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Author Topic: 17 metes dead after dark  (Read 759 times)

W4AEG

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17 metes dead after dark
« on: September 09, 2022, 02:46:22 PM »

Why ia 17 meters totally dead after dark even when propagation forecast predict good propagation?
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W7CXC

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Re: 17 metes dead after dark
« Reply #1 on: September 09, 2022, 03:56:30 PM »

Forecast... Predict....  Its kind of like the weather. ;)
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K1VSK

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Re: 17 metes dead after dark
« Reply #2 on: September 09, 2022, 04:22:39 PM »

Why ia 17 meters totally dead after dark even when propagation forecast predict good propagation?
must be something to do with propagation forecasts.
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GRUMPY2021

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Re: 17 metes dead after dark
« Reply #3 on: September 09, 2022, 05:04:57 PM »

Predicting a good forecast for where?  Dr. Skov has an excellent talk about how the forecasts for propagation are location specific.   What's good in California won't be true in Maine.   I'm simple minded.... 10mhz and above during the day... 10mhz and below at night.   So...
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W4FID

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Re: 17 metes dead after dark
« Reply #4 on: September 10, 2022, 03:55:41 AM »

I think --- not to be confused with I know -- that the QRZ forecast for example (a common popular one) is based on the center of the USA. Kansas? That's about 1150 miles from me in north central Florida. Some days when propagation is overall good what I experience is close to what they forecast. But many days it is quite different -- some days even the opposite for good or poor propagation forecast. In the first place it's a forecast. In the second place it will vary from where it was based and where you are. With two variables involved there will be differences between what you read and who you work. Conventional wisdom is 20 is a "daytime band" Yet for months now it has been already open before dawn and still wide open at midnight here. Also people tend to congregate around "watering holes" So if the propagation is declining --   like in the evening -- there will be more on popular modes and frequencies. 17 may actually be open but it's a less popular band than 20 or 40 so at night they are on 20 or 40 and no one is on 17 to hear you call or for you to hear and realize it's open. Not sure if it's my antenna -- a marginal one in a HOA environment -- or the MUF just hasn't risen but I am not finding much above 15 meters at any time.
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G8FXC

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Re: 17 metes dead after dark
« Reply #5 on: September 10, 2022, 04:32:36 AM »

To talk to anyone much beyond the horizon, you need your signal to be reflected off the ionosphere - to go round to the other side of the world, you need multiple reflections from both the ionosphere and the surface of the earth. It is the effect of solar radiation that makes the ionosphere reflective to radio waves - this is why propagation is so much better at solar maxima than at solar minima. The level of ionization - and hence reflectivity - will also vary throughout the day. In darkness, the level of ionization will fall and the ionosphere will become less reflective - but this is also frequency dependent. The propagation forecasts are based on the predicted values of several metrics of which the most relevant to us is usually the MUF - Maximum Usable Frequency. The MUF is related to the propagation path - the figure for you to Europe will not be the same as it is to South America - and it increases during the day as solar radiation ionizes the atmosphere above you and falls over night as the ionization level decays away. I've just run the prediction between my QTH near London and a point somewhere round the west coast of the USA and the figure ranges from something like 7MHz at 6am this morning and 16MHz at 3:30pm this afternoon.

Martin (G8FXC)
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WA3SKN

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Re: 17 metes dead after dark
« Reply #6 on: September 10, 2022, 04:42:18 AM »

Its called reality.
17M is known as a "daytime band", however you can usually make contacts after dusk for about 2-3 hrs if you have a LOW angle radiating antenna. (also 2-3 hrs before dawn).
So what antenna are you using?

-Mike.
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W4AEG

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Re: 17 metes dead after dark
« Reply #7 on: September 12, 2022, 02:59:39 PM »

My antenna is an EFHW 80-10 inv. l at 50 feet
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W4AEG

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Re: 17 metes dead after dark
« Reply #8 on: September 13, 2022, 02:49:42 PM »

Correction. Antenna is an inverted L
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N7EKU

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Re: 17 metes dead after dark
« Reply #9 on: September 13, 2022, 06:20:19 PM »

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Mark -- N7EKU/VE3

WA3SKN

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Re: 17 metes dead after dark
« Reply #10 on: September 14, 2022, 05:01:47 AM »

Your antenna is radiating at 27-25 degrees.
Try a vertical dipole.

-Mike.
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AA6YQ

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Re: 17 metes dead after dark
« Reply #11 on: September 15, 2022, 05:01:04 PM »

What I'm decoding on 17m FT8 at 0Z from my QTH just west of Boston MA, about an hour after local sunset:



antenna: Force 12 4BA at 90 feet, aimed due west

SFI: 140

A-index: 7

K-index: 1
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W1VT

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Re: 17 metes dead after dark
« Reply #12 on: September 16, 2022, 06:29:47 AM »

I run wires in the half dozen trees around my 0.3 acres in the suburbs of Hartford CT.
Confirmed LoTW contacts
Details   W1VT   3D2RRR   2022-06-02 02:37:26   17M   SSB   18.15000   ROTUMA
Details   W1VT   K4BH   2022-05-30 04:25:30   17M   FT8   18.10082   UNITED STATES OF AMERICA
Details   W1VT   WP4BRI   2022-05-30 04:19:45   17M   FT8   18.10225   PUERTO RICO
Details   W1VT   LZ2VQ   2022-05-25 03:27:15   17M   FT8   18.10217   BULGARIA
Details   W1VT   UD8S   2022-05-25 03:26:00   17M   FT8   18.10217   ASIATIC RUSSIA

Nothing recently as it is now golfing season for me.  I also have three hundred roses that need a lot of attention.
« Last Edit: September 16, 2022, 06:32:00 AM by W1VT »
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RENTON481

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Re: 17 metes dead after dark
« Reply #13 on: September 19, 2022, 08:37:38 PM »

There are forecasts and then there is the reality. Also, as another member here said, conditions might be great in some regions of the US and not so great in other regions. Although I've SWLed and DXed MW and SW for several decades, I've never paid much attention to any forecasts. I turn on the radio and tune around. That usually tells me all I need to know.
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AA6YQ

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Re: 17 metes dead after dark
« Reply #14 on: September 19, 2022, 10:41:52 PM »

There are forecasts and then there is the reality. Also, as another member here said, conditions might be great in some regions of the US and not so great in other regions. Although I've SWLed and DXed MW and SW for several decades, I've never paid much attention to any forecasts. I turn on the radio and tune around. That usually tells me all I need to know.

Tuning around to look for propagation openings on all possibly active bands takes time - time during which a station you'd like to work might go QRT before you find it.

Propagation forecasts are occasionally wrong, but on average are better than nothing when it comes to determining which bands are likely open to what locations.

DX Cluster spots are also occasionally wrong, but on average are better than propagation forecasts because they reveal actual openings.



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