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LF: LF Receiving (was Alex (R7NT) reports)

To: rsgb_lf_group[email protected]
Subject: LF: LF Receiving (was Alex (R7NT) reports)
From: "Mike Dennison" <[email protected]>
Date: Wed, 20 Apr 2016 11:25:37 +0100
In-reply-to: <[email protected]>
References: <[email protected]>, <[email protected]>, <[email protected]>
Reply-to: [email protected]
Sender: [email protected]
Hugh's advice is excellent - adequate sensitvity, a resonant antenna 
and good front-end filtering. I would add good dynamic range, an 
effective noise blanker and ideally a way to reduce or switch off the 
AGC. After fittng the filters, there should still be a large 
difference in background noise when the antenna is connected.

Local noise is a major factor, and it may be necessary to have a 
separate receive antenna, situated and oriented away from the noise 
source.

Lastly, it can help to have a directional (preferably steerable) 
antenna to reduce lightning noise away from the wanted direction.

Mike, G3XDV
============
 

> For LF reception there's no great secret. A decent communications
> receiver tuning down to 30kHz combined with a wire  aerial broadly (or
> sharply) tuned to 136kHz, a correct loading coil should do the same
> job, this reduces broadcast signals to more acceptable levels. The
> receiver should have no attenuation below (say) 550khz, most of them
> have a bandpass filter on the front end, the older ones with a tuned
> front end were good but not stable enough. If you can get a circuit of
> the front end and re-draw it in a software program such as Tina it
> will display the frequency response and allow modifications to be set.
> I altered one inductor only. Beware of the remaining stations on Long
> Wave, it may require a notch filter, this is where software helps
> again. I think many transceivers for Amateur use have very poor,
> mediocre or just average receiver response at LF so I'm not sure if a
> preamplifier would help unless it's tuned. A notch filter on the
> receiver is essential and a good USB filter as well. It's worth buying
> extra filters according to the receiver as supplied. There is some
> choice but an internet search may help.
> 
> Hugh, M0DSZ
> 
> > Hello Hugh,
> >
> > Sunday, April 17, 2016
> >
> >    Likewise, many thanks to Alex, it is a generous and useful
> >    service, and I look forward to seeing who heard who. Thanks
> >    Alex!!
> >
> >    BTW  Hugh,  may  I ask what you are using for LF reception
> >    please? I want  to  get  a better RX setup here, it isn't very
> >    good compared to what you are achieving. Thanks.
> >
> >
> > Best regards,
> >   Chris  2E0ILY                          mailto:[email protected]
> >
> >
> >
> >> I must thank Alex (R7NT) for his carefully collated, weekly
> >> reports, it helps to coordinate everyone's LF tests. For some
> >> reason I haven't been receiving him well or often though there are
> >> times when I'm not in Rx mode by virtue of being on HF fro a while,
> >> especially on Sunday mornings. Hugh, M0DSZ
> >
> >
> >
> 
> 
> 
> 
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