[time-nuts] On choosing reasonable synthesizer PN requirements

[bill]

Hi again Karen,
Have you seen this app designed specifically for the Es'hail QO-100?

https://play.google.com/store/apps/details?id=com.antmodstudios.eshail2linkbudget&hl=nl

Any extra margin on C/N0 can be used to estimate permissible LO phase noise.
Otherwise, you can put together a link budget in Excel or Libreoffice to 
add whatever parameters you want.

Cheers,
Bill



On 24.04.20 15:37, Karen Tadevosyan via time-nuts wrote:
> Hello Bill,
>
>   
>
> Thank you for the clarification. It is especially pleasant that our opinions
> are 100% the same.
>
> However, I would like to find some tool for calculating the balance of the
> radio link in order to understand exactly the reasonable requirements for
> synthesizer's PN.
>
> The issue of stability is now gone - I use a good OCXO with the well-known
> Allan deviation values
> (http://www.ra3apw.ru/wp-content/uploads/2020/04/OCXO_Allan_dev_photo-768x48
> 3.jpg &
> http://www.ra3apw.ru/wp-content/uploads/2019/10/OCXO_AllanDeviation_1-768x37
> 4.jpg ) and sufficient stability is confirmed by the successful work in FT8
> mode via QO-100.
>
>
>
> Regards,
> Karen ra3apw
>
>   
>
>> Hello Karen,
>> As a general rule of thumb, if uplink LO phase noise power ends up being
>> at least 15-20dB below the expected kTB noise received at the satellite
>> transponder, its contribution is not really significant. With -98dBc-Hz,
>> on Tx, you should be in good shape because, to simplify things a bit,
>> Tx SNR at the transmitter far exceeds the SNR at the QO-100 receive
>> antenna.  Thermal noise from the antenna and receiver LNA will dominate
>> the received signal noise at the satellite.  It's more important to keep
>> your Tx frequency stable.  A GPSDO or Rb reference will be useful here.
>> It's also important to keep the DL 10.45GHz receive on frequency as well
>> (even more important, given the freq. multiplication up to 10GHz).
>> On the DL side, antenna temperature and LNA noise should be the dominant
>> signal degradation factors, so good antenna/LNA G/T is all-important.
>> Cheers,
>> Bill
>   
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.