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[KD0VE]

I participate a few times a week on a net that includes a regular in NY state and a couple operators in WA.  MY QTH is rural MN, SSB ops with 500w. as needed.

The propagation path from MN to NY on 20M is very reliable over the past couple of years.  Yesterday I could barely hear the NY contact and he made the same comment about me.  Same problem on 2 different antennas, an OCF dipole and a hexbeam.  Different feedlines.  Signal strengths to/from Washington state to MN were normal.  WA to NY also reported as normal.

About 1/2 hours after we started the signal path from MN to NY came back to "normal" by itself.  No change in the path to WA.

I've read about various things that can enhance a prop path but never came across a reference to some occurrence that can trash a normally good path.

Thx to anyone taking the time to educate a fellow ham.

KD0ZGW

[K1VSK]

Very simply, conditions  change from day to day, hour to hour.

[K1VSK]

Very simply, conditions  change from day to day, hour to hour.

to exemplify and elaborate - I was listening to the VP6R expedition recently and their signal on 15M went from S9 to nil in less than 30 minutes and then peaked shortly thereafter. There are entire books explaining the variabilities.

[W1VT]

Aurora can impact high latitude paths even at times of low solar activity.  Most of the time predictions are for visible aurora that can be photographed, but daytime aurora will impact propagation.

[AA6YQ]

On HF, the only "very reliable contact path" is one that exclusively employs surface wave, and thus has no dependence on reflection from a tropospheric or ionospheric layer.

All other HF paths involve one or more reflections by layers of particles ionized by atmospheric conditions or solar radiation. The degree to which a layer reflects an incoming HF signal back to earth (instead of absorbing it or allowing it to pass through and interact with higher layers) depends on the signal's frequency, the layer's composition, the recent history of solar radiation, and the recent history of the earth's geomagnetic field. Time of day, month of year, and year of the 11-year solar cycle all impact the composition of the ionosphere's multiple layers. At any time, a solar storm can unleash a torrent of particles that perturb or enhance propagation on some paths; given earth's distance from the sun, we get advanced warning of such events from sites like this one.

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

[N9FB]

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

ugh, that went out of stock quickly!

[AA6YQ]

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

ugh, that went out of stock quickly!

Always happens when I recommend a book.

[N9FB]

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

ugh, that went out of stock quickly!

Always happens when I recommend a book.

note-to-self: if/when u get book published, send AA6YQ a free copy IMMEDIATELY!!!! 

[N9FB]

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

ugh, that went out of stock quickly!

Always happens when I recommend a book.

we are in luck, looks like it is now back in stock at CQ Magazine:
 The New Shortwave Propagation Handbook

yesterday, i received the very affordable used copy i ordered from a 3rd party seller; thank you for recommending this book! The discussion of HF propagation that is the heart of this book makes it a must have!   Being from 1995, it has great sub-sections which cover solar cycles 19 thru 22.  It would be really cool to see similar coverage of 23 and 24, but i guess if i study the book well and do some homework i can find that information on my own using the internet (libraries are becoming so old school), right?   
Thanks again. 

[G8YMW]

Probably, as we're at the bottom of the sunspot cycle, the ionosphere was on the ragged edge of propagation.
The F layer(s) not supporting the signal reliably

[AA6YQ]

The best source of information about HF propagation I've encountered is The New Shortwave Propagation Handbook, available from CQ Magazine.

ugh, that went out of stock quickly!

Always happens when I recommend a book.

we are in luck, looks like it is now back in stock at CQ Magazine:
 The New Shortwave Propagation Handbook

yesterday, i received the very affordable used copy i ordered from a 3rd party seller; thank you for recommending this book! The discussion of HF propagation that is the heart of this book makes it a must have!   Being from 1995, it has great sub-sections which cover solar cycles 19 thru 22.  It would be really cool to see similar coverage of 23 and 24, but i guess if i study the book well and do some homework i can find that information on my own using the internet (libraries are becoming so old school), right?   
Thanks again.

Sorry, just now saw your response from 2 months ago. Yes, the data for cycles 23 and 23 is available online. Glad you found the book useful! I still refer to it from time to time.

[KC6RWI]

I'm studying an upgrade, that title sounds like one of the questions you might encounter on the test.