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AO-91 Rceive Frequency

Discussion in 'Satellite and Space Communications' started by K4BAD, Dec 2, 2017.

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  1. K4BAD

    K4BAD Ham Member QRZ Page

    Hello fellow sky bird talkers!
    Just for the heck of it I connected my Wouxun KG-UV9D HT to a Slim Jim antenna attached to my living room ceiling.As expected,I heard many strong signals through out the pass.
    I did notice the audio was becoming distorted towards the end of the pass.Lowered the receive frequency to 145.955 MHz resulted in perfectly clear audio.

    So....I'm wondering if the change in optimum receive frequency could be related to the discussions on AO-91's AFC?...use or not use,etc.

    Intend to program the HTand take a shot at a contact during a low usage period.

    Thanks for reading....73. ..K4BAD. Harry
    WE4B likes this.
  2. N1PEB

    N1PEB Ham Member QRZ Page

  3. KG4AKV

    KG4AKV XML Subscriber QRZ Page

    Even though you don't have to adjust the 2m uplink for SO-50 to compensate for the doppler effect, I find it does help when receiving AO-85, AO-91, and sometimes even the incredibly strong signals from the ISS (145.800). So what you experienced is normal, and almost certainly a result of the doppler effect. You can start out at 145.965 at the beginning of the pass and it may help too.

    The AFC discussion was about the receiver on the bird. It doesn't adjust its transmit signal. I'm not sure if commercial ham gear has similar AFC abilities.
  4. WD9EWK

    WD9EWK Ham Member QRZ Page

    As others mentioned, AO-91's AFC relates to your uplink. What you are probably seeing is what I saw when I tried a bunch of Chinese-made HTs with AO-85 a couple of years ago, and in the last week or so with AO-91. The Chinese-made HTs, like your KG-UV9D (I have one of those, too), appear to have tighter receive filtering than what is normally seen in the Icom/Kenwood/Yaesu ham FM HTs and mobile transceivers.

    The KG-UV9D should support a 2.5 kHz tuning step. Using that on the downlink VFO, you can start AO-91 passes on 145.9625 MHz, then move to 145.960 MHz and finally 145.9575 MHz near LOS. That will probably make the portions of the passes near AOS and LOS sound better on the KG-UV9D. You can still use 5 kHz tuning steps for the uplink VFO, as each VFO can be set to different tuning steps, and using 2.5 kHz steps for the uplink VFO means more tuning than is really necessary.

    Last edited: Dec 3, 2017
  5. WD9EWK

    WD9EWK Ham Member QRZ Page

    Most ham transceivers don't come with AFC. Some of the wide-band receivers that include coverage of the 2m and 70cm ham bands may have AFC that would work fine for FM downlinks. I had an AOR AR8200 receiver many years ago that had AFC which worked well with AO-51, and OK with SO-50 if there weren't many long periods of silence. Many programs used with SDR receivers will include AFC for FM. I use HDSDR, and it has AFC for FM that works well with AO-85 and AO-91.

    W5PFG likes this.
  6. WE4B

    WE4B Ham Member QRZ Page

    I have yet to log EM71 via AO-91 so I'm counting on you, K4BAD or KE4AL. 73!
  7. W5PFG

    W5PFG Ham Member QRZ Page

    KK4CF is on linear satellites frequently in EM71, same town as K4BAD. ;)
    NJ4Y and WE4B like this.
  8. N8HM

    N8HM Premium Subscriber QRZ Page

    The FT-817 also seems to need more Doppler adjustment. Signals are clear with my Kenwood TH-D72A just sitting on 960, but I have to tune my 817 for receive.
    NJ4Y likes this.
  9. WE4B

    WE4B Ham Member QRZ Page

    I've got EM71 confirmed many times from KE4AL, I just haven't gotten to work Harry yet via AO-91 :)
  10. VE3CGA

    VE3CGA XML Subscriber QRZ Page

    is there anyone here who uses an ICOM 9100 on the fm birds. I'm new to this but have worked the xw-2 satellites on SSB with very little problems. I can hear ao-91 and ao-85 on the icom and my rtlsdr but cant seem to get into them. I use satpc32 for tracking.
    the ic9100 has afc but I leave it off when using tracking from satpc32. I have the pl set at 67hz and have played with offsetting the uplink freq.
    Do I turn off downlink tracking for these birds and if so how do I do that in satpc32, its blanked out in the mode menu.

    the last ao91 pass was very busy here today.

    thanks, Bob VE3CGA

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