Backscatter Radar

[VK4CZ]

Brilliant news Andrew and Phil.... well deserved.

[VK2ZRH]

And well deserved

Two VKs get an RSGB trophy? Isn't that unheard-of ?

73, Roger Harrison VK2ZRH

[VK4MIL]

Well done guys congrats

[VK5BC]

Well done Andrew & Phil.

Despite the negativity from some of the so called 6m Guru's, there is life after analogue TV.

Great stuff.

73 Brian
VK5BC

[VK5PO]

Sterling Effort gentlemen...

Well deserved accolades for your tireless research and developmental work
in this field.
Justly acknowledged

Well done Andrew and Phil.

73, John

[VK3BJM]

And well deserved

Two VKs get an RSGB trophy? Isn't that unheard-of ?

73, Roger Harrison VK2ZRH

Surely this is better than winning the Ashes?

Well done, Andrew and Phil!

73,
Barry
VK3BJM

[VK3OE]

Hello,

During some nice 6M DX today, I did a run of the chirp radar on 28MHz @ 60 degrees just to see what was there.

28MHz Chirp Radar, 60 degrees, 7Dec 2013, 9:03UTC

This is a good indication for 6m possibilities, it does not necessarily mean that 6m is open to over 11,000km, but looking would be most productive! it may be that 3Es is letting 6m down, but 1Es and 2Es
are certainly strong enough for 6m. The distance between each reflection determines if the reflection is Es or F, Es 2500km max, F 3000Km min. Strong Es will blanket any response from a higher F layer.

Unfortunately my rotator is broken at home QTH so cannot look in any other direction.


73
Andrew
VK3OE/VK3OER

[VK2FAK]

Hi all.

Its good your continuing with that work and with some interesting results....

Now without me going back and checking..(hey its sunday Morning..hihi) what sort of antenna are you using on transmit and receive.....

I have always beeing interest in my HF loop in respect that it picks up signals coming in at many elevations, its not always the low elevation signal thats doing the work, so guessing that a beam may not always be the best choice for all conditions..many are using beams for 6m and I was wondering if something different may lead to better outcomes..?

John

[VK3OE]

Hello John,

Well, you raise a most interesting issue,,,
Firstly, when using the chirp radar I use a 3 element 28MHz yagi for transmit and a 2 element yagi for 28MHz receive at the remote. On 6m, I use 6 elements for transmit and receive.
That is the short answer, now for the issue of different radaition angles....
On 6 m and 10m, there is a vast difference in the performance of the home station and the remote. This difference in performance mostly favours the remote but sometimes the home station outperforms the remote. The radiation angles for 28MHz are mostly OK, I think, but only because of the small antennas, as you have indicated. On 6m the radiation angel (angle) effect is very evident, and sometimes stations with antennas at 4m above ground out perform the remote. Another observation is that 11 elements on 6m seem to mostly work better than 6 elements, better than the increase in gain would indicate.
So, I am coming to the conclusion that there is no shuch thing as the optimum station that will always work better especially on 6m and maybe on 10m. On 20M VK3MO has demonstarted that a big stack does indeed out perform anything else, all the time, but that is 20m.

On 2m and above is another story altogether, see my article about this, see "Facts and myths about tropospheric ducting" at http://www.df5ai.net/Material/articles3 ... lesDucting
you can down load the complete article.

So, The radiation angles are a critical issueand one worthy of a lot more study.

73
Andrew
VK3OE/VK3OER

[VK2FAK]

Hi all....

Andrew....I wonder have you moved on to test the theory..

Have you tried to test whether what you are seeing on your charts works out the same in an actual link between 2 operators..and the same when you see nothing.....is there a link or not between the same Op's..


John

[VK3OE]

Hello John,

Love your interesting questions.....

The chirp radar is set up so that I transmit from VK3OE and receive at VK3OER, 145 km away. The result of this is that often there is Es around but there is no common Es for a signal from the transmitter to get to the receiver, that is Es !!!
However, when the radar sees good returns on 6m then there have ALWAYS been contacts happening, so in one sense the 6m radar is less sensitive than direct 6m contacts. But, considering that I am using 50 watts and relying on surface backscatter is is a wonder that the radar works as well as it does.
Sometimes the radar will see propagation conditions good enough for multi Es contacts but there are no operators present.

By using 10m for the radar, it is a lot more sensitive to nEs and often is a good predictor of possible 6m contacts, as is the case with the most recent record above.

73,
Andrew
VK3OE/VK3OER

[VK3OE]

Hello,
Here is the 28MHz radar echo from today when KH6 and KH7 were worked from VK3.

There is 1E and then 2F hops, the SF is around 123 so is probably sufficient to support 50MHz on F layer propagation.

28MHz Chirp radar @ 50 degrees, 4:50UTC 26 Dec 2013

If there was strong Es past the first Es hop then the F layer would be blanketed and shorter skips would be evident, see post above for 7Dec 2013 where there is only Es evident.

I have put on the ionspheric map the approximate locations of the radar reflections to show how they coincide with the ion density and the geomagnetic equator towards KH6/7.

Approximate location of radar reflections for 05:00UTC 26Dec 2013.

The JA's appeared later in VK3 and 7 as the ion blob mover further West, the Es linkage to F remained so the JA opening into VK3 and 7 was very selective, no JAs heard at VK3OER but 5x9 at VK3OE.


73,
Andrew,
VK3OE/VK3OER

[VK3OE]

Hello,

Here is the 28MHz radar return taken 16 Feb 2104 during a 6m opening to JA at around 03:00 UTC.

28MHz Chirp radar @ 0 degrees, 03:00UTC

I have shown the distances between the hops at 2250km, 4050km and 2250km. There is no Es present and the propagation to JA is only by the F layer. If there was Es it would be present before 2250km.
The first hop is up to the F layer and down to the sea surface which provided the first reflection. The second hop is longer as it is the trans-equatorial hop at 4050km, while the third hop is back to 2250km. Total path length measured is 8550km, the 6m contacts to JA were 8200 to 8900km. SSN was 135and SF was 162.

This is classical equinox propagation where there is no Es present as the Es is at a minimum occurrence at the equinoxes.

This is contrast to the solstice where Es is most likely present and can provide a link to F or even provide very long haul multi-hop Es.

So, the first radar response above was nice and simple, completely dominated by F layer propagation.

Here is the next measurement at 04:40UTC, completely changed and now dominated by E/F mixed modes, now out to 12,000km.

The first hop is via F, but after things get a bit messy.

28MHz, 0 degrees, 04:40UTC 16 Feb 2014

See what you can make of that, it is still open to JA on 6m but signals are weak.

73,
Andrew
VK3OE/VK3OER

[VK2ZRH]

Brilliant stuff, Andrew!

That second sounding is a doozy, getting very complex where the signals cross the equatorial region. In days of yore, analysing that would be have been a suitable PhD research project for some hapless physics student.

[VK3OE]

Hello,
Here is the 28MHz radar picture at 70 degrees taken 2:09 UTC 24 dec 2014. I tried 50MHz as well but the Es link was not good enough. VK4 and VK2 into K land around this time.

28MHz Chrip radar @ 70 degrees.

The direct signal is at 800ms, 6Es hops evident, signal stops at 95ms from the direct signal at 14,250km.
The signal at 937ms is the first around the world signal.

73,
Andrew
VK3OE/VK3OER

[VK4BZ]

Fascinating. Glad you have the know-how to do it, Andrew.

[VK3OE]

Hello Again,

After a lot of work I have finally converted the backscatter RF chirp Radar concept into an acoustic backscatter radar (SODAR) for measuring the wind in the lower 300m of the atmosphere. The system provides the highest resolution measurements of the wind speed and direction when compared to any other technology or system available today. It has 1m vertical resolution and measures the wind to 300m every 9 seconds.

Wind Change at Melbourne Airport

The wind direction is on the left, wind speed in the middle and the backscatter signal level is on the right. A passing frontal change is clearly evident.
The wind speed is obtained by using an anemometer at 10m and adding the wind profiler data to the anemometer data to achieve a complete wind profile to 300m.
Signal-to-noise is above 10dB at 300m. Vertical red lines are excess noise due to aircraft passing close to the wind profiler.

The whole system is visible in Google Earth street view by going to the corner of Sunbury Road and Oaklands Road looking back towards the airport. The black boxes with white tops on the left (East) is an aircraft wake turbulence detection system which uses the acoustic chirp, the acoustic chirp wind profiler is on the right (West) up near the portable shed, black boxes with white tops again.

A long journey, 16 years from original concept to a working system.

Andrew
VK3OE/VK3OER

[VK3ZAZ]

yay maybe now they will turn off those 49 MHX profilers

[VK3OE]

Hello Steve,

Well, now with the critical bottom 1000ft covered, and satellites covering down to 1km, there is very little need for the 49MHz devices. It is just that BOM will take a little time to get their act together!!

regards.

Andrew.

[VK3OE]

Hello,
Here is the 28MHz bistatic chirp radar return for 02:07UTC today at an angle of 60 degrees. It shows the direct signal at 0km and the returns out to 14500km.
The first return is the first Es hop which goes from 700 to 1500km.
The next 3 hops are all via F layer from 2800km out to 10500km with 3000km between hops.
The last three hops apear to be Es over N America because the spacing between the returns is around 1500km instead of the 3000km spacing for the F layer hops.
If there are multiple Es hop, the Es will blanket the F layer return so only the Es will show up.

Transmit power 50 watts, Receiver 145km from Transmitter, Transmit antenna 4 el at VK3OE, receive antenna 2 el at VK3OER