7

It's probably an ionosonde — sending out HF radio signals not to communicate but to measure the reflections and thereby determine the current characteristics of the ionosphere. The signal is probably not actually a series of brief transmissions, but a continuous chirp transmission with continuously increasing frequency. Two reasons: As far as I know, this ...


6

Yes, you'll have to look at it. I can't go into detail about every possible modulation, because there's just too many. But typically, a look at the spectral representation gives you an idea of whether you're dealing with a straightforward single-carrier signal a spread-spectrum signal or a multicarrier signal. One place to see some examples is the Signal ...


5

You should use a four-port multiplexer, more commonly known as a triplexer: As shown in the diagram, a triplexer is a bidirectional device comprising three filters that separate (or combine) the signals from the input (or output) port into band-limited signals at the three output (or input) ports. A properly designed triplexer will present 50$\Omega$ at all ...


5

The fact that they align properly to the FT8 15-second period, and have 8 tones (the same as FT8) is a sign that these may be distorted FT8 signals, caused by AF harmonics in the transmitter or the receiver. The one on the right, being about 100Hz wide, is a second harmonic, and the one on the left, being about 150Hz wide, may be a third harmonic. But ...


3

Could very well be someone who is bored and opens the repeater without actually transmitting anything useful. Happens on a lot of repeaters. You only need one person to do this to bother all users of the relay...


3

Both marked signals follow an 8 tone MFSK pattern. The one on the left is about 125 hertz wide while the one on the right is about 100 hertz wide. The signal on the left appears to follow the waterfall that would be expected from an Olivia 8/125 (8 tones with 125 hertz bandwidth) signal although this is not a common Olivia mode. Olivia is a free typing, ...


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