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From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <017801ca66fb$0bf91c60$0517aac0@jimdesk> <CDD52DF1F4BE4A6197305E939E2F7572@JimPC> <20091118085815.7282031E703@smtps01.kuleuven.be> <02ac01ca6832$39e82890$0517aac0@jimdesk>
In-Reply-To: <02ac01ca6832$39e82890$0517aac0@jimdesk>
Date: Thu, 19 Nov 2009 10:17:21 -0000
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Subject: Re: LF: Re: G7NKS sidebands
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Dear Rik, Pete, Jim, LF Group,

I don't doubt that supply ripple to the PA could produce unwanted sidebands 
on a signal, but there are a couple of reasons why I don't think this is so 
in the case of G7NKS's signal:

1) The sidebands are spaced at +/-50Hz, 150Hz, while one would expect 100Hz 
and multiples due to power supply ripple - this would require a very odd 
ripple waveform, and at least several percent ripple, to get sidebands 
at -30dB as they are.

2) The sidebands on G7NKS's transmitted signal are mirrored by the apparent 
sidebands on signals received at G7NKS, for example:

G7NKS received at M0BMU:
      2009-11-15 17:50   G7NKS   0.503802   -27   -1   IO92ub   0.02   M0BMU 
IO91vr   38   171
       2009-11-15 17:50   G7NKS   0.503852   +5   -1   IO92ub   0.02   M0BMU 
IO91vr   38   171
       2009-11-15 17:50   G7NKS   0.503902   -25   -1   IO92ub   0.02 
M0BMU   IO91vr   38   171


M0BMU received at G7NKS:
      2009-11-02 08:00   M0BMU   0.503899   -19   -1   IO91vr   2   G7NKS 
IO92ub   38   351
       2009-11-02 08:00   M0BMU   0.503948   +12   -1   IO91vr   2   G7NKS 
IO92ub   38   351
       2009-11-02 08:00   M0BMU   0.503998   -18   -1   IO91vr   2   G7NKS 
IO92ub   38   351


The apparent sideband levels and frequency offsets are virtually the same, 
but the PA can hardly be responsible for the sidebands on the received 
signal, and even if supply ripple was causing the problem on receive in some 
other way, it is remarkable that the relative levels are virtually the same. 
So I think Jim's problem must be being caused by a component of his system 
that is common to both TX and RX. Overheating of the PA, etc. is a different 
issue.

Cheers, Jim Moritz
73 de M0BMU


----- Original Message ----- 
From: "James Cowburn" <james.cowburn@virgin.net>
To: <rsgb_lf_group@blacksheep.org>
Sent: Wednesday, November 18, 2009 9:33 AM
Subject: RE: LF: Re: G7NKS sidebands


> Hi Rik
>
> That's exactly what mine are.  I think it's a mixture of stretching the Pa
> on the IC735 so its at the edge of its envelope (the radio equivalent of a
> stick shaker or stall horn on a plane!) and also RF leakage and mains
> leakage into the soundcard system on the Dell lappy.  It's only apparent 
> on
> Rx and Tx of strong/local signals where the fundamental is so high (>0db)
> that the first side lobes at -30dB are still within WSPR capture range.
>