The 75 Meter Swisher?

[W9GT]

I realize that I might be digging up old bones, but having heard this thing for a long time, I was just wondering what it might be.  I have frequently heard a signal that drifts across a large portion of the 80/75 M band.  It has a rough tone with some FMing and a "wiggly" sound to it.  I think it starts lower in frequency and moves up through the band.  It sometimes turns off and on, but always seems to drift across the band.
I have noticed it primarily on week days and in the morning, but I have heard it at other times as well.

It seems that I remember hearing somewhere that it might be some sort of industrial RF heating unit or other similar equipment.  It is possibly just an incidental radiator, but should not be producing such a widely propagated interfering signal.  This thing seems to be heard over much of the eastern US.  Anyone know what it is?  It seems that the FCC ought to be able to do something about it, but reality dictates that they do not regard such things as high priority.

I'm just curious.  It is an annoyance, but normally doesn't cause any major disruption of QSOs, as it drifts through and doesn't seem to stay in one place very long.

What is the swisher?

73,  Jack, W9GT

[W5AMI]

Not sure, but it could be an ionospheric sounder, Jack.  They are used by the military mainly to determine where the best propagation is 2-30 mcs and above.  They usually move at a faster rate than what you describe however.

Brian / wa5am

[KB2WIG]

Up here in the NE, a famous Constitutional authority named  a propagation sounder, such as you described, the "Boston Buzzie".

The swisher.... some moron keys his rig on a frequency in use, and gentely twists the dial back and forth.   "" wea uhh we uhhh weah uhhh  we sque sque squae"   The last time I regularly heard this was in the early 90's on 3885 when I got home after the bars closed..    This time frame was called the " Atomic Chainsaw  Yeah-a-loow " period of phone activity, if I recall corectely. I listend to the guys all the time.   klc

[W9GT]

I haven't heard what an ionosonde system sounds like, but I think this thing is much too slow and unstable sounding to be anything like that.  It doesn't sound like it has any regular pulsing pattern or coordinated movement in frequency.  It almost sounds like a drifting VFO that is very mechanically unstable and microphonic and has a poorly filtered power supply.   It slowly drifts across the band and sounds like something mechanically "modulates" the signal.  At times it is quite strong and well in excess of S 9 at this location.

Yes I have heard the VFO swisher (knuckle dragging ,AM hating retard).  But this is different.  It slowly moves across the band in one direction and occasionally switches on and off at irregular intervals.

I know I have heard others discussing it.  Anyone else know what I am referring to?

73,  Jack, W9GT

[W1UJR]

There is a noise which sounds like some sort of free running oscillator, starts in the lower part of 3800 and moves up the band. It is not quite strong enough to preclude moderate signal strength communication on or about the freq., the annoying part is that it moves up band, and onto existing QSOs.

Seems to operate around business hours, someone, think it was W1VZR, thought it was some sort of RF heating system used to dry wood. I believe that Tim HLR also knows something about this, he mentioned during one of our conversations. Don't think anyone has determined the source for certain, just speculation at this point.

It's a pretty nasty sound, and unlike the "Boston Buzzie" (RIP Irb), it is constant, about a S9 noise level here in Wiscasset.


73 Bruce W1UJR

[k4kyv]

During the last sunspot peak when 10m was open during most days, the band was full of similar sounding ones.  They often made the band nearly unusable because of their constant swishing.  Lately I've been hearing the thing on 75m. down here.  It is sometimes pretty strong, but not as disruptive as the ones on 10m.

[WA3VJB]

Maybe make a sound file?

If it's on often enough, just record randomly when you're on an AM QSO, and maybe it will come across the frequency.

There are people who routinely "roll tape"  and perhaps there's an example in the archives.

[W3LSN]

I too have heard that noise since before I was licensed in 1975, and it always reminded me of someone keyed up and simply swishing by the frequency in one direction. This would always happen oonly nce unlike the disgruntled SSB swishers found elsewhere on 75.

Several times since I got my SDR-14 I've been able to see that mystery signal on my display. It is a noisy signal that appears out of nowhere on the lower side of my passband, and which moves rapidly through and past the high end. The overall level is somewhat weakish in my locale and its mainly a curiosity not a nuisance. This seems to have the characteristics of a sounder.

73, Jim
WA2AJM/3

[Bacon, WA3WDR]

I've heard the hummy drifty kind of signal called a 'zwizzsh', as opposed to a 'swish'.  The ones I heard had 60 or 120 Hz hum on them.

[W3RSW]

I've always assumed it was a kind of natural occurance.... sort of like Northern lights, magnetically induced or focused electrons or something.   Possibly it's some sort of mirage effect whereby the streaming fields are reflected back numerous times by the ionosphere.  Anyway, it seems to move about 1 kHz/minute or slower. I think I hear it going up freq. some days and down other days but you know how memory is.
    ************
Alternate and more edgy explanation.  - Oh yeah, an "Independence Day" sounder.  They're gettin' the lowdown on high altitude ionospherics in preparation for a general heating of the atmosphere to bake us.  Some enemies just take their good ol time.  What's a year to an out-of-solar-system being anyway? Very arbitrary.. just one little planet's time of orbit around a very small G2 star.
     So, there you have it; many years study for a few minutes of action. Reminds you of some Chinese proverbs.

[John K5PRO]

Plenty of industrial or medical processes, including plasma generation, medical cauterization, induction heating and annealing, ion sources for accelerators and physics experiments, chemical analysis machines that use ionized species, and things like RF-driven fluorescent ballasts use Medium Freq RF (hundreds of KHz up to 13.56 MHz). Some of these processes are free-running as far as frequency stability go, as long as the emissions are below certain limits as specified in part 18 of FCC R&R for ISM equipment. It makes for much simpler coupling to the load not having to constrain frequency with a crystal and adjust loading control in real time. Letting it slide around in freq, as the capacitance or inductance of the load to the power oscillator changes with proximity, heat, plasma impedance, blood resistivity, etc.... is much easier from a control standpoint. But it puts the burden of proof on the OEM to keep radiated and conducted leakage under control. Sometimes, as we all are aware, this doesn't work. RF gaskets begin to wear and leak, grounding isn't always perfect for powerline outlets (for RF ground). Cheap uncertified equipment may ignore federal regulations entirely. My doctor used a tiny portable RF torch to remove a small mole on my leg a few years ago, and of course, it didn't hurt much due to the high frequency. The smell was familiar from having touched a few RF sources in my years, and having burnt flesh. I was explaining to him how it worked, while he used it. A lesson for both of us.

Some dielectric heating also works at this low frequency, but usually is 13.56, 27.12 and higher, close to or locked on the ISM frequencies. The RF fluorescent ballasts tend to make a horrible racket that is more of a loud hum, on my TR7 on the workbench in my garage. 

As for the swisher, it could easily be one of these processes, or a mixed product of a fixed signal and a process at a higher frequency, that is getting propagated on the HF bands via the ionosphere or just locally via ground wave.