Radio Detection Basics

Forward scatter



HROfft is a freeware authored in Japan. It is the software of choice for the Japanese HRO group.

The software records a FFT image at 10 minute intervals. The left and right edge of the image has the audio frequency axis running from 0 to 1200 Hz. The user can select a narrower range to meet his or her needs. If there is a carrier at 500 Hz then you can set the listen for echoes to say, 700-950 HZ and avoid the carrier in the counts. There is also a volume control built into the program.

HRO 10 min Image

In the image above I have the program set to only count signals between 870 Hz to 1200 Hz as indicated by the bar on the left vertical axis. At the bottom of the image is a small signal strength indicator with 10, 20, and 30 dB lines. Spikes with blue instead of yellow are not counted as their signal strengths were below the triggering level. The solid bluish line is a low power ( a few watts) TV translator station. At about 1556 UT and continuing until 1600 UT is a nearly parallel line which is caused by an aircraft (WestJet 736 in this case) flying nearly parallel to the low power TV station near Oliver/Osoyoos, B.C. Jets flying directly to and from the carrier shows a S-curve Doppler. When worked out it shows a typical cruise speed for an airliner in level flight. The carriers producing the echoes are from Utah, Montana and Oregon.

Not so long ago anyone using HROftt would have to hand record the echo counts per hour.  The echo count for the ten minute period is summarized as can be seen in the upper left header information. It list the date 08-09-13, UT time, and meteor count of 26. There was no way to get an hourly count without looking at each image for the hour. This is no longer the case. Cologramme/Color Lab has a selection that will scan the png image and summarize the duration of echoes and the echo count for each 10 minute period. It then produces six files for duration and counts for each of the three power levels.

To down load HROfft go to:


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