[HCDX] DRM in the Pacific and NZ tests on 657/662 kHz

[info@xxxxxxxxxxxxxxxxx]

Hi everyone

Some more information on the New Zealand DRM tests using the AM 
Network/Southern Star 657 MW transmitter at Titahi Bay over the past
3 days.

Chris Mackerell here in Wellington has very accurately recorded a lot
of what's 
been going on. 

In this region, every MW station has a usable bandwidth of 18kHz, so
for 657, 
it means they can (within certain parameters) broadcast a signal that
extends 
from 648-666. 

DRM is about 'fitting in' a number of additional signals depending on
how the 
18kHz is carved up for different standards such as data, voice only,
and music, 
and whether you want mono, partial stereo or full stereo and whether
you wish 
to simply simulcast on analog/DRM.

The tests have juggled around different uses such as 657 in analog,
and 661.5 
in DRM (shown on most DRM receivers as 662), using 657 in analog and
652.5 
(briefly) in DRM, and, both yesterday and today, a world first with
the DRM 
signal extending the full 18kHz bandwidth to deliver full stereo.

The DRM power used yesterday was 1.25kW and at times this afternoon
was powered 
at 10kW DRM whilst mobile testing took place of signal degradation at
a 
distance from Titahi Bay in the Wairarapa, over the Rimutakas hill
range about 
40km north of Wellington, and about 30km from Titahi Bay.

The signal clearly dropped out at times on the Rimutaka Hill Road,
gaining as 
much as 10db when at the summit, in fact, very similar to FM
reception. 
Yesterday, the signals were tested for reception within the 'concrete
canyon' 
of central Wellington's highrise building district where they
performed well.

The program feeds have been mostly Southern Star, although yesterday,
output 
from a series of CD's in Radio NZ House was carried by a Telecom link
to the 
transmitter and covered a range of musical genres as well as voice. 

With direct links to the transmitter and several professional DRM
receivers, it 
was possible to hear the original CD quality in the room, AM quality
(analog) 
and DRM quality during simulcasting tests and make instant quality
comparisons.

This afternoon, the full DRM signal relayed RNZ's Concert FM for a
short while, 
and then EZL music was inserted at the transmitter site. 

The DRM tests are allowing observations relating to such things as
robustness 
of the signal, maintaining same coverage as AM but using a lower DRM
power 
consumption at the transmitter, quality of bandwidth used for DRM
such as 4.5, 
9 and 18 kHz, effect on the 657 analog reception when in simulcast
mode, effect 
on 648 and 666 kHz stations and a heap of other stuff.

The effect of running 10kW DRM power is a bit like having a 200kW
analog signal 
being broadcast, so not only do you get full stereo, but your
coverage area 
remains much the same as that achieved by the original analog signal.
Well, 
that's the theory.

I'll be presenting a radio heritage documentary on the DRM tests and
DRM in the 
Pacific over RNZI in June, with major excerpts from the symposium, in 
particular speakers Andy Giefer from Deutsche Welle, Lindsay Cornell
(BBCWS) 
and a number of other speakers including the ABU.

The Radio Heritage Foundation was kindly hosted by RNZI and RNZ to
ensure that 
the heritage aspects of the event were recorded, as the shift to the
digital 
era in radio broadcasting is in danger of under reporting and
preservation 
worldwide. In this case, the full 18kHz bandwidth DRM transmissions
are a world 
first, as in Europe they're restricted to 9kHz. Pacific radio
heritage in the 
making.

There are many issues I'll attempt to cover in the documentary, and
in comments 
at www.radioheritage.net in the coming weeks. As a MW DXer, I'm also
interested 
in seeing how the DRM 'hiss' can be reduced or eliminated, and the
imperative, 
in my view, will probably come from adjoining and co-channel stations
who see 
their coverage areas being threatened and a commercial cost as a
result.

There seems no doubt that day/night switching will be a key issue.
One option 
is to reduce the number of DRM channels at night (say from 2 or 3 to
just 1)and 
reduce DRM power at night because of skywave issues.

The quality of receivers also impacts on 'hiss', because most
(estimated 95%) 
of tuners have narrow bandwidth sensitivity only, with mainly older
valve sets 
having the greater bandwidth we DXers demand. 

>From discussions with a variety of broadcasters, it also became
apparent that 
the value of 'on the spot' monitoring by 'ordinary listeners' of
signals and 
DRM interference, is going to take on more importance. Yes folks, DX
reports 
will become wanted again by the technical people. 

In fact, leaving DRM aside, reception reports for specific tests
and/or 
frequencies and 'comparison' rating of reception of a number of AM
transmitters 
in a defined area will clearly be welcomed. It will be 'DXing to
order', but 
offers some interesting opportunities for MW DX around the Pacific.
Watch the 
usual chat groups and www.radioheritage.net for more details in
coming months.

Warm regards
David Ricquish
www.radioheritage.net   

 







 



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