Be very careful pointing lasers upwards...
73, and thanks,
Dave (NK7Z)
https://www.nk7z.net
ARRL Volunteer Examiner
ARRL Technical Specialist, RFI
ARRL Asst. Director, NW Division, Technical Resources
On 5/13/21 4:06 AM, Mike Martin wrote:
Charlie considered using a mounted green laser sight. During the winter months when
the Sun goes down it makes it very difficult to see where you're pointing. If
I remember correctly, green seems to produce the most noticeable color for day and
nighttime spotting.
Be safe,
Mike
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On May 13, 2021, 6:12 AM, at 6:12 AM, Charlie Delta via RFI
<rfi@contesting.com> wrote:
Hi Mike
I have studied the various datasheets for Ultrasonic receivers. Most
have a broad beam width that is something like more than 60 degrees.
This includes the widely used Kobitone transducer. I have check many
datasheets including those from Murata, Monacor, Kobitone and those
from many expensive USA made sonar transducers. All seem to have
similar sensitivity figures all the Kobitone transducer appears to be
6db more sensitive. I just assumed that the perfect FD ratio with the
perfect parabolic shape when combined with the broad beam-width would
be sufficient to flood the transducer.
I will be using a laser beam and LED endoscope light source and I will
test all of the variables as I have some time.
I have also been informed that the Radar Engineers unit uses the 25khz
frequency rather than the 40khz frequency. This apparently makes a big
different in the usable detection range. So the assumption that 40khz
would produce similar results to the RE unit is clearly incorrect since
the lower detection frequency would have a propagation distance
advantage.
73CraigVK3OD
"One aspect of the design that may be
overlooked is the beamwidth of the
ultrasound transducer itself. Even
with a proper F/D ratio, the transducer
may not fully illuminate the reflector
or instead spill over the edge, both reducing
gain. The transducer's sensitivity is
another obvious factor. Getting the perfect
reflector geometry won't mean much if
it's not matched to the transducer beamwidth.
Mike, K8CN
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