Sporadic E

Moulder
15th March 2007, 22:44
(EEK) Has any member every experienced any VHF contact over excessive distances - due to 'sporadic E' - an increase in ionisation of the E layer in the atmoshphere?

I remember in 1975 when bound for the Gulf - I managed to put through a R/T call on VHF for the second engineer via Karachi Radio. We were 400 miles south of Karachi!!

The shore operator nearly threw a wobbly when I told them our position as he didn't believe me!!

Regards,

Steve.
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K urgess
15th March 2007, 23:53
Having just passed Capetown we heard the "Himalaya" calling Dakar radio on channel 16. He was getting no joy and was told to be quiet (impolitely) by a Hull trawler down at the Falklands.
We regularly heard distant VHF stations on this route mostly transmitters that appeared to be in almost a north/south line.
This was in the 60s/70s.
Cheers
Kris

John Briggs
16th March 2007, 00:51
Running up the Persian Gulf in the sixties it was common to get a few hundred miles reception. As you approached the station however, reception was lost until within normal VHF range.

billyboy
16th March 2007, 01:32
I have a brother "marsat2" who used a "CB radio" when he was living in Queensland (towoomba area) he made a DX call to a guy from luton who believed it to be a wind up. however they exchanged cards by post to prove each others locations. think they said it was made possible by skip conditions or something.

tunatownshipwreck
16th March 2007, 03:53
Long-range on CB is not uncommon at all, as it uses the upper frequencies of the shortwave bands (27 megahertz). Anytime we're around sunspot maximum (most recent 1979, 1989, 2000) a CB'er on the west coast of the US can make contacts in Japan or even Australia.

Graham Wallace
17th March 2007, 02:05
In 2002 was travelling around Nova Scotia on the East Coast of Canada and had switched on my 2 meter Ham radio to see if any locals were around, caught a partial conversation between two guys in Sydney. Just up the road I thought, I'll stay there tonight. Reached down to pick up the mike and heard them talk about Melbourne and thought......Nah
Graham Wallace

trotterdotpom
17th March 2007, 09:49
Sporadic E propogation is caused by densly ionised patches in the E layer of the ionosphere. Different densities affect different frequencies. There are various theories about what causes extreme ionisation, as far as I know, none are proven. On VHF the "skywave" component of the radio wave, ie the portion that is radiated upwards, normally passes straight through the ionosphere and into space. When the same skywave strikes a Sproadic E cloud, it is reflected back to earth and consequently the transmission is heard over vast distances.

If any of that is wrong it's because I learned it 40 odd years ago and it was probably in black and white in those days!

I recall on a trip from Fremantle to Durban giving an eta to the port authorities on VHF from the middle of the Indian Ocean. As has already been mentioned, it was often quite easy to communicate from the north to the south of the Persian Gulf, and stations continuously interfered with each other. Similar effects caused odd targets on radar screens.

John T.

Hague
18th March 2007, 00:07
I recall hearing Las Palmas off (or just North of) Cape Town on many occasions.
Brgds
Hague

Moulder
18th March 2007, 11:03
I recall hearing Las Palmas off (or just North of) Cape Town on many occasions.
Brgds
Hague

Hi Hague,

Ah Las Palmas - the area around the bridge VHF was never so busy when that female op was transmitting! Then there was those female voices operating Klang Exchange around Port Swettenham - in the '70s - sad weren't we??

Regards,

Steve.
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King Ratt
18th March 2007, 15:24
The sweetness of the voice was often indirectly proportional to the beauty.

K urgess
18th March 2007, 15:29
King Ratt

Shouldn't that be "inversely" proportional to the beauty?(LOL)

Kris

R651400
18th March 2007, 15:33
Those of us not familiar with radio jargon such as sporadic E propagation may also remember the days of 405 line b&w TV interference from continental stations during such activity.

K urgess
18th March 2007, 15:41
We still get FM interference these days from continental stations. Last year I think it was Radio Moscow that was breaking through.
Channel 4 seems particularly prone to continental interference during warm weather. Although they all seem to take turns at disappearing.
It was simpler in the old VHF TV days because your aerial was either horizontal or vertical to pick up a particular polarisation.
I was always fascinated that our local TV aerials were vertical and up in North Yorkshire, Cleveland and Tyneside they were horizontal. Looked very strange.
I didn't expect it to happen on satellite and it may be a different phenomena affecting the uplink but that seems to "block" out sometimes and not just from local rain.

trotterdotpom
18th March 2007, 16:34
I installed Satellite TV for a while when it first appeared in Australia. Naturally people would ask about interference to the signal. I used to tell them that the main interference would come from heavy rain but also, with it coming in from space, there was a possibility of interference from Uranus. I only recall two people ever getting it!

John T.

ron hansen
18th March 2007, 16:52
have heard scottish inshore boats talking while lying up at spitzberegen here some funny stuff up there