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    Is Russia safe from F-22 and Β-2?

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    Erlindur

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    Re: Is Russia safe from F-22 and Β-2?

    Post  Erlindur on Sat Jul 29, 2017 2:28 pm

    I've been wondering about something for a while now and I think this is a nice place to ask. My last encounter with electromagnetic wave physics was back in my university days, decades back and I do not have the will to look them up again, so sorry in advance if what I ask is stupid.

    OK, I have an X-band radar with a very narrow beam. Instead of simply sending pulses with it, I preform a typical amplitude modulation on them with a frequency of UHF or even VHF wavelengths. No matter what happens to the x-band carrier (due to stealth shape), wouldn't I get back the low frequency harmonic, provided I have an appropriate receiver listening? If my beam is narrow enough, maybe it is possible to get enough data for detection or even tracking, just by using its position when I get the harmonic back.

    Do you think something like that could work?
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    Singular_Transform

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    Re: Is Russia safe from F-22 and Β-2?

    Post  Singular_Transform on Sun Jul 30, 2017 2:32 pm

    Erlindur wrote:I've been wondering about something for a while now and I think this is a nice place to ask. My last encounter with electromagnetic wave physics was back in my university days, decades back and I do not have the will to look them up again, so sorry in advance if what I ask is stupid.

    OK, I have an X-band radar with a very narrow beam. Instead of simply sending pulses with it, I preform a typical amplitude modulation on them with a frequency of UHF or even VHF wavelengths. No matter what happens to the x-band carrier (due to stealth shape), wouldn't I get back the low frequency harmonic, provided I have an appropriate receiver listening? If my beam is narrow enough, maybe it is possible to get enough data for detection or even tracking, just by using its position when I get the harmonic back.

    Do you think something like that could work?
    Nothing prevent from you to do that ,but it won't make any benefit.


    First, the transmitter will be very expensive.
    Second, the low frequency signal won't match the resonant frequency of the phased array, means that in good case it will have no directional amplification .Bad case it will burn out the transmitter.


    And the returning signal won't have any amplification as well.


    The antennas works only with very close frequencies, say a 100 mhz antenna will works well with +/- 10 mhz
    A very high frequency antenna , like a 10000 mhz one will works well with +/-100 mhz frequency.

    It can works with wide band as well, but the amplification will be smaller at the edge.

    The data rate proportional to the frequency, say a 10 MHz means 10 megabyte .

    So, if you want to deliver a 100 mhz signal with a 10 GHz transmitter then it has to have 10 Gbyte bandwidth, and the 100 mhz will be so out from the resonant frequency it won't receive any signal at all practically.

    http://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/Borderless_Networks/Unified_Access/CMX/CMX_RFOpFreqDataRates.pdf
    https://en.wikipedia.org/wiki/Bandwidth_(signal_processing)

    Erlindur

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    Re: Is Russia safe from F-22 and Β-2?

    Post  Erlindur on Sun Jul 30, 2017 5:26 pm

    Yeah you are right but I was thinking a slightly different scenario. First not a phased array radar. I guess the math would be way too complicated. Maybe use one typical older generation conventional system.

    Second, I wouldn't dream of trying to get the reflection with the same hardware, that is why I said "provided I have an appropriate receiver listening". I was thinking about a separate receiver antenna (of the appropriate length) for the returning harmonic. One with its own circuit to amplify and analyze it and send the results back to the main radar's cpu. I only want it to work as a trigger confirming that we got a return.




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