Problem with 60KHz


Allan Isaacs
 

For the last few weeks I've had trouble with our radio clocks and the reason is a very strong signal around 58KHz which has evaded attempts to find its source.
I assume that it's local interference. Picture attached.
Allan G3PIY


Pete Ferrand
 

Yes, those things happen, happened to me almost 20 years ago.

I was living in a rural area of New Hampshire and heard a broad noise that prevented the clocks from working, had to drive them some miles away to get them to work. It was around 55-58 kHz. 

I called the local electric utility and they sent their interference specialist, who was a ham, around with some very expensive gear and it heard it as well. He drove around and said it could be heard for a couple miles around but didn't peak up anywhere. His conclusion was that it was not coming from nor was it propagated by the utility's wiring or equipment, and so he had no further authority to investigate. There was no industry in the area.

So I had to live with it until I moved a year or two later.

Pete
WB2QLL


-----Original Message-----
From: Allan Isaacs
Sent: Oct 22, 2020 3:11 AM
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Problem with 60KHz

For the last few weeks I've had trouble with our radio clocks and the reason is a very strong signal around 58KHz which has evaded attempts to find its source.
I assume that it's local interference. Picture attached.
Allan G3PIY


Siegfried Jackstien
 

sometimes such noise is coming from switching psu or power inverters

smartphone charger ... or other small switching thingy ...

maybe direction could be found with a directional antenna

good luck

dg9bfc sigi

Am 22.10.2020 um 08:54 schrieb Pete Ferrand:

Yes, those things happen, happened to me almost 20 years ago.

I was living in a rural area of New Hampshire and heard a broad noise that prevented the clocks from working, had to drive them some miles away to get them to work. It was around 55-58 kHz. 

I called the local electric utility and they sent their interference specialist, who was a ham, around with some very expensive gear and it heard it as well. He drove around and said it could be heard for a couple miles around but didn't peak up anywhere. His conclusion was that it was not coming from nor was it propagated by the utility's wiring or equipment, and so he had no further authority to investigate. There was no industry in the area.

So I had to live with it until I moved a year or two later.

Pete
WB2QLL


-----Original Message-----
From: Allan Isaacs
Sent: Oct 22, 2020 3:11 AM
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Problem with 60KHz

For the last few weeks I've had trouble with our radio clocks and the reason is a very strong signal around 58KHz which has evaded attempts to find its source.
I assume that it's local interference. Picture attached.
Allan G3PIY


Allan Isaacs
 

Cracked it Sigi

A few weeks ago I fitted a new Ethernet switch to give me more ports and I used a spare old one using a non-standard coaxial power supply lead.

The PSU was obviously failing and although it produced 12 volts it was extremely noisy.

Because it was a network switch the noise was getting into all the CAT5 cables including the one used for my remote SDR.

I also found my charger for my electric drill battery was very noisy. It was permanently on so the PSU was in poor shape.

Attached the 60KHz signal is now in the clear. An amazing difference!

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Siegfried Jackstien
Sent: 22 October 2020 11:37
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Problem with 60KHz

 

sometimes such noise is coming from switching psu or power inverters

smartphone charger ... or other small switching thingy ...

maybe direction could be found with a directional antenna

good luck

dg9bfc sigi

Am 22.10.2020 um 08:54 schrieb Pete Ferrand:

Yes, those things happen, happened to me almost 20 years ago.

 

I was living in a rural area of New Hampshire and heard a broad noise that prevented the clocks from working, had to drive them some miles away to get them to work. It was around 55-58 kHz. 

 

I called the local electric utility and they sent their interference specialist, who was a ham, around with some very expensive gear and it heard it as well. He drove around and said it could be heard for a couple miles around but didn't peak up anywhere. His conclusion was that it was not coming from nor was it propagated by the utility's wiring or equipment, and so he had no further authority to investigate. There was no industry in the area.

 

So I had to live with it until I moved a year or two later.

 

Pete

WB2QLL

 

-----Original Message-----
From: Allan Isaacs
Sent: Oct 22, 2020 3:11 AM
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Problem with 60KHz

For the last few weeks I've had trouble with our radio clocks and the reason is a very strong signal around 58KHz which has evaded attempts to find its source.
I assume that it's local interference. Picture attached.
Allan G3PIY


Max
 

Does not surprise me at all Allan. I have traced nearly every single case of similar noises to SM PSUs, usually of the plug-top variety.

Couple of weeks ago, sudden appearance of some sort of unstable but very strong "warbling" on 20m and also similar second harmonic at 28 MHz, audible but less so.

Went around house with my trusty Sony SW1E. Traced it to a SM PSU that had previously been totally quiet, and was still generating 12 volts perfectly and at full current, but was for some reason producing this HF warble. Changed it out, noise gone. I was surprised that a SM PSU would so readily generate noise at such a high frequency because, like you, I find they are most often on the LF frequencies, but there it was. Popped capacitor somewhere is my hunch.

73

Max


Allan Isaacs
 

Hi Max

Yes, a duff capacitor. Most PSUs develop a low voltage from rectified mains for control of the chopper circuit. This voltage is maintained by something like 47uF and this gradually loses capacity and its ESR rises. The chopper circuit is then stressed and gets noisier and noisier until eventually the thing will fail to start up after being unplugged. The other weak point is the high voltage smoothing capacitor which has got physically smaller over the years and consequently has a shorter life. Quite often this capacitor is located inside the end cap on a modern mains lamp which acts like an oven and once the capacitor degrades the lamp will become an RF noise generator.

Some chopper circuits (like the STR-L472) oscillate at a square-wave frequency dictated by the HF transformer primary and can be so stable as to produce rock solid VHF signals. Our local Isle of Wight ferry had a problem with an air conditioner using one of these new fangled power supplies which was blocking his ship to shore comms channel.

73 Allan G3PIY

 


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Max
Sent: 22 October 2020 13:38
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Problem with 60KHz

 

Does not surprise me at all Allan. I have traced nearly every single case of similar noises to SM PSUs, usually of the plug-top variety.

Couple of weeks ago, sudden appearance of some sort of unstable but very strong "warbling" on 20m and also similar second harmonic at 28 MHz, audible but less so.

Went around house with my trusty Sony SW1E. Traced it to a SM PSU that had previously been totally quiet, and was still generating 12 volts perfectly and at full current, but was for some reason producing this HF warble. Changed it out, noise gone. I was surprised that a SM PSU would so readily generate noise at such a high frequency because, like you, I find they are most often on the LF frequencies, but there it was. Popped capacitor somewhere is my hunch.

73

Max

 


Siegfried Jackstien
 

i swapped the "modern" but noisy switching psu for my router to an old one (with tranformator inside) ... heavy ... lossy ... but totally quiet ;-)

a linear regulator (like 7809 or 7812) is hams best friend

greetz sigi dg9bfc


Am 22.10.2020 um 11:37 schrieb Allan Isaacs:

Cracked it Sigi

A few weeks ago I fitted a new Ethernet switch to give me more ports and I used a spare old one using a non-standard coaxial power supply lead.

The PSU was obviously failing and although it produced 12 volts it was extremely noisy.

Because it was a network switch the noise was getting into all the CAT5 cables including the one used for my remote SDR.

I also found my charger for my electric drill battery was very noisy. It was permanently on so the PSU was in poor shape.

Attached the 60KHz signal is now in the clear. An amazing difference!

Allan G3PIY


From: main@SDR-Radio.groups.io [mailto:main@SDR-Radio.groups.io] On Behalf Of Siegfried Jackstien
Sent: 22 October 2020 11:37
To: main@SDR-Radio.groups.io
Subject: Re: [SDR-Radio] Problem with 60KHz

 

sometimes such noise is coming from switching psu or power inverters

smartphone charger ... or other small switching thingy ...

maybe direction could be found with a directional antenna

good luck

dg9bfc sigi

Am 22.10.2020 um 08:54 schrieb Pete Ferrand:

Yes, those things happen, happened to me almost 20 years ago.

 

I was living in a rural area of New Hampshire and heard a broad noise that prevented the clocks from working, had to drive them some miles away to get them to work. It was around 55-58 kHz. 

 

I called the local electric utility and they sent their interference specialist, who was a ham, around with some very expensive gear and it heard it as well. He drove around and said it could be heard for a couple miles around but didn't peak up anywhere. His conclusion was that it was not coming from nor was it propagated by the utility's wiring or equipment, and so he had no further authority to investigate. There was no industry in the area.

 

So I had to live with it until I moved a year or two later.

 

Pete

WB2QLL

 

-----Original Message-----
From: Allan Isaacs
Sent: Oct 22, 2020 3:11 AM
To: main@SDR-Radio.groups.io
Subject: [SDR-Radio] Problem with 60KHz

For the last few weeks I've had trouble with our radio clocks and the reason is a very strong signal around 58KHz which has evaded attempts to find its source.
I assume that it's local interference. Picture attached.
Allan G3PIY


Max
 

Many thanks Allan. All very interesting stuff. Yes, SM PSUs. Love 'em sometimes, loathe them others. Always my first suspicion when any noise source is evident. And I found branded is no sure-fire guarantee that they will not be noisy. One of my worst offenders for low frequency mush was Netgear branded supplied with a brand new LAN switch about a year ago.

73

Max


On Thu, Oct 22, 2020 at 02:05 PM, Allan Isaacs wrote:

Hi Max

Yes, a duff capacitor. Most PSUs develop a low voltage from rectified mains for control of the chopper circuit. This voltage is maintained by something like 47uF and this gradually loses capacity and its ESR rises. The chopper circuit is then stressed and gets noisier and noisier until eventually the thing will fail to start up after being unplugged. The other weak point is the high voltage smoothing capacitor which has got physically smaller over the years and consequently has a shorter life. Quite often this capacitor is located inside the end cap on a modern mains lamp which acts like an oven and once the capacitor degrades the lamp will become an RF noise generator.

Some chopper circuits (like the STR-L472) oscillate at a square-wave frequency dictated by the HF transformer primary and can be so stable as to produce rock solid VHF signals. Our local Isle of Wight ferry had a problem with an air conditioner using one of these new fangled power supplies which was blocking his ship to shore comms channel.

73 Allan G3PIY


Max
 

That's true Sigi but to be fair I also have many perfectly quiet SMs so really a question of whether they are designed properly.

73

Max



On Thu, Oct 22, 2020 at 07:56 PM, Siegfried Jackstien wrote:

i swapped the "modern" but noisy switching psu for my router to an old one (with tranformator inside) ... heavy ... lossy ... but totally quiet ;-)

a linear regulator (like 7809 or 7812) is hams best friend

greetz sigi dg9bfc