Being that it seems to be "a heater", I would guess that this is, perhaps, a signal from HAARP (High Altitude Atmospheric Research Project...think that's what it stands for). This is a large array operated by the US government, and located in Gakona, Alaska. It operates by heating up the ionosphere, apparently....so I think that might be your culprit.
Just to point out, HAARP is a pretty weird cookie. There are several conspiracy theories surrounding it....one of them is that HAARP can/has been used to "create weather", such as severe hurricanes. Another is that HAARP is really a defense against nuclear missiles for the US, ala the "Star Wars" program. Don't ask me how I know these things....LOL!! 
A few points.
HAARP is not operated by the US Government. Yes, HAARP was originally funded by the US Government, and operated under a US Air Force administered contract, however the US G shut down and started dismantling HAARP in 2015. Sometime after that the facility was turned over to the University of Alaska, Fairbanks, Geophysical Institute. UoA actually had to rebuild the transmitters, as they had been stripped of their tubes when the gov started dismantling the facility.
You can rent research time on HAARP today, at the paltry fee of $5k / hour of air time.
Even when HAARP was operated by the USG there was an online, web based, spectrum monitor that anyone could access. This monitor confirmed operations times and frequencies. Today that spectrum monitor web page no longer exists, but HAARP pre-announces periods of activities. They even have a Twitter account for HAARP that posts frequencies and times of operation.
As for the conspiracy theory stuff about HAARP…while amusing most of it is pretty patently out to lunch. Results of tests conducted there were regularly published, no security clearance was required to visit the facility, and they regularly held open houses.
However, HAARP was NOT the source of the signal in my video from 2012, and I rather doubt it was the source of Traveling Waves reported signal from this month.
How can I say it was not the source of the signal in my video? The HAARP spectrum monitoring system was online during that video, and showed no transmitter activity during that time period and on that frequency.
How can I say HAARP was probably not the source of the transmission reported this month? HAARP no longer operates year round, periods of operation are planned months in advance, with significant ramp up operations involved with any period of activity. Because of setup and checkout requirements, as well as power requirements (for example, getting fuel in for the big generators as opposed to the utility generators), they can’t just turn it on or off anytime they want. To the best of my knowledge they are not currently ramped up for operation.
So while the signal reported might indeed be a heater of some kind (without further detail, such as a recording, it is impossible to say), it probably was not HAARP. I would say it was definitely not HAARP, however that would be hard to prove one way or the other.
But, HAARP is not the only heater around, there are laterally over a dozen such facilities Worldwide, HAARP is just among the most famous. And, like I said before, Arecibo was active at the time of this reported signal. I just am not sure if Arecibo would be using that frequency.
But I am still not convinced the reported signal is a heater. Yes, it absolutely could be, but, especially without more detail, there are other explanations that also fit.
T!