Topographic map

This is the place to discuss any general CB radio related topics. Getting started, installations, operation etc.
Post Reply
Hair Bear
Regular
Regular
Posts: 58
Joined: 03 Oct 2020, 20:46
Location: Hampshire

Topographic map

Post by Hair Bear »

Hi,
Found this and thought I'd share it. If you're looking for a good height dx point, this map can be scrolled and zoomed all over the place.
Have fun... :thumbup:
https://en-gb.topographic-map.com/maps/b9/England/
One person in ten understands binary, the other one doesn't.
User avatar
Stronty
Veteran
Veteran
Posts: 2795
Joined: 24 Sep 2007, 17:48
Location: Up North

Re: Topographic map

Post by Stronty »

Very handy, have used Hey What’s That over the years https://www.heywhatsthat.com/profiler.html

Can give you an idea of what’s around you.
Can't help but love an Adams.

Image
Hair Bear
Regular
Regular
Posts: 58
Joined: 03 Oct 2020, 20:46
Location: Hampshire

Re: Topographic map

Post by Hair Bear »

Looks interesting, there goes another evening!
One person in ten understands binary, the other one doesn't.
The Collector
Legend
Legend
Posts: 8666
Joined: 23 Jan 2010, 19:26
Location: Bristol-ish

Re: Topographic map

Post by The Collector »

Finally zoomed in to my town (took a while to keep loading), to find we're about 25-30m above sea level here. Seeing as we're quite close to the coast it's not too bad. However, the neighbouring towns of Portishead and Clevedon are both gone if the ice caps melt or there's a big tsunami!
User avatar
Mitch
Radio Addict
Radio Addict
Posts: 597
Joined: 02 Nov 2012, 21:26
Call Sign: M1TCH
Location: Leicestershire UK

Re: Topographic map

Post by Mitch »

If (when?) the ice caps melt, here's the one for that: http://flood.firetree.net/
The perfect face for radio.
The Collector
Legend
Legend
Posts: 8666
Joined: 23 Jan 2010, 19:26
Location: Bristol-ish

Re: Topographic map

Post by The Collector »

Mitch wrote: 08 Aug 2022, 21:29 If (when?) the ice caps melt, here's the one for that: http://flood.firetree.net/
Cheers Mitch.

Ooo... as suspected, Nailsea survives intact (just) but nearby Clevedon and Portishead are partly submerged...glug glug.
User avatar
Mudslinger
Legend
Legend
Posts: 7483
Joined: 28 Jul 2010, 07:11
Location: Oxfordshire

Re: Topographic map

Post by Mudslinger »

Google earth pro displays elevation too, if you hover the pointer it shows the height above sea level at that location.

There is more to finding a good spot than simply height though. Some of the best DX I have had were when the car was parked near the sea.
Mudslinger - Simon
26TM274
26CT612

There is no such thing as a Fidelity 1000 which is too good to scrap.
User avatar
Stronty
Veteran
Veteran
Posts: 2795
Joined: 24 Sep 2007, 17:48
Location: Up North

Re: Topographic map

Post by Stronty »

There is more to finding a good spot than simply height though. Some of the best DX I have had were when the car was parked near the sea.
That's it in a nutshell, height is a lot of it but if you are trying for a certain point Hey Whats That compliments the elevation and let's you see where you are in respect to where you want to hit with your signal. However, its not the most intuitive, well at least I don't think so, but its handy once you get to know it.

From me to you near Portishead :D
to Portishead.png
You do not have the required permissions to view the files attached to this post.
Can't help but love an Adams.

Image
The Collector
Legend
Legend
Posts: 8666
Joined: 23 Jan 2010, 19:26
Location: Bristol-ish

Re: Topographic map

Post by The Collector »

Well we might be moving near Weston-super-Mare next year to be closer to my wife's parents, so I'll check if we might be underwater there and buy some scuba gear well in advance ;)
InTheClouds
Super Member
Super Member
Posts: 232
Joined: 15 Mar 2020, 15:36

Re: Topographic map

Post by InTheClouds »

Being up a hill should increase your low angle radiation. When you TX and RX radio waves what hits our antennas is a combination of direct sky wave and reflected ground waves. The sloping ground creates a favourable TX and RX in that direction. A lot of the DX from outside of Europe on 11m band (95pct) is coming in between 1 and 10 degrees off the horizon. Pretty low eh ? I was surprised to learn this as well.

The reason is that sloping ground makes the reflections more favourable at low angles. When there are 2 waves (one direct and one reflected combining together), in part they cancel each other and in part they reinforce each other. This is known as the phase of the waves. So the slope means there is greater reinforcement at lower angles than flat ground would allow.

This following image shows a ground reflection but for a line of sight contact, not propagated by the ionosphere. However the principle is the rather the same.

Image

Phase of 2 waves they either add or subtract at different points of the combining. These are just example phases.

Image

Low angles generally create the longest possible DX paths (when those paths are open).

At the seaside you get about 9dB extra gain on your TX and RX in the sea's direction. This is because the salt water reduces the "ground" losses associated with the summed reflections on tx and rx. It also increases the strength of your low angle radiation. Some research has suggested that you do not even need to be right on the beach to get some benefits.Though this is more likely at lower frequencies (with longer wavelengths) Read the first paragraph for more information:

http://www.on5au.be/Cebik-2/ThePseudo-b ... isited.pdf

I know a couple of CBers (also hams) went to the seaside to activate a location for an event on 11m and I was on a hill, I could here them just about. Sadly for some reason they had a bad day DX and I was doing quite well on the hill... in the same hours.

Both will often have 1 single major advantage, low noise floor. You will hear so much more with a low noise floor.

This is worth a look:

Low incidence angles can travel longer distances, longest is about 2,500 miles per hop from what is known as the F2 layer.

Image

And in the early morning (say between 7am and 11am when conditions allow) you can make long path contacts to Aus and New Zealand
using a slightly different propagation called Chordal hop. (this is only theorized) A type of propagation where your radio waves become trapped
in the upper atmosphere due to a expansion/distortion of the layers which allow the waves to becomes ducted in the F2 layer. This is normally associated with the grey line. The grey line is a line around the planet where the sun is rising and setting in a distant location. Unique properties
at this time allow such "chordal" contacts. Rather than come back down with multiple lossy bounces it remains in the layers of the atmosphere themselves.

Image

Have a read here:

https://www.pa9x.com/long-path-or-short ... opagation/

CB'er s are amateur radio people as well. It is just you are not called amateurs.

Even if you don't want to be a ham you can still learn a lot and it will help your dx chances.
User avatar
Mitch
Radio Addict
Radio Addict
Posts: 597
Joined: 02 Nov 2012, 21:26
Call Sign: M1TCH
Location: Leicestershire UK

Re: Topographic map

Post by Mitch »

Here's one that might be useful for next week:

https://www.lightningmaps.org
The perfect face for radio.
User avatar
Stronty
Veteran
Veteran
Posts: 2795
Joined: 24 Sep 2007, 17:48
Location: Up North

Re: Topographic map

Post by Stronty »

Mitch wrote: 13 Aug 2022, 17:13 Here's one that might be useful for next week:

https://www.lightningmaps.org
Nice!

Here's another one! i even find this one nice to look at :D :D :D

https://earth.nullschool.net/#current/w ... 12,-52.248
Can't help but love an Adams.

Image
User avatar
Mitch
Radio Addict
Radio Addict
Posts: 597
Joined: 02 Nov 2012, 21:26
Call Sign: M1TCH
Location: Leicestershire UK

Re: Topographic map

Post by Mitch »

^ How about this one in colour, with options: :lol:

https://www.ventusky.com
The perfect face for radio.
User avatar
Stronty
Veteran
Veteran
Posts: 2795
Joined: 24 Sep 2007, 17:48
Location: Up North

Re: Topographic map

Post by Stronty »

Mitch wrote: 13 Aug 2022, 19:04
^ How about this one in colour, with options: :lol:

https://www.ventusky.com
Ohhhh! Trippy that one :D
Can't help but love an Adams.

Image
Post Reply