Many of you will by now have seen the proposed application by the Wellington VHF Group for a Digital Amateur Television Repeater. Information missing from the proposal was the frequencies to be used. Many of you have also asked why has this suddenly appeared? Do we have a new frequency for an ATV repeater to replace the Channel 39 allocation? Has the Channel 39 allocation been retained?
The following background and information will, I hope, provide you with some answers.
Our old allocation for analogue television transmissions at 615.25 MHz (Channel 39) has been re-allocated in most parts of the country and will not be available in the future for amateur television use. The frequency now forms part of the new UHF digital terrestrial spectrum. We were advised in 2009 that Government decisions did not provide for Amateur digital television transmissions in the UHF bands, but there was spectrum available post digital switch-over (DSO) of VHF spectrum around 60 MHz (Channel 2). In early 2010 the licence renewal process found only three parties seeking Amateur TV repeater (analogue) licences and these were provided on a temporary basis until DSO.
You may be aware that negotiations have been underway for some time with our regulatory authority, the Ministry for Business, Innovation, and Employment’s Radio Spectrum Policy and Planning and Radio Spectrum Management Groups to evaluate some portion of the UHF spectrum for use by radio amateurs for transmitting digital television signals. These negotiations have now reached the stage where the Ministry has been advised that there are a number of interested groups around New Zealand who want to participate and the Ministry has requested evidence that we can in fact transmit digital television signals without causing interference to the holders of the adjacent spectrum.
At the time of publication in Infoline 261, the Ministry’s Radio Spectrum Management (RSM) had not allocated a transmit frequency for such a repeater. On the 7th of November, as the result of a meeting between FMTAG Secretary Doug Ingham ZL2TAR and the RSM, a frequency band from 502 MHz to 510 MHz has been chosen to allow the evaluation of amateur digital television transmissions to take place. The input frequency of the repeater will be the same as previously used for analogue television transmissions, 431.25 MHz. However, for the spectrum compatibility tests, requested by RSM, a local ident generator will be used which will generate an output signal.
Selection of this frequency band for amateur digital television transmissions means that our “neighbours” in terms of spectrum use is the Land Mobile band extending up to 502 MHz on the lower side and the bottom channel of the Freeview Television spectrum which begins at 510 MHz on the upper side.
The application from Branch 74 is intended to prove to the RSM and adjacent spectrum users that radio amateurs in New Zealand do have the capability to successfully design, construct and operate a digital television transmitter in the band 502 to 510 MHz without producing interfering out-of-band emissions or degrading the signal to noise ratio of stations in the adjacent land mobile band. As such it will assist in developing licence conditions or other RSM requirements for future use.
The Wellington VHF Group has members with the necessary competence and technical ability to produce the UHF digital television transmitter and to conduct the trial and evaluation of emitted digital television signal. The location, in Wellington for the test transmissions, is also convenient in that those users of the land mobile spectrum who have an interest in ensuring that the amateur television transmissions will not cause interference or degradation also have their head office engineering sections in Wellington. The technical requirements for a digital television transmitter which meets the out-of-band radiation conditions of a commercial digital television licence in New Zealand is not easily achieved. A high level of output filtering is required to meet the stringent technical standard.
Branch 74’s aim is to prove that the required performance can be achieved and your Council has every confidence that this will be the outcome. So please bear with us as these trial transmissions take place. The successful outcome may permit other groups around New Zealand to go ahead with the design and construction of similar equipment.
Vaughan Henderson ZL1TGC
Next NZART Official Broadcast is on Sunday 25th November 2012. Next HQ-Infoline e-mailed on FRIDAY 16th November 2012. Closing date for this is Thursday 15th November
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