Digital Interference 40 meters

Discussion in 'Ham Radio Discussions' started by K0UO, Jul 14, 2021.

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  1. KP4SX

    KP4SX Premium Subscriber QRZ Page

    Occam's Razor again - If its an attempt to 'jam ham radio' its pretty lame and pathetic. Six weenie discrete carriers on one band doesn't seem to qualify. Meanwhile, Cubans are hamming, emailing, posting on Facebook, etc, etc
     
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  2. W0IS

    W0IS Ham Member QRZ Page

    I have no doubt that the Cubans are doing it, and that they're doing it for some nefarious purpose. But the "jamming message traffic in and out of Cuba" makes no sense. First of all, and most importantly, I have seen zero evidence that there was any kind of message traffic in and out of Cuba relating to their current unrest. I have seen Cuban hams on the air (admittedly, just FT8, but nobody has told me that they've stopped hearing Cubans on other modes).

    Secondly, it seems like it would be very difficult to jam such traffic, and what they are using would not be effective. They're only jamming a few discrete frequencies on 40 meters, as far as I've been able to determine. If I really wanted to send a message to Uncle Jose in Miami that I had survived the riots, then it seems to me that 80 meters would be a better choice of frequency. Or send it to someone on 20 meters and ask them to make a phone call. (Believe it or not, we have a third party agreement with Cuba).

    What actually does make some sense is that the Cubans want to make navigation in the Caribbean more difficult and dangerous, to make American and other boat owners more reluctant to come down and pick up refugees. The last time around, Ol' Fidel actually encouraged that activity, and sent people he didn't like away from Mariel, but they might have decided to handle it differently this time.

    If they want to be prepared to jam marine communications, and show the world that they are ready to do so at a moments notice, then keeping the transmitters fired up on 7 MHz is one way of showing that they are ready. I suspect they have crystals for the other frequencies they would need. It would be interesting to know if they are doing any sabre rattling on VHF marine frequencies. If they want to be in a position to discourage American boats from showing up, one good way to do that would be to suggest the possibility that channel 16 could be jammed right at the time that the boat is experiencing some kind of unfortunate "accident".
     
    Last edited: Jul 21, 2021
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  3. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I agree. And also why do they need help from Venezuela, reportedly, to jam marine HF frequencies?

    Maybe all the good jammers are busy on R. Marti, and all they had available was a big noisy tobacco dryer. So they took the RFI filters off, if any, and connected an antenna. o_O
     
  4. W2AAT

    W2AAT XML Subscriber QRZ Page

    Bring the country to a standstill ... restrict the flow of 1955 - 57 Chevrolet repair parts!
     
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  5. W0IS

    W0IS Ham Member QRZ Page

    If you want to do effective jamming, then you need to be able to fill in gaps in your skip zone. When the Soviets were jamming western broadcasts, they had a problem with higher frequencies, since their own jamming transmitters were too close to the listeners. They solved this problem by having agreements in place with their European satellites. For example, the transmitter in Gorky could jam the Radio Free Europe 21 MHz program to Hungary, and the Hungarian jamming transmitter could jam the Radio Liberty 21 MHz program to Russia.

    If you have jammers in both Cuba and Venezuela, you can probably blanket the entire Caribbean pretty well if you need to. But if you have transmitters only in Cuba, you'll probably have some gaps.
     
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  6. K4PDX

    K4PDX Ham Member QRZ Page

    You guy should hear it in South Florida, basically all of 40m phone is being jammed/wiped out with a s9+10-15 from 7.105Mhz-7.182 and some other spot just above.
     
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  7. W0PV

    W0PV Ham Member QRZ Page

    At 20:45Z 072121 I am hearing many of the 40m QRM "streams" also on their second harmonic at the top end of 20 meters.

    Here in Tampa Bay its 14 MHz signal is down in strength considerably but can't tell if that is from propagation, antenna gain/loss differential, or just poor tuning at the source. (sample audio clip from approx 14310 kHz)

    Being such an unfocused emission adds to it not being very efficient or effective for any intentional "jamming" purpose. Just a harassment? :rolleyes:

    To me the noise audio "fingerprint" just sounds more like nasty switch-mode PS RFI, ie like some wall-warts or other poor designs I have encountered.

    So how about this explanation instead -

    Cuba on a greener path with new 10MW solar power plant

    or

    China donates solar photovoltaic power systems to 5,000 Cuban households

    :(
     
    Last edited: Jul 21, 2021
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  8. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    But the jamming/noise is heard at night too. I didn’t see anything about batteries in the articles.
     
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  9. K8XG

    K8XG XML Subscriber QRZ Page

    And that is not what my Solar noise sounds like on many systems I have tested; better ones I still own. And Solar Charge Controllers tend to "swish" and march down the band; and go silent at night. Massive 10MW bank was setup in 2019 and home systems have no way to be such a large ERP.

    Next, what about the jamming worms that have followed "certain" people at times?
     
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  10. K8XG

    K8XG XML Subscriber QRZ Page

    Up hear in NW-Ohio it is mostly all in late afternoon/night; I have detected it in early morning at the beginning of this thread and disappears here 8:40-9-ish am. Propagation loss from my site/antenna
     
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