Backscatter Radar

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Re: Backscatter Radar

Postby VK5PJ » Thu Jun 14, 2012 5:23 pm

Andrew,
when do you find time to sleep? looking bloody good, now all we need is the HPSDR group to decide on a hardware spec for a compact sounder?

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Re: Backscatter Radar

Postby VK3OE » Thu Jun 14, 2012 5:36 pm

Hello Peter,

I am reliably informed by Phil Harman (VK6APH) that the HPSDR hardware with the operating chirp modes is nearly in production. There is also a PC application for the chirp decode. (see the HPSDR pages). There is also the possibility of a small LINUX based processor for signal processing and a GPS module and 100W PA pin switched so that the radar can be operated in monostatic mode. I am also informed that many chirp modes are already programmed in so we wait with great interest. As this system is GPS locked it can also be well used as a beacon and provide a direct reading distance. Phil has programmed in the beacon ID capability using coded forward and reverse chirps. The possibilities are most interesting. :D

I am now also speculating how good an early warning is provided by the 28MHz radar signals as an indicator for 50MHz. There is of course a much lower probability of 50MHz openings that 28MHz openings but given past experience in previous sun spot cycles when 28.885 was widely used as a liason, this idea looks very good.

Roger may be able to comment further, please?

73,
Andrew.
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Re: Backscatter Radar

Postby VK3OE » Tue Jun 26, 2012 7:39 pm

Hello,

I have updated some of the comentary on the twice around the world result and the 7 hops Es (see the results in an earlier post). A few more ideas have come to me in the last week so I thought that it would be worthwhile to share them.

I am also in the process of further observations so will post them if anything interesting turns up.

73
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Re: Backscatter Radar

Postby VK3OE » Thu Jul 12, 2012 10:34 am

On 14 June I posted a result showing 7 hops of Es out to 11,000km.

In the most recent publication of GippsTech 2011, pages 91 to 123 Roger Harrison has an very extensive paper on Es " Sparodic E - MUF Myths, Summer Solstice Short Path Propagation and Forecasting Openings". This paper is well worth a read!! My particular interest here is Roger's description of SSSP (page 111 to 118 ) where he reports after much analysis that "The remaining option is that SSSP propagation is supported by multi-hopEs, nEs, Figure 25. The next step is to find the evidence to match the contacts."

So, The measurement of the 7 hops Es from the radar is indeed the evidence needed to show that summer solstice short path propagation is dominated by multi hop Es.

This is excellent news as it indicates that there must be many opportunities for long distance Es contacts on 6m, many more than previously suspected.

So, I could say if Es is around, forget the local contacts (VK) and look further out. 110 to 150 is much more important if this multi hop Es is as common as it seems to be. Good antennas and good operating practices will be rewarded!!!

73
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Re: Backscatter Radar

Postby VK3OE » Thu Aug 02, 2012 2:42 pm

Hello,

Here is a radar trace for 28MHz, 0430UTC, 2 August 2012, transmit 80- receive 260 deg. averaged 64 times, processing gain = 54dB

Trace shows out to 2nd F hop plus twice around. No Es showing so no possibility of 6m linking to F, nothing on 6m from the radar.

28MHz, 0430UTC, 2 August 2012, 80-260 deg..png
28MHz, 0430UTC, 2 Aug 2012, TX 80 - Rx 260 deg


Here is the CW skimmer spectrum showing the direct and the first around the world signal delayed from the direct.
This indicates that a CW contact could be made under these conditions although the S/N is very low and would push CW skills a bit, but achievable.
41,000km on 28MHz!!! Would need antennas to be side on to get direct signal to the noise.

CW skimmer 28MHz, 0450UTC, 2 Aug 2012.png
CW Skimmer Spectrum showing direct and first around the world signals.


73
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Re: Backscatter Radar

Postby VK2ZRH » Thu Aug 02, 2012 7:31 pm

Blaaardy hell, Andrew. Brilliant stuff ! :mrgreen:

73, Roger Harrison VK2ZRH
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Re: Backscatter Radar

Postby VK3OE » Sun Dec 16, 2012 1:55 pm

Hello again,

Here is the latest effort with the backscatter radar, three times around the world on 28MHz.
New Picture (7).png
Three times around the world on 28MHz

There is about 15dB loss between each around the world signal indicating that the loss is linear with distance (not square) which indicates that the signal is guided in one plane.
There were very good openings to Europe at the time of this measurement which followed a proton event.
Now all I need to do is to get 6m to do the same.
It also shows that a 41000km contact on 28MHz could have been possible also.
Here is the CW Skimmer picture also showing three around the world signals, the third around the world is just visible in 6 of the chirp traces.
CW Skimmer, 28MHz, Three times around.png
CW Skimmer Showing around the world chirps.

The first trace is the direct chirp signal (one second chirps of 500Hz to 2500Hz) while the second trace is the first around the world signal. With beams side on (to remove the direct signal completely and pointing 150 degrees and 330 degrees the CW Skimmer traces indicate that a CW contact could also have been made on 28MHz over a distance of 41,000km, the longest possible contact.

Transmit was from VK3OE at 150 degrees, receive was from VK3OER at 330 degrees.

Andrew.
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Last edited by VK3OE on Sun Dec 16, 2012 9:12 pm, edited 1 time in total.
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Re: Backscatter Radar

Postby VK2ZRH » Sun Dec 16, 2012 2:43 pm

Phe-bloody-nominal !

Next trick - four times :?:

You'll probably need a 5-over-5 LFA Yagi array at Harcourt and a bit more wick at Ferny Creek :wink:

Keep it up, Andrew 8)

73, Roger Harrison VK2ZRH
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Re: Backscatter Radar

Postby VK3OE » Thu Dec 27, 2012 8:57 am

Hello,

Just in case anyone wishes to follow up on how this chirp radar works and some of the results achieved, I have published an article in AR for December and a slightly shorter version in DUBUS 4/2012. I look forward to you questions.

Good reading when there is no nEs.

73.

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Re: Backscatter Radar

Postby VK3OE » Sun Apr 28, 2013 3:34 pm

Hello,

At its AGM on 20 April the RSGB awarded the Wortley-Talbot Trophy jointly to myself and Phil Harman "to recognise outstanding experimental work in amateur radio" for the work on chirp modulation.

This award is indeed a great recognition by the RSGB for the chirp work and Phil and I are very honoured.

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Re: Backscatter Radar

Postby VK4CZ » Sun Apr 28, 2013 4:08 pm

Brilliant news Andrew and Phil.... well deserved. :D
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Re: Backscatter Radar

Postby VK2ZRH » Sun Apr 28, 2013 4:08 pm

And well deserved :D

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

73, Roger Harrison VK2ZRH
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Re: Backscatter Radar

Postby VK4MIL » Sun Apr 28, 2013 4:09 pm

Well done guys congrats
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Re: Backscatter Radar

Postby VK5BC » Sun Apr 28, 2013 8:32 pm

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
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Re: Backscatter Radar

Postby VK5PO » Mon Apr 29, 2013 7:39 am

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
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Re: Backscatter Radar

Postby VK3BJM » Mon Apr 29, 2013 10:51 am

VK2ZRH wrote:And well deserved :D

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

73, Roger Harrison VK2ZRH



Surely this is better than winning the Ashes?

Well done, Andrew and Phil!

73,
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Re: Backscatter Radar

Postby VK3OE » Sat Dec 07, 2013 7:31 pm

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 deg, 7Dec2013_903UTC.png
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
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Re: Backscatter Radar

Postby VK2FAK » Sun Dec 08, 2013 7:38 am

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..?

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Re: Backscatter Radar

Postby VK3OE » Sun Dec 08, 2013 10:27 am

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
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Re: Backscatter Radar

Postby VK2FAK » Mon Dec 09, 2013 9:24 am

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..


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