ARLA/CLUSTER: SSTV - imagem enviada a 100 Km usando Luz Vernelha (670 nanometros)

[João Costa > CT1FBF]

Video of 105 km Nanowave SSTV contact

This video shows the first time in the UK that SSTV has been sent over
a distance exceeding 100 km using red light (670 nanometres)

On Sept 14, 2013, Barry G8AGN and Richard G0RPH with Monica G0VCS
successfully passed SSTV pictures both ways over the 66 km path
between High Bradfield near Sheffield and Manton near Kirton in
Lindsey, Lincs.

Taking advantage of the continuing good (for optics) weather they had
a further contact on Sunday, September 22. Barry G8AGN and Gordon
G0EWN set up at 20.00 BST at Holme Moss (SE097038), while Monica G0VCS
and Richard G0RPH set up at Walesby Hill (TF147933) to test out a new
path of length 105.3 km.  They had tried this path much earlier in the
year, but were beaten then by poorer weather conditions.

Visibility was good with a slight mist, though at Holme Moss they
reported some condensation problems on the lenses as the temperatures
fell. At Walesby, temperatures held steady and the initial winds died
to give a calm night, with a bright enough Harvest moon to work by!

Using their usual Phlatlight rigs, contact was quickly established and
voice exchanges resulted in reports of 5/7 (Barry's transmission) and
5/6 (Richard/Monica). There was moderately severe scintillation on the
link resulting in signals dipping to 3 at times.

Encouraged by the good conditions, they tried an exchange of SSTV
pictures and achieved good images of about P4 quality. The FM
modulation inherent in the SSTV mode coped brilliantly with the
scintillation effects.

Watch G8AGN/P works G0RPH/P on lightwaves SSTV over 105km



The transmitters used Luminus Phlatlight PT39 or CBT40 high power
LEDs. These run at a standing current of typically 5-6 amps and are
amplitude modulated  with up to 15 amps on modulation peaks. These
devices illuminate an A4 size Fresnel lens via an intermediate lens
which increases the amount of light from the LED passing through the
Fresnel to form a collimated beam probably 0.5-1 degree wide. The
transmitters can cope with MCW, Speech or Data such as Hell, SSTV,
WSJT.

Barry G8AGN's receiver is based on Clint KA7OEI's front end which uses
a photodiode fed from another A4 size Fresnel lens. The front end
feeds a LM386 audio amp. He also has a KA7OEI designed PIC based hum
filter which can take out harmonics of the mains frequency (50 or
60Hz) since there is lots of optical QRM from streetlights.

It's essential to have a good tripod with fine az/el adjustment for
the rig. A telescopic sight with adjustable cross hairs is also very
useful.

Nanowave Slow Scan TV
http://www.southgatearc.org/news/september2013/
nanowave_slow_scan_tv.htm

Radio hams 83 km red LED daylight DX
http://www.southgatearc.org/news/august2013/
radio_hams_83_km_red_led_daylight_dx.htm

UK Nanowaves Yahoo Group
http://groups.yahoo.com/group/uknanowaves/