From: "James Cowburn" <james.cowburn@virgin.net>
To: <rsgb_lf_group@blacksheep.org>
References: <4AFB477C.5090604@sighthound.demon.co.uk> <001501ca6326$ff28c710$0617aac0@jimdesk> <00f301ca6329$8ba907c0$0900a8c0@lark>
Date: Wed, 11 Nov 2009 23:58:11 -0000
Message-ID: <001901ca632a$d3356ab0$0617aac0@jimdesk>
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Subject: LF: RE: Re: RE: G7NKS multiple WSPR decodes!
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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
>
>
>