In article ,
jc wrote:

Probably the best (cheap) method would be noise with digital
transmissions (as per psuedo random code no need to crack the
encryption) on the correct frequencies. 1W dosn't sound much but with
the low recieved power of the GPS signal it dosn't take much to
overwhelm or confuse it.

The cellphone industry has ensured VERY low cost components eg power
output transistors/amplifiers for a few cents. No need for elaborate
environmental enclosures just attach balloon and battery stick a
ziplok bag over the electronics and release. To avoid ECCM attacks
change location immeadiately to another school, hospital etc although
a vehicle outside the Chinese embassy for a release point is a
possible.

The cost of hitting the balloons once they are released makes them a
rather assymetric weapon.

You're forgetting something.

Power.

For a 1 watt output, you're going to need a battery or other power
supply that can supply at least twice that for a significant period of
time. If you're going for a balloon launch, to get to significant
altitude, you're going to need a couple of hours of capacity, at
*least*. Increased weight equal increased balloon size, by the way.
With increased tankage for your lifting gas, and massively increased
transportation costs.

Not to mention, of course, that you're transmitting that 1 watt
omnidirectionally, which means that you're only going to cover a couple
of square miles with one jammer, at *best*. If you're going for a pure
white noise "drown them out" system, plan on a *hundred* watts or more
(to beat the directional antennas used on most modern weapons systems).
If you're going for digital spoofing, use lower power levels, but spend
a lot of money on electronically-steerable transmitters and high-end
hardware to make the signal work past the dozen or so GPS sats in view
at any one time.

Suddenly, the "$5 balloon-borne jammer" is a "$500 balloon-borne jammer
that only lasts a few hours."

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.