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K2 / KX3 receiver observation - need explanation

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gt-i

K2 / KX3 receiver observation - need explanation

Hello everybody,
during the WPX contest I noticed some weird sounds in the K2 when tuning
to strong (>S9+20db) stations.
The sound was distorted, kind of ripple, but it did not sound like
typical ringing.
I also noticed LZ9W booming in on 80m with S9+40db, producing 3 images
in the K2 and the KX3. However, in the K2 the 2 ghost signals were
frequency modulated. How could this happen?
Another big one, LY2W, also produced 3 signals in the KX3 but all the 3
were nice and clean.

I thought these ghost images would depend on the receiver architecture,
or am I wrong here?

Regarding the first observation: Since the K2 is already > 10 years old,
could component aging already play a role. If so, where to look for?

Thanks for any ideas!
73
Gernot
DF5RF

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Don Wilhelm-4

Re: K2 / KX3 receiver observation - need explanation

Gernot,

Because you are hearing the same thing (or almost the same thing) on 2
receivers, give thought to the possibility that the source may be
outside the receivers.
Even mild corrosion in the antenna system can produce a connection that
acts like a diode and will mix strange frequencies together and produce
unexpected results.

Faulty solder connections in the receiver can produce the same results.
Yes, unwanted mixing products from strong signals can occur in the
receiver. I do not think it is a sign of aging.

I have never seen symptoms like you describe when driving a K2 with a
very large signal from my workbench signal generator.

Does your K2 have the Extremely Strong Signal Handling mod installed?
If not, install two 1N4148 diodes back to back across the input to RF
board U12 - those diodes can be installed either between pins 4 and 6 of
U12 or across leads 3 and 4 of T7. The newer schematics identify those
diodes as D40 and D41. If you have an older K2 with the 2nd Xtal
Flattening Mod installed, that covers the leads of T7 and you will have
to install the diodes across the U12 pins.

73,
Don W3FPR

On 6/5/2015 10:07 AM, [hidden email] wrote:

> Hello everybody,
> during the WPX contest I noticed some weird sounds in the K2 when
> tuning to strong (>S9+20db) stations.
> The sound was distorted, kind of ripple, but it did not sound like
> typical ringing.
> I also noticed LZ9W booming in on 80m with S9+40db, producing 3 images
> in the K2 and the KX3. However, in the K2 the 2 ghost signals were
> frequency modulated. How could this happen?
> Another big one, LY2W, also produced 3 signals in the KX3 but all the
> 3 were nice and clean.
>
> I thought these ghost images would depend on the receiver
> architecture, or am I wrong here?
>
> Regarding the first observation: Since the K2 is already > 10 years
> old, could component aging already play a role. If so, where to look for?
>
> Thanks for any ideas!
> 73
> Gernot
> DF5RF
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Oliver Dröse

Re: K2 / KX3 receiver observation - need explanation

In reply to this post by gt-i

Hi Gernot,

as I am hearing lots of similar signals from a few of the very very big
guns here in Europe contest after contest and no matter if using my
K3's, the KX3, or whatever other rig (i.e. FT-817, TS-590, ...), I'd
suppose this is rather a TX quality problem of them than one with your
receivers. If you would hear it on *every* strong signal than it would
sound like an RX problem but I suppose you also heard all the strong but
clean signals, did you?

73, Olli - DH8BQA

Contest, DX & radio projects: http://www.dh8bqa.de

Am 05.06.2015 um 16:07 schrieb [hidden email]:

Vic Rosenthal

Re: K2 / KX3 receiver observation - need explanation

Perhaps it was 3-phase hum? The really big amps run on 400V 3-phase circuits (no, Elecraft won't be making these)!

Vic 4X6GP/K2VCO

> On Jun 6, 2015, at 12:54 AM, Oliver Dröse <[hidden email]> wrote:
>
> Hi Gernot,
>
> as I am hearing lots of similar signals from a few of the very very big guns here in Europe contest after contest and no matter if using my K3's, the KX3, or whatever other rig (i.e. FT-817, TS-590, ...), I'd suppose this is rather a TX quality problem of them than one with your receivers. If you would hear it on *every* strong signal than it would sound like an RX problem but I suppose you also heard all the strong but clean signals, did you?
>
> 73, Olli - DH8BQA
>
> Contest, DX & radio projects: http://www.dh8bqa.de
>
>
>> Am 05.06.2015 um 16:07 schrieb [hidden email]:
>> Hello everybody,
>> during the WPX contest I noticed some weird sounds in the K2 when tuning to strong (>S9+20db) stations.
>> The sound was distorted, kind of ripple, but it did not sound like typical ringing.
>> I also noticed LZ9W booming in on 80m with S9+40db, producing 3 images in the K2 and the KX3. However, in the K2 the 2 ghost signals were frequency modulated. How could this happen?
>> Another big one, LY2W, also produced 3 signals in the KX3 but all the 3 were nice and clean.
>>
>> I thought these ghost images would depend on the receiver architecture, or am I wrong here?
>>
>> Regarding the first observation: Since the K2 is already > 10 years old, could component aging already play a role. If so, where to look for?
>>
>> Thanks for any ideas!
>> 73
>> Gernot
>> DF5RF
>>

gt-i

Re: K2 / KX3 receiver observation - need explanation

In reply to this post by Oliver Dröse

Hi Olli,
yep, this might be the case ... but I did not check during the contest
using other receivers than those mentioned - I was quite busy :-)
73, Gernot DF5RF

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gt-i

Re: K2 / KX3 receiver observation - need explanation

In reply to this post by Don Wilhelm-4

Don,
thanks for the hints. The K2 is almost original with some simple mods
that had been published during the "early days".
I pulled out my XG3 and tried to reproduce the problem. But I could not
hear a clean 2nd or 3rd signal, but a lot of hard noise nearby.
I guess the XG3 is just not clean enough - on my scope it produces
squares not a sine - to let me do this comparison.

I guess I need to do some more observations to nail it down.
Tnx, 73 Gernot, DF5RF
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