NGOs.

While I am more than willing to test this setup out for my brother on a
pair of CB radios, I told him I might need an STA from the FCC to
communicate data on CB channel 40. He tells me that in an emergency,
anyone can use any frequencies they want, any power, any mode. I told
him true, but that does not help me as an OEM getting fined for testing
out an emergency scenario in a nonemergency situation.

Suggestions?

The Eternal Squire

I for one think this is a bit hairbrained. But here goes...

Actually you can break the task down two several larger problems.

Is AM modulation suitable?

What connectors? The average CB uses one of ten different mic
connectors and of those the same type none are wired the same!

Forget internal mods, they are very different from unit and
some are surface mount construction. Also type acceptance
and operating rules) prohibit most data, image and modifications.

How will they power the CB radio? A 5W radio under full TX
modulation want about 15-20W of power (1.5-2A) SSB versions are
far more power hungry (2-4A on TX for legal radios and the import
illegals can run far higher.).

Radios vary widely from real junk to near decent so you need to find
examples of the worst to be sure your not encouraging an interference
generator.

At this time RS is closing stores and I think at most they carry only
a few (if any instock) different CB sets. You'd have better luck at a
truck stop!

What do thy expect to use for an antenna? The average CB set will
fry the finals if the antenna isn't tuned reasonably well.

You can test the basics using dummy loads before you get into
the STA.

FYI: GMRS radios present a better choice and are more widely sold.
GMRS being higher power thn FRS and often better radios for short
range (UHF FM) ops.

Allison

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