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Author Topic: Power  (Read 1003 times)
WD6GLA
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Posts: 86




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« on: November 02, 2017, 07:02:27 AM »

Why the low power rules on the new VLF bands ?  I know its  "experimenters bands " but with antennas so hard to put up because of their size , why do they further hobble us with these ridiculously low power restrictions ?   
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AE5X
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Posts: 1010




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« Reply #1 on: November 02, 2017, 07:06:59 AM »

Because they are shared bands (like 30 meters).
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K0OD
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Posts: 2953




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« Reply #2 on: November 02, 2017, 08:10:25 AM »

And perhaps because highly shortened longwave antennas can have lethal voltages at their base. 

"Hobbled?" My longest 630-meter reception report is over 4,000 miles. Others are seeing much more than that, with the year's best propagation yet to come.   
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WD6GLA
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« Reply #3 on: November 02, 2017, 09:38:16 AM »

I don't have any dedicated equipment ,  just listening on a Grundig portable and wire antenna .  I hear nothing at all , I thought it was because of the low power . I also have a high noise level at night sometimes and that may be covering up signals .  Whats the best time to listen ?  I'm a night owl but hear nothing even in the wee hours .
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AE5X
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Posts: 1010




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« Reply #4 on: November 02, 2017, 10:04:50 AM »

I don't have any dedicated equipment ,  just listening on a Grundig portable and wire antenna .  I hear nothing at all , I thought it was because of the low power . I also have a high noise level at night sometimes and that may be covering up signals .  Whats the best time to listen ?  I'm a night owl but hear nothing even in the wee hours .

Can you feed the audio of that Grundig to the input of your sound card and does it have a CW, SSB or BFO mode? If so, you stand a chance at decoding (but probably not "hearing") 630m activity while running the appropriate software. Most of the activity is in digital modes: WSPR, JT9 and FT8. Very little CW and no SSB. Hours of darkness are when activity takes place.

Here's where I was decoded (but not heard) last night from my sunset till my sunrise:



73,
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AA2UK
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Posts: 289




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« Reply #5 on: November 02, 2017, 10:44:32 AM »

Many of the stations signal levels are so high it's not unusual to hear the actual WSPR tones.
I'm using an Icom IC7410 with a small external horizontal loop. I've also copied numerous CW stations.
Bill, AA2UK
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KM1H
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Posts: 2458




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« Reply #6 on: November 02, 2017, 03:39:38 PM »

Using CW and 5W Ive been heard as far as Calif. and Sweden; FT8 is in the future.

Carl
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K0OD
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Posts: 2953




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« Reply #7 on: November 02, 2017, 05:52:40 PM »

Another reason for low power is that the 630-meters band is only 7 kHz wide, plenty of room for WSPR and other narrow digital modes. But a single high power voice signal could be that wide.

A good way to find stations is to use the Reverse Beacon Network. Listen around local sunset especially. You'll hear some CW beacons, CQs and sometimes two-way contacts.   
http://www.reversebeacon.net/dxsd1/dxsd1.php?f=34313

I monitor WSPR unattended on 474.200 kHz generally with the bandwidth on my Flex-5000 set at 2.50 kHz. I guess I could widen it to 7 kHz to hear all signals.
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AA2UK
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Posts: 289




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« Reply #8 on: November 03, 2017, 08:32:46 AM »

Looking over the math for my location using a very short Marconi T, I may need to run as much as +55dBm to achieve 5 watts EIRP. The current unknown is my soil conductivity.
Bill, AA2UK
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AA2UK
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Posts: 289




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« Reply #9 on: November 03, 2017, 10:02:23 AM »

I plan on running a converted Robert Hafler 9505 to generate the power I'll need.
W1VD, Jay has a write up that includes input and output matching which is really "the" conversion.
It's not against the rules to use SSB on 630 meters. Common courtesy should dictate when and where SSB could be used.
Bill, AA2UK
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K0OD
Member

Posts: 2953




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« Reply #10 on: November 03, 2017, 10:58:49 AM »

There are low power QRSS type voice modes being developed. Perfect for longwave.

But QRSS voice actually dates back to the 1960s. Here's a demonstration:

https://www.youtube.com/watch?v=doeNS4LBaCA

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AA2UK
Member

Posts: 289




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« Reply #11 on: November 03, 2017, 11:50:16 AM »

There are low power QRSS type voice modes being developed. Perfect for longwave.

But QRSS voice actually dates back to the 1960s. Here's a demonstration:

https://www.youtube.com/watch?v=doeNS4LBaCA


Thanks for the link but I'm aware of the tests going on in the Eu. I don't see regular SSB during the daytime between close stations interfering with anyone.
Bill, AA2UK
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KM1H
Member

Posts: 2458




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« Reply #12 on: November 04, 2017, 06:26:38 AM »

Daytime SSB is often used to compare notes and go thru various testing. That is pretty useless on other modes.
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