[amsat-bb] EO-80 FM Transponder doubt

Pavel Milanes Costa co7wt at frcuba.co.cu
Mon Jun 22 13:36:07 UTC 2015

Ha ha!

Thanks for the explanation... I see i was wrong.

Now i can program my radios in the correct way.

73 and thanks.

El 21/06/15 a las 21:56, Greg D escibió:
> Yes, Pavel, but since the frequency heard by the satellite as it
> approaches is higher than what you sent, you need to send at a lower
> frequency to compensate.  The idea is that you want the frequency heard
> at the satellite to be constant.
> As the satellite passes the midpoint, and recedes from view, the
> frequency it hears is lower than what you transmitted.  So you need to
> send at a higher frequency to compensate, again so that the satellite
> hears a constant signal.
> So, during the pass your transmitter needs to go from lower to higher.
> The physics works the same for your reception (it better!), but since
> the satellite isn't changing its frequency to be constant at your end,
> you need to move from higher (on approach) to lower (towards LOS) to
> conpensate.
> Greg  KO6TH
> Pavel Milanes Costa wrote:
>> I have a doubt...
>> A few days ago Paul put a list of the proposed channel for EO-80..
>> I have noted that the TX freqs are from lower to higher (AOS to LOS),
>> is that correct?
>> From the sat point of view a Tx on the center freq will appears as
>> shifted up at the AOS because the two point are getting closer
>> (doppler is summing), in fact no matter is the freq is for TX or RX if
>> at AOS the shift must be + not -
>> I'm right?
>> PS: with the 2.5 Khz of the new Chinese radios the 2m downlink can be
>> shifted to +2.5 Khz at AOS and -2.5 Khz at LOS to improve reception
>> quality
>> El 17/06/15 a las 12:59, Paul Stoetzer escibió:
>>> Anyone who wants to program memories for EO-80 should follow this plan:
>>> EO-80 AOS - TX 435.070 MHz 210.7 Hz CTCSS, RX 145.840 MHz
>>> EO-80 2      -  TX 435.075 MHz 210.7 Hz CTCSS, RX 145.840 MHz
>>> EO-80 TCA  -  TX 435.080 MHz 210.7 Hz CTCSS, RX 145.840 MHz
>>> EO-80 4      -  TX 435.085 MHz 210.7 Hz CTCSS, RX 145.840 MHz
>>> EO-80 LOS -  TX 435.090 MHz 210.7 Hz CTCSS, RX 145.840 MHz
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