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THE AM BULLETIN BOARD => QSO => Topic started by: PA0NVD on December 17, 2018, 08:20:02 AM



Title: 1924 Alexanderson machine transmitter in the air!!!
Post by: PA0NVD on December 17, 2018, 08:20:02 AM
At Christmas eve there will be a 1924 200 kW LF machine transmitter fired up and sending a Cristmas  message
Listen, listen listen!!!



Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: WA2SQQ on December 17, 2018, 08:51:29 AM
Evey year I intend to listen, but forget. What is the Dec 24th - time (Z) and freq?


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: W7TFO on December 17, 2018, 11:21:31 AM
http://www.arrl.org/news/saq-alexanderson-alternator-transmission-set-for-christmas-eve

73DG


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: SM6OID on December 19, 2018, 03:02:31 AM
Hi!

I live approx. a two hour drive (?) from the site, have been there a couple of times and seen it live.
It is truly an amazing piece of machinery!

Needless to say, copying the transmission from where I live a piece of cake.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 20, 2018, 06:47:57 PM
I am going to try to copy with my Wandell und Goltermann AT-611 Selective Level Meter which tunes from 6 kHz continuously to 18 MHz.  Essentially a quadruple conversion receiver with a product detector ,no AGC, and a dBm meter that can measure from about -120 dBm to maybe +40 dBm.  Will take it down to a quiet shoreline location in the Tacoma and use just my 75 meter Hamstick for an antenna.  This setup has copied the various MFSK naval VLF stations really well,  NPM from the west side of Oahu comes in with about 20 dB SNR down at Stonington Point around local sunrise here.  I tried to copy SAQ from there a couple of years ago but overslept my alarm and by the time I was on the Point the transmission had ended.  

Last weekend when we all were chasing the 3890 mystery broadband, I noticed that the Penn State KiWi SDR had very good reception down at VLF.  Not many of the others I have listened to do.  The one out in the Mojave desert in CA is also good. The NA5B SDR in northern VA which call itself a VLF SDR has a so-so reception with lots of spurs EMI and a high noise floor.  Will see if I can copy SAQ on maybe the PSU SDR on my iPhone.

May try Point Judith RI as a prime reception spot.  Public access  privately owned parking lot used by surfers and fisherman, lot sits above the water on a cliff about 50 to 75 feet. Ill throw a big surf rod in the truck as a cover for why I will be parked there at 0200 local!  Or I may drop over to the W1NZR compound just above Beavertail Point in Jamestown RI and cliplead onto his ex-1900 kHz radio location 90 foot vertical. Would be interesting to see how the GRC-9 in the Tacoma loads up to that on 75, will give that a try as well.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 20, 2018, 07:08:16 PM
I May try Point Judith RI as a prime reception spot.

...or catch an Interstate Navigation ferry from there to Block Island, the ultimate listening spot!


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 20, 2018, 08:04:38 PM
The PJ location is pretty spectacular!  Here’s a couple of pix I took up there a few weeks ago.

The BI sugguestion is pretty tempting.   Maybe I’ll book a room  at a B&B for Monday Night and Diane and I will have mini getaway, I’ll go down to Southwest Light and listen from there.  Been many years since we’ve been there.  One of our first dates when we were at URI was a day trip trip over there on a warm Sunday December day, we at least went wading down on the beach below the light.

The ride back that night to PJ was really rough.  Two huge St. Bernard’s in the passenger salon on the ferry got seasick, we went topside and hung out in the fresh air aft of the bridge for the remainder of the trip.  

I think I brought my GRC-9 over there on a Boy Scout camping trip when sons Ben and Dave were in Scouts.  


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: W1ITT on December 21, 2018, 08:37:39 AM
Here's a VLF receiver software setup that uses the sound card in your laptop computer as the front end.It's not an SDR, just an old fashioned "straight" receiver.

https://sites.google.com/site/sm6lkm/saqrx

Be careful that there's no precipitation static or loads of nearby RF on whatever antenna you use, as you don't want to blow the front end of the sound card.  The antenna plugs into the microphone input.   I have received the Cutler VLF station here in Maine with it.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 21, 2018, 11:59:37 AM
Here's a VLF receiver software setup that uses the sound card in your laptop computer as the front end...

That's fantastic! In fact, a simple opamp can be added to the mic input to isolate it from possible static damage and as an impedance converter so a much smaller antenna can be used.

In the case of most JFET opamps like the LF353, the positive input has an impedance in the megohms and would require minimal, if any, feedback (output to - input). Perhaps the chip could also be run off the bias voltage present at soundcard mic inputs. The downside of this is the reduced input impedance due to the bias resistors. An audio choke would need to be connected between the mic connector and VCC and a DC blocking cap added at the output of the opamp.

Can you tell this is "on the fly thinking"? Hmmm...

(http://stompville.co.uk/wp-content/uploads/2013/06/149SV.png)


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 23, 2018, 11:33:41 AM
With snow in the forecast for the overnight, will stay close to home and try for SAQ down at Stonington Point.  Did a dry run down there early this morning around 0600 local and received signals with from good to rockcrushing (NAA) from all the naval VLF transmitters in Maine, North Dakota, Washington State, Hawaii, and Northwest Cape, Australia with just the 40 meter Hamstick on the Tacoma into the Wandell u Goltermann AT-611.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 23, 2018, 12:42:23 PM
Well this IS interesting!  Now it's just a matter of finding out if I'm hearing actual stations or the neighborhood plasma TVs...

https://en.wikipedia.org/wiki/List_of_VLF-transmitters (https://en.wikipedia.org/wiki/List_of_VLF-transmitters)



Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 23, 2018, 03:25:33 PM
Start by looking for NAA on 24.0. They should be very loud.  Just saw them at -62dBm with the WuG set for 75 ohm input bridge mode, which I assume is an unterminated input, as signals are about 20 dB louder in bridge vs non bridged input.  About 32 dB SNR with 400 Hz bandwidth, using the Tacoma 40 meter Hamstick parked in th driveway.  

Now here’s something else interesting.  Hooked up about 100 feet of two conductor thermostat wire ( tied in parallel of course) to the Tacoma mobile antenna feet point on the left rear corner of the truck instead of the Hamstick,ran the wire approximately east about 5 feet off the ground, Beverage style on trees and shrubs big opportunity. Results pllwere disappointing, levels actually down several dB for NAA re the Hamstick. Re positioned the wire so the truck feed point was at the head vs tail of the wire, and lay it on an axis NE/SW with the feed point at the NE end.  WHOA!  Levels went up to -48 dBm up 14 from the Hamstick-62 dBm. So, will have to figure out how to deploy in a quiet location for SAQ in the overnight.  Good luck on your attempt Clark.  Can’t emphasize enough how important a quiet location is for VLF.  What is showing on your spectrum at about 21.5 might be NPM Oahu should sound like narrow shift RTTY.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 23, 2018, 04:38:09 PM
The SAQ program tunes up to 22kHz, so no NAA on that one, but I just discovered that the RSP1A SDR tunes the whole VLF spectrum! Yeah! I am also experimenting with an L-match to optimize reception for my 3AM (OMG) reception of SAQ tomorrow.

Amazing how a 0.01uF disc across the input actually helps.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 23, 2018, 09:03:41 PM
After a lot of experimenting on improving VLF reception, I decided to try something very different for antenna matching... an audio transformer. Incredibly, this led to a *dramatic* improvement in reception, so much so that I was able to hear stations I hadn't heard previously.

A simple 1k to 8 Ohm transformer worked wonders, and I found a 10k to 1k line matching transformer to be ideal. The antenna and ground connect to the high impedance windings. It's important to note that this was with a 100' longwire and an RSP1A SDR receiver, however, I'm sure this will help other receivers as well.

Not only does it provide impedance matching and isolation, but it also gives the antenna a D.C. ground as well as shunting higher frequencies that could desense VLF reception.

Incredibly, even frequencies at 60kHz and higher were received better with the small transformer compared to a direct connection.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: KL7OF on December 23, 2018, 09:31:35 PM
https://time.is/London
0730 tune up.....0800 message...


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: Opcom on December 23, 2018, 10:30:35 PM
Racal R1307A/GR for me!
http://www.bunkerofdoom.com/lit/rycom/index.html

I'll give it a spin!


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 24, 2018, 03:07:38 AM
There they are.  CQ de SAQ!😊 Snowing here on Stonington Point.  539X -93dBm on the WuG. 100 foot wire lying on the rip-rap stones along the east side of the Point.  Generally NE-SW.  Merry Christmas!


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 24, 2018, 03:48:57 AM
Here’s a pix of the WuG deployed in the jump seat of the Tacoma, uses little 100 watt DC to AC inverter, it only draws 20 watts.  And weighs about 50 pounds!


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 24, 2018, 07:24:50 AM
I decided to sleep in and catch it on a European SDR at 0800Z rather than have to be up at 3am (!) EST in order to listen here. Much more convenient!


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: KL7OF on December 24, 2018, 09:52:02 AM
I couldn't stay awake ...I missed it......


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: Opcom on December 24, 2018, 10:16:02 AM
A pity they do not bring out the old water cooled carbon mike and do a little AM Fessenden style!

But I did not pick up the stattion, unfortunately.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 24, 2018, 11:41:59 AM
For those who missed it, it's out on video!

https://www.youtube.com/watch?v=shqi43EV07c (https://www.youtube.com/watch?v=shqi43EV07c)


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: PA0NVD on December 24, 2018, 02:15:00 PM
Unfortunately, I couldn't receive it There was a whole lot of noise, probably LED lighting or so.
But thanks for the youtube link, I did enjoy seeing it


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: W2PFY on December 24, 2018, 09:20:22 PM
Where are the tubes? I didn't see a single tube? I wonder if those Morse senders are metric?

All kidding aside, From what I have read on the net, all you need to receive that signal and others in that band, is your sound card on your computer. I guess it would be helpful to be in a very quiet area? I also found a sdr just for that low band but the download site is no longer working. That sdr had filters on it to focus on the part of the band that you were interested in. The one I downloaded was called SiDiRa 099 but I don't have the antenna here near Albany, NY to try it out. I'll try it on a long wire at camp before the static picks up in the spring.

So AG1G Chris, I guess you are the only one in our area to hear it? Any recordings?

Terry
 



Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 24, 2018, 09:45:26 PM
I didn’t make a recording.  While the signal was solid copy the SNR was not that high and lthere was a fair amount of buzz in the noise floor probably from the inverter powering the WuG AT-611.  There are now a number of YouTube videos put up by folks who copied it, mainly from Europe.  Beautiful CW, note shaping seemed on the soft side.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 24, 2018, 10:11:02 PM
Now that we couldn’t be further from the next SAQ transmission, I just got the nutty idea to build an op amp mixing circuit that uses an audio transformer to couple RF from the antenna to the + input and connect an audio oscillator to the - input.

The idea is to set the oscillator to a frequency 600 Hz off the desired station in order to create an audible beat note.

I might breadboard it in the next few days to see if there’s any merit to the idea...


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 25, 2018, 05:20:48 AM

The idea is to set the oscillator to a frequency 600 Hz off the desired station in order to create an audible beat note.

I take it from your comment that the app you downloaded to use with the computer sound card doesn’t provide the means to demodulate CW, FSK, or SSB signals. Seems like a major shortcoming considering it’s intended purpose was specifically for reception of a CW signal.
 
Why not just loosely capacitively couple the beat frequency oscillator to the signal path? At such a low frequency you could use something like an HP-200 audio oscillator, and use the output level attenuator to present a beat signal amplitude that doesn’t overwhelm the received signal.

I use this technique with my E. H. Scott SLRM to improve its performance on CW and SSB.  The SLRM in fact does have an internal BFO, but it has a very low injection level into the 12H6 detector, as there is no direct connection of the BFO signal by any sort of coupling capacitor in the original as-built design. I suspect this was deliberate by design so that the set would meet the Navy’s incidental radiation specs to qualify it as a super low radiation (SLR) shipboard receiver. I use a twisted wire gimmick cap to loose couple the output of a URM-25 sig gen at the nominal IF frequency into the grid of the last IF stage. The band spread at 465 kHz on the 25 provides for really smooth setting of the beat note, and careful setting of the output level permits using it with the AVC on without excessively driving the receiver gain down when listening to a wide range of incoming signal levels. It’s also useful to crank up the injection level when I want to use the SLRM as a local off-air  monitor of a transmitted CW or SSB signal.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: N1BCG on December 25, 2018, 11:49:37 AM
I take it from your comment that the app you downloaded to use with the computer sound card doesn’t provide the means to demodulate CW, FSK, or SSB signals. Seems like a major shortcoming considering it’s intended purpose was specifically for reception of a CW signal.

The SAQrx.exe is a great app and includes the USB mode and selectable bandwidth filtering. It's ideal for listening to SAQ, but that means for only a few minutes twice a  year and it's top frequency is 22kHz. That's fine for tuning in 17.2 kHz, but somewhat limited for exploring higher VLF frequencies.

SAQrx v9.8 can be downloaded here: http://dl1dbc.net/SAQ/SAQrx/SAQrx_0-98.zip (http://dl1dbc.net/SAQ/SAQrx/SAQrx_0-98.zip)

Instant listening on a European Web SDR makes things as simple as possible:

http://websdr.ewi.utwente.nl:8901/?tune=17.20cw (http://websdr.ewi.utwente.nl:8901/?tune=17.20cw)

The RSP1A SDR tunes down to 1 kHz (!) and offers lots of mode and filtering choices. That's what I used for testing audio transformers, and the spectrum display and signal level metering helped tremendously in the comparisons of the various transformers.

You bring up a good point about signal levels. The audio oscillator injection point should be at a higher level compared to the antenna input. Most op amps are dual section so theoretically one half could be used for antenna input amplification with transformer isolation/filter/matching and the second half for unity gain mixing. The output would then be line level for driving an audio amplifier. The downside is the lack of bandwidth control so I imagine it would be a lot like tuning in CW using a direct conversion receiver (like the HW-7 I had!).


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: AJ1G on December 25, 2018, 12:39:33 PM
Clark, following your suggestion, I cleared out the BCB spurs from my NooLec RTL SDR and upconverter.  Feeding my 75 meter dipole in with a .01 bypass across the input cleared out the BCB junk and I could hear and see a whisper of NAA at 24 Hz but the signal level was just above the electrical noise floor of the upconverter.  Using an amplifier of opportunity, the one available in my Ballentine Labs AC VTVM, which has an amplified signal output jack, I cranked in some gain and now NAA is banging in with and SNR about 25 dB above vs system noise floor.  I can also hear several other VLF signals that are down in the noise and only faintly tracing on the waterfall.  Should be able to improve the SNR with added gain but I am at the limit of the Ballentine at this point and it’s time to head out to Christmas activities!  Again, thanks for the tip.


Title: Re: 1924 Alexanderson machine transmitter in the air!!!
Post by: Steve - K4HX on February 28, 2019, 09:48:31 PM
Listener reports at the link.

https://alexander.n.se/wp-content/uploads/2018/12/FINAL-SUMMARY-REPORT-ON-CHRISTMAS-TRANSMISSION-2018-2.pdf


Even heard in Alaska!
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands