KX3 generating signal

[Roger Meadows-2]

Today when operating QRP, the gentleman I was at the park with wanted to
compare receiving a CW signal. We weren't comparing rigs but antennas. He
had a FT 817.

When he tuned to the frequency I was listening to it sounded like someone
was tuning up on frequency on his radio. I changed frequencies and the
noise went away.  When I tuned back to where he was, it came back. We could
only hear it on his radio but my KX3 was definitely generating the signal.

This was on 40m around 7020.

What would cause this? It does not seem normal.
--
73,
Roger Meadows
AE4RM
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[Richard Ferch-2]

The KX3 is a direct-conversion transceiver, not a superhet. The behaviour
you observed is normal with any direct-conversion receiver. The local
oscillator operates directly on the signal frequency and can be heard in a
nearby receiver.

73,
Rich VE3KI

AE4RM wrote:

> Today when operating QRP, the gentleman I was at the park with wanted to
> compare receiving a CW signal. We weren't comparing rigs but antennas. He
> had a FT 817.
>
> When he tuned to the frequency I was listening to it sounded like someone
> was tuning up on frequency on his radio. I changed frequencies and the
> noise went away.  When I tuned back to where he was, it came back. We
could
> only hear it on his radio but my KX3 was definitely generating the signal.
>
> This was on 40m around 7020.
>
> What would cause this? It does not seem normal.
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[Mike Harris-9]

Not quite the full story, so no cigar. From the KX3 Owners Manual p49
"RF band-pass filters":

<quote>
Following the band pass filters and T/R switching are two RF
preamplifiers and an attenuator. These provide various tradeoffs between
RF gain and noise figure (or MDS), as well as local oscillator (LO)
isolation. The latter would be useful in situations where another
receiver in close proximity could be tuned to the same
frequency. A problem inherent in most direct conversion (zero IF)
receivers is that some LO energy leaks to the antenna and is radiated.
This can be a problem when another receiver & antenna is in very close
proximity and is tuned to the same frequency. The isolation preamp in
the KX3 (RX ISO menu entry) virtually eliminates this signal leakage.
<unquote>

Regards,

Mike VP8NO

On 19/08/2017 10:00, Richard Ferch wrote:

> The KX3 is a direct-conversion transceiver, not a superhet. The behaviour
> you observed is normal with any direct-conversion receiver. The local
> oscillator operates directly on the signal frequency and can be heard in a
> nearby receiver.
>
> 73,
> Rich VE3KI
>
> AE4RM wrote:
>
>> Today when operating QRP, the gentleman I was at the park with wanted to
>> compare receiving a CW signal. We weren't comparing rigs but antennas. He
>> had a FT 817.
>>
>> When he tuned to the frequency I was listening to it sounded like someone
>> was tuning up on frequency on his radio. I changed frequencies and the
>> noise went away.  When I tuned back to where he was, it came back. We
> could
>> only hear it on his radio but my KX3 was definitely generating the signal.
>>
>> This was on 40m around 7020.
>>
>> What would cause this? It does not seem normal.

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