duncansayers said..

MorningBird said..

I flew Grumman Trackers from 1973 until 1984. Were you on O boats or Collins?
It wasn't uncommon when operating in the East Australia Exercise Area to get Clark USAF base in the Philippines or a station in Hawaii and nothing in between. The ionosphere or maybe a ground wave rules what reception you get.

I was on both. I did the commissioning trails of HMAS Farncomb (boat #2 of the Collins class), but got my dolphins (submarine qualification) on HMAS Onslow (now in the National Maritime Museum - Sydney). Having your old workplace/home in a museum is a sobering reminder of my own ageing process :)

I know ROs who got QSL cards from ham operators in the West Coast USA, so yep...it can go a long way.

I served most of my operational time on HMAS MELBOURNE CVS21 but converted to helicopters after the fixed wing and deployed on HMAS SYDNEY 03 in 1984 with a helicopter. I paid off in 1998 as CO HMAS PLATYPUS and did a bit of sea time on OTAMA AND ONSLOW so we may have crossed paths.

shaggybaxter said..
If I look at the frequency scale, the next 'system' in that low frequency band next to HF would be ...what?
VHF (of course) - 30 to 300mhz.
Terrestrial TV - 45-860mhz.
I am sure there are others, but stuff like mobiles and wireless network are all ghz stuff.

What I find interesting is the difference in RF transmission characteristics or performance. Nothing else has anywhere near the mannerisms of HF transmission. Yet VHF and TV are pretty close to the same band at least, and I wouldn't expect that much of a difference.

Question form the peanut gallery for you more experienced chaps, Is the higher order bands (like 30mhz) used that often in HF communications? Or does it kinda suck so much it is not used?
Cheers!
SB

Ok, I'll have a crack. DISCLAIMER - I was an operator (dial twiddler in other words), not a physicist.

* high frequencies go in straight lines and reflect off things - poor penetration
* low frequencies bend around things, but attenuate faster - can penetrate objects.

Think about your next door neighbour cranking up the doof doof. What do you hear - a dimmed bass, but not much not treble.

So sticking with the HF range, at the lower end of the frequency range the signal attenuates more, and refracts in a lower part of the ionosphere. At higher frequencies in the range, the signal refracts in a higher layer of the ionosphere. So using basic geometry, the higher frequency skips further. It might skip over who you're trying to talk to - drop frequency and hello sailor.

If the frequency is too high, it wont refract, but will carry on through the ionosphere out into space. We used UHF (300Mhz - 3Ghz) in the Navy to communicate via satellites.

Drop frequencies much lower and you have VLF (Very Low Frequency). 3-30 Khz. Handy if you happen to be a radio operator on a submarine, because this magic stuff not only follows a waveguide between the ionosphere and the Earth, bending around the planet, but it also penetrates water (a bit). So you can be at periscope depth (or deeper with a towed antenna) and receive a signal without having to raise your radio mast, staying nice and stealthy. Can't transmit on VLF from a submarine, because you need a bloody big antenna, and loads of power. And with wavelengths measured in 10s of kilometers, the bit rate is soooo slow. Only good for slow data transmissions, not voice. Which is why 5G, Wifi etc are in the Ghz.

Clear as mud?

duncansayers said..

shaggybaxter said..
If I look at the frequency scale, the next 'system' in that low frequency band next to HF would be ...what?
VHF (of course) - 30 to 300mhz.
Terrestrial TV - 45-860mhz.
I am sure there are others, but stuff like mobiles and wireless network are all ghz stuff.

What I find interesting is the difference in RF transmission characteristics or performance. Nothing else has anywhere near the mannerisms of HF transmission. Yet VHF and TV are pretty close to the same band at least, and I wouldn't expect that much of a difference.

Question form the peanut gallery for you more experienced chaps, Is the higher order bands (like 30mhz) used that often in HF communications? Or does it kinda suck so much it is not used?
Cheers!
SB

Ok, I'll have a crack. DISCLAIMER - I was an operator (dial twiddler in other words), not a physicist.

* high frequencies go in straight lines and reflect off things - poor penetration
* low frequencies bend around things, but attenuate faster - can penetrate objects.

Think about your next door neighbour cranking up the doof doof. What do you hear - a dimmed bass, but not much not treble.

So sticking with the HF range, at the lower end of the frequency range the signal attenuates more, and refracts in a lower part of the ionosphere. At higher frequencies in the range, the signal refracts in a higher layer of the ionosphere. So using basic geometry, the higher frequency skips further. It might skip over who you're trying to talk to - drop frequency and hello sailor.

If the frequency is too high, it wont refract, but will carry on through the ionosphere out into space. We used UHF (300Mhz - 3Ghz) in the Navy to communicate via satellites.

Drop frequencies much lower and you have VLF (Very Low Frequency). 3-30 Khz. Handy if you happen to be a radio operator on a submarine, because this magic stuff not only follows a waveguide between the ionosphere and the Earth, bending around the planet, but it also penetrates water (a bit). So you can be at periscope depth (or deeper with a towed antenna) and receive a signal without having to raise your radio mast, staying nice and stealthy. Can't transmit on VLF from a submarine, because you need a bloody big antenna, and loads of power. And with wavelengths measured in 10s of kilometers, the bit rate is soooo slow. Only good for slow data transmissions, not voice. Which is why 5G, Wifi etc are in the Ghz.

Clear as mud?

My understanding exactly and I am not a physicist, but I will generally back myself with a HF set.
You need to understand if you are bouncing off concrete or sand and how far away the hoop is.
In simple terms!!

Chris 249 said..

MorningBird said..

duncansayers said..

MorningBird said..

I flew Grumman Trackers from 1973 until 1984. Were you on O boats or Collins?
It wasn't uncommon when operating in the East Australia Exercise Area to get Clark USAF base in the Philippines or a station in Hawaii and nothing in between. The ionosphere or maybe a ground wave rules what reception you get.

I was on both. I did the commissioning trails of HMAS Farncomb (boat #2 of the Collins class), but got my dolphins (submarine qualification) on HMAS Onslow (now in the National Maritime Museum - Sydney). Having your old workplace/home in a museum is a sobering reminder of my own ageing process :)

I know ROs who got QSL cards from ham operators in the West Coast USA, so yep...it can go a long way.

I served most of my operational time on HMAS MELBOURNE CVS21 but converted to helicopters after the fixed wing and deployed on HMAS SYDNEY 03 in 1984 with a helicopter. I paid off in 1998 as CO HMAS PLATYPUS and did a bit of sea time on OTAMA AND ONSLOW so we may have crossed paths.

Didn't the Trackers have something like 3-4m of wingtip clearance from the island when landing? Amazing stuff.

About 4 metres/12 ft from memory. Rare for us to land right of centreline. On one occasion when I was squadron duty officer a Tracker ended up with his port wheel on the port deck edge coaming, a severe case of drifting left to avoid the island.
Clearance to the back of the ship was the other problem with a pitching ship. The back end of the flight deck, the round down, was only a couple of metres away when operating near the limits. A few shots of the deck from a Tracker. Some shots here.

www.wikiwand.com/en/816_Squadron_RAN