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Phantom signals

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N4ZR

Phantom signals

I recently started using N1MM+'s spectrum display with my K3, and it
made me notice that I have some phantom signals on the display.
Specifically, there are steady carriers at 14039.6 and 28039.6. Each of
these carriers has "sidebands" spaced 1 KHZ apart on either side. There
is a slight AC roughness to the tones as heard in CW mode, particularly
on 20M. On 7039.6 and 21039.6 a single carrier is audible, much weaker
than on 20 or 10 meters.

Disconnecting the antenna from the K3 does not affect these signals, nor
does disconnecting my Airspy HF+ from the IF Out jack.

Any idea what these might be? Because they are discrete frequencies and
relatively weak, they aren't particularly an operational problem, but

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

.
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k6dgw

Re: Phantom signals

I have a clean carrier at 7039.6, about S4, but nothing on 20. It's
pretty hard to build a double conversion superhet that doesn't have a
few weak spurs.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 11/26/2018 2:20 PM, N4ZR wrote:

> I recently started using N1MM+'s spectrum display with my K3, and it
> made me notice that I have some phantom signals on the display.
> Specifically, there are steady carriers at 14039.6 and 28039.6. Each
> of these carriers has "sidebands" spaced 1 KHZ apart on either side.
> There is a slight AC roughness to the tones as heard in CW mode,
> particularly on 20M. On 7039.6 and 21039.6 a single carrier is
> audible, much weaker than on 20 or 10 meters.
>
> Disconnecting the antenna from the K3 does not affect these signals,
> nor does disconnecting my Airspy HF+ from the IF Out jack.
>
> Any idea what these might be? Because they are discrete frequencies
> and relatively weak, they aren't particularly an operational problem, but
>
> 73, Pete N4ZR
> Check out the Reverse Beacon Network
> at <http://reversebeacon.net>, now
> spotting RTTY activity worldwide.
> For spots, please use your favorite
> "retail" DX cluster.

tomb18

Re: Phantom signals

In reply to this post by N4ZR

This is pretty common. One thing that can help is to wrap your USB cable through an ft241 31 to rid. About 6 turns gets rig of lots of picked up garbage. 73 Tom

Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Fred Jensen <[hidden email]> Date: 2018-11-26 6:14 PM (GMT-05:00) To: [hidden email] Subject: Re: [Elecraft] Phantom signals
I have a clean carrier at 7039.6, about S4, but nothing on 20. It's
pretty hard to build a double conversion superhet that doesn't have a
few weak spurs.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 11/26/2018 2:20 PM, N4ZR wrote:

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ab2tc

Re: Phantom signals

Hi,

Absolutely no sign of any of these spurs here with my K3S. Since they are at
constant frequencies they must be coming in through the K3 front end (*not*
at the IF level). So either your K3 front end is generating them (which it
shouldn't) or they are present in your environment. Again, since they are at
constant frequencies, the P3 or any other SDR connected to the K3 IF output
should not be the culprit. Send me an E-mail and I will give you spectral
plots collected with LP-PAN/NAP3 with K3 connected to a well shielded dummy
load.

AB2TC

tomb18 wrote
> This is pretty common. One thing that can help is to wrap your USB cable
> through an ft241 31 to rid. About 6 turns gets rig of lots of picked up
> garbage. 73 Tom
>
>
> Sent from my Samsung Galaxy smartphone.
> -------- Original message --------From: Fred Jensen <

> k6dgw@

> > Date: 2018-11-26 6:14 PM (GMT-05:00) To:

> elecraft@.qth

> Subject: Re: [Elecraft] Phantom signals
> I have a clean carrier at 7039.6, about S4, but nothing on 20. It's
> pretty hard to build a double conversion superhet that doesn't have a
> few weak spurs.
>
> 73,
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
>
> On 11/26/2018 2:20 PM, N4ZR wrote:
>> I recently started using N1MM+'s spectrum display with my K3, and it
>> made me notice that I have some phantom signals on the display.
>> Specifically, there are steady carriers at 14039.6 and 28039.6. Each
>> of these carriers has "sidebands" spaced 1 KHZ apart on either side.
>> There is a slight AC roughness to the tones as heard in CW mode,
>> particularly on 20M. On 7039.6 and 21039.6 a single carrier is
>> audible, much weaker than on 20 or 10 meters.
>>
>> Disconnecting the antenna from the K3 does not affect these signals,
>> nor does disconnecting my Airspy HF+ from the IF Out jack.
>>
>> Any idea what these might be? Because they are discrete frequencies
>> and relatively weak, they aren't particularly an operational problem, but
>>
>> 73, Pete N4ZR
>> Check out the Reverse Beacon Network
>> at <http://reversebeacon.net>, now
>> spotting RTTY activity worldwide.
>> For spots, please use your favorite
>> "retail" DX cluster.
>
> ______________________________________________________________
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>
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> tomb18@

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Don Wilhelm

Re: Phantom signals

Another thing to suspect is noise generated by a computer, or ethernet
modems and routers and being routed to the K3 and P3 via the K3 to
computer connection. I believe that is why Tom suggested winding the
USB cable through a type 31 ferrite core. BTW, that core should be near
the computer end).

Disconnect and power down the computer to see if that is contributing to
the "spurs".

73,
Don W3FPR

On 11/27/2018 5:57 PM, ab2tc wrote:

> Hi,
>
> Absolutely no sign of any of these spurs here with my K3S. Since they are at
> constant frequencies they must be coming in through the K3 front end (*not*
> at the IF level). So either your K3 front end is generating them (which it
> shouldn't) or they are present in your environment. Again, since they are at
> constant frequencies, the P3 or any other SDR connected to the K3 IF output
> should not be the culprit. Send me an E-mail and I will give you spectral
> plots collected with LP-PAN/NAP3 with K3 connected to a well shielded dummy
> load.
>
> AB2TC
>
>
> tomb18 wrote
>> This is pretty common. One thing that can help is to wrap your USB cable
>> through an ft241 31 to rid. About 6 turns gets rig of lots of picked up
>> garbage. 73 Tom
>>
>>

Grant Youngman-2

Re: Phantom signals

I sometimes notice a host of phantoms that follow the tuning, but only when the preamp is off. Turning on the preamp generally kills them all.

This doesn’t help with the fixed frequency junk being generated by the myriad of switchers in the house, though. Different issue.

Grant NQ5T

> On Nov 27, 2018, at 6:16 PM, Don Wilhelm <[hidden email]> wrote:
>
> Another thing to suspect is noise generated by a computer, or ethernet modems and routers and being routed to the K3 and P3 via the K3 to computer connection. I believe that is why Tom suggested winding the USB cable through a type 31 ferrite core. BTW, that core should be near the computer end).
>
> Disconnect and power down the computer to see if that is contributing to the "spurs".
>
> 73,
> Don W3FPR
>
>>

N4ZR

Re: Phantom signals

In reply to this post by Don Wilhelm

Trouble is, my computer supplies N1MM+, including its spectrum display.
Catch 22

73, Pete N4ZR
Check out the Reverse Beacon Network
at <http://reversebeacon.net>, now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

On 11/27/2018 6:16 PM, Don Wilhelm wrote:

> Another thing to suspect is noise generated by a computer, or ethernet
> modems and routers and being routed to the K3 and P3 via the K3 to
> computer connection. I believe that is why Tom suggested winding the
> USB cable through a type 31 ferrite core. BTW, that core should be
> near the computer end).
>
> Disconnect and power down the computer to see if that is contributing
> to the "spurs".
>
> 73,
> Don W3FPR
>
> On 11/27/2018 5:57 PM, ab2tc wrote:
>> Hi,
>>
>> Absolutely no sign of any of these spurs here with my K3S. Since they
>> are at
>> constant frequencies they must be coming in through the K3 front end
>> (*not*
>> at the IF level). So either your K3 front end is generating them
>> (which it
>> shouldn't) or they are present in your environment. Again, since they
>> are at
>> constant frequencies, the P3 or any other SDR connected to the K3 IF
>> output
>> should not be the culprit. Send me an E-mail and I will give you
>> spectral
>> plots collected with LP-PAN/NAP3 with K3 connected to a well shielded
>> dummy
>> load.
>>
>> AB2TC
>>
>>
>> tomb18 wrote
>>> This is pretty common. One thing that can help is to wrap your USB
>>> cable
>>> through an ft241 31 to rid. About 6 turns gets rig of lots of picked up
>>> garbage. 73 Tom
>>>
>>>
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>
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Don Wilhelm

Re: Phantom signals

Pete,

Any chance you can borrow a P3 to see if those spurs are present both
with and without the computer?
That would be a good test if you can manage it.

The other thing that may help is to bond the K3 to the other gear,
following the paths of the IF out coax and also the audio cables. Bond
from box to box rather than trying to "ground" everything to a single
point (which may cause additional noise pickup. Use the information on
that subject from Jim Brown K9YC.
If everything else other than the K3 is plastic cased, bond to BNC
connector shells and/or computer I/O connector jackscrews.

73,
Don W3FPR

On 11/27/2018 9:44 PM, N4ZR wrote:
>
> Trouble is, my computer supplies N1MM+, including its spectrum
> display. Catch 22
>
>

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ab2tc

Re: Phantom signals

Hi again,

But if they are fixed (not following the tuning of the K3) you should be
able to tune to them and hear them in your K3 without any computers or SDRs
running. So Don's advice to turn everything except the K3 off seems sound to
me.

AB2TC - Knut

Don Wilhelm wrote

> Pete,
>
> Any chance you can borrow a P3 to see if those spurs are present both
> with and without the computer?
> That would be a good test if you can manage it.
>
> The other thing that may help is to bond the K3 to the other gear,
> following the paths of the IF out coax and also the audio cables. Bond
> from box to box rather than trying to "ground" everything to a single
> point (which may cause additional noise pickup. Use the information on
> that subject from Jim Brown K9YC.
> If everything else other than the K3 is plastic cased, bond to BNC
> connector shells and/or computer I/O connector jackscrews.
>
> 73,
> Don W3FPR
>
> On 11/27/2018 9:44 PM, N4ZR wrote:
>>
>> Trouble is, my computer supplies N1MM+, including its spectrum
>> display. Catch 22
>>
>>
> <snip>

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