Ron J wrote:
So I was doing some reading and one article mentioned that a group
mounted an FM transmitter on a hot air balloon. I was also researching
on the methods used by the FCC to measured field strengths. So how does
one go about measuring field strength levels if a company somewhere,
somehow, sometime decides to mount their transmitter on a hot air
balloon to avoid building a tower?

Because the communications are likely to be line of sight, you could use
inverse square law equations to predict the signal strength.

Would the FCC procedures still be valid? I wondering how the field
strength tester would go mobile 30 meters from the radial or
measurement point if the transmitter is changing position constantly.

FCC test procedures? How about FAA procedures? Keep in mind that with
balloon launches such as this group does, there are notices issued
warning aviators and air traffic controllers about it's existence. If
you poke something any higher than 700 or 1200 feet in the air
(depending where you are), you're in controlled airspace. You must
notify the local flight service station and provide position information
IN ADVANCE.


Jake Brodsky, AB3A
PP-ASEL-IA, Cessna Cardinal N30946 based KFME

Jake Brodsky ) writes:
Ron J wrote:
So I was doing some reading and one article mentioned that a group
mounted an FM transmitter on a hot air balloon. I was also researching
on the methods used by the FCC to measured field strengths. So how does
one go about measuring field strength levels if a company somewhere,
somehow, sometime decides to mount their transmitter on a hot air
balloon to avoid building a tower?

Because the communications are likely to be line of sight, you could use
inverse square law equations to predict the signal strength.

I was reading the problem as "since the balloon is moving, how can
you even fix on a pattern"

A lot of that isn't so much about field strength as pattern. They want
that controlled. And that's arrangeable when the antenna is fixed.

But if the antenna is moving about, then the pattern will change as
it moves, so you can't guarantee that it won't interfere with that
station in the next town over, while a fixed antenna would allow some
sort of directionality to provide a shadow in that direction.

Reminds me of people using 2M FM in the early seventies, from
small airplanes. They had no problem with a handie-talkie's low
power output, they had all kinds of problems with not being
able to control it so transmitting on a popular frequency would
trigger a bunch of repeaters at one time.


Michael VE2BVW

On Jan 25, 8:14 pm, Jake Brodsky wrote:
Ron J wrote:
So I was doing some reading and one article mentioned that a group
mounted anFMtransmitteron ahotairballoon. I was also researching
on the methods used by the FCC to measured field strengths. So how does
one go about measuring field strength levels if a company somewhere,
somehow, sometime decides to mount theirtransmitteron ahotair
balloonto avoid building a tower?

Because the communications are likely to be line of sight, you could
use
inverse square law equations to predict the signal strength.

Actually, no, inverse square (free space) will underestimate the
received signal strength. There's also a "height above the ground"
factor that would need to be taken into account for UHF and VHF links,
because the ground reflections are significant on both ends of the
link.

A program called Radio Mobile (google for it) can do the modeling over
your terrain.
Or, you can probably find one of the quick approximations for uniform
terrain. The usual model is called Longley-Rice, but Bullington has a
quick approximation.