DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws;
  s=s1024; d=btinternet.com;
  h=Received:X-Yahoo-SMTP:X-YMail-OSG:X-Yahoo-Newman-Property:Message-ID:From:To:References:Subject:Date:MIME-Version:Content-Type:Content-Transfer-Encoding:X-Priority:X-MSMail-Priority:X-Mailer:X-MimeOLE;
  b=yZ0HYV62eac4y9mS8ZxA1TeKSOT9sdU4HRmRC/Mkej1SgH2gLF/qEoaW6PC18BHWlLLbsAmqt/9QwJCSvBU9s0nUal3akoVzqhRFMEKF/atM41Z0UL/Ciw8Uoeavbv+boauDTmnzaNSHuCsSdBKaQT5Otbzvx+FN7F50xdvaMmI=  ;
Message-ID: <011201ca6332$23e930c0$0900a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4AFB477C.5090604@sighthound.demon.co.uk> <001501ca6326$ff28c710$0617aac0@jimdesk> <00f301ca6329$8ba907c0$0900a8c0@lark> <001901ca632a$d3356ab0$0617aac0@jimdesk>
Date: Thu, 12 Nov 2009 00:25:06 -0000
MIME-Version: 1.0
DomainKey-Status: good (testing) 
Subject: LF: Re: RE: Re: RE: G7NKS multiple WSPR decodes!
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Ah the dreaded laptop. Ok the isolation that is agood idea in that case you
must make sure you have some Rf grounds somewhere. Laptops seem to float
there is not reason (for the digital engineers who designed them anyway) to
put an earth on the metalwork. The RF circuitating in those leads might be
inducing hum. It might be worth trying an earth on any suitable but of the
laptop metalwork....socket pillars ?? It definitely sounds as though it is
hum getting into the PC sound system.

Good Luck with it.
Alan G3NYK

----- Original Message -----
From: "James Cowburn" <james.cowburn@virgin.net>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, November 11, 2009 11:58 PM
Subject: LF: RE: Re: RE: G7NKS multiple WSPR decodes!


> The soundcard leads are via an opto-isolator interface and the leads from
> the interface to laptop are wound on ferrite cores, approx 8 turns each
for
> tx and rx.
>
> I will check the mains psu for the dell d610 laptop as that could be
> introducing hum or picking up rf from the tx (IC-735).  It might need
> ferrites on the leads to and from the SMPSU
>
> I've just turned "the wick" down on the tx/rx inputs and also the rf gain
on
> ic 735 till the needle just shifted in case it was being over-driven so
I'll
> see how that works.
>
> Not a prob when I was QRPpp but as sigs improve with dark nights I'd
noticed
> it too
>
> Thanks to John and others for heads up and suggestions
>
> With best regards
>
>
> Jim
>
>
> Dr. James Cowburn G7NKS
> -----Original Message-----
> From: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Alan Melia
> Sent: 11 November 2009 23:49
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: Re: RE: G7NKS multiple WSPR decodes!
>
> Hi Jim what kind of PC are you using. If a desktop are to sure it has the
> mains safety earth connected.....I have come across this problem before
some
> 3 connecter IEC moulded leads with only two wires in them!! If a laptop
then
> unless you use a radio earth that may all be floating. Sometimes it is
> necessary to use an tranformer on the audio leads to and from the PC to
gain
> isolation from the hum and noise. I use old telephone hybrid transformers
> 600ohm to 600 ohm ferrite cored.
>
> Best Wishes
> Alan G3NYK
>
> ----- Original Message -----
> From: "James Cowburn" <james.cowburn@virgin.net>
> To: <rsgb_lf_group@blacksheep.org>
> Sent: Wednesday, November 11, 2009 11:30 PM
> Subject: LF: RE: G7NKS multiple WSPR decodes!
>
>
> > Hi John
> >
> > I'll have a look see.  I've noticed on strong sigs from me (few and far
> > between!) I get multiple decodes +50 and -50.   I'm not aware of any
> obvious
> > mains hum if I monitor my outgoing sigs and all leads are wound on
ferrite
> > cores, but clearly something is amiss.
> >
> > I shall look into it and see what I can find
> >
> > Cheers for the heads up
> >
> > With best regards
> >
> >
> > Jim
> >
> >
> > Dr. James Cowburn
> > -----Original Message-----
> > From: owner-rsgb_lf_group@blacksheep.org
> > [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of John P-G
> > Sent: 11 November 2009 23:24
> > To: rsgb_lf_group@blacksheep.org
> > Subject: LF: G7NKS multiple WSPR decodes!
> >
> > Jim. LF
> >
> > It looks like G7NKS has a 50/100Hz problem on the audio - both in TX and
> > RX directions - there are up to 3 decodes by Jim of a single station (eg
> > G3YXM), spaced by 50 & 100Hz and I see also that M0BMU is also reporting
> > multiple decodes of G7NKS with the same 50/100Hz spacing.
> >
> > Jim, have you some mains hum affecting the audio in/out of the PC?
> >
> > Cheers,
> >
> > John
> > GM4SLV
> >
> >
> >
>
>
>