Re: Wideband qrm above 7.385MHz
Posted by
Stephen Prior on
Nov 17, 2010; 10:28pm
URL: http://elecraft.85.s1.nabble.com/Wideband-qrm-above-7-385MHz-tp5749686p5749754.html
Further to my last posting, I observe now that the appearance of the 'qrm'
depends upon the filter and shift settings, what is observed to be a problem
in AM mode completely disappears in cw/ssb modes, for example this occurs at
and below FC = 0.81kHz.
Stephen G4SJP
On 17/11/2010 22:05, "Stephen Prior" <
[hidden email]> wrote:
> In tuning above 7.385MHz, listening to broadcast stations on AM, I noticed a
> very strong and broadband interference extending to just above 7.500 MHz.
>
> At 7.385MHz on AM mode I hear a relay click in, and I'm assuming that this is
> the K3 changing over to the KBPF3 which I have installed. Looking at the P3's
> display, the spectrum which is hf of 7.385 MHz is completely clear of such
> 'qrm' until the VFO goes above 7.385 MHz, and then the qrm appears about 35dB
> above my noise floor, not only above 7.385 MHz, but extending below it to the
> extent that the P3 will show. Since this is not even observed on the P3 (with
> its maximum span set) until the VFO is tuned above 7.385 MHz, I can't help but
> to think that this is an unexpected artefact. Removing the antenna clears
> this completely, so it is not internally generated.
>
> But what is causing it I wonder. I have never noticed this effect before.
> Since it only occurs above a set frequency and then is apparent below that
> frequency too, to my mind it has to be a fault with the K3 that I haven't
> observed with any previous firmware version. I am running with latest beta
> for both the K3 and P3.
>
> 73 Stephen G4SJP
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