- some data on an ancient R&S SDB-M DVB-T modulator, that is beginning to come back to life in my shack
- one way field experiments started with this 2 W setup on my kitchen table ( 62k)
- there were sevaral stations that copied the QPSK carrier with satellite DVB-S receivers and different antennas
- OH2JCP, OH2KTB and OH2JRD were mobile finding several locations with _no_ coverage :-)
- most testing was with OH2LH located at his home QTH, signals ~30 dB out of the noise (non line of sight about 7 km away)
- best DX was OH2AXH at about 28 km away, non line of sight
- also spanned 29 km with this (11k) triple hop, mixed mode test with P4/P5 picture quality
- tests lasted about 6 hours, here is the TX antenna (57k) used, drawing of the antenna here (93k)
- closer, top view (85k) of temporary setup including power couplers, modified GSM SSPA, circulator + terminator etc.
- view (80k) of the XCOM DVB-S receiver module and MPEG-2 decoder
- major packaging took place to make the equipment (70k) field worthy for the upcoming National Microwave Round Table
- no little thanks to the OH2LH family metal workshop for doing some sheet work on the rear panel :-)
- the Nokia 9110 Communicator is used for configuring and monitoring the MPEG-2 transmitter and receiver
- remember the +5 to +30 V required on pin 7 of the 9110 data cable (39k) for powering the built in level translator !!!
- a screen shot of the 9110 being used for receiver analysis (109k) (ID, locking, Eb/No etc.)
- overall rear view of the almost ready 1.3 GHz DVB ATV (63k) transceiver (still need some metering, cable ties, etc.)
- closeup view (54k) of video, audio & M/C control interfaces (control by PC, Communicator or other terminal
- closeup view (75k) of the DC input and RF I/O panel with sample outputs of Exciter and SSPA RF signals
- the 3 W DVB transmitter has built-in SWR protection and will withstand any SWR indefinitely
- inside (88k) ratsnest view (I _said_ it still needs some cable ties !!!) of the DVB transceiver
- this is what a QPSK spectra looks like at 1.3 GHz (10k) (occupied bandwidth measurement)
- 3rd. order IMD is a real spectral purity issue and at worst, this and 1st. order products can distort eye height and constellation
- here the SSPA is being driven a bit (10k) too hard (Adjacent Channel Power measurement), increasing level of shoulders
- accurate true RMS power analysis is a fairly complex issue (10k) (sample detection, form factor compensation etc.)
- previous three plots are before bandpass filtering
- reference plot of final DATV transceiver non-harmonic related spurious levels (4k) at RF output
- reference plot of final DATV transceiver Exciter (4k) Sample Output
- reference plot of final DATV transceiver SSPA (4k) Sample Output
