VE7CNF – Lightwave Operations

Toby Haynes VE7CNF
May, 2016

1         Contents

VE7CNF – Lightwave Operations. 1

My First Lightwave QSO – VE7SL to VE7CNF/7. 1

Lightwave Backscatter from Clouds and Clear Air. 4

Clear Air Backscatter using QRSS and Digital Modes. 5

Weak Cloud Backscatter CW... 7

Strong Cloud Backscatter using CW and Digital Modes. 7


My First Lightwave QSO – VE7SL to VE7CNF/7

VE7SL and I have completed a lightwave QSO between Mayne Island and Cypress Quarry Lookout, a line-of-sight path over 51 km. This was using CW with tones amplitude-modulated on deep red LEDs around 660 nm wavelength.


Link to an audio recording of VE7SL from this QSO: VE7SL_660nm_20160419_0439z.wav

Steve’s signal is strong and easy copy. There is interesting rapid QSB from atmospheric turbulence. After dark we could easily see each other’s transmitter by eye.

Receiver (left) and transmitter (right) at Cypress Quarry Lookout.
Mark VA7MM, May VA7MAY, Toby VE7CNF.

Beginning transmission. Markus VE7CA and Toby VE7CNF.

QSO in progress. Steve VE7SL’s transmitter is the red dot just above the tree line in upper right.

Lightwave Backscatter from Clouds and Clear Air

I have done some experiments sending signals from the front of my home to the back, via backscatter from the air or clouds above the house. The setup is:

Transmitter located on the south balcony of my townhouse.

Transmitter pointed straight up, confirmed using a carpenter’s level.

House rises approximately 30 ft to block direct light from transmitter to receiver.

Receiver just north of the house.

Receiver aimed either straight up (elevation 90 deg), or lower elevation as measured by protractor.

Deep red 660nm 1W LED transmitter and unfiltered BPW43 PIN photodiode receiver, with 10 inch square plastic Fresnel lenses. Both tx and rx have about 1 degree beam width. See VE7CNF_Lightwave. See some transmitter and receiver circuits at VE7CNF_Lightwave_Circuits.

If I aim the receiver high to the south, through the transmitter’s beam, I receive weak backscatter signals from particles in the air. If I aim the receiver straight up and there’s low cloud then I get strong signals at audible CW levels.

Clear Air Backscatter using QRSS and Digital Modes

I receive weak signals in clear air if I aim the receiver at about 80 deg elevation and to the south. The receiver is pointing through the transmitter’s beam high above the house, where particles in the air can scatter some signal back. Signals are received from about 70 to 85 degrees elevation. There is nothing detectable from straight up if there’s no low cloud.

On early May 8 UTC, in darkness here, clouds were very high and I was detecting only clear air backscatter signals. Here is the cloud report from the local airport:

May 8, 2016 UTC CYVR clouds and temperature/dewpoint data:
0500 FEW CLOUDS (1/8 - 2/8) 14000  FT, SCATTERED CLOUDS (3/8 - 4/8) 24000  FT, 14 C / 11 C
0600 FEW CLOUDS (1/8 - 2/8) 14000  FT, SCATTERED CLOUDS (3/8 - 4/8) 24000  FT, 14 C / 9 C
0700 FEW CLOUDS (1/8 - 2/8) 12000  FT, FEW CLOUDS (1/8 - 2/8) 22000  FT, 13 C / 7 C

With the receiver at 80 degress elevation, I used Argo to receive QRSS CW, while transmitting FSK CW using mark=570, space=584.6 Hz tones. At QRSS3 speed the signal was barely detectable, but this was useful for aiming the receiver to find the best signal. At QRSS10 the code was easy to copy visually.

Lightwave QRSS10 received by clear air backscatter. Lower trace is the ”mark” tone at 570 Hz sending “CNF”. Upper trace is the “space” tone at 584.6 Hz.

Lightwave WSPR by clear air backscatter. All transmissions were decoded.

Lightwave JT9 by clear air backscatter. About 70% of transmissions were decoded.

Weak Cloud Backscatter CW

On May 4 there was some lower but thin cloud:

May 4, 2016 UTC CYVR clouds and temperature/dewpoint data:
0600 FEW CLOUDS (1/8 - 2/8) 2500  FT, BROKEN CLOUDS (5/8 - 7/8) 5500  FT, OVERCAST 9000  FT,
14 C / 13 C.
0700 FEW CLOUDS (1/8 - 2/8) 2500  FT, BROKEN CLOUDS (5/8 - 7/8) 6000  FT, OVERCAST 10000  FT,
14 C / 13 C.

I was receiving a barely audible signal at CW speed with the receiver pointed straight up. The CW is at 570 Hz and starts “VVV DE VE7CNF/7...” Link to audio: 20160504_0642_CW1_Wideband.wav.

Strong Cloud Backscatter using CW and Digital Modes

May 15 started with high overcast and occasional thin low cloud around 0000 PDT 0700 UTC. Low cloud built to continuous after 0100 PDT 0800 UTC. My altitude is 240 ft, so the cloud was only 1000 to 2000 ft above me.

May 15, 2016 UTC CYVR clouds and temperature/dewpoint data:
0700 BROKEN CLOUDS (5/8 - 7/8) 1600 FT, BROKEN CLOUDS (5/8 - 7/8) 12000 FT, 14 C / 11 C
0800 OVERCAST 1900 FT, 13 C / 10 C
0900 OVERCAST 1300 FT, 13 C / 11 C

For these experiments the received signal was strongest with the receiver aimed straight up. Moving +/-1 degree from vertical caused a significant signal drop, and there was no signal a few degrees from vertical.

CW started audible with QSB as low clouds passed (link to recording 0741 UTC: 20160515_0741_CW_QSB.wav). Later the CW was steady and strong from the continuous low cloud (link to recording 0919 UTC: 20160515_0919_CW15_WIDE.wav). CW audio is 570 Hz.

From 0750 to 0900 UTC I tried various digital modes using audio tones near 1500 Hz. I tested WSPR2, JT9, and JT65A Using K1JT’s software. MultiPSK was used for BPSK31, MFSK8, RTTY45, and picture modes FMHELL245 and MFSK16+SSTV. All worked well, with solid copy or close to it.


WSPR2 at 0804 UTC with variable SNR. QSB can be seen on the waterfall as clouds passed.

JT9 by cloud bounce at 0815 UTC.

JT65A by cloud bounce at 0824 UTC (link to audio recording: 20160515_0820b_JT65.wav).

Waterfall of JT65A cloud bounce signal with CWID.

Link to recording of MFSK8 at 0838 UTC: 20160515_0838_MFSK8.wav.

Link to recording of RTTY45 at 0850 UTC: 20160515_0850_RTTY45.wav.


Waterfall of BPSK31 by cloud bounce. The nonlinear transmitter adds some sideband energy by copy was perfect. Link to recording of BPSK31 at 0856 UTC: 20160515_0856_BPSK31.wav.


FMHELL245 showed a little noise and QSB. (link to recording of FMHELL at 0843 UTC: 20160515_0843_FMHELL.wav).


MFSK16+SSTV Picture by cloud bounce. Ignore the “630 Meter Band,” as this was the only picture file with my call sign that I had available. Link to recording of MFSK+SSTV at 0913 UTC: 20160515_0913_SSTV.wav.