DMR Interference on 435.350

Discussion in 'Satellite and Space Communications' started by K6LCS, Aug 27, 2018.

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  1. WE4B

    WE4B Ham Member QRZ Page

    I really miss AO-27, that was a fun bird on which I made LOTS of contacts. I just wish I had been as serious logging them as I am now.
     
  2. WD9EWK

    WD9EWK Ham Member QRZ Page

    Hi!

    Getting back to the DMR issue...

    Does anyone have some good recordings of satellite passes where the DMR interference is present? I could just listen to a local DMR repeater to hear what a DMR signal sounds like, but I would like to get some recordings that show the interference through a satellite. I haven't been in most of the AO-92 passes along the east coast where this was happening on a regular basis, so I don't have my own recordings of this.

    Thanks, and 73!
     
  3. K3RLD

    K3RLD Ham Member QRZ Page

    Check out this link. Really bad at about 7:38 into the recording.

    2018-07-18_1557z_AO-92

    Might have to "right click" and "save as"

    [edit] I am not entirely sure that this particular instance was through the satellite, as at some point I was picking up DMR like noise on the uplink frequency locally....

    [edit, again] After listening to it again, I am pretty sure it is indeed through the sat, as I can hear the DUV "hum" underneath it.
     
    Last edited: Sep 7, 2018
    WD9EWK likes this.
  4. ND5Y

    ND5Y Ham Member QRZ Page

    The user radios on the input will sound different than the output.
    A DMR repeater transmits continuously but the user radios transmit a chopped 27.5 mS on / 30 mS off TDMA signal.
     
  5. WD9EWK

    WD9EWK Ham Member QRZ Page

    It is likely that the issues reported by AMSAT were from hotspots on a single channel, not from a repeater. When I looked through the Brandmeister web site, I did not see repeaters or hotspots using separate transmit and receive frequencies around the uplinks of our FM satellites with 70cm uplinks (435.170 MHz for AO-85, 435.250 MHz for AO-91, or 435.350 MHz for AO-92). Even if it is from a repeater instead of a hotspot or a user's HT or mobile radio, I'd like to get examples of those signals being heard through AO-92 or any of our satellites.

    73!
     
  6. AD7DB

    AD7DB Ham Member QRZ Page

    The noise I heard on AO-91 on 9/5/18 sounded more like PAVE-PAWS (radar) but I could be mistaken.
    Unfortunately it's a familiar sound on 70cm FM repeaters out here.
     
  7. WD9EWK

    WD9EWK Ham Member QRZ Page

    I have heard what I thought was PAVE PAWS on AO-7 passes that go over northern California in the past. This is why I asked for recordings where the noise was certainly from something DMR. That was what AMSAT sounded the alarm about, leading to posts on this forum to tweets to news items.

    73!
     
  8. W5PFG

    W5PFG Ham Member QRZ Page

    When you can really hear PAVE PAWS is when you are working FO-29 on "The 'Cape" (Cape Cod.) It's not through the satellite, but the pulses are very distinctive.
     
  9. W9EXP

    W9EXP Ham Member QRZ Page

    Well this morning's pass had some nice DMR on it. Pass came in from the North and was fairly strong. Also heard it on AO91 yesterday weak but there.
     

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