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blakeyboy

Anyone here do VHF listening or FM DXing?

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I just wondered if any of the Esteemed Members  was a radio nut?

I'm trying to get a shack together in my workshop.

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Its been about {way too many years} since I did anything that wild.

But then that was USB on a Tristar 747, with a 400w burner,  Sadelta base mic and hygain something 18ft antenna.....

 

 

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Perhaps a little off subject. I was in South Australia 900 km from Gosford NSW where I was living at the time. My wife was fiddling with the car radio which had 2GO (Gosford) on 107.9 MHz. Anyhow this station came in loud and clear. Obviously the signal was  reflected off the ionized layers surrounding the earth. As a retired electrical engineer specializing in antennas and propagation I was impressed to experience something normally described in text books.

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In 1957 some film producer in Oz picked up BBC 1  TV....

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I think at the time BBC1 TV was on about 50MHz which is just above the shortwave band where long distance propagation is far more possible. However the UK to Oz is pretty impressive.

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I was on an Army exercise in Australia's Shoal Water Bay, North of Brisbane in 1982 using HF radios. We kept getting other people cutting across our broadcasts - it took us a while to work out it was a US Army exercise in Texas! Unfortunately they couldn't hear us, so we had no conversation.

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Posted (edited)
1 hour ago, Paddy said:

I was on an Army exercise in Australia's Shoal Water Bay, North of Brisbane in 1982 using HF radios. We kept getting other people cutting across our broadcasts - it took us a while to work out it was a US Army exercise in Texas! Unfortunately they couldn't hear us, so we had no conversation.

Yes HF propagation can amaze us. A few watts of ERP can be heard clearly over 1000s of Km. Not so easy at VHF as the radio waves penetrate the ionized layers surrounding the earth. Meter showers and solar storms can enhance the ionized layers to allow propagation over long distanced. When I was working for the Dept. of Aviation we had a troposcatter link between Point lookout in Northern NSW to Mt. Glorious to the West of Brisbane about 3 to 400 km. In this case a high power microwave transmitter was aimed at the troposphere to graze it. Sufficient power was received at the far end to complete the link. This link worked reliably for many years carrying radar and communications over the distance. From memory it operated at about 2 GHz using a Traveling Wave Tube (TWT) as the transmitter tube.    As it happens I live in Brisbane at a place called Redcliffe which is on the shore of Morton  Bay.

Edited by ozjohn
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On 10/4/2019 at 10:15 PM, blakeyboy said:

I just wondered if any of the Esteemed Members  was a radio nut?

I'm trying to get a shack together in my workshop.

Widely known I am just a nut LOL

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There are degrees of radio nuttiness.
I have two lifeboat radio transmitters, an Atlanta receiver by Marconi of the type I sat in front of on and off for 11 years and various other esoteric bits of radio kit but I'm not a ham.

Propogation of radio was essential knowledge in order to clear radio traffic. After the end of the area radio scheme in the 60s it became necessary to try and contact the UK on HF with a transmitter that was 120 watts radiated at best. Bouncing off layers was either an art or pure luck.

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I've been offered my friends Racal RA17 receiver with the SSB auto module on top.

I asked him if it was any good yesterday afternoon, and he connected a piece of wire and hung it over a beam in his garage- a 3 foot aerial indoors...

I tuned for 30 seconds and got a guy in Italy talking to someone in Pennsylvania.  Both sides of the conversation clear as clear. Amazing piece of kit.

Trouble is, it's a 2 foot cube and heavy......built like a tank.

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Posted (edited)
On 10/6/2019 at 8:39 AM, ozjohn said:

Yes HF propagation can amaze us. A few watts of ERP can be heard clearly over 1000s of Km. Not so easy at VHF as the radio waves penetrate the ionized layers surrounding the earth. Meter showers and solar storms can enhance the ionized layers to allow propagation over long distanced. When I was working for the Dept. of Aviation we had a troposcatter link between Point lookout in Northern NSW to Mt. Glorious to the West of Brisbane about 3 to 400 km. In this case a high power microwave transmitter was aimed at the troposphere to graze it. Sufficient power was received at the far end to complete the link. This link worked reliably for many years carrying radar and communications over the distance. From memory it operated at about 2 GHz using a Traveling Wave Tube (TWT) as the transmitter tube.    As it happens I live in Brisbane at a place called Redcliffe which is on the shore of Morton  Bay.

This reminds me of my time in submarines some 40-50 years ago when from time to time we would have difficulty in clearing our 'check reports' (during non-covert ops these were mandatory signals we had to transmit during fixed time-slots to confirm to MOD at Northwood that we hadn't sunk). The South China Sea, North Atlantic and Southern Arctic were (if I remember correctly) particularly difficult areas and more often than not we could only clear the signal via say, Cape Town or some other equally distant station.  This was quite remarkable if you consider that frequently we would transmit these signals while submerged at periscope depth with the radio mast only a few feet above the surface. I seem to remember references made to 'sky wave' effect. I was just a simple navigator and while I was quite used to using the equipment, the science behind radio communications was all very mysterious to me; somewhat of a 'black art'. Those were the days!

Frank

Edited by hibernianscribe
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From memory (radio college was 50 odd years ago) ground wave propagation is limited and most HF long distance communication relies on sky wave (radio waves travel along the surface and off into the sky).
As the earth cools at sunset the boundary layers move and it's possible to "bounce" the sky wave off the layers in ever increasing distances of bounce. HF works well with this phenomenon because of wavelength and density of layers. MF has not enough power to bounce more than a couple of times but in sunspot activity this can change. The same goes for VHF which normally passes straight through the layers with no bounce.
It's an age related thing that these facts, possibly well garbled, pop in consciousness every so often.

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17 minutes ago, Fubar said:


It's an age related thing that these facts, possibly well garbled, pop in consciousness every so often.

Yes....this morning I remembered who I was.....

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