Messages

166

HF Mystery Signals / Re: 6505 kHz digital signal - mixed modes

« on: December 31, 2020, 1313 UTC »

Yes, that is the Saab Grintek MHF-50 modem you are hearing.  Yes it is used by the South African Navy.  Yes it can be hear din the US, I can even hear it here on the west coast.  The 6504 kHz USB channel has been RFDFed and TDOA geolocated to South Africa.  You can often find it on 3 or 4 frequencies simultaneously, for example when you hear it on 6504 kHz USB also check 8580 kHz, 12982 kHz, and 16986 kHz.

T!

167

HF Beacons / Re: New dasher beacon at 7999.10?

« on: December 29, 2020, 1459 UTC »

Dasher doing fine here this afternoon and it appears a new ditter is being heard as well right next to the dasher.

7999.140 ditter
7999.212 dasher

those are the freq's that I measure them to.

73, Mark

So this 7999.212 kHz dasher is not the same one as the 7997.2 kHz dasher?

The 7997.2 kHz dasher appears to be a 2 second on, 2 second off, dash, reasonably stable in timing although some variation in frequency has been reported.  I guess we need to figure out if the 7999.212 kHz dasher is a different animal or the same one (as 7997.2 kHz) on a different freq.

Unfortunately the 7997.2 kHz dasher is a rare critter here at the house.  Maybe once a week I see it for a few minutes, always very weak.  It appears very similar / identical to the 4097.2 kHz dasher, which also is not seen often here, but somewhat more often than the 7997.2 dasher.

T!

168

HF Mystery Signals / Re: 8 kHz wide bursts on HF - probably a common one...

« on: December 27, 2020, 1334 UTC »

The Woodpecker also moved around in frequency, just not as fast as some of todays OTHRS might.  And the Woodpecker used multiple frequencies in sets, as many of todays radars do.  A big difference is that the Woodpecker was a pulsed radar, that is one of the reasons it seemed so wide.

Some radars are more continuous, sometimes setting on one frequency for hours at a time.  For example, the Chinese OTH-B radars, the French Nostrodamus, the Russian 29B6, and the British PLUTO, all might set on a freq for hours at a time.  By the same token, all of those radars can, when needed, change frequency, and sometimes might do it in minutes.

OTHRs changing frequency is part of how they control what portion of the Earths surface they are illuminating.  Think of it this way, OTHR antennas typically can steer the beam in Azimuth, but not in Elevation.  So they can point the beam in the direction they want, but to control where on the Earth it is going to "come down" they must control the takeoff angle, and so the angle of reflection off the ionosphere.  You could build an antenna that could control elevation, that is not problem technically, but that by itself would not do you much good, the ionosphere must also be reflective at that angle.  Instead of building an array that steers in elevation if you just pick the frequency that currently reflects off the right altitude of ionosphere to give you the angle you want you can still achieve the same thing, in a more simple antenna design.

So that accounts for OTHRs gross frequency steps (think of this like bands), but not the small frequency steps around the same band segments (specific frequencies within the bands).

The small bursts and frequency steps serve a few different purposes.  For example, jumping around like that might make you less susceptible to interference.  Setting on one frequency if there is any interference in your bandpass it hits you all the time, jumping around it only hits you part of the time and you can integrate it out.  Another issue is that a specific pulse repetition interval and a specific frequency will have a specific set of "blind speeds" and ranges.  Jumping around in frequency and PRI will eliminate those blind speeds and ranges.

ANd of course there are other factors, but that is a 101 level partial introduction to why they hop and move.

T!

169

HF Mystery Signals / Re: 8 kHz wide bursts on HF - probably a common one...

« on: December 27, 2020, 0431 UTC »

This is either a radar (OTHR, Over The Horizon Radar) or it is an ionospheric sounder.  In this case probably a radar.

Why do I say it can be either?

Ionospheric sounders are, at their cores, radars.  The target set is the ionosphere, instead of man made things like ships, aircraft, or missiles.  Since they are radars they can use transmission waveforms that are very similar to OTHRs.  In fact, they can use techniques that are identical to what an OTHR might use, although typically there are slight differences.

In this case your waveform appears to be FMCW, and that is used by both OTHRs and sounders.  However, the burst looks a bit short and the rep rate a bit high to be an ionosonde, so it is most likely an OTHR.

One way to narrow down the possibilities is to look at how often the particular signal hits.  Think about the target sets for each, an ionosonde and an OTHR.  The OTHR looks for man made targets that tend to move fairly rapidly, while the sounder looks at the ionosphere which tends to move (or change) more slowly.  So sounders tend to transmit less often, say a few times an hour, while OTHRs tend to transmit more often, either continuously or several times a minute (sometimes across multiple freqs) is not uncommon.

There are also other ways to ID the signals, such as frequency excursion limits, burst pre-tones, and rep rates / specific bandwidth combinations.

T!

170

Spy Numbers / Re: Number station 9.330mhz

« on: December 21, 2020, 1725 UTC »

Look up "Cuban HM01 numbers station", that is what you are describing, and 9330 kHz is one of their long standing frequencies.  You could look here:   https://priyom.org/number-stations/digital/hm01

The "jamming" noise is not jamming, rather it is digital data sent by the station.

The below is not being a spelling/grammar Nazi, just an FYI if you did not already know.  I don't particularly care if you use the right units or not, that is up to you.

We all know what you meant by "mhz", it is in somewhat common, if incorrect, use, however the format is wrong and does not mean what you think it means (shades of Inigo Montoya there).  MegaHertz is written MHz (capital M, Capital H).  When you write it with a small "m" you are actually saying "milliHertz".  Since both are real things, it can't be both.  9.330 mHz is real and is a different frequency different from 9.330 MHz.

T!

171

HF Beacons / Re: New Dasher 4097.22 KHz ?

« on: December 15, 2020, 0032 UTC »

Sorry, I am easily confused.  Is the 4097.2 the old Inyo Whooper?  Or rather do you mean the new DW is the old Whooper?

T!

172

HF Mystery Signals / MOVED: UNID 10340.10 KHZ USB

« on: December 13, 2020, 0456 UTC »

This topic has been moved to Utility.

https://www.hfunderground.com/board/index.php?topic=75413.0

173

HF Beacons / Re: New Dasher 4097.22 KHz ?

« on: December 11, 2020, 0124 UTC »

Here is the video I did of that one a couple weeks ago.

https://www.youtube.com/watch?v=nvp8x96CkdU

T!

174

HF Beacons / Re: New dasher beacon at 7999.10?

« on: December 11, 2020, 0123 UTC »

I would think it might be this one:
https://www.youtube.com/watch?v=AQIl2Zdr-lo

I saw that one about 4 or 5 weeks ago, and mentioned it here in another thread, but did not start a new thread about it.  I don't know how many others have seen it to date, but I don't think it is seen or heard much.

T!

175

HF Beacons / Re: New Dasher 4097.22 KHz ?

« on: December 10, 2020, 1821 UTC »

I would assume that is this one (  https://www.hfunderground.com/board/index.php/topic,74397.msg247748.html#msg247748  ).  I have seen that dasher at night though, so I do not think it is solar powered.

T!

176

HF Mystery Signals / MOVED: The Siren or Alarm sound at 4770KHz

« on: December 08, 2020, 0401 UTC »

This topic has been moved to Utility.

https://www.hfunderground.com/board/index.php?topic=75274.0

177

HF Beacons / Re: New whooper beacon on 4095.6

« on: December 05, 2020, 1411 UTC »

Since it went to this new format it has been very weak here at the house.  I can, sometimes, see it and hear it, but just right at and in and out of the noise floor.

T!

178

HF Mystery Signals / Re: Natural phenomenon?

« on: December 01, 2020, 1447 UTC »

No, this is not natural, this signal is a type of ionosonde called a chirp sounder.  And yes, they are propagation monitoring tools.  They start from some defined frequency and transmit continuously (sometimes except for specific skipped frequencies, which vary per installation) to another defined frequency.  For example, it might start at 5000 kHz and chirp up to say 28000 kHz, at 100 or 150 kHz per second.  In one example, 5000 kHz to 28000 kHz at 100 kHz / sec, it would take about 230 seconds, just under 4 minutes, to make the entire sweep.  Since the target set is the ionosphere, and that is pretty slow to change, it does not have to do this very often, a few times an hour is enough to keep up with changes.

It absolutely can be thought of as a radar for tracking what is going on in the ionosphere.  And there are dozens of these scattered around the World, so you often can hear two or three zipping by a given frequency in just a few minutes.

T!

179

HF Beacons / Re: New whooper beacon on 4095.6

« on: December 01, 2020, 0431 UTC »

The DW Whooper changed it's "whoop". 

It now sweeps low to high with the very first whoop going from 4095.65 to 4096.35 and the next 21 whoops from 4095.65 to 4096.25 KHz. The sweep is a bit more linear and no longer has that "fishhook" look.


The CW ID of "DW" is still at the low end at 4095.65

Coming in S3 on the KFS Kiwi SE radio

Yeah, I noticed that.  I grabbed some SDR recordings of it right after it changed and will do a new video sometime this week.  I also noticed the ID has a small whoop on the entirety of the letter D that was not present before.

T!

180

Spy Numbers / South Korean V24 may be inactive since late Sep, 2020

« on: November 29, 2020, 2346 UTC »

I have not been doing much radio stuff recently, but I have been doing my scheduled and programmed recordings and spectrum captures.  Those go on automatically as long as the hardware is turned on, and it has been on 24/7 even if I have been doing other things.  For V24 I capture and chart signal levels on all known past V24 freqs, including freqs they have not used in years, and record IQ files of scheduled transmission windows plus a bit more spectrum just in case.

Today I sat down to update the V24 schedule, which I last updated in March of 2020.  To do that I basically played back all the recordings and spectrum captures since March during the time period of 1000 to 1700 UTC daily.

It turns out V24 has not transmitted, to the best of my knowledge, since late September.  In September V24 made two of its nine schedules, or 6 of a possible 27 transmission.  It transmitted on 6215 kHz, on days 5, 7, and 9, at 1500 UTC each day, and it transmitted on 4900 kHz, on days 23, 25, and 27, at 1530 UTC.  So the last V24 transmission I am aware of was September 27, at 1530 UTC, on 4900 kHz.  And for several months prior to that it was at a much lower than normal rate of activity.

Of course there are several possibilities, the simplest is they may have shifted to a new schedule with new times and frequencies I have not captured.  Or they may have just taken one of their unexplained pauses.  In 2015 V24 did not transmit from 16 June to 26 November, one theory is that they changed transmitter facilities during that time period.

So, is V24 gone?  Or is it just taking a rest?  Or did COVID slow it down?

T!