Tuesday, December 15, 2020

Intruder at the top of the 20 meter amateur band?

It wasn't my intent to have this next post be about locating a source of a transmitter - but the temptation proved irresistible.

Over the past several days I'd been working on an addition to the Northern Utah WebSDR: A temperature-based frequency control of the local oscillators on some of the receive chains.  The receivers in question are based on the Si570 synthesizer and are prone to temperature-based frequency drift, and since they have internal reference oscillators, there is no way to externally lock them.

For this temperature-based stabilization to work, I have correlated the room temperature with the actual frequency, so I have been frequenting the bands/receivers with the aforementioned issues and making measurements - but I digress:  It was during this activity that I noticed this massive signal at the top of the 20 meter band, occasionally firing up and clobbering ongoing conversations by U.S. amateurs.

Figure 1:
  Waterfall display of the signal around 14.350 MHz.  Nearly invisible, on and in the left edge of this monster carrier, are ongoing QSOs underneath this strong signal.  No audio recording was made of this signal as its acoustic property was unremarkable:  It sounded pretty much like a DRM (Digital Radio Mondiale) signal - that is, white noise with selective fading.
Click on the image for a larger version.

What is it?

Upon seeing this, I had my suspicions based on articles that I'd read earlier - but I fired up the TDOA (Time Direction of Arrival) system on the KiwiSDR network, using five receivers within the zone of reception scattered across the continental U.S.  Multiple sessions of direction-finding over several days yielded similar results to this map:

Figure 2:
  TDOA results of the above transmission.  Note that long-distance HF direction finding has significant uncertainties, so the above location is likely accurate to only a few 10s of km at best.
Click on the image for a larger version.

This clinched it - it was likely shortwave-based high-frequency trading.

Who are they?

As you may (or may not) know, the so-called "High-Frequency" trading utilizes the very small differences in the prices of trading instruments (stocks, etc.) that occur over time.  The idea has nothing to do with "HF" like shortwave radio, but rather it is the notion that if one can buy or sell a tiny fraction of a second before someone else, differences in prices may be exploited.  One of the aspects of this type of trading is that conventional means of data transport (e.g. fiber optics) is too "slow":  Light travels at about 1/3 the speed of that of free space through a glass fiber and this means that compared to a radio wave on a "direct" path, data transmitted via fiber will arrive later - and this does not include delays due to the equipment in that data network.

What this means is that some entities are experimenting with the use of the HF bands for the most direct, point-to-point means of conveying this information possible - and it seems that some of this information is being transmitted on amateur bands, as the above indicates.

Not surprisingly, these entities are very secretive - but others have done a bit of digging in public, FCC databases.

Here are a few links:

As noted in the QRZ thread, the Part 5 experimental license frequency includes the entirety of the 20 meter band, with no requirement for identification.

While many amateurs seem to be surprised about this, I was not:  There are several instances where Part 5 licenses have been issued (I can provide an example via email) - the applicant providing frequency ranges in their application that encroach on any number of other services - and been issued permission to operate there - but there's typically a caveat:  They are not to interfere with existing, licensed services.

It's this last point that's a bit tricky.  Anyone that has operated on HF knows that this is a dicey proposition as it's entirely possible that other users of a particular frequency may not be able to hear - or be heard by - the "offending" station.  As an example, if station "A" and "B" are in QSO - but the offending station can only hear - or be heard by - station "A", it cannot "know" to avoid transmitting while station "B" is transmitting.  It would seem that those who make the rules have overlooked this particular of aspect of HF propagation when it comes to utilizing HF "whitespaces" (e.g. seemingly-unused frequencies.)

"I've been getting QRM'ed - what can I do?"

The complete list frequencies on which these operations are currently unknown - and the fact that they are not assigned specific channels may make such information impossible to know other than by direct observation.  So far, the two frequencies of which I'm aware is that depicted above (around 14.350 MHz) and another around 4.4 MHz - but I have little doubt that there are others:  If you spot similar signals on other frequencies, please comment.

If you note similar interference issues, please contact your amateur radio representative.  In the U.S., you may contact the Volunteer Monitor program at the ARRL (see information here.)  Unfortunately, a quick search did not reveal any specific contact information regarding this program:  If you have such information, please let me know via a comment. 

* * *


"Luke" noticed this post and tweeted it, emailing me a few links:  Here's a bit of information others have dug up:

This page stolen from ka7oei.blogspot.com.



  1. There is this antenna nearby:

    Other towers in the area:

    1. Thank you for the comment - but those are "bog standard" cellphone towers: Those antennas/towers aren't at all the sort used for this type of transmission.

      The types of antennas that work at these frequencies are much larger - see the pictures included in the links embedded within the article - typically being large arrays of wires strung between multiple towers, or very large versions that look vaguely similar to old-style TV antennas.

  2. Hi,
    Shouldn't the FCC be notified? Since the operators probably have no license for this type of operation and obviously don't care about frequency allocation.

    1. It is likely that the *do* have a license to operate on the frequencies that they are observed using - but that license likely stipulates that they are obligated to "listen" before transmitting.

      Given the nature of HF propagation, it is possible/likely that there may be an ongoing conversation between to licensed amateurs on a frequency that they choose to operate. I suspect that their means of detecting that a frequency might be "in use" may not be as good as it should be and that - coupled with their likely high radiated power - means that they will clobber ongoing QSO.

      As for complaints: Document what is going on (recordings, screen captures of waterfall displays) including the time, date and frequency. If one chooses to make a complaint to the FCC, I would suggest that one also include the relevant people at the ARRL as well.

  3. We've been investigating interference in N. IL and came to a place here:

    2 log periodics (satellite view). At one point, another ham drove to the place and sat out front. The 1 second pings pegged the S-meter on the HF radio with no antenna connected. Fairly close to your coordinates, but: 41.787602569599535, -88.11499319662377


    1. Interesting. The address at the location that you note on the Google earth is that of a licensed amateur (It was easy to find - I'll leave it as an exercise to the reader.

    2. To your point about fiber optic, this address has "on-net" fiber to it via Crown Castle, which is point-to-point fiber (easy to find via search online), which would be rather odd for a residential address. The log periodicals are also relatively new, looking at sat images. At least, the two out buildings with the antennas were built within the past 5 years based sat views.

      I think your theory of HF trading and front running is a good one.

  4. If they really are doing trades on HF, and since we are alowed to receive, if someone could some up with a software package that could decode their trades ... ;-) ;-)
    Im still working hard on my portfolio for my retirement.... :-)

  5. § 5.308 Stop buzzer.

    A “Stop Buzzer” point of contact must be identified and available at all times during operation of each experiment conducted under a program license. A “stop buzzer” point of contact is a person who can address interference concerns and cease all transmissions immediately if interference occurs.

    1. Excellent point. The actual law is cited here:


      The obvious problem is that given the seemingly-anonymous nature of the signals in question, what is the intended mechanism by which this particular statute to be exercised?

  6. https://www.reddit.com/r/amateurradio/comments/l8q13w/new_hf_trading_site_in_wayne_nj/?utm_medium=android_app&utm_source=share

  7. There seems to be a new site that just popped up in Wayne NJ - Just west of NYC. I posted about it on Reddit. FCC ULS is down currently for maintenance so I can't get any more info than a giant log periodic has appeared...

  8. Most likely related to:



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