eHam Forums => Elmers => Topic started by: TANAKASAN on November 23, 2012, 01:41:21 PM

Title: What Causes 'Sweepers'
Post by: TANAKASAN on November 23, 2012, 01:41:21 PM
Last night I was listening on 20m and I noticed a number of 'sweepers'. After a while I began to notice a pattern to these events.

1) The waterfall display showed up to four sweepers about 80 KHz apart.

2) The sweepers occurred every four minutes twenty three seconds.

3) After moving up in frequency for eighteen seconds the sweepers slowed their rate of change then gradually faded out.

A Google search using the term 'sweepers' just uncovers machinery used to clean the highways so does anyone have an idea how these events occur?


Title: RE: What Causes 'Sweepers'
Post by: AC5UP on November 23, 2012, 02:51:34 PM
You haven't heard of naturally occurring terrestrial radio signals?
Could be that's what you're hearing, or it could be from millions and millions of miles away... (

Like Chicken Man, they're everywhere, they're everywhere! (

And, as you recall from high school, the Doppler Effect raises the pitch of signals from an approaching object while lowering the pitch from objects moving away...... Same deal with radio.  Maybe that was Vger ringing your phone? (

Title: RE: What Causes 'Sweepers'
Post by: KE3WD on November 23, 2012, 03:11:24 PM

Quit about it...

Title: RE: What Causes 'Sweepers'
Post by: AC5UP on November 23, 2012, 03:15:28 PM
Does this mean that if Tanakasan ever figures out exactly what he heard, the CIA will... Uhhhhh... Do something with extreme prejudice...?


Glad I didn't start this thread !!

Title: RE: What Causes 'Sweepers'
Post by: STAYVERTICAL on November 23, 2012, 06:42:45 PM
I also hear those things periodically, and they are always pretty strong as well.

Could it be ionospheric sounding equipment?
Or perhaps some sort of over the horizon radar sounding, in prelude to activation?
The periodic pattern you have observed tends to indicate some sort of man made emissions.

Alternatively, it is only a short time to December 21st, so maybe this is the first indications of E.T. returning.

Or it could just be some guy who bought an Eico 753 on Ebay and decided to hook it up to his KW linear.

If you are interested, the ELF region is full of whistlers, sweepers and lots of other naturally produced terrestrial radio signals.
This is a peculiar time in the solar cycle as well - there are lots of weird signals around during geomagnetic storms and such.
It is a lot of fun listening to the burps and gurgles produced naturally on H.F. during these events - Gaia with indigestion?
It's easy to see the difference on long and short paths, just from these noises.

Happy hunting,

73 - Rob

Title: RE: What Causes 'Sweepers'
Post by: AA4HA on November 23, 2012, 08:22:43 PM
It could be harmonics from a switching power supply, the 80 Khz spacing sounds "familiar". Switchers are not renowned for their frequency stability and it can sometimes vary by load.

I have seen the same thing on a spectrum analyzer and it was often caused by a computer.

This does not rule out that it could be some form of government/military tech or radar system.

Title: RE: What Causes 'Sweepers'
Post by: K6AER on November 23, 2012, 09:09:47 PM
The sweep carriers you hear are most likely a product of a 2.4/5.8  GHz 802 wireless transceiver like the Motorola Canopy unit. We have several units in the neighborhood including one at my home and when the power is removed the interference stops.

I had the WISP replace the unit and the interference stopped at my home.

Title: RE: What Causes 'Sweepers'
Post by: NM3G on November 24, 2012, 09:06:28 AM
What you are hearing are in all likelihood Radiosonde transmitters. These are used by remote stations for real-time ionospheric measurements.

Here is one link that has a great deal of information ... enter ionosonde into google (or your choice of search engines), and happy reading.

Simple way to determine the difference between accidental (natural or man-made) noise is periodicity ... if it keeps a constant schedule, it is most likely deliberate, and desirable.

As to it cutting off ... well, if the ionosphere won't support propagation, you won't hear the transmitter. I'm not sure about it slowing down though.

Hope this helps.


Title: RE: What Causes 'Sweepers'
Post by: N0YXB on November 24, 2012, 10:24:39 AM

Like Chicken Man, they're everywhere, they're everywhere! (

Chicken Man!  Thanks for the reminder, I haven't thought about Chicken Man in eons.

Title: RE: What Causes 'Sweepers'
Post by: G8JNJ on November 24, 2012, 11:02:01 AM
Hate to spoil everyones fun...............

They are ionospheric chirp sounders. If you know the timing schedule you can track them.

Radiosondes tend to operate on 27MHz 406-413MHz and 1660 -1700MHz and usually sound like warbling tones.


Martin - G8JNJ

Title: RE: What Causes 'Sweepers'
Post by: N6AJR on November 24, 2012, 11:49:54 AM
No, no, no.  They are the  high power beams of energy emitted by GRB and are sweeping the earth with gamma rays. ( Gamma Ray Bursters, a type of rapidly spinning core of a very large star after it dies,) so since we are all really just stardust ourselves, it's just mom saying hello :)

Title: RE: What Causes 'Sweepers'
Post by: TANAKASAN on November 24, 2012, 12:05:03 PM
From reading the replies and following the links I think NM3G has the correct answer. One of the graphs shown in the link he gave covers the entire 20m band but it doesn't explain the series of signals a nominal 80 KHz apart. So far I haven't been visited by the Men in Black so I presume that there is an explanation that doesn't involve ET.


Title: RE: What Causes 'Sweepers'
Post by: KL3HY on November 24, 2012, 11:43:15 PM
I hear these myself from time to time, and I can tell you exactly what they are not:

1.  Ionosondes (aka chirpsounders)
2.  Any form of radar

Ionosondes sweep a given frequency range very quickly, which is why you typically just hear a chirp as it sweeps past your frequency.  Any slow moving signal traversing a relatively small slice of the HF bands would have no practical value in a sounder role.

Over The Horizon Radars operating on HF also do not exhibit any of the mentioned characteristics.  OTHR might hop around in frequency, but they certainly don't lazily migrate up or down in frequency and then fade out.  CODAR is another form of radar using HF, but it also doesn't do what Tanakasan's signal is doing.  Do some searches on Youtube--there are many examples of OTHR and CODAR signals as well as ionosondes.  You can hear what they sound like and compare them to what you're hearing.

One basic but important question is whether the signal exhibits fading as any non-local signal would.  If it doesn't, that's almost a dead giveaway that it's locally generated noise.  And noise is almost certainly what it is.


Title: RE: What Causes 'Sweepers'
Post by: G3RZP on November 25, 2012, 02:01:18 AM
Radiosondes for meteorological purposes are in the band 400.15 to 406 MHz, not 406 to 413.. 402 to 405 MHz is also used by the Medical Implant Communication System, while 401 to 402 and 405 to 406 is used by the Medical Equipment Data System. Much of the band is also used by the Earth Exploration Satellite Systems (EESS)

Title: RE: What Causes 'Sweepers'
Post by: G8JNJ on November 25, 2012, 04:46:11 AM

I was wrong on two counts.

The 80KHz spacing suggests it is actually a spurious emission from a switched mode power supply, as correctly stated by several others.

Peter - you are correct 400.15 to 406MHz was stated in the second document I linked to.

Perhaps I shouldn't trust my memory quite so much these days  :-[


Martin - G8JNJ

Title: RE: What Causes 'Sweepers'
Post by: AC5UP on November 25, 2012, 06:43:12 AM I presume that there is an explanation that doesn't involve ET.

I still say you're hearing a signal from Uranus...................

< The pun was begging to be made... Someone had to do it! >

Title: RE: What Causes 'Sweepers'
Post by: AC2Q on November 26, 2012, 06:42:57 PM
I'll wager it's a cheap switching power supply. Start unplugging your laptops and newer wall warts.

Title: RE: What Causes 'Sweepers'
Post by: SWMAN on November 26, 2012, 07:57:19 PM
 What does the Starship Enterprise and hemroids have in common ?

 They both circle uranus looking for Clingons.

Title: RE: What Causes 'Sweepers'
Post by: K4JSR on December 01, 2012, 07:06:22 PM
 ;D Relax  They are all caused by the newest ham radio contest: