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Author Topic: Live and dead subbands  (Read 5964 times)
WX2S
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Posts: 697




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« on: March 29, 2013, 07:50:10 AM »

Here's the question that prompted me to suggest this forum.

How close are the live vs. dead parts of a band? A few kHz, or many hundreds?

73,
Wx2s.
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
W5CPT
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Posts: 557




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« Reply #1 on: March 29, 2013, 08:08:01 AM »

Not the answer you wanted but:  It depends - I have seen where the whole band is dead and at other times the space between the dead and the open portions is only a few KHs, and also where the top of a band is dead and the bottom is open (and visa-versa).

What it depends on is what is causing the anomaly in the propagation.  Early in the morning listening to 10M, I would start at the bottom (CW portion) because as the sun comes up that is the part of the band most likely to open first.  In the evening the inverse would be true. Listening to 40M late in the afternoon the upper end of the band is most likely to open before the bottom.

Notice that I tempered both statements with "most likely".  That is because while what I said is true most of the time, it does not always happen that way.

Some of my most fun "finds" were when I was listening to a band that was supposed to be dead.

Clint - W5CPT -
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WX2S
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Posts: 697




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« Reply #2 on: March 29, 2013, 08:15:48 AM »

Actually, that was the answer I wanted. I've noticed in certain big pileups that portions of the pileups seemed to be dead. This could be because stations are tracking where the DX is listening, or because propagation is dead in some very narrow subbands. Or both.

73,
Wx2s.


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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
N0XE
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Posts: 197




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« Reply #3 on: April 07, 2013, 10:09:31 AM »

 Huh
OK , if 80 is open, it is open, if 40 , if 20 and so on,  I have been a ham for near 40 years and never seen any propagation that would have one small segment open and aother segment in the same band  dead with the exception of maybe 10 meters as that band is 2 MhZ wide and it might be possible that the MUF is splitting it but I would still find that to be very rare. I think when you hear what sounds like dead segments is due to just no one is on the band. Example,  you can hear some fair amount of SSB on 40 in the day, usually regional stuff, less then 500 miles but go down to the lower CW part and it sounds pretty dead down below,  that does not mean the band it dead just that so many CW ops like to get on 40 in the evenings when the band tends to go much longer and signals are stronger, also a lot of folks are working and don't get on the bands until they get home.  Activity is your real culprit, or lack of,  in the 70s 40 was raging 24/7, lots of ops on, same goes for the other bands when we had good sun spots, these days it is a different story, we are in the era of computers, cell phones and many other things competing for our time so many times even when the bands are in good shape, you may still hear many parts within the same band that seems dead.  Another example is contest, signals come out of no where wall to wall, as soon as the contest ends, like someone flipped a switch, bands can go real quiet very fast,   the band did not change, the activity did,
Just my 2 cents,   73 Jim N0XE
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KG6YV
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Posts: 508




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« Reply #4 on: April 09, 2013, 11:12:50 AM »

I would agree with N0XE.  Activity is totally independent of propagation if the MUF is higher than the band and absorbtion isn't a factor.  BTW, I have seen 10M have no signals anywhere yet if I call CQ I get several contacts.  Since 1968 I have never seen or verified a band segment where there is no propagation if there are signals elsewhere in the band...
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