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Alexanderson Alternator on VLF 17.2 kHz




 
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Author Topic: Alexanderson Alternator on VLF 17.2 kHz  (Read 1268 times)
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SM6OID
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« on: June 11, 2020, 06:33:52 AM »

Hi!

The great alternator will be started on Sunday the 5th of July.
There will be two transmissions;
Startup and tuning at 08:30 Z, transmission of message at 09:00 Z
Startup and tuning at 11:30 Z, transmission of message at 12:00 Z

https://alexander.n.se/alexanderson-day-2020/?lang=en

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ENGINE: Zvezda M50 F6L (V12), Rolls-Royce Meteor mk4B/2 (V12), Rolls-Royce B80 (inline 8 ) and much more
AJ1G
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« Reply #1 on: June 11, 2020, 09:57:45 AM »

Thanks for the headsup.  Glad they are having a 0830Z tune up/0900Z transmission, that will occur right around local sunrise here on the east coast of the US.  Might have a chance to copy here.  I did copy the Christmas Eve transmission back in December, the last Marconi Day transmission in late June of last year was not copyable, the summer static noise floor was about 20 dB higher than usually observed in December.  I am hoping  to try to copy this Marconi Day from the Watch Hill Point, RI lighthouse parking lot.  It is currently closed for vehicle access due to construction at the light, hopefully will have access restored by late June.  There used to be a LF NDB on the site, and its grounding radial  system is still installed under the lawn and parking lot, including the old antenna mounting base with a 4 foot by 4 foot copper plate and a circle of  nominal inch and a half bronze bolts that the base of the antenna apparently was bolted on to.  May try to tap on to that as a counterpoise for a beverage laid out on the lawn and seawall there to copy SAQ and also work some 40 and 80 meter mobile DX there this summer.  I am working up a nominal 24 foot fixed location mobile vertical for the back of the Tacoma based on a 24 foot Mr. Long Arm painter's pole, 40 bucks at Home Depot.  More to follow on that on a separate thread.
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Chris, AJ1G
Stonington, CT
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« Reply #2 on: July 05, 2020, 01:54:24 PM »

Copied both the early 0830Z and later 1130Z transmissions this morning.  Copied first at Weekapaug Point in Westerly, RI and the second from Watch Hill Point RI a few miles further west.  Could not get all the way out to the lighthouse at WHP, gate was locked for some reason.  Vehicle access to WHP was restored late in June, have been down there a few times already.  Solid near Q5 copy at a nominal -95 dBm signal level, slightly better for the 2nd transmission at WHP.  Comments on the video stream said the antenna loaded better that time, rain during the first transmission was affecting loading. Guess we’ve all BTDT got the T-shirt!

Links to YouTube streams of 1st and 2nd of today’s transmissions.  Excellent narration!

https://youtu.be/I47HNbxNQcw

https://youtu.be/vU91iLrkrDM

Image of the Wandell und Goltermann AT-611 Selective Level Meter, tunes 6 kHz continuous to 18.6 MHz, measures from -120 dBM to at least +40 dBm, nearly 80 pounds solid state, only draws 20 watts.  Powered from Harbor Freight jump start battery and Home Depot 100 watt DC to AC inverter.  Used just a 40 meter mobile hamstick for an antenna.  Power arrangement allows shutting down vehicle to eliminate any vehicle EMI.  No EMI at VLF from the HD AC inverter!  Switching freq above VLF apparently.

Chris AJ1G Stonington CT





* 291E6BB5-FA93-4F73-8E83-55D2F4A5C8D0.jpeg (1912.38 KB, 4096x2304 - viewed 114 times.)
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Chris, AJ1G
Stonington, CT
kb3ouk
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The Voice of Fulton County


« Reply #3 on: July 06, 2020, 04:51:29 PM »

Just another reason i need to get my newly acquired RAK-7 running, for the next time.
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Chris P.
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« Reply #4 on: July 08, 2020, 06:22:02 PM »

I listened with the RAK for the Christmas Eve transmission and heard nothing and this time I used the RBA. Still nothing.

There is a continuous very light carrier almost on 17.2 I need to track down. If that wasn't there I believe I'd have a chance at hearing the transmission.
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AJ1G
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« Reply #5 on: July 09, 2020, 04:19:27 AM »

You will need to bein a very low noise floor location away from  any power lines or other EMI.   It’s generally hopeless to attempt copying SAQ from any location unless  you can only hear atmospheric noise, and you can detect the signals from NWC and NPM at 19.8 and 21.4 kHz respectively.  The SAQ signal  level here generally is only about  -95 dBm with only a few dB SNR with a 400 Hz IF filter bandwidth.  You might have a shot at it if your location has underground utility services.  If you want to use that RAK will need to get it out to a quiet location and power it perhaps with a deep cycle battery and an DC to 120VAC converter.

I also heard  a weak MFSK signal near SAQ here, not sure of its source.  The frequencies of known signals in the VLF spectrum are posted on a number of SWL /VLF web sites.

The SAQ Alexanderson web site is posting a map of reception reports, a few other USA listeners also copied Sunday’s transmissions directly.    Furthest noted reception I saw on the map was in Australia.  I just submitted my report so it is not yet posted, only postings received through July 6 are posted so far.

Link to list of VLF transmissions by frequency:

https://en.wikipedia.org/wiki/Very_low_frequency
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Chris, AJ1G
Stonington, CT
Chris P.
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« Reply #6 on: July 09, 2020, 03:07:37 PM »

The noise floor here seems to be low, but yes getting out in the field away from everything should certainly help. I can hear what I believe to be NWC, NPM, and quite a few others. NAA of course blasts in. I can hear it with the antenna disconnected!

I did a quick measurement of the carrier I am hearing. I used a signal generator and frequency counter to zero beat the carrier so there is no doubt some error, but I came up with 17.21 khz. There were also carriers on 16.27, 15.37, 14.45. All somewhat close to multiples of 60. Could they be power line harmonics?

The carriers are extremely weak but still possibly strong enough to cover up SAQ.
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WU2D
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CW is just a narrower version of AM


« Reply #7 on: July 13, 2020, 09:27:45 AM »

When I was doing Lowfer stuff, I moved to the car and an active whip. Chris is correct. You don't wait for low noise conditions - you find low noise conditions and mark those spots.

Otherwise you need digital and exotic antennas and a pretty low noise QTH.

With my primitive homebrew receiver consisting of a simple low noise amp and a bandpass filter, backwards DBM converting up to 4.9 MHz and 8 crystals in a ladder filter and a 1496 product detector, LM390 Audio and active whip on the car - BINGO now I could hear LF stuff in the car going 60 MPH I could not even touch that performance in the shack at midnight on the coldest night of the year!

But going under power lines! WHOA!
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AJ1G
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« Reply #8 on: July 13, 2020, 10:17:43 AM »

When I was doing Lowfer stuff, I moved to the car and an active whip. Chris is correct. You don't wait for low noise conditions - you find low noise conditions and mark those spots.

But going under power lines! WHOA!

Energized power lines yes - yikes!  With the W u G in operation in the Tacoma using a 75 meter Hamstick for an antenna, just getting 500 feet out of my neighborhood with overhead power and cable internet lines into the next neighborhood with underground utilities makes the noise floor at VLF frequencies drop at least 20dBm.

However, going under DEENERGIZED power lines is very interesting- I once, with the W u G in the Tacoma, took a drive through a nearby CT state park (Hopewell Pond)  in the  winter.  They had apparently secured power to the few overhead power lines in the park during the off season, and the VLF noise floor was very low.  However, when driving directly under a line, the signal level from NPM Oahu on 17.2 kHz went UP about 20 dB.  I repeatedly drove under and then away from the line, and sure enough, as long as the
Tacoma was directly under the power line, which was maybe about 20 feet up, or about 7 feet above the top of the mobile antenna, the NPM signal level was enhanced by 20
dB, I wonder How much more improvement would have occurred with tighter or direct coupling to that line.  As far as I could tell, the deenergized section of power line was at least a mile long.


 
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Chris, AJ1G
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« Reply #9 on: July 13, 2020, 01:25:36 PM »



Location, noise floor, multipath makes things interesting. As a young JN, I found it interesting how driving under powerlines either enhanced or detracted  from the AM Bcash band.

I was suprized being able to hit a 2m repeater 70+  miles away while being under the interstate.....

KLC
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« Reply #10 on: July 14, 2020, 08:38:24 AM »

I wasn't able to monitor this time, but have heard them in the past here at home with a lw and my Rycom SLM.

73DG
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