Wideband qrm above 7.385MHz

[Stephen Prior]

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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[Stephen Prior]

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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[Stephen Prior]

I do wish I'd read this last one more carefully before posting, what I had
intended to say was that the noise only disappears (but only in cw/ssb
modes) below FC = 0.81 kHz.



On 17/11/2010 22:28, "Stephen  Prior" <[hidden email]> wrote:

> 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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