Backscatter Radar

[VK2ZRH]

As always, great stuff Andrew.

[VK3OE]

Thank you Roger.

I acquired a 4 el fo 28Mhz and it has improved the system quite a lot. Only requires 16 averages now so system gain is 45dB below noise in a 2Khz bandwidth.

[VK3OE]

Hi,

Here is the pic from the backscatter radar for today at 01:00 UTC on 28MHz @ 80 degrees. The propagation was 1 x Es, 1 X F, 5 or maybe 6 X Es to 13500km.

28MHz Backscatter @ 80 degrees.

.

The Es did not manage to be strong enough to blanket the F layer at 3900km. As A result the 6m link to the Central America was relying on the F hop and so even though there was Es for the rest of the way, the F layer hop was not strong enough to get 6m signal through.

73,

[VK2ZRH]

Great stuff, Andrew !

That 1F hop in there tells you that the Es was 'patchy', with holes between the clouds.

Lots of Es to 10,000km+. Not surprising, seeing as we're a week past the solstice.

[VK3OE]

Hello,

Here is another application of the bistatic backscatter chirp radar, this time using acoustic siganls with the antenna pointing straight up (so it is a SODAR instead of a RADAR) and uses the same chirp pulse compression signal processing as the RADAR above. The chirp SODAR yields 33dB of processing gain and a resolution of better than 1m. Output power is 130dBa and antenna diameter is 1.2m.

Inversion layer at 620m

The picture shows the signal-to-noise ratio of the backscattered acoustic signals from ground level of 150m ASL to a height of 750m ASL. An Inversion layer is evident at 620m at the start of the above record which is 3 hours long. At the start of the record at 7:30 (left hand side at 180 minutes) the Albany 2m beacon was 5 X 5 and dissapeared around 9:30 (at 60 minutes).

As the sun was heathing the surface and causing rising convective plumes (strong red signals near the ground) to disrupt the inversion layer by pushing it upwards and dispersing it, the Albany beacon signal dissapears. This effect becomes very evident after 8:30AM (at 120 minutes).

When the sun heating goes away at night the duct can reform over land if the subsidence is still present in a high pressure system.

If a high pressure system is present over the sea, then because there is no convective effect, a duct can remain present during the day, as we have seen today with excellent signals from VK7 to VK3 all day with an over-sea path.

The convection also increases the backscattered acoustic signal level above 300m (compared to that at the begining of the record) due to increasing air turbulence from the rising convective cells.

The signal backscattered from the inversion layer is up to 10dB above the backgorund acoustic signals. Measurements are updated every 28 seconds.

As the system is at Melbourne Airport, it is subject to aircraft noise which shows up as the vertical red lines.

This result is from a very high resolution, precision wind profiler which is the subject of several Patents, applied for and granted.

73,

[VK2ZRH]

That is just awesome, Andrew.

Keep up the good work.

[VK3OE]

Thanks Roger.

Happy New Year to you and Val.

73,

[VK2ZRH]

And the very same to you guys.