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Author Topic: A report for those who are considering 630m  (Read 7909 times)
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wd8das
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« on: October 12, 2014, 01:13:37 PM »


Here's a report for those who are considering getting active on 475 kHz. 630m isn't a ham band yet but there is already ham-style activity...

Last night I had a lot of fun on 630 meters.  Quite a few experimental-licensed stations were transmitting in the WSPR mode, and even more non-licensed stations were receiving and reporting.

Here's a map showing everyone my station heard, or was heard by, on the WSPR mode...

     http://www.wd8das.net/WSPR-WH2XHY.jpg

Here's a map showing everyone that was active on 630m WSPR last night...

     http://www.wd8das.net/WSPRactivity.jpg

Notice the reports from Europe, Alaska, and Hawaii.  Very cool!

WSPR's S/N reporting is useful to know when propagation is good enough to support normal contacts.  When the S/N ratios are higher then it is time to go to CW... where I made two CW contacts with Pennsylvania and Texas experimental stations.  Conditions seem to be getting better as we move into winter.

Details on my 630m station...

     http://www.wd8das.net/630m.html


Steve WD8DAS / WH2XHY
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KA0HCP
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« Reply #1 on: October 12, 2014, 03:35:42 PM »

Thanks Steve.  Glad to hear there is still experimental activity keeping the flame alive.  Maybe, someday, the FCC will get around to authorizing our privileges!

bill
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Steve - K4HX
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« Reply #2 on: October 12, 2014, 04:40:57 PM »

Steve, how much variation in propagation is there on 630 meters? I would think the SNR numbers would speak to the local QRM/QRN at the receiving site as much as propagation. Maybe I'm off base. What say?
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wd8das
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« Reply #3 on: October 12, 2014, 04:51:43 PM »

There is some similarity with 160m propagation, with mostly groundwave during the day, interesting stuff happening at gray-line, and then skywave at night.  Skywave fading changes sloooowwwly, which is a nice experience.  Once night is upon both stations I usually see variations on individual stations of perhaps 10 dB within an hour or so.  It is much like the bottom of the broadcast band.

The WSPR software is looking for slowly freq-shifting carriers and it seem to a remarkable job ignoring local noise. I had a power line periodically bzzz-ing last night and I could take it out with the noise blanker but it made no difference to the performance of the WSPR decodes and the S/N ratio numbers seemed the same with or without.   The noise blanker was effective when I was manually listening for CW.

Steve WD8DAS

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W4EWH
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« Reply #4 on: October 12, 2014, 04:54:20 PM »


Here's a report for those who are considering getting active on 475 kHz. 630m isn't a ham band yet but there is already ham-style activity...

Last night I had a lot of fun on 630 meters.  Quite a few experimental-licensed stations were transmitting in the WSPR mode, and even more non-licensed stations were receiving and reporting.

Please provide more details on the antenna setup you're using: I understand that it's an inverted-L, but I'd appreciate knowing what ground you're working it against, and how you built it.

I'd also be grateful for a rundown on the cost of WSPR mode. TIA.

73,

W1AC
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wd8das
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« Reply #5 on: October 12, 2014, 05:20:23 PM »

The ground side of the antenna is just my regular station ground.  The central ground point is along a section of wall where the all the utility service entrances are located. This central ground is a few feet of 1/2" copper pipe with 1" copper straps connecting to the power entrance ground, an 8' rod driven right outside the house, the iron and copper water pipes (before and after water meter), and the metal HVAC ductwork in my house.    To this ground system I have connected to this (with more 1" copper strap) the operating desk star ground, my two Gates BC-1T transmitters, the 630m transmitters, and the shields of all my various antenna feedlines. 

I made no special ground for the 630 meter antenna system - just made sure its ground side was well-attached to my existing station ground.  The outside of the various coaxial cable shields form accidental counterpoises and radials I'm sure.

The WSPR software is a free download, and the website where the reports are organized and displayed is free to use.  No cost at all.  It is used on all bands, not just 630 meters.

Steve WD8DAS
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wd8das
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« Reply #6 on: October 12, 2014, 05:25:08 PM »


I received an email asking about my receive antenna...  My best choices are my 75-meter inverted vee dipole (with the transceiver preamp turned on), or my ground mounted 8' whip with a preamp at the base (preamp off in the receiver).

I've been very dilligent about keeping noise sources in my house to a minimum, but neighbors and powerlines do cause noises at times.  I made a 10-foot shielded loop out of coax inside PVC pipe but it is stored in the garage right now - too unwieldy and has to be turned to peak signals or null noise.

Steve WD8DAS

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« Reply #7 on: October 12, 2014, 06:57:40 PM »

Very interesting. Thanks Steve.
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W0BTU
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« Reply #8 on: October 12, 2014, 08:33:28 PM »

Here's a map showing everyone my station heard, or was heard by, on the WSPR mode...

     http://www.wd8das.net/WSPR-WH2XHY.jpg

Here's a map showing everyone that was active on 630m WSPR last night...

     http://www.wd8das.net/WSPRactivity.jpg

Wow! This 630m report amazes me, because this is MUCH better than I experienced on 160 WSPR last night!

I was transmitting on an inverted-L, but listening on two switchable-direction 580' Beverages. And I often changed directions. And I was on 160 WSPR between 3:30 AM until after sunrise.

I live in a quiet rural location, but there was lightning QRN (which had to be worse on 630).

I'm going to take a listen there soon.
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73 Mike 
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« Reply #9 on: October 13, 2014, 08:24:57 AM »

Hi!

Steve, what is your output power?

Here in Sweden we are allowed to operate between 472-479 kHz.
I have a Skanti capable of 750 W output on MF and HF, how ever, so far only using HF.
I understand that it will not be possible with "the ultimate antenna" were I live, but I will have to work out something...    Wink
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wd8das
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« Reply #10 on: October 13, 2014, 07:59:34 PM »


The transmitter power output is 30 ~ 50 watts but I'd say that no more than a few watts are being radiated thanks to low efficiency in the antenna.   

My estimate of ERP is very rough as I am having a hard time determining with any certainty the ground losses I have.  I can confirm I'm putting about 1.5 amps of RF into the antenna system with the LPB amp, and maybe 1.2 amps with the maritime CW transmitter.   

The power limit on the experimental licenses here in the US are based on what we individually request - in my application I indicated I expected to run no more than 20 W ERP. 


Steve WD8DAS / WH2XHY

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Steve - K4HX
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« Reply #11 on: October 13, 2014, 09:17:06 PM »

You can estimate the ground loss by modeling your antenna system over a perfect ground and noting the feed point R. Then measure your actual feed point R. The difference should give you a decent idea of the ground loss.

I would imagine that there is some loss in the loading coil too.
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wd8das
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« Reply #12 on: October 18, 2014, 10:37:34 PM »


That's how I made my estimate of less than a few watts ERP.  Call it EERP - Estimated Effective Radiated Power.  There are several handy MF calculators for Marconi antennas online but all include guestimates of the true conditions.  As long as they all roughly agree with my readings I'm comfortable. 

Steve WD8DAS
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« Reply #13 on: October 19, 2014, 07:04:03 AM »

Is 630m going to continue? I seem to recall that it was temporary.
And how can one get a license for it?
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73 Mike 
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wd8das
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« Reply #14 on: October 24, 2014, 07:02:53 PM »


630-meters temporary?  I'm not sure what you mean. 

A couple years ago international spectrum authorities authorized 472-479 kHz for a ham band if a country would like to designate it for that purpose.  The governments of a number of countries around the world have gone ahead and made it a ham band.  So far here in the United States the FCC has not allocated it for ham use.  I hope they will do so soon.

Meanwhile, some guys have applied for and received experimental authorizations under Part 5 of the FCC rules.  Some are operating around 630-meters, some around 600 meters (500 kHz).  Those licenses are of fixed duration 2 years, but can usually be extended up to 5 years. 

Steve WD8DAS
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« Reply #15 on: October 24, 2014, 10:56:52 PM »

Quite a few AMers active now or in the recent past on those bands.

W1NZR
KW1I
W1VD
W2ZM
K2ORS
W2ILA
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