Ron J wrote:
On Jan 25, 12:35 pm, wrote:
I didn't bother to read the ad, but if it can be calibrated to NIST
standards, yes.

You can also do it with a spectrum analyzer and a calibrated antenna.

--
Jim Pennino


I think my school will lend me a spectrum analyzer, but not sure if I
can get access to a calibrated antenna. One of my school projects
involves in measuring the field strength of a low power FM transmitter
mounted in a "smart" flyer. Really the flyer is just a toy helicopter
fitted with sensors and given a "brain" by the computer science folks.
The idea behind it is that it's suppose to monitor local traffic
conditions using a video feed and then it will broadcast some
pre-recorded messages via the FM transmitter warning on-coming drivers
of potential road blocks.

However, the drivers will need to tune their radio station to a
specified frequency. I'm not involved with the frequency stuff, so I
don't know how it's going to play out with the feds.

Anyway, I'm supposed to determine the range of the FM transmitter by
measuring the field strength. But I'm reading some propagation text
like Les Barclay's Propogation of Radio Waves and found out that field
strength varies with antenna height, distance from receiver and
transmitter, and also the landscape. I've also scoped out some FCC
procedures for measuring radio broadcast, and they have some 50,50
curves that I don't understand too much. But the FCC assumes that the
transmitter is fixed. In this thing, the transmitter is moving around,
so I'm having a difficult time figuring out how to come up with some
transmission range diagram.

The intent of my original question is to find out how someone would
measure it. I'm sure the balloon folks had the same issue.

"Real" calibrated antennas that meet FCC requirements with calibration
traceable to NIST aren't cheap.

Though if all you are doing is trying to estimate range and don't
have to send traceable data to the FCC, you could get a good idea
by using antenna modeling software and modeling the antenna in free
space.

--
Jim Pennino

Remove .spam.sux to reply.