DCF39 and HGA22 are clearly evident of course, but I note there is
something on 133 kHz that comes up in sync with those two. It's not
DCF49 which is lower, around 129 kHz. I suspect either the receiver
is overloaded, not enough front end filtering yet, or a combination
of the two. It may be more of challenge to get the filtering tight
enough in Europe where you have the strong signals from DCF49,
HGA22, DFC39 and some very strong broadcast stations not much higher
in frequency...
Regarding the noise "hump" in or around the 137 kHz band, could this
be just the resonance of the transmitting antenna? I use a separate
receiving antenna which is nearby (about 15 meters from the
transmitting vertical). When the transmitting antenna is resonated
on 137 kHz I see a very pronounced noise "hump" over a 2 to 3 kHz
range. When the transmitting antenna is not resonated for LF, I do
not see that and the noise floor is fairly constant over several
tens of kHz (the passband of the front end filter).
73,
Paul
On 02/12/2018 12:08 PM, John Rabson wrote:
Possibly DCF39 and its companion? I believe they are used to control some sort
of electricity grid.
John F5VLF
On 12 Feb 2018, at 17:47, Chris Wilson <[email protected]> wrote:
Hello Mike, I just listened to what looks like the AM modulated bursts
around 139 and 135.5 kHz and they sound like bursts of data, nothing
intelligible whatsoever.
Monday, February 12, 2018, 4:26:13 PM, you wrote:
Chris,
It looks like you have a broadcast station where it shouldn't be (at
132.65kHz) and several other spurious stations in that area, so you
may well have unwanted signals within the 136kHz band, especially at
night (your recording seems to have been done during the middle of
the day). You might improve things by by-passing the pre-amp. It
would do no harm just by experimenting with an attenuator but why
attenuate and amplify at the same time unless the preamp also
provides another function such as matching? It seems the only
front-end selectivity on that receiver is a narrow bandpass so you
would really benefit from some additional wider filtering, eg an LPF
with a cut-off just below the LW BC band.
Mike, G3XDV
--
Best regards,
Chris mailto:[email protected]
--
Paul
N1BUG 160m-2m DXCC Honor Roll
WI2XTC 2200m-630m Experimental license
FN55mf ME Piscataquis County
http://www.n1bug.com
http://www.aurorasentry.com
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