Licensing 136kHz.
Gibraltar has about 15 licensed radio amateurs and due of the small size of
the community, has a very good relationship with the local Department of
Trade and Industry.
Although ZB2 generally follows the licence allocations of the UK, there are
differences and new allocations must be approved at a local DTI frequency
co-ordination meeting. 136kHz is not yet available mainly because no one has
requested it!
ZB2 does not operate the CEPT agreement ( despite being told otherwise by
RSGB) and if you want to operate from Gibraltar then you need to obtain a
reciprocal licence. This will be ZB2/ own call for A licensees or ZB0 / own
call for B licensees. The new A/B has not been approved yet and is likely to
be implemented differently from the UK. The only practical difference from
CEPT operation is that, as you have a defined station address, you don't have
to use the /P suffix.
The licence document is a rather nice A4 sheet which also contains some local
restrictions. e.g. No operation on the "Upper Rock" - Due to the numerous
communications installations.
I met the DTI at their offices at Europort and the local GARS club members
at their regular Tuesday meeting. - I hope I gave a good account of 136k.
Licensing the band should be discussed at the next meeting of the frequency
co-ordination group, ( every 6 months) although I get the impression that
this will be successful if supported by the Gibraltar club.
For information:
Wireless office (Gibraltar DTI) 00350 52052 09.00 to 12.30
GARS - Wilfred ZB2IB 00350 75452. [email protected]
There is also a GARS web site. URL not known - sri
Propagation into the Southern Med'.
During my visit I tried to assess the potential for 136k communication by
monitoring some of the well known "beacons" : DCF39 on 138.83, MSF on
60.0kHz BBC on 198k and the Swiss time standard on 77.5k
BBC 198k: Although strong, S9 + 20, this signal suffers from co-channel QRM
which is at a similar signal level. - Essentially unusable without a loop.
77.5k. An enormous signal from frequency standard station. Stronger than
it's received in the UK although a longer path length. ( Sea path and reduced
attenuation?)
MSF and DCF39 (sorry can't ever remember if it's DBF or DCF).
To make a useful measurement of signal levels without a selective level meter
is a difficult task. My receiver for the visit was an ICOM 756 which does
have a reliable 6 / 12 /18dB attenuator and a spectrum display, which has a
reasonable calibration albeit "relative" and not absolute. The signals on
138.83 and 60kHz were weaker than the two above and were more suited to
measurement. Both signals were audible 24hrs a day at good strength and
showed similar propagation characteristics.
Over the past few months there have been several postings to the reflector
about the levels of day / night time signal strengths. At a minimum distance
of 1800km, (a guess) listening to these two stations clearly showed a
distinct, as opposed to marginal, difference between day and night time
propagation.
On 138.83 the German data signal could be received from dawn throughout the
day at about S8 -S9 with a background noise level of S4.
Monitoring at night showed an increase throughout the hours of darkness
peaking at 02.30 to 04.00. Signal levels began to drop at around 2 hours
before dawn.
The signal level difference was around 8-10 dB in general but a peak one
morning at 03.45UTC was estimated at +12db on daytime levels and + 4dB on the
level seen between 22.00 and 00.00hrs the previous night.
The only other anomaly of note was a single deep fade 8dB peak to trough,
which took a full 15 minutes from start to finish and occurred between 23.30
and 23.45 one evening. Unfortunately I did not have the time or technology to
keep monitoring or recording the signal to see if this recurred on a regular
basis.
QRM?
After unplugging a TV from the mains ( to disconnect the SMPSU) the band was
fairly QRM free. Loran on 100k can be seen but no obvious trace could be
found on 137k.
The Greek RTTY station was ever-present, but the strongest signal close to
the band was at 145.00k. This was 20dB stronger than 138.83 and appeared as
data with a +/- 35Hz shift.
The only in-band QRM was a pulsing signal centred on 137.370. This had about
48 short pulses per minute arranged in groups of 5. Each pulse was followed
by a short burst of data. The groups were separated by a small gap. I have no
idea what this was, but it was weak.
So overall, an interesting time. For those looking for differences in signal
level on 138.83 It could be that you are not far enough away to see any
significant change due to non ground wave propagation modes......but at
1800km+ it's there to see.
I have recorded some .wav files of MSF on 60kHz and 138.83 as heard at night
in Gibraltar. I can send those to anyone who may be interested and I will
add the spectrogram images to my web site in a week or so.
Vy 73
David. No longer ZB2/G0MRF
|
