The BATC, AGAF and the Swiss ATV Association have offered
donations to the ARCOL project (Amateur Radio on Columbus).
They would also like advice for the ARCOL ATV project.
Should it use ATV or DATV ?
Please consider the preferences and the equipment of the ATV community
now and in the near future. Also the technical issue related to the
considerable doppler effect on S-band for a low orbiting satellite.
Gaston Bertels, ON4WF
Submitted By Trevor Brown G8CJS
DATV v ATV for Columbus
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This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: DATV v ATV for Columbus
Re Columbus,
What will the worstcase doppler shift be at 2.3Ghz on a typical orbit. Do we have some one who has this info?
The afc range on most single channel COFDM DVBT transmisions is quite wide, from memory 200Khz is of slowly changing shift is not a problem.
I have not measured a QPSK transmission recently but I have an offest on my 70cm QPSK transmission of about +125Khz on 436.125Mhz, and the Sat Rx is quite happy set on a multiple of 1Mhx at L band from the up converted 436Mhz signal.
Subject to confirmation of the anticipated doppler shift I think we should use DATV on the down link if we can. We will occupy the least amount of spectrum and we might expect to benefit from low C/N and little or no multipath , so QPSK
would be my choice. There are plenty of "Free to air"satelite boxes.
Uplink is a different question, being pragmatic about available equipment , FM will be the choice. The cost of a DATV RX and an FM Rx is probably quite lw, so maybe we could have default as FM and auto switch if the digital RX decoder locked ok.
Regards Peter G3PYB
What will the worstcase doppler shift be at 2.3Ghz on a typical orbit. Do we have some one who has this info?
The afc range on most single channel COFDM DVBT transmisions is quite wide, from memory 200Khz is of slowly changing shift is not a problem.
I have not measured a QPSK transmission recently but I have an offest on my 70cm QPSK transmission of about +125Khz on 436.125Mhz, and the Sat Rx is quite happy set on a multiple of 1Mhx at L band from the up converted 436Mhz signal.
Subject to confirmation of the anticipated doppler shift I think we should use DATV on the down link if we can. We will occupy the least amount of spectrum and we might expect to benefit from low C/N and little or no multipath , so QPSK
would be my choice. There are plenty of "Free to air"satelite boxes.
Uplink is a different question, being pragmatic about available equipment , FM will be the choice. The cost of a DATV RX and an FM Rx is probably quite lw, so maybe we could have default as FM and auto switch if the digital RX decoder locked ok.
Regards Peter G3PYB
Re: DATV v ATV for Columbus
I will run some simulations on the satellite tracker module of HAM Radio Deluxe to evaluate the worst case doppler shift (30-35 KHz ?). I will also test the maximum offset I could set on my SR-System on 2.4 GHz and still receive it on my DVB-S SL 55.
73 de Michel HB9DUG
swissATV
home.swissatv.ch
73 de Michel HB9DUG
swissATV
home.swissatv.ch
Re: DATV v ATV for Columbus
To HB9DUG.
Thank you Michel tthe information will be most helpful.
Thank you Michel tthe information will be most helpful.