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K3 on 50 MHz - noise and possible harmonics

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Chris Hallinan

K3 on 50 MHz - noise and possible harmonics

I've been playing around with 50 MHz USB/CW down at the low end of the band
with a plain ol' dipole. I'm curious about noise and birdies and other
people's experience, as I really don't know what to expect.

I have a steady S3/4 noise level at all frequencies with the preamp off,
jumping to solid S5 with the preamp engaged. I have several strong signals
(probably harmonics of some interference??) as follows listening in USB
mode, preamp off:

50.026: S4
50.057: S6
50.087: S5
50.117: S6
50.148: S6
50:178: S4
and more as I tune up. Notice the 30KHz spacing.

These are all steady 2-tone signals with perhaps a couple hundred hertz
difference in the two tones. No variation with day/night or propagation as
far as I can tell. They all disappear when the antenna is disconnected.

First, is my background noise level local or should that be expected on 50
MHz? And what are these signals spaced every 30 KHz or so?

Could this be broadcast overload way up here on 50 MHz? I do have a fairly
close 1580 KHz AM station broadcasting 1100 watts during daytime, and 110
at night, but I use an Array Solutions BCB filter.

What have others experienced?

Thanks and 73,

Chris
K1AY

--
Life is like Linux - it never stands still.
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KD7PY

Re: K3 on 50 MHz - noise and possible harmonics

This post was updated on .

If you are unlucky as me and live in the city you will have a high noise level. during the morning hours my
noise level is S1 with the 2nd bar just blinking with the preamp in the K3 on. later in the day when everyone is home the noise goes to S3>S4 as the load on the power grid goes up.

I checked my K3 on a dummy load and I found only a few birdies internal to the K3
50.028
50.044
50.075.8
50.147.3
50.195.4 I didn't check above 50.200

watching the birds on the P3 they move as I turn the VFO
Interesting that I only hear the birds with the preamp in the K3 turned on or off. with the external ARR preamp on I don't hear them, but with my 5 el beam the noise is high enough that I only use the K3's preamp. I only notice the bird at 50.147, the rest are below the noise floor with the antenna on.

the only way to check for internal birds in the K3 is to check it with a dummy load connected.
you say that the birds are spaced 30 khz apart should tell you that some device external to the K3 is causing them. a beam is very helpful in nulling out the interference. it's best to check out your house 1st for the offending device, unplug everything one at a time and check to see if they are gone.
Ed

Steve Lund

Re: K3 on 50 MHz - noise and possible harmonics

In reply to this post by Chris Hallinan

I have all these spurious signals in my K3, too.

They are caused by my wireless router. But are the result of using wired
connections to my office computers. When I remove the LAN cables these
signals disappear, along with many on the hf bands.

I have received the ferrites recommended by K9YC. The plan is to install
them on Wednesday. I have both the #43 and #61 material.

Steve, K6UM

On Mon, Jun 29, 2015 at 7:43 PM, Chris Hallinan <[hidden email]> wrote:

> I've been playing around with 50 MHz USB/CW down at the low end of the band
> with a plain ol' dipole. I'm curious about noise and birdies and other
> people's experience, as I really don't know what to expect.
>
> I have a steady S3/4 noise level at all frequencies with the preamp off,
> jumping to solid S5 with the preamp engaged. I have several strong signals
> (probably harmonics of some interference??) as follows listening in USB
> mode, preamp off:
>
> 50.026: S4
> 50.057: S6
> 50.087: S5
> 50.117: S6
> 50.148: S6
> 50:178: S4
> and more as I tune up. Notice the 30KHz spacing.
>
> These are all steady 2-tone signals with perhaps a couple hundred hertz
> difference in the two tones. No variation with day/night or propagation as
> far as I can tell. They all disappear when the antenna is disconnected.
>
> First, is my background noise level local or should that be expected on 50
> MHz? And what are these signals spaced every 30 KHz or so?
>
> Could this be broadcast overload way up here on 50 MHz? I do have a fairly
> close 1580 KHz AM station broadcasting 1100 watts during daytime, and 110
> at night, but I use an Array Solutions BCB filter.
>
> What have others experienced?
>
> Thanks and 73,
>
> Chris
> K1AY
>
>
>
>
> --
> Life is like Linux - it never stands still.
> ______________________________________________________________
> 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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Mike Murphree

Re: K3 on 50 MHz - noise and possible harmonics

In recent testing of a new Cloud-IQ SDR, I found the same thing at home.
Two tones about 500 Hz apart and reoccurring at about the same interval.
I used my KX3 to track it down to the 100BASE-T ethernet cables. The noise
floor on the SDR is <140 dB and was able to pick it up.

73
Mike N4MHO

On Mon, Jun 29, 2015 at 11:26 PM, Steve Lund <[hidden email]> wrote:

> I have all these spurious signals in my K3, too.
>
> They are caused by my wireless router. But are the result of using wired
> connections to my office computers. When I remove the LAN cables these
> signals disappear, along with many on the hf bands.
>
> I have received the ferrites recommended by K9YC. The plan is to install
> them on Wednesday. I have both the #43 and #61 material.
>
> Steve, K6UM
>
> On Mon, Jun 29, 2015 at 7:43 PM, Chris Hallinan <[hidden email]>
> wrote:
>
> > I've been playing around with 50 MHz USB/CW down at the low end of the
> band
> > with a plain ol' dipole. I'm curious about noise and birdies and other
> > people's experience, as I really don't know what to expect.
> >
> > I have a steady S3/4 noise level at all frequencies with the preamp off,
> > jumping to solid S5 with the preamp engaged. I have several strong
> signals
> > (probably harmonics of some interference??) as follows listening in USB
> > mode, preamp off:
> >
> > 50.026: S4
> > 50.057: S6
> > 50.087: S5
> > 50.117: S6
> > 50.148: S6
> > 50:178: S4
> > and more as I tune up. Notice the 30KHz spacing.
> >
> > These are all steady 2-tone signals with perhaps a couple hundred hertz
> > difference in the two tones. No variation with day/night or propagation
> as
> > far as I can tell. They all disappear when the antenna is disconnected.
> >
> > First, is my background noise level local or should that be expected on
> 50
> > MHz? And what are these signals spaced every 30 KHz or so?
> >
> > Could this be broadcast overload way up here on 50 MHz? I do have a
> fairly
> > close 1580 KHz AM station broadcasting 1100 watts during daytime, and 110
> > at night, but I use an Array Solutions BCB filter.
> >
> > What have others experienced?
> >
> > Thanks and 73,
> >
> > Chris
> > K1AY
> >
> >
> >
> >
> > --
> > Life is like Linux - it never stands still.
> > ______________________________________________________________
> > 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]
> >
> ______________________________________________________________
> 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]
>

Jim Brown-10

Re: K3 on 50 MHz - noise and possible harmonics

In reply to this post by Steve Lund

On Mon,6/29/2015 9:26 PM, Steve Lund wrote:
> I have received the ferrites recommended by K9YC. The plan is to install
> them on Wednesday. I have both the #43 and #61 material

Hi Steve,

A clarification. #31 is the first weapon of choice for the HF bands --
it is effective from the AM broadcast band up to 50 MHz. #43 is slightly
better above 10 MHz, but much less effective on 80 and 160M. #61 is NOT
useful to kill noise below 2M -- it's loss is far too low, low enough
that it can be used for transformers that handle power at HF.

2-3 turns through a #31 or #43 core puts the choke in the range of 50
MHz. Because you're using only 2-3 turns, more than one choke may be
needed. The chokes go on both ends of all the cables connected to the
router and the modem.

That gear often creates birdies on 30M, 20M, and the low end of 10M.
Follow my guidelines for RG58/8X coax for these chokes. These birdies
are created by clocks local to the router, and their frequencies are not
precise (although they are crystal-controlled). If you have neighbors,
you'll likely hear their routers too, a few hundred Hz from yours. To
identify yours, kill power to it.

73, Jim K9YC
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Steve Lund

Re: K3 on 50 MHz - noise and possible harmonics

In reply to this post by Steve Lund

Well great success on the ferrite core experiments today.

I aimed my yagi directly at the house, which are separated by approximately
40'. The 24960 signal was around S5-6. I wrapped 9 turns of the LAN cable
going to my old XP computer around a 2.4" #31 core. The signal dropped to
S0 - still lightly audible. The one at 24900 was completely gone. The 6m
ones also dropped to the S0 - lightly audible. I have more cores, but my
other LAN cable going to my newer Win7 machine is too short to wind any
turns around the core. Disconnecting power to the wireless router
completely removes all spurious signals on 6m. So, I know I can make
improvements, but for now it is livable.

The home theatre system audio problem was totally fixed. The right surround
channel was totally overloaded by anything more than 150w on 20m. Because
the connectors on the audio cable would take time to remove, I wrapped 9
turns around the 'Biggest #31 clamp on'. No trace of interference at 600w.

So, a big thank to Jim, K9YC, for his tutorial (and experiments) on curing
RFI.

Steve, K6UM

On Mon, Jun 29, 2015 at 9:26 PM, Steve Lund <[hidden email]> wrote:

> I have all these spurious signals in my K3, too.
>
> They are caused by my wireless router. But are the result of using wired
> connections to my office computers. When I remove the LAN cables these
> signals disappear, along with many on the hf bands.
>
> I have received the ferrites recommended by K9YC. The plan is to install
> them on Wednesday. I have both the #43 and #61 material.
>
> Steve, K6UM
>
> On Mon, Jun 29, 2015 at 7:43 PM, Chris Hallinan <[hidden email]>
> wrote:
>
>> I've been playing around with 50 MHz USB/CW down at the low end of the
>> band
>> with a plain ol' dipole. I'm curious about noise and birdies and other
>> people's experience, as I really don't know what to expect.
>>
>> I have a steady S3/4 noise level at all frequencies with the preamp off,
>> jumping to solid S5 with the preamp engaged. I have several strong
>> signals
>> (probably harmonics of some interference??) as follows listening in USB
>> mode, preamp off:
>>
>> 50.026: S4
>> 50.057: S6
>> 50.087: S5
>> 50.117: S6
>> 50.148: S6
>> 50:178: S4
>> and more as I tune up. Notice the 30KHz spacing.
>>
>> These are all steady 2-tone signals with perhaps a couple hundred hertz
>> difference in the two tones. No variation with day/night or propagation
>> as
>> far as I can tell. They all disappear when the antenna is disconnected.
>>
>> First, is my background noise level local or should that be expected on 50
>> MHz? And what are these signals spaced every 30 KHz or so?
>>
>> Could this be broadcast overload way up here on 50 MHz? I do have a
>> fairly
>> close 1580 KHz AM station broadcasting 1100 watts during daytime, and 110
>> at night, but I use an Array Solutions BCB filter.
>>
>> What have others experienced?
>>
>> Thanks and 73,
>>
>> Chris
>> K1AY
>>
>>
>>
>>
>> --
>> Life is like Linux - it never stands still.
>> ______________________________________________________________
>> 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]
>>
>
>