Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

Questions tagged [hf]

The frequency range 3-30 MHz. HF radio waves often propagate by bouncing off the ionosphere, allowing communication between continents. 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.

Radio frequencies are commonly divided into ranges by frequency. Here are some of the ranges:

  • Medium Frequency (MF), 300 kHz - 3 MHz
  • High Frequency (HF), 3 - 30 MHz
  • Very High Frequency (VHF), 30 - 300 MHz

HF frequencies have been used since the very earliest days of radio, and the HF bands remain very popular in amateur radio. HF radio signals often bounce off the ionosphere, allowing communication far beyond line-of-sight ranges; ham radio contacts between continents are common.

More information about HF is available at Wikipedia.

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Can I reduce RFI/noise at the antenna?

Recently, the power was out in my neighborhood for an extended period of time. I fired up my HF rig using battery power and was amazed at the lack of noise across the HF bands. When the power grid came back online, the noise returned. The…
The Driver
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Which HF bands are best during the day and which are better at night?

I am rather new to HF operation and have recently purchased my first HF rig. I have read about bands being "open" and "closed" based on various conditions including time of day. As I have been listening, I have been bouncing around all the bands…
ghendricks
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Is there a way to listen to live HF communications using the internet?

I'd like to be able to show people what a QSO sounds like without having my transceiver available. Is there a way I can listen to amateurs talking in real-time (or using Morse code) on the HF bands using my internet connection and the speakers on my…
dcaswell
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Why do we use LSB below 10 MHz and USB above 10 MHz when operating SSB HF?

As a relatively new ham operator, I understand that it is customary to use lower-sideband below 10 MHz and upper-side band above 10Mhz when operating single-sideband HF. I'm curious how we got to such a standard instead of just picking one or the…
BenSwayne
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What is a "random wire antenna"?

Some antenna tuners claim to match any “random wire” to any HF frequency. Can one really use a random wire as a practical antenna system? From everything I have heard, the resonance of the antenna (length, material) is what defines its performance…
Ron J. KD2EQS
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Should I chose a vertical or a horizontal HF antenna?

If I only have the budget for one HF antenna, should I chose a vertical or a horizontal antenna?
Timtech
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What does a noise blanker really do, and what are the side effects?

Most HF rigs have a noise blanker (NB) feature. It does reduce some types of noise (car ignition noise and such). How does it really work? I've read it has negative side-effects with strong signals, which is why it is not enabled all the time.
oh7lzb
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What is the cause of this unusually long period of terrible HF band conditions?

I've been a ham for over 40 years, but never has there been such a prolonged period of such poor propagation. This has been especially the case over the past six months or so, and they continue to deteriorate. What could possibly be the cause? This…
Mike Waters
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What bands and modes will give me voice at 3,000 miles?

I pursued Amateur Radio primarily for local emergency communications and as part of my electronics education. My only radio right now is an inexpensive 2m/70cm HT which is good for local weather spotting and emergency operations. I'm interested in…
Adam Davis
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How does selecting the opposite sideband when receiving CW on HF reduce interference?

I am studying for my FCC General Class license, and question/answer G4A02 reads as follows: Q: What is one advantage of selecting the opposite or "reverse" sideband when receiving CW signals on a typical HF transceiver? A: It may be possible to…
Bryson
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Why are Wullenweber CDAAs obsolete?

Wullenweber circularly-disposed antenna arrays (CDAAs) are large HF direction-finding antennas, sometimes colloquially referred to as "elephant cages", that were popular in the Cold War. They allowed the bearing of an incoming signal to be located…
rclocher3
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How to do APRS in real wilderness?

I'm a relatively new ham (licensed a couple of years ago, occasional activity on 70cm and 2m, mostly repeaters). I'm looking to extend my ham experience and am interested in digital and packet modes. I'm interested in APRS. The main reason is to…
hamster
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What is the origin, history behind "Ben's Best Bent Wire"?

Bens Best Bent Wire My uncle, who was a Merchant Marine in WWII used to tell me this. He was a ham, and said it would develop my fist musically. I was a small child at the time, and through his enthusiasm for all things geeky, especially Ham Radio,…
tallship
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What are the relative bandwidths of the amateur bands?

While I was operating on 40 m for Field Day, I noticed a higher SWR than when I first set my antenna tuner for the band. This happened, of course, because I was in a different part of the band, but I hadn’t done enough HF operation to expect the…
Kevin Reid AG6YO
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What is generally considered "too much" power for JT-65 on HF?

Recently, I have begun experimenting with JT-65A, mostly on 20 meters. I usually run about 5 watts with that mode, since I know that JT-65 is a weak-signal mode. Is that still too much power? What is generally considered excessive power on JT-65?
krzysz00 KF5SOQ
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