HF Doppler RADAR Signal Examination

Discussion in 'Amateur Radio News' started by KA0KA, Feb 4, 2019.

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  1. KA0KA

    KA0KA Ham Member QRZ Page

    I want to thank everyone who has offered suggestions and info on the signal, as to N1SZ he and I spoke off this thread, a few days ago, I wrote him and thanked him personally for his help and am looking for ways to give credit where it is due.

    I removed the mislabeled video as not to have misleading info up there, why keep up a mislabeled video??? When it gets re-posted N1SZ as we have spoken in privet was going to be brought up for his help... All this was in privet communications. I can see how disabling comments can be interpreted in a negative light, I just thought it made a cleaner video with less clutter, but all those comments are restored, I did not want to have any misunderstanding there and sorry if by disabling them it somehow came across like that.
    Thanks again for all the help.
    Last edited: Feb 8, 2019
    K3DCW and N1SZ like this.
  2. N1SZ

    N1SZ QRZ Lifetime Member #233 Platinum Subscriber Life Member QRZ Page

    Great question. Here is somewhat of a crappy answer: It will depend on the type of receiver technology used. Clearly, greater bandwidth will help with resolution in most cases. Timing is always critical in pulse transmission (PRF/PRI) and the quality of the returned target signal. I may have failed to mention, modulation technique is just as important. Phase interferometry is a preferred technique in this received application. IQ analysis of the signal is very instrumental in determining targets from clutter.

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  3. N1SZ

    N1SZ QRZ Lifetime Member #233 Platinum Subscriber Life Member QRZ Page

    Always glad to help in any way possible. Our license is just that, a license to keep learning.......

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  4. N1SZ

    N1SZ QRZ Lifetime Member #233 Platinum Subscriber Life Member QRZ Page

    I also failed to mention that as far back as the DUGA, many HF Radar signals have had pseudorandom (binary and other) signals encoded into their transmissions to avoid spoofing. - (cited) multiple sources.. including Wikipedia.
    W1YW, KA0KA and WA1ZMS like this.
  5. KY5U

    KY5U Premium Subscriber QRZ Page

    Thanks. I worked on Marine radar for 10 years. I was putting itin the language I understood. An off the wall comment, the transmit signal looks a lot like an Orthogonal pattern.
    N1SZ likes this.
  6. N1SZ

    N1SZ QRZ Lifetime Member #233 Platinum Subscriber Life Member QRZ Page

    No problem. Concepts are nearly identical....except for the range and propagation issues.:)
    WA1ZMS likes this.
  7. KA0KA

    KA0KA Ham Member QRZ Page

    Had some time to re-edit this, thanks to N1SZ & K3DCW for helping with ID I think this should provide a basic sample of the signature.
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  8. KY5U

    KY5U Premium Subscriber QRZ Page

    I'd like to record that 3 pulse 2000hz (aprox) tone and play it back on the FCY to see if the radar responds. :)
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  9. K3DCW

    K3DCW QRZ Lifetime Member #212 Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    That 3-pulse emission right before the ROTHR (AN/TPS-71) burst is used to make sure the antenna is properly tuned. As one can imagine, when beaming massive amounts of power into a wideband antenna array, you want to make sure you won't blow-up or melt any components. You see similar emissions with a lot of frequency agile radars.
    N1SZ, WA1ZMS and KA0KA like this.
  10. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    BTW, when the first test USN ROTHR was installed at Comm Station Northwest (Southeast of Norfolk, VA), a friend of mine had the job of surveying the receiving antenna element locations. Extreme accuracy was required, within 1/10th of an Inch. The array had the appearance of dozens of square, white 'croquet hoops" on concrete pads, over a mile long, oriented towards the Caribbean. GPS was just coming into place and was used for the surveying.

    There was an auxiliary video display of the radar in the intelligence center at Atlantic Fleet Headquarters for a few months, where I was stationed. The appearance was that of large colored 'blobs" ranging across the Southern US, Gulf of Mexico and the Caribbean which seemed to be similar to propagation maps. I never saw any active target detection or tracking. Following the end of the Cold War, the array was dismantled and removed sometime in the mid 1990's. b.

    p.s. The term "Relocatable" OTH Radar, was widely winked at, since the antenna was no more relocatable than any permanent building or structure. The word in the intelligence community was that it was dreamed up as a way to differentiate the Navy program from other ongoing USAF OTH programs, in order to sell it to Congress. ;)
    Last edited: Feb 9, 2019

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