uhf radio query

no. for one richmond is flat geographically and higher than mckinley. and tv would not have been transmitted on uhf in the 1960's.

samsgoneagain.
You know your beginning to Pi$$ me off mate , I did not say TV was transmitted on UHF in the 60s you clown, I said we recieved signals from WA the same way a radio uhf signal would be piped , Have you studied for an Amature Lic' , was you even alive in 1961/2, you come on here and rattle on about BS you know nothing about .
And you have the hide to tell me I and my family didn't see Perth TV in SA during freak conditions , rack off .

samsgoneagain
And another thing ....you asked a very good sensible question and when you got a sensible honest answer you shot me down , .I don't know why I bother

Doug

This is a common occurrence. The mechanism is generally the result of a temperature inversion rather than ionospheric. This is what samsgoneagain experienced - generally happens at night time but can happen during the day. The quick change in the density of the air between the cool air and the warmer air that drifts over the top of it. Cloudy conditions can also produce the effect. What time of day did you hear the Shell roadhouse

We used to get herringbone interference on CH8 from Orange at Dubbo when the ducting conducted CH7 from Canberra into our area (TV sets are very poor at rejecting adjacent channel interference.)

PeterD

Peter
The time was about 6:30am and cool .Just had a thought ...samsgoneagain might have been on Duplex going through a repeater, the one I was talking about was on Ch 40

Doug

That would be a good time for a temperature inversion.

PeterD

Signals with frequencies above about 30 MHz (VHF and UHF for example) are progressively not returned to the Earth's surface, because they penetrate the ionosphere. (This includes most communications with spacecraft and satellites.) Exceptions include rare occasions of E-skip, when FM and TV signals are reflected. Skywave may be disrupted during geomagnetic storms.

Low to mid frequencies below approximately 10 MHz (longer than 30 meters), including broadcasts in the mediumwave and shortwave bands (and to some extent longwave), travel most efficiently by skywave at night. Frequencies above 10 MHz (shorter than 30 meters) travel better during the day. Frequencies lower than 3 kHz have a wavelength longer than the distance between the Earth and the ionosphere. The Maximum usable frequency for skywave propagation is strongly influenced by sunspot number.

Because the lower-altitude layers (the E-layer in particular) of the ionosphere largely disappear at night, the refractive layer of the ionosphere is much higher above the surface at night. This leads to an increase in the "skip" or "hop" distance of the skywave at night.

its called ducting if I remember correctly from when I learned amatuer radio.

Owen

Owen
SPOT ON MATE

Ducting is the very name I was looking for , just that I didn't make it to the end of amatuer classes . I got a job and couldn't make it to courses , that was about 1976/7 ,

Doug, FYI there are various kinds of ducting such as tropospheric and ionaspheric. They affect different bands of frequencies.
We used tropo as secure comms over 800k in asia, by bouncing the signals on ionized meteor trails.
The mechanism is temporary but relatively easy to predict. However it is a specialist field, used largely by radio amateurs for long distance contacts.
Interestingly enough, HF waves can also be reflected back off objects, and this is the basis of our over the horizon radar systems in Australia. So the next time a plane goes over your aerial, listen for a bit of "flutter" .
BTW I heard some South Oz amateurs on the TV around Xmas in 1958. That's what started me interested in getting my license. I also heard Taxis, but I never wanted to drive one :)))

We used to call that surface ducting in the Navy. It results from a low level temperature inversion and can also affect VHF and radar.

I can recall a night in the Indian Ocean in the 1980's when the surface search radar was picking up ships at over 150 nautical miles whe its normal range for all but supertankers was about 30.

Cheers

Pete

i will not believe it unless someone can provide a recording on a cassette.
would this be called 'duct tape'
seriously, occasionally get bothered on vhf when flying at 1000ft at bunbury by very clear calls from aircraft on downwind (1000ft also) at geraldton (over 500 km away).
mentioned height because as we all know, it greatly affects range so this must be ducting.

Ahhhhh Doug your bringing back memerys from the Eyre Penninsula now! 40ft high antenae and not knowing what you will get when you turn on the tele - complete snow? intermitant pictures/sound? (yes we still watched it) or crystal clear TV. Discussion all week would be wheather or not there might be a semi watchable reception for prisoner. Kids today get the ABC and Imparja no worries - never used to be that easy

Davoe
Yeh you got it mate , We were pushing our luck to get reception at the best of times at Sunlands, near Waikerie/ Ramco b/w , the signal had to come from Mt Lofty , Just using Mapsource it shows 144klm , amazed to see on T4A all the roads in Sunlands, IMPARJA ....that wasn't even thought of in 1961 , Nah we had all the Fab Westerns, The Wrestling , Laural and Hardy Movies. oh and Test Patterns, , then earlier when we first got TV at Eden Valley ....yeh we watched the snow waiting for the transmission to begin and went to bed after the National Anthem, Oh we had Lionel Williams and Kevin Crease on CH9s Adelaide Tonight .



" Now Look what Youv'e gotten us into Stan "

Doug

Common frequencies ranged from between 30-70 meg on VHF AFAIK. Ducting on those frequencies is fairly common especially where temperature inversion occurs.
No doubt the Pommies were using the same kind of radio, and I bet it startled them, also :))