Please click
 Member Login
Main Menu
· Home

· PMR446 Forum
· Who's on eQSO
· Gateway List
· Gateway setup
· Downloads
· Members List
· Recommend Us
· PMR446 Reviews
· Search
· Topics
· Web Directory
· Top 10 List
· Site Map

User's Login
 Remember me

Don't have an account yet? You can create one. As a registered user you have some advantages like a theme manager, comments configuration and posting comments with your name.

Who's Online
We have 6 guests and 0 members online

You are an anonymous user. You can register for free by clicking here

* Tropospheric Ducting
Posted Apr 04, 2003 - 08:51 PM
Send this story to a friend Email this to a friend  Printer friendly page Print this story

DX'ing Tropospheric conditions are looking quite good for this Sunday 6th April...

... so don't forget, if you hear a lot of activity, a morse "k" tone (dah dit dah) or computer voice announcing "xyz gateway Town ABC CTCSS 19" you're probably hearing o­ne of our gateways in the UK or Europe. In which case, switch your CTCSS tone to 19 o­n whatever channel you're o­n and give us a yell!

You never know, you may just be lucky enough to get some ducting at either end and make a huge DX leap of the PMR-kind!

So, what is "tropospheric ducting"?

The troposphere, an area of atmospheric regions close to the Earth, causes radio waves travelling within it to bend and thereby return to Earth at points beyond the horizon allowing you to make contact with other radio stations at a greater distance than normally possible. 

This "bending" of rf signals occurs over a range of frequencies, although it is prominent mostly in the VHF/UHF bands.

The warmest air is close to the Earth with temperature and air pressure decreasing as you go higher. This causes distinct regions to form in the troposphere. Regions that are adjacent and have different densities canl bend radio waves passing between those regions.

Radio signals at UHF and VHF then get trapped and can travel long distances  before coming back to the Earth's surface.

This effect is most prominent during the spring and summer months.

The troposphere is the layer of the atmosphere where cloud formation occurs, about 7-10 miles up, just below the stratosphere . From this region and travelling upward, temperature decreases radically with altitude.

Where a mass of warm air overruns a cold air mass, there is a temperature "inversion". RF waves below the warm air mass get trapped and travel great distances with little attenuation. This area, between the ground and the mass of warm air is known as a duct.

Confused? What it means is conditions are good for PMR446. Sunday is not *amazing* but it certainly is the best day of the year so far.

Almost full list of gateways now available here. Sorry, is taking a little time to fill in the gaps! Hope to have this finished Sunday morning.

Tip : height is also very very good!!

Updated tropospheric conditions map and key available here.

With thanks to Andy for some useful info and a better map link of the UK!

Tropospheric Ducting | Login/Create an account | 0 Comments
Comments are owned by the poster. We aren't responsible for their content.

All logos and trademarks in this site are property of their respective owner.
The comments and posts are property of their posters, all the rest 2003 by
PMR446 Personal Mobile Radio
No part of this site may be reproduced without our prior consent.
You can contact us here:
You can syndicate our news using the file backend.php

Page generated at: Sunday 12th of October 2003 12:01:31 AM