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
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