VLF Amateur News 2011

Please let me know dates/times/frequencies/modes if you plan any VLF tests so I can publish information here. As I don't always get told of tests and am sometimes away and unable to update news, please check the RSGB's LF Reflector email list or the Sub 9kHz Amateur Radio Yahoo group for late news of tests.

News items and recent/new VLF activity

28.12.11

Chris G3XIZ has now received his sub-9kHz NoV renewal and is building his improved loading coil in readiness for further radiated VLF tests.

Roger G3XBM will restart earth-mode tests in the new year hoping to improve on the 6km DX achieved last year. These next tests will be around 8.97kHz (where most grabbers are looking) rather than 8.76kHz and possibly with considerably more power (100W) and a longer TX earth electrode spacing. Far field reception may just be possible.

30.11.11

Chris G3XVL has set up a new VLF grabber in Ipswich UK. See http://dl.dropbox.com/u/15836400/XVL_grab.jpg

27.11.11

Yesterday's test by DK7FC from his fixed location was a resounding success with reception all over Europe by many stations and what is believed to be the first time reception of an amateur transatlantic VLF signal in the Eastern USA. More on this later when the data has been carefully checked. His ERP was later re-calculated as around 800uW.

Marcus DF6NM ran a 8.9kHz test this afternoon using a kite flown antenna. G3ZJO received a nice signal in IO92ng 20dB above the noise in 424uHz. Marcus was also well received by many stations in Europe.

In summary, this weekend has been a BUSY one on the Dreamer's Band!

25.11.11

Stefan DK7FC 8.970kHz test Saturday November 26th. This test is the first time using DK7FC's fixed antenna system at his research institute rather than his portable kite antenna.

Stefan writes:

The coil and PA and all the parts are here now and maybe i will do first tests tomorrow in the afternoon on 8970 Hz.

The goals would be to resonate on the frequency and apply 50 kV rms or more. Oh i just calculated: My coil has about 550 mH and the antenna 473 pF. So i need about 100 pF from somewhere else, remembering my homemade plate capacitor with the cola bottles as the spacing insolator ;-) The coil has about 320 Ohm DC resistance and if i actually want to apply 50 kV, i would need 1.2 kW for that. No problem for the PA i think. The ERP will be below 1 mW anyway :-(

But the background noise is extremely low in the last time and if i can a stable signal over several hours i expect to be visible in many spectrograms.

73, Stefan/DK7FC

On Saturday afternoon Marcus DF6NM was copying DK7FC at 20dB over noise in 0.48mHz. He has also been seen by OK2BVG. In the UK he has been copied by Paul Nicholson (Todmorden) who has an excellent receiving set-up and by Eddie G3ZJO. The trace on Eddie's 424uHz grabber is shown on the right, which is very clear indeed. Signals were also seen by G3KEV.Stefan is TXing overnight on 8.970000kHz with 200uW ERP with a GPS locked, very stable signal. He is hoping to be positively identified in the USA for the first time.

15.11.11

DK7FC is planning some tests on 8.97kHz shortly using his FIXED antenna at his research institute. ERP will be between 100uW and 2mW but with very long and stable transmissions (possibly with carriers as long as 24 hours with 500W RF into the antenna) this signal may be detectable across Europe and even, hopefully, to sensitive detectors in the USA, Canada and Alaska. These tests could be within the next 1-2 weeks. Watch this page and the LF-reflector for breaking news of this.

G3XBM has received a 12 months extension to his 8.7-9.1kHz NoV. G3XIZ was still awaiting his extension but may have received it by now.

6.11.11

Lubos OK2BVG repeated his kite antenna VLF tests on Nov 6th 2011 and was copied by several stations including DK7FC and Paul Nicholson in the UK.

Hello VLF!

When the wind is suitable, I will realize my second kite fly tomorrow:

***INFO***

Date: 06.11.2011

Time: 08:00 UT - 11:00 UT

Antenna: Kite GP 150m long (130m effective height)

PA: 120W

Identification: K

Mode: DFCW 3000

FRQ: 8970.045

Shift: 10mHz

Lubos, OK2BVG

Later Lubos reported his signal was received by several stations:

Hello VLF fans!

I started my transmission at 08:00UT and I was transmitting to 09:10UT. Than I had to stop, because the wind was getting weaker. After 10UT the weather was nice, but windless :-(

I am glad to saw my signal on the Stefan´s, Gerhard´s and Paul´s grabbers.

73!

Lubos, OK2BVG

25.10.11

More activity from central Europe with this test reported by Lubos OK2BVG

Hello VLF friends!

I did my first test with kite as an antenna for 8970Hz today:

***INFO***

Date: 25.10.2011

Time: 14:00 UT - 16:00 UT

Antenna: Kite GP 150m long (120m effective height)

PA: 120W

Identification: K

Mode: DFCW 3000

FRQ: 8970.045

Shift: 10mHz

It was "last minute" activity due to wind conditions.

Lubos, OK2BVG

22.10.11

News from Norway of experiments at 8.970kHz by LA5VNA

I have been using SpecLab a long time on 10.140MHz playing with qrss3. I

have tested many waterfall programs, but SpecLab is my absolute favorite.

I have been on qrz.com and looked at your systems. I have no ambitions

to come up to the same level with the first. I am concentrating now on

local communications. My latest experiment is with an Earth dipole. I'm

using a 1-meter copper pipe in the ground as one end of the dipole. The

other is connected to water pipes in my house. The distance between them

is about 20m. As a PA I am now using a 150W power amplifier from HH

Electronic (V150-L). This has a 100volts line output (100W RMS at 1 kHz

into 100ohm). I have tested different modes; MSK01 with SpecLab, WOLF,

THROBX and PSKAM10 in Multipsk. ZL2AFP's CMSK8, and various versions of

qrss. Right now, I am sending in the qrss120 on 8970 and hoping that an

amateur friend of my about 10 km away, will receive me.

My antenna receiving systems on VLF is not the best. I use my 10X10m

loop in the garden. With this I can receive the Alphas pretty well, but

now I am building an active antenna (after your drawing). It will be

exciting to see how it will work in my neighborhood. I hope it does not

pick up too much noise.

Best regards and 73

Steinar LA5VNA

LOC: JO59JQ

19.10.11

News from OK2BVG about upcoming tests:

Hello VLF!

I will be testing my new Rubidium frequency reference tomorrow:

***INFO***

Date: 20.10.2011

Time: 08:00 UT - 11:00 UT

Antenna: Marconi L 24m up + 220m top load

PA: 120W

Identification: K

Mode: DFCW 3000

FRQ: 8970.040 (+/- some few mHz :-)

Shift: 10mHz

I hope, the propagation will be good!

Lubos, OK2BVG

2.10.11

News from LA5VNA in Norway of some VLF tests

A test of cmsk on 8.97kHz

Hi all,

The last few days I've been doing some digi mode testing at 8.97 khz;

"dreamers band", mostly with use of the QRSS mode.

On the transmitter side, I have been using a 5 turn 10 x 10 m antenna

and an audio amplifier 100W. The system is feeded with a signal from the

program "Spectrum Lab".

On the receiver side, I have been using a 70 x 70 cm 60 turns loop,

tuned with a capacitor. The loop was connected to the microphone input

on my laptop and decoded with "Spectrum Lab".

The result has been interesting . With this simple arrangement, I have

reach a distance of 2.5 km.

Yesterday I tried out CMSK8 made by ZL1BPU Murray. I had to make some

changes in the ini-file to get the CMSK work om 8.97khz. The sampling

rate was adjusted with the program CheckSR and the transmitting

frequency was set to 8970Hz. Waterfall has a 2000Hz limit so this was

black and useless on 8790Hz.

It would makes it easier to track the signal if the developer could

extend waterfall to 10 kHz. Iam aware that one can get the view of the

waterfall by going down in frequency, but 8.97khz has become a de facto

water hole of VLF .

The result was exciting. A clean copy of the signal was received at

about 2 km.

I would also try to test out some of the VLF mode in multipsk ,

especially PSK10 and PSKAM10, but I have not find a way to fool the

program to work on 8.97Khz yet.

73 and good dx the VLF Steinar LA5VNA

In the October edition of the RSGB RadCom Magazine there was a 3 page article entitled "VLF experiments through the ground" by G3XBM.

G3XIZ is building a new loading coil for his VLF radiated experiments.

OFCOM has confirmed that the UK 8.7-9.1kHz NoV permits will be renewed, if requested by current holders.

12.9.11

Activity today on VLF: OE5ODL was TXing on 8969.968Hz and visible on the DK7FC grabber. Conditions on VLF are reported to be good as the DX season gets under way.

6.9.11

From DK7FC about the low noise at VLF currently and an update on VLF grabbers

VLF,

The noise on the Dreamers Band / 8970 Hz is as low as never before in this season, just like in winther! At least is that small time slot of about 4 hours, tests could be done again.

Up to date grabbers, as far as i can see:

http://www.ok2bvg.cz/vlfgrabber/

http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html

http://simnet.is/halldorgudmunds/TF3HZ_VLFgrabber/index.html

http://members.aon.at/grabber/VLF/index.html

http://qsl.net/4x1rf/yo/vlfgrabber.htm

http://abelian.org/vlf/fbins.shtml#p=1315202400&b=100&s=sp

http://www3.telus.net/sthed/argo/

73, Stefan/DK7FC

30.8.11

From DK7FC

VLF,

My VLF grabber is back online repairing a boken wire (that CAT5 twisted pair cable is not the robustest one...).

Noise is very low today, not only on LF. Seems the DX season slowly starts...

http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html

73, Stefan/DK7FC

13.6.11

OE3GHB has been testing a new VLF transmitter around 8.970kHz and has appeared on some of the European VLF grabbers. See http://members.aon.at/grabber/VLF/index.html . This was an unannounced test, so sadly few were looking.

30.7.11

Stefan DK7FC reports that the QTH used for his last 11 VLF kite experiments is no longer available because a wind turbine is being installed there, but he has found another suitable location 1km away.

Marcus DF6NM was active last night and did more tests again today on 8.970002kHz. During the Saturday transmission Marcus was copied by many stations across Europe at good strength including by TF3HZ (2547 km) and YO/4X1RF (1253 km).

Dear LF,

today around noon, I will attempt another kite transmission from the same site. If all works well, I will send a 1 mW carrier on 8970.002 from around 11 to 14 UT.

Best regards,

Markus (DF6NM)

Dear Dreamers,

thanks very much to everyone who commented on my signal yesterday night, and all who are running their VLF grabbers.

Transmission:

My signal was on air on 8970.002 Hz from 18:52 to 22:01, with a long break from 19:26 to 19:52 due to a prolonged rain period, and many shorter interruptions caused by precipitation, low wind, a coil falling over, or a breaking antenna connection.

I'm aware that an advanced notice would have been valuable for potential receiving stations. But I find it difficult to plan ahead this type of activity. Yesterday even while setting things up on the site, I was not at all sure whether I would be able to actually get on air for any significant time.

Site:

The location (49.3874 N 11.1692 E, "JN59OJ02HX" for those who prefer cryptic notations ;-) was the same as in the experiment on Nov 13 last year (see email copy at bottom). While Google Maps still shows large patches of unused land around the former US airfield, "my" field is now one of very few undeveloped plots in the middle of an industrial area, inhabited mostly by large logistics companies. Though I had originally not intended to work into darkness, I found there was still plenty of light from the surrounding truck parking and unloading areas.

Kite antenna and ground:

This time I used a 4 sqm lifter kite (HQ Power Sled L3.0, similar to Stefan's smaller kite). It is held by a 150 m line. This may be stretching the limit a bit, but due to the slope and sag of the line I am sure that the peak altitude always stayed below 100 m.

The previously used 0.4 mm magnet wire had a voltage limit of about 12 kV due to corona appearing along the whole length. It has now been replaced by insulated wire (0.25 sqmm, outer diameter 1.3 mm). The total length is 180 m, with the last 30 m dangling down from the kite, intended to act as a sort of extra top load. Effective height would be around 50 m, giving 3.5 milliohm radiation resistance, or 1.3 mW EMRP at 0.6 A.

At the western end of the unused site, there is a long mesh wire fence running north-south, held by solid metal posts which served very well both for anchoring and grounding. Total resistance of the antenna circuit was around 280 ohms (including 140 ohms for the coil). This is about half of that when I used the same kite antenna in Bamberg with only a few short ground pegs.

The coil was placed below the kite line at about 3 m from the anchor point, hoping to keep the wire well above ground. However this turned out to be problematic due to the horizontal and vertical movement of the connection point. When the kite was low and due west, the wire was too long and touched the wet grass, exhibiting pretty little fireworks. When it went up or drifted aside, the wire became too short, and either plugged itself off, or tipped over the whole coil. You guess how much I like having to reconnect the ungrounded wire, with dark clouds overhead and a slight drizzle going down... I twice found myself holding down the kite line with my foot, then slowly stepping forward until the open end at least touched the earth. Next time I will definitely place the coil much closer to the anchor, and try to hold the connection up by means of some elastic plastic tube.

Coil:

From the previous experiment I knew that the wire capacitance was very close to 900 pF. During the afternoon, I experimented with different coil configurations, and found that I could either use four buckets (184 ohms) with a large 10 cm pitch (ie. 9 Lego blocks), giving about 8 mm radial clearance between one coil layer and the inner radius of the next bucket. The other option was three buckets (138 ohms), stuffed into one another 3 cm pitch and 2 mm clearance (see picture http://df6nm.bplaced.net/VLF/pictures/two_coils_350mH.jpg).

Mainly for mechanical reasons, I opted for the more compact three-bucket solution, but this turned out to be the wrong choice. With power applied, I heard corona sizzles around the coil at about 0.55 A (11 kV). In darkness I could see violet seams near the bottom end of the upper two windings. This means that the maximum usable layer-to-layer voltage for this design is about 3.7 kV. Next time I will definitely go for the longer version, which also has more surface exposed to the wind for heat removal.

BTW all seven buckets connected to 900 pF resonate at about 4.6 kHz - Stefan, how about a 65 km band ;-)

Amplifier and power supply:

Like before, I used one channel of a class-B car-audio amp (Nitro 3000), feeding a 12 : 80 turns ferrite transformer originally wound by DJ2LF. It delivered 0.6 A antenna current (~ 100 W) from 12V x 13 A DC input. It was possible to turn the volume up to 0.7A, but I did not dare to run that level of corona permanently. The amp was fed by a standalone 35 Ah lead-acid battery, which was repeatedly recharged via jumper wires from the car engine during the latter half of the experiment.

Signal generation:

SpecLab's samplerate was locked to DHO, which is very slightly (3 ppb) above its nominal frequency 23.4 kHz. To keep the average phase steady, I took care to never interrupt the software generator whenever I had to take the carrier off air. Anyway the time series recorded by Paul Nicholson shows two major phase jumps around 19:40 (while the TX was off) and 21:20, perhaps due to soundcard buffering issues. One problem I did not see immediately was that the DHO ferrite antenna was too close to one of the jumper wires, temporarily picking up interference when the car alternator was running - once found, this one was easily fixed.

Results:

Though the traces at TF3HZ (2547 km) and YO/4X1RF (1253 km) are close to the noise, they are at the right time and frequency, and I do not think that they are random pixels. Halldór's trace even seems to show the outage period after the first bright dot.

On my own grabber, I attempted to compare signal levels from DK7FC (-71 dB, 180 km) and myself (-43 dB, 4.5 km). Correcting this difference (28 dB) by the EMRP ratio (26 mW / 1.2 mW = 13 dB), distance ratio (1/r = 32 dB) plus an additional nearfield correction (1/r³ instead of 1/r from 4.5 to 5.3 km = 3 dB), we find that Stefan was 28+13-35 dB = 6 dB weaker than we would expect by pure groundwave. This corresponds very well to the earlier experience that there is a midday skywave cancellation effect for about 200 km.

Best wishes,

Markus (DF6NM)

G3XBM is giving a talk on simple LF and VLF radio at the Braintree and District Radio Club on Monday August 1st at 8pm. This will cover 500, 136 and 8.97kHz experiments with simple homemade equipment and antennas, as well as an update on radiated DX work by the "big boys" in Europe. Slides from the talk will be added here later.

17.7.11

Stefan DK7FC is planning a new kite test on Saturday June 18th:

Dear VLF group,

Since more than 4 months the wind and rain situation looks promising for the weekend on my /p QTH in JN49IS36VH. So i plan to do my 11th VLF kite experiment this weekend, either on Sat 18th or Sun 19th June 2011, will be announced on friday. I already announced it at the German air traffic control and just got a phone call were the permission was granted.

The plan is to come on air at about 6 UTC.

The antenna will be the 300m vertical kite antenna. I'll plan to serve the bands 33km and 46km, i.e. 8970 Hz and 6470 Hz. Since i made a new tap on the TX coil i can now resonate the 300m antenna on 6470 Hz too. This should give a about 4 dB stronger signal on 46km.

Since the gap of low QRN is much smaller now, the experiment will not take many hours, maybe just 4 or 5.

Maybe i can get the 4 kVA generator and will produce a 6 dB stronger signal but this is not clear so far. Otherwise i am limited to 550 W TX power. I will limit my antenna current to 2 A in order to prevent a HV breakdown on the coil and due to thermal losses. At 2 A antenna current i should have up to 250 mW ERP!

The program is to start a longer dash, about 40 minutes, GPS locked on 8970.00000 Hz, then a message in DFCW-600. Depending on the feedback of receiving stations i will try to send DFCW-60 or DFCW-10 or DFCW-3 and CW.

Then i'll move to 6470 Hz, transmitting a 40 minutes dash and a "K" in DFCW-600 or so.

As usual the signals will be visible on my grabber in 40 km distance:

http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html for 8970 Hz and

http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber2.html for 6470 Hz (spectrogram still not available)

but surely visible on many other grabbers too ( see https://sites.google.com/site/sub9khz/vlf-grabbers for a list of available Dreamer Band grabbers).

Some new VLF receivers appeared since my last experiment. Two of them are:

http://qsl.net/4x1rf/yo/vlfgrabber.htm (1435 km)

http://www.ok2bvg.cz/vlfgrabber/ (598 km)

Leaving a trace on these and all other new and old VLF stations is the goal! Despite high QRN and the longest days in the year (here in EU) i am optimistic.

Maybe Markus/DF6NM or Marco/DD7PC or someone else in DL wants to be available on the phone for QSP to the reflector?

Looking forward to the weekend and hope all works well and we'll have much activity.

Best 73, Stefan/DK7FC

José, EA1PX is considering setting up a RX station in Spain. As he is in a city location he may have to experiment with E-field probes or loops to get an effective and low noise system in place.

9.6.11

DK7FC testing shortly from his fixed QTH starting 10.6.11

VLF,

Tomorrow i plan to do first tests on 8970 Hz on my fixed antenna in Heidelberg, http://no.nonsense.ee/qthmap/?qth=JN49IK00WG&from=jn49ik00WD It is about 30m up.

I'll start doing some resonating tests and may come on air in the afternoon. The small PA (max. 300W) will be used in this first test since it is easier to manage. Maybe the resonance will be some kHz higher but i hope to come down into the Dreamers Band (TM). I expect to be visible on "local" grabbers like DF6NM, OE3GHB and OK2BVG. If all works well i plan to transmit a longer dash, maybe 6000 seconds and later a short message in DFCW-600, like "K" or so, just for the proof and to get a first impression about the efficiency of this antenna. I had the idea to buy some flexible aluminium tube to form a toroid that will be placed on the top of the coil. Tis reduces the maximum E field and adds some C, that might be needed to come down to 8970 Hz... Of course all this depends on the absence of rain but now i don't need wind! Therefore, the signals will be about 20 dB lower, probably. The signal will be overload my grabber http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html that is in about 20 m (!) distance. Hopefully it gets not damaged due to several 10 kV on the wire.

Is there someone who will watch for that signal?

Reports would be very apprechiated!

73, CU, Stefan/DK7F

5.6.11

Uwe DJ8WX is testing again...

Hi all,

Im testing a new DJ PA.

carrier on 8970.022Hz.

seems the PA doesnt like high frequencies.

we will see.

GL

Uwe/dj8wx

4.6.11

VLF news from Germany

Dreamers,

VLF may be difficult these times, but certainly not dead!

During the traditional fieldday near Bamberg, we raised a kite at

http://no.nonsense.ee/qthmap/?qth=JN59LU23HA

during two afternoons. Due to the less than optimal wind the kite hovered mostly at a low angle, with estimated peak hight 50 to 70 m and a lot of sag. With only a few short ground pegs, we had 0.3 to 0.45 amps, and probably radiated around 0.2 mW (EMRP) on average. The carrier was DHO-locked on 8970.00, on air at 2011-06-02 13:15 - 14 UT and 2011-06-03 13:40 - 14:15 UT.

On my own grabber in Nuernberg (50 km from the site),

http://www.mydarc.de/df6nm/vlf/vlfgrabber.htm

the two short dashes are brightly visible, with about 17dB SNR in 0.48 mHz. Unfortunately we did hit the maximum daily QRN period, during the morning the noise would have been about 12 dB less.

At DK7FC in Heidelberg (170 km) we hardly overcame the QRN, but there is indeed a hint of yesterdays dash on the 6000 window

http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_VLF_Grabber.html

To my surprise, both transmissions were clearly picked up by Paul Nicholson's "miracle loops" at 980 km, and can be seen on

http://abelian.org/vlf/fbins.shtml#p=1307044800&b=120&s=sp

when the virtual beam rotator (compass) is dragged to about to 120 degrees.

Good luck to Chris for today's experiment!

Best wishes,

Markus (DF6NM)

G3XIZ active with an improved antenna system this weekend June 4/5th:

LF,

I have permission a

G3XIZ has now gone QRT after a weekend of tests on 8.9766616kHz. Chris appears to have reached a limit in terms of range and reporting stations but there are still further stations looking for him such as M0DTS, G3PLX and DK7FC.

16.4.11

G3PLX has started an interesting discussion thread on the Sub-9kHz Yahoo group exploring the physics behind earth mode propagation (including utilities assisted). This discussion could run and run!

G3XIZ has been active today and received by G3XBM, G3ZJO, G3WCD and M0FMT and no doubt others. This was M0FMT's first

has been doing further earth mode tests, this time at 1.095kHz. See G3XBM Earth Mode blog on this site for details and results. This was the 5W QRSS3 signal today at 4.5km from the home QTH.This is the small low input impedance preamp tuned to 1.1kHz used in the tests today with a small loop antenna on RX.PA3CPM has now

OE5ODL has been testing several times in the last few days and has been well received by many including G3XIZ and G3ZJO. This is the screen shot from G3XIZ yesterday (424uHz bandwidth). As you can see, good copy on the loop and M0BMU preamp.

10.4.11

PA3CPM is TXing overnight on 8.970kHz.

Hi LF,

The tx will be on overnight with a long carrier,frequentie 8.970Khz,power 40 Watt,antenna curent 250mA

henny pa3cpm

best 73's to all.

OE5ODL is testing with a balloon supported antenna today and has been widely received including in Iceland. G3ZJO has

had good copy in DFCW600 bandwidth (4.52mHz) and I was getting Ossi at 10-15dB S/N in 715uHz bandwidth. Unfortunately my Spectrum Lab froze as I changed settings, so I only had copy for around 30 minutes (0930-1000z) today. My trace is shown right and G3ZJO's below.

hallo vlfers test transmission with ballonsapport

around 8969,977

73 oe5odl

PA3CPM is again active on 8.970kHz and has been copied by DK7FC and others

Hello Roger,LF

After a little smoke,i am on the air again with 250 mA antenna curent on 8.970Khz,

henny pa3cpm

73's

9.4.11

M0DTS (Rob) has started earth mode tests at 8.9kHz with 17m spaced electrodes in a field receiving with a loop antenna. Best DX so far is 1.1km with 1W. More experiments to follow.

8.4.11

OE5ODL has been a good signal at G3ZJO today 4-5dB S/N on 8.96997kHz. He is testing most days recently running 400mA antenna current and is visible in the UK regularly. Mal G3KEV has produced traces of Ossi in a DFCW 600 window.

7.4.11

G3XIZ (Chris) was testing overnight April 7/8th on 8.9766616kHz and welcomed reports.

19.3.11

G3XIZ has been using his balloon supported antenna March 19th and he getting 13dB over noise reports from G3ZJO at about 50km. Paul Nicholson (Todmorden, Yorkshire) managed to copy Chris 20dB over noise in 278uHz bandwidth despite Chris using QRSS. A very successful day!

18.3.11

Sensitive spectrogram online