On 1/5/16 10:46 AM, David Gilbert wrote:
I've suggested before that it should be possible to attach something
like a Softrock to a drone along with a small 3-axis sampling
antenna. The output could either be stored in memory or fed real time
back to the ground via some sort of link. The drone could be
programmed via GPS (or simply positioned via a tether) to run
concentric circles around any existing antenna in place at it's normal
location to plot the radiation pattern. The result would take into
account not only the antenna itself but also the impact of its
surroundings (terrain, buildings, other antennas).
I started to work on this using a powered paraglider and a GPS.
Actually, what you want to do is put the transmitter on the drone (it
can just step through frequencies and various axes of antennas). The
recording of the data gets done at the (fixed) antenna location.
SRI did this with RELEDOP among other systems, hanging the probe from a
helicopter 30 years ago. There's another form used for some broadcast
installations (there's a cool spherical probe that measures both E and H
fields in all 3 axes at once)
There's a lot of complexities in actually doing it.
1) you need to be far enough away to get a good pattern, and that
increases the flight time needed.
Say you're 1000 ft away, then a complete circle is 6280 feet (or about a
mile). If your probe goes 10 mi/hr, that's 6-7 minutes per circle. And
you're going to want to do different elevation angles, etc.
2) Wind is a bigger problem than you might think. A 10 mi/hr wind makes
for a very slow upwind leg. Even 5 mi
The DJI Phantoms have a top speed of around 30 mi/hr, which helps a lot.
They claim an endurance of 20+ minutes, so you can get about 10 miles of
measurements out of them.
Today, there's all kinds of "programmable path following" too.. so it's
a lot more practical. You can preprogram the circles (or squares or
hexagons or whatever) and easily log the GPS data as you go.
It's probably a several month sort of project.
I don't think it would take too much engineering or cost to put
something like this together, but I suspect that not many people would
be willing to pay to cover the hassle of doing so. Maybe cell tower
owners ...
I still think it's an interesting idea, though.
73,
Dave AB7E
On 1/5/2016 8:05 AM, Chris wrote:
## whats needed is a ham version of consumer reports.
Jim VE7RF
Steve and Ward's Tribander comparison book is the closest thing we
have. Too bad it's so much work to set up a fair antenna test range;
I would love to see dozens of antennas compared. Of course, it could
put some people out of business....
Chris
KF7P
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