Hi Mike and Alan,
I believe
Mike is right in that the FSK bursts in the upper half of the band actually do
come from DCF39.
Since April 2nd, they have switched to a new Transradio
solid state transmitter, which unfortunately appears to have much less efficient
modulation waveform shaping. The old TX is still used as a backup and has come
on for a few hours from time to time. This is also the reason for the different
reported idle frequencies (138830.03 Hz before, 138830.6 Hz now).
There
is a grabber shot on http://members.aol.com/df6nm2/QRM/DCF39_sidebands_070404.png which shows the difference of the spectral characteristics.
Especially in quiet conditions, the new burst sidebands can be seen down to
about 137.1 kHz and do significantly affect QRSS reception here. I have been in
contact with a person at the German regulatory body "Bundesnetzagentur", who was
involved in the on-site acceptance testing. He was quite understanding and
helpful, but basically said that the emitted spectrum had been confirmed to be
within the prescribed mask, and there was little he could do to enforce a
reduction of the remaining out-of-band emissions.
Due to the modulation
characteristics there are however a few spectral gaps in the sidebands which
could be useful to us. The appended plot shows a spectrogram between 137.5 and
137.8 kHz (audio frequencies above 135.5 kHz zero beat). The vertical streaks
show visible minima at
137.762 to 137.773 kHz (shown as 2262 to 2273
Hz),
137.620 to 137.655 kHz, and
137.560 to 137.575
kHz.
One possible suggestion would be to move our activity regions for TA
(currently ~137.778) and QRSS (~137.700) down into the first two gaps. Before we
decide to change our habits, it would be interesting to know how much others in
the LF group are affected.
73 and best wishes
Markus, DF6NM
PS:
A strong blue trace appeared near 136.319 around 19:20 - Mike's test
signal?
----- Original Message -----
From: "Alan Melia"
<[email protected]>
To:
<[email protected]>
Sent: Monday, November 12, 2007 7:16 PM
Subject: LF: Re:
136kHz DX 11/12 Nov
> Hi Mike I think the data bursts are actually
probably from Lakihegy
> (Budapest) 135.5 or thereabouts, which is very
strong at night and shifts
> "into" the band a couple of hundred
Hz.
> Loran from Rugby went off in July and it has been a lot quieter
since then,
> but it doesnt seem to be fully running 24/7 yet at
Anthorn.
>
> Alan G3NYK
>
> ----- Original Message
-----
> From: "Mike Dennison" <[email protected]>
>
To: <[email protected]>
> Sent: Monday, November 12, 2007 6:06 PM
> Subject: LF:
136kHz DX 11/12 Nov
>
>> I have at last got my station fully
running again. Having been off
>> the air for a few months I notice
much less Loran QRM which will make
>> CW contacts possible again. But
more QRM from DCF39 data bursts which
>> makes QRSS
harder.
>>
>> Monitored last night and received the following
(using Argo set to
>> 30s slow) :
>>
>> 1800 - 1850
Unidentified station on 137.776kHz (who?)
>> 1900 - 2000 UA4WPF
137.777.2kHz, 'O'
>> 0610 - 0700 XKO 137.777.4kHz One complete call,
'O'
>>
>> Very noisy overnight.
>>
>> Will
test my beacon on 136.318.7kHz this evening, but not overnight.
>> Hope
to run an overnight beacon later this week. Please let me know
>> if
this frequency causes anyone a problem.
>>
>> de Mike,
G3XDV
>> ============
>>
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