On 6/2/2011 2:43 PM, Jim Lux wrote:
On 6/2/2011 11:07 AM, John S wrote:


In addition to that, I think the emission is frequency-hopping and may
have a duty factor associated with the scheme. I think he may need a
peak-power capture scheme.

It doesn't hop, per se, but it does pulse.


Also, how is a field strength meter calibrated for emitted power with
all the variables involved?


It isn't..

The field strength meter measures power density (W/sq meter) or field
(V/m), and you have to figure out how that relates back to transmitted
power.

The OP wasn't actually reading it in power, he was using the meter as a
sort of transfer standard. i.e. say it reads linearly in relative power
from 0-100. You put a known 1 W source at 10 feet, and it reads, say, 88.

You put your unknown at 10 feet, and it reads, say, 44, so you calculate
that the source must have been 1/2 Watt.

The problem is that you're really making more of an ERP (Tx power +
antenna effects) measurement assuming an isotropic source/meter, which
can easily have 10 dB of error from a variety of factors.

That makes sense. But, what about reflections, exact positioning, etc?
For example, in a low-signal location, moving my cell phone a fraction
of an inch can change the signal from "no connection" to two bars. In a
room with light fixtures, power wiring in the walls, picture frames,
computers, etc, I doubt the reading can be of much value. It might be
better to move the detector all around while recording readings to get
an average.

But, you know all that.