Digital Amateur Television


First Amateur DVB transmissions in Finland !

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- 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


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Updated 26.03.2011