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HF/MW/LW General Discussion - General discussion on monitoring the HF (High Frequency), MW (Medium Wave), and LW (Long Wave) spectrum (0.5 - 30 MHz)

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Old 04-23-2012, 9:24 PM
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Cool HF Propagation Quick Reference

I've been asked by a few people how I tell when it's a good time to monitor HF.

Here's a quick reference tutorial. Hopefully Mike can make this a sticky.

Here's a simple way to understand HF propagation:

1. K-Index -- the higher this value (0-9) the worse HF will sound -- from no impact to minor fade to fluttery signals to zero signal.

2. Solar flux (SN) -- the sunspot number is what determines the overall band conditions. The higher the number the better the propagation of HF (especially the upper HF bands.)

3. X-Ray -- (integrated into the K-Index) but this value is what determines the severity of the absorption of HF radio signals. The class range is from A/B, C, M and X. Large X-Class solar flares are the least desirable.

4. WWV/CHU -- the time beacons are great for checking propagation. The usual North American time beacons are: 2.5 Mhz, 3.330 Mhz, 5 Mhz, 7.850 Mhz, 10 Mhz, 14670 Khz, 15 Mhz and 20 Mhz in AM mode.

5. RWM -- The time beacon from Moscow, Russia transmits on 9996 and 14996 Khz in CW mode. If you can hear/see RWM then you know you have good propagation!

One point that is confusing to some people is that while conditions are "bad" this doesn't mean you won't hear stations. It just means that the signals could be weak, have poor audio and/or a combination of both. Usually the strong stations (aka SW Broadcast) will still be heard but their audio quality could be affected.

Usually, the bad HF conditions will generally mean improved VHF conditions from 6m to 2m because the ionosphere is in an excited state. This is why 11m (CB) and 10m (HAM) will become very active during these "bad" HF periods.

A couple of great web sites to check:

SpaceWeather.com -- News and information about meteor showers, solar flares, auroras, and near-Earth asteroids
HF Propagation and Solar-Terrestrial Data Website

Last edited by nickcarr; 04-23-2012 at 9:27 PM..
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Old 04-23-2012, 11:50 PM
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thanks Nick, thats an easy way of understanding it
Much appreciated
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Old 04-25-2012, 12:49 AM
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Good review, but since I'm a trouble maker ...

If you can hear RWM, then you have good propagation *to Europe*. They are also on 4996khz. There are other good stations to watch for as well. Pick your favorite from different parts of the world to give you a quick check on conditions.

Lower solar flux usually aids in lower band propagation, and high K values may lead to good / odd ball skewed paths allowing stations not normally heard, to be heard. That's what many folks love to hear ... the unusual stuff. So, when conditions are messed up, you just might get the once in a lifetime logging. Tune around anyway, you can always turn it off and go back to bed again later, but you just *might* hear something that you never even imagined!
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Last edited by k9rzz; 04-25-2012 at 12:58 AM..
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Old 04-25-2012, 3:58 AM
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I will make this a sticky -

In addition to Nick's very easy to understand description, the AE4RV website has a Flash-based very basic tutorial on HF propagation. Between this and the description above you should have a pretty good start on how to interpret all that gobbedly gook you hear and sometimes read about.

There's even software that will allow you to project how propagation will be on a given day. Just keep in mind that it's just that - a projection - and won't always be accurate

The sites in our wiki range from the basic to the very complex - as always feel free to add/subtract to it.

HF Propagation - The RadioReference Wiki

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Old 07-08-2013, 9:45 AM
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As somebody relatively new to SW, I really appreciate the consolidated info! Many thanks!
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Old 10-10-2013, 9:58 PM
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Okay, been glancing at solar indices for a couple of years and still don't have it down-pat.

Everywhere I look, they list "SFI" and I have looked for an official definition, not found one. I have "assumed" (and we all know how dangerous that can be) that it stood for Solar Flux Index. Am I correct or way out in right field (I'm a conservative so I'm never in left field) :-)

You also indicate that we should reference the SN (sunspot number) where I have looked at the SFI.

Now I am really turned around. SFI or SN?
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Last edited by poppafred; 10-10-2013 at 10:02 PM.. Reason: additional thoughts
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Old 10-11-2013, 1:45 AM
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Quote:
Originally Posted by poppafred View Post
Everywhere I look, they list "SFI" and I have looked for an official definition, not found one. I have "assumed" (and we all know how dangerous that can be) that it stood for Solar Flux Index. You also indicate that we should reference the SN (sunspot number) where I have looked at the SFI. Now I am really turned around. SFI or SN?
You know scientists they love to make things confusing by default.

Definition for "sunspot number" --

A daily index of sunspot activity (R), defined as R = k(10g + s) where s = number of individual spots, g = number of sunspot groups, and k is an observatory factor (equal to 1 for the Zurich Observatory and adjusted for all other observatories to obtain approximately the same R number). The standard number, RI, once derived at Zurich (see Wolf number), is now being derived at Brussels and is denoted by RI. Often, the term ”sunspot number” is used in reference to the widely distributed smoothed sunspot number.
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Old 10-11-2013, 1:48 AM
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Here's a very cool PDF to read when you have a chance:

http://www.swpc.noaa.gov/info/swx_booklet.pdf
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Old 10-11-2013, 1:51 AM
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Here's a neat summary view:

Space Weather Warnings Currently in Effect
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Old 10-11-2013, 11:16 AM
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ANY time is a good time to listen (short of having a thunderstorm over your head). If prop. is generally lousy, that may block loud stations that you normally hear and leave new stuff in the open. The more you tune around (years), the more you learn what's normal and not. Even in the AM BC band, you might catch a 50Kw local off the air ... WHOA! DX TIME! If you've got the time, then spin the dial. You have little to loose and potentially a lot to gain.
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Old 10-11-2013, 7:37 PM
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every day is a propagation check at this shack-with just a spinning dial, an analog meter and a fuzzy ear well two actually.
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Old 10-13-2013, 4:26 PM
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Just want to add my thanks to you guys for your knowledge share - appreciated
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Old 03-20-2014, 9:18 AM
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This also came up here as well. united states - Are there any good, consistently receivable signals in the US for HF receiver testing? - Amateur Radio Stack Exchange
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Old 06-11-2014, 8:57 PM
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If you want to know why this solar cycle maximum and HF propagation is a bust -- a very weak showing compared to the fabulous IGY of 1957-58 that I will not forget -- this article tells all. I guess we can blame Bush, global warming and the Washington gridlock. Seriously, have a look. Quite telling why all the comments on no signals and poor propagation are here on RR.

http://science.nasa.gov/science-news..._solarminimax/

Alternatives to hoping conditions improve are learning how to use the terminator grayline and all the tools the Internet provides. BC (before computers) the only "current" data I had were the 3-hr updates at H+18 broadcast by WWV.
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