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High Frequency is the frequency range 3-30 MHz. This tag may also be used for questions about the 160 meter band (1.8 MHz), which while not HF is often referred to as such due to its similar propagation.

This is actually quite a standard question that any non-hobby HF user will have, so there is good software to help. I recommend starting with VOACAP online to make predictions for the best bands and … choice when setting up an HF link. You can download it to run on your computer, but the web version is really easy to use. Then there is great real-time information available from WSPRnet, which plots …
answered Feb 7 '15 by tomnexus
The most sensible antenna is a wire dipole extending above and below the electronics package. This seems to be how all the QRP Labs transmitters work. Self-supporting radials, or a coax cable feed t …
answered Jul 27 '17 by tomnexus
will be a good place to start. Experimental Confirmation of an HF Channel Model The abstract describes the model quite well. Unfortunately to read the whole article and find the coefficients, you … need to subscribe, or find it elsewhere. Specially designed HF ionospheric propagation measurements were made and analyzed to confirm the validity and bandwidth limitations of a proposed stationary …
answered Apr 20 '16 by tomnexus
At HF there are almost no limits on how bad your splice can be, as long as: there's no short circuit braid is connected to braid and inner to inner You could even use a "chocolate block … first class measurement cable, but for radio transmission a tiny, short impedance mismatch won't hurt. At HF the whole joint is 1/1000 of a wavelength, it will be fine no matter how ugly it is. …
answered May 14 '19 by tomnexus
Satellites can and do use HF for communications. The first example would of course be Sputnik, which transmitted at 20 and 40 MHz. Amateurs use HF to communicate with satellites. According to Amsat … mode is unique in that it can be done with a simple HF rig. HF has advantages in its smaller Doppler shift, and reduced path loss, allowing omnidirectional antennas to be used more easily. For the …
answered Jun 21 '15 by tomnexus
I don't think it's correct to connect the end of the coil to the common point of S1. Shorted turns, because they're magnetically coupled to the active turns in the coil, increase the loss in the indu …
answered May 17 '19 by tomnexus