Articles

Technical articles written for - or by - Wellington VHF Group members and friends.

Digital Television Tests – Bulletin No.7

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Transmission of the unmodulated CW carrier continues on 506 MHz, with horizontal polarisation. Reception reports are welcome.

Four power amplifier modules have been constructed and tested one-at-a-time with the digital exciter. Their gain and linearity match within half a dB. The four modules will operate in parallel to achieve the licensed power.

A 4-way drive splitter and 4-way output combiner have been designed and are under construction.

Digital Television Tests – Bulletin No.6

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Transmission of the unmodulated CW carrier continues on 506 MHz, with horizontal polarisation. Reception reports are welcome.

Adjustment and testing of the digital modulator is complete.

The prototype power amplifier module has been constructed and is now undergoing quality testing. Once testing is complete another three modules will be constructed. The four modules will operate in parallel to achieve the licensed power.

Digital Television Tests – Bulletin No.5

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Transmission of the unmodulated CW carrier continues on 506 MHz, with horizontal polarisation. The maximum EIRP is +20 dBW (100 Watts) towards the North East.

Calibrated coverage measurements, at more than twelve locations, confirm that the transmit antenna is performing as expected. Additional reception reports are welcome.

Digital Television Tests – Bulletin No 3

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Since update number 2, the quality of the prototype exciter and power amplifier, has been tested using professional test equipment.
These tests used both an unmodulated CW carrier, and a 7.6 MHz wide modulated spectrum, both centred on 506 MHz.
Both items performed better than expected and did not require any adjustment.

We are now working on getting the antenna system ready for the CW test transmissions.

Digital Television Tests – Bulletin No 2

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Update number 1, as at 21st January, was published in January Q-Bit magazine, recently posted to members.

In summary, the update included a block diagram of the digital test system and discussed the various factors influencing the quality of the radiated transmission, such as the exciter quality, adjustment of the power amplifier, and the impedance matching of the output filter and antenna.

DIGITAL TELEVISION BULLETIN No 1 - RSM grants the first Digital Amateur TV (DATV) Licence.

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New Zealand Radio Spectrum Management (RSM) has granted the first Digital Amateur TV Licence to NZART Branch 74, The Wellington VHF Group, for use at its main station located on Mount Belmont, in Wellington.

The main features of Licence 236831 are:

  • Digital TV Channel 25 (DTV25)
  • 502 MHz to 510 MHz
  • DVB-T format
  • 7.7 MHz emission bandwidth
  • 100 W mean effective isotropic radiated power (eirp)
  • Horizontal polarisation
  • The licence is valid for an initial period of 6 months, from 1st January 2013 to 30th June 2013.

    Belmont Site Update

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    Belmont tower now has some of the panel antennas mounted on it, thanks to a couple of long hard days on site.

    Peter ZL3TC Gavin ZL2TVM and Brian ZL2BRF spent time with Peter's new winch to lift and bolt the panels on. Peter built the electric winch on a member that can be bolted on the lower tower and used to lift heavy parts aloft ver quickly and precisely.

    The NS and the 710 antennas are still the dual band vertical on the shed, but progress is being made.

    The tower is expected to be compeleted by late summer, hopefully before Easter 2009.