Air Band on UHF FM mode

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Werthers
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Air Band on UHF FM mode

Post by Werthers »

I was sitting in a park with a Baofeng just scanning and I'm picking up air band crystal clear in FM on UHF of the following frequencies.

455.525 MHz
455.487 MHz
455.700 MHz
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Re: Air Band on UHF FM mode

Post by dc260 »

Some airports relay their tower control on to UHF for ground crews to hear.
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Re: Air Band on UHF FM mode

Post by Mototrbo2020 »

NATs airport Tower relays.
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Re: Air Band on UHF FM mode

Post by Andy Richards »

I am also hearing traffic on all three of those frequencies in NW.London.

I am guessing it must be Heathrow as there is a lot of activity but I am about 8 miles from there.
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Re: Air Band on UHF FM mode

Post by Metradio »

Yes all three are in use at Heathrow and are receivable for quite a distance.

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Re: Air Band on UHF FM mode

Post by Werthers »

I'm about 40 maybe 50 miles from Heathrow. It just goes to show how good UHF can be.
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Re: Air Band on UHF FM mode

Post by Metradio »

The NAT's UHF tower rebroadcast frequencies are reused all over the country, so they can be found on London City, Southend, Luton, Stanstead, Gatwick airport etc as well.

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Re: Air Band on UHF FM mode

Post by Mikel »

Werthers wrote: 11 Jun 2021, 18:42 I'm about 40 maybe 50 miles from Heathrow. It just goes to show how good UHF can be.
I find it fascinating how the propagation works at UHF and some would have you believe that it is strictly line of sight.

However I can reliably hear the Bristol Airport UHF relay service and I am 25 miles away, and even though the airport is in an elevated position, it has to get over some big hills to my position in the bottom of the Rhymney valley.

Take a look at the topographic profile below, I am at the zero point on the left and Bristol Airport is on the 25 mile mark on the right

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Re: Air Band on UHF FM mode

Post by Andy Richards »

I am surprised UHF can travel so far.

Does anyone have any idea what kind of power these use?
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Re: Air Band on UHF FM mode

Post by Werthers »

Mikel wrote: 12 Jun 2021, 07:51
Werthers wrote: 11 Jun 2021, 18:42 I'm about 40 maybe 50 miles from Heathrow. It just goes to show how good UHF can be.
I find it fascinating how the propagation works at UHF and some would have you believe that it is strictly line of sight.

However I can reliably hear the Bristol Airport UHF relay service and I am 25 miles away, and even though the airport is in an elevated position, it has to get over some big hills to my position in the bottom of the Rhymney valley.

Take a look at the topographic profile below, I am at the zero point on the left and Bristol Airport is on the 25 mile mark on the right


profile.png
I got stuck on a QSO 6 miles away with a handheld indoors on 70cms simplex, not that I use a handheld indoors I was just testing it with another radio back to back when I heard a strong station and then we ended up in a QSO handheld to handheld indoors over a 6 mile distance with all sorts in the way of our signal paths.
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Re: Air Band on UHF FM mode

Post by Mikel »

Andy Richards wrote: 12 Jun 2021, 09:35 I am surprised UHF can travel so far.

Does anyone have any idea what kind of power these use?
Power wise, I have no idea, maybe someone on here will know.

If I had to guess, I would say maybe 50 watts or less, as it only has to reliably cover the airport for the ground crew.

I could be completely wrong mind you, It wouldn't be the first time :)
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Re: Air Band on UHF FM mode

Post by Merkin »

Werthers wrote: 12 Jun 2021, 13:28
Mikel wrote: 12 Jun 2021, 07:51
Werthers wrote: 11 Jun 2021, 18:42 I'm about 40 maybe 50 miles from Heathrow. It just goes to show how good UHF can be.
I find it fascinating how the propagation works at UHF and some would have you believe that it is strictly line of sight.

However I can reliably hear the Bristol Airport UHF relay service and I am 25 miles away, and even though the airport is in an elevated position, it has to get over some big hills to my position in the bottom of the Rhymney valley.

Take a look at the topographic profile below, I am at the zero point on the left and Bristol Airport is on the 25 mile mark on the right


profile.png
I got stuck on a QSO 6 miles away with a handheld indoors on 70cms simplex, not that I use a handheld indoors I was just testing it with another radio back to back when I heard a strong station and then we ended up in a QSO handheld to handheld indoors over a 6 mile distance with all sorts in the way of our signal paths.
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Re: Air Band on UHF FM mode

Post by Werthers »

The area coverage is pretty vast for UHF. They could be using a repeater system.

I remember back in the day listening to the police on UHF there were some distant stations like for example Manchester to London on UHF. Thats not done with simplex.

From high ground on one of my hill tops I can get almost 100 miles on UHF 70cms 5 watts and thats with a standard rubber duck antenna.
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Re: Air Band on UHF FM mode

Post by bigpimp347 »

Merkin wrote: 13 Jun 2021, 20:49
What is your callsign then? Or is it a fantasy island job? Send me a PM with it in
reading a few of his post's i'd say he's a foundation licence holder or at least someone who should have his licence revoked.
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Re: Air Band on UHF FM mode

Post by paulears »

Why all the mystery with ranges? VHF and UHF keep getting mentioned as being radically different, when they're not really - the just behave differently in urban or rural environments.

I'm busy with marine band, and people often get quite depressed with their ranges because they don't have hills. So the range is really the horizon. There are quite a few useful versions of the maths but the one I like is
d = 1.25 ∗ √hf

Where d = range in nautical miles and hf = the height of your antenna in feet.

So your handheld in your boat about 4ft above the water will get you 2 and a half miles to the horizon - it carries on the other side, so your mate in his boat can be about 2 and a half miles the other side - so maximum range less than five miles!

If the sea has loads of obstacles - like marinas and harbours with metal obstructions - then that 5 miles can be much less. Norwich to the coast is pretty flat and in my van I can hear the airport Volmet continuous broadcast in quite a few places and that's pretty good with no hills to speak of in this part of the country.
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