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[KA5QMA]

I assume this is the forum to post my observation in since there is no "general band conditions" forum, so here goes:
20m has been VERY noisy with QRN here in Austin, TX these last few days, about S7. Anyone else notice a lot of noise on 20 (cw) lately?

[KG6YV]

The Sunspot count and flux are higher the past 4-6 days than they have been.  Also, we are moving toward summer.  AS a result, ionospheric absorbtion is affecting the higher frequencies like 20M.  As we move toward the summer solstice June 21st the daylight hours are longer and if the sunspot count and flux is high enough the ionosphere tends to absorb signals and get noisier during the daylight hours ( longer daylight hrs in the hemisphere)....

Here's an interesting thing to watch.  In summer the absorption tends to decay rapidly toward sundown but the ionosphere remains ionized for communication on 20M.  Some of the best DX on 20m then shows up from an hour or so before sunset till 4-6 hrs after sunset.  20M becomes an early evening DX band since there is no absorption but the F layer is still ionized because it was ionized for longer overall. . 

FYI,

greg

[AE5J]

While Greg's explanation is most likely the case, there is another intriguing thought. Given the rise in tensions with regard to certain rogue states threatening to launch nuclear missiles, it is possible that some OTH radar systems have been causing some of the hash.

Since high accuracy target acquisition/tracking radars operate on more or less conventional frequencies (for radar), they also are much more expensive to deploy in a constant surveillance mode. OTH systems have seen a return in usefulness since they are less expensive to deploy for covering large geographic areas. They provide useful launch detection which then is tracked by more conventional systems. Since the most effective range of frequencies for these systems is 3-30MHz, it is possible we could notice them operating by the presence of "hash" on our allocated frequencies. Perhaps some radar system design engineer will chime in here.

I too have noticed the very abrupt rise of this "hash" which seems to almost be switched on and off. Very curious.

[K1CJS]

Just a thought--you may get a better answer by posting in the RFI / EMI forum.  73!

[W7AIT]

Been studying propagation for many years as a ham, and I don't claim to be any kind of expert; below is my opinion. 
I now monitor about 7 or 8 different propagation charts every day.  Yes I have noticed the noisy conditions on 20 and also on 17, 15 as well.  Bands have been especially bad the last 2 or 3 weeks.
What I have noticed, in my crude scientific measurements, observations, and opinion is:
1.   X-ray bursts at C level or higher tend to shut down the upper bands, and make a mess of the lower bands like daytime 40 meters, especially with a high A index occurring right after an X-ray event. 
2.   For the past 2 weeks we have had both, X-ray to the low C levels with occasional M bursts AND high A index, running into A=19 or higher for periods.  A should normally be 2-5. 
3.   My general rule is anytime A index above 10, DX is difficult.  This past week or two I have been seeing A shoot up as high as 25 or so!  All the bands sound dead and I can't get over my backyard fence on 40 and the upper bands sound like the antenna is disconnected. 
a.   Seen this happen back in the 70's and 80's right at he start of field day, a big burst would shut everything down Friday night and we wouldn't recover  until Sunday afternoon, ruining Field Day, except for nighttime operations.
4.   When the solar wind GSM speeds gets above 300 km/s, or higher, and or particle density gets above 1 cm³, or rises, especially near 10 cm³, static goes up dramatically, making the upper bands very noisy.  I think its because we are getting bombarded with a whole bunch of particles.
5.   The new 304A data also shows some correlation to band noise, though I haven't studied that enough yet.

[KA5QMA]

Thank you for the thoughtful and informative reply. The solar wind must be a very important factor imho. Still noisy, but 20m is hopping with eastern european dx tonight!

[NO9E]

The band are very noisy at home. Usually S2 to S7. Most seem like white noise.

The bands were much more quieter at a mountaintop. Amazingly often S0 with weak far-away DX that I seldom hear at home.

Ignacy, NO9E