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VHF Propagation explained

DWL-1000AP

D-Link DWL-1000 Wireless Access Point

This device is very easy to get going if you have a DHCP server running on your network, just plug it in and it will pick up a free IP address.

If you do not have a DHCP server the Access Server (AP) will default to your network settings and a .2 address.

i.e. If your network is 192.168.0.0 the AP will come up with an IP address of 192.168.0.2

You can then use the software that came with the AP to change the IP address if you wish, this means that you need to get your network running first, do not use the .2 address, then plug in the AP.

The configuration utility (APManager) can be downloaded from  http://www.dlink.com

Alan  VK4YAR

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How to Pass Your CW Exams

"The SAR-MAJOR Edition" of How to Pass Your CW Exams.

Because I didn't have anyone to help me when I first started to learn Morse, I developed bad techniques and made many fundamental mistakes... and looking back, it was no wonder I had terrible trouble passing "those" Morse Exams.

Anyway... with all the good advice I had collected over the years... I decided to put it all down on paper in the hope that others would find it useful. Despite all the Bold Type in this "SAR-MAJOR Edition" of "How to Pass Your CW Exams"... it's an approach to learning which really works!

If I had to point to the most important skill that almost always has to be developed... it would be concentration! I'd go so far as to say, that lack of concentration guarantees failure! Morse Students are never taught that very high levels of concentration are needed to overcome the pressure of exam nerves and to achieve good exam results! I have heard stories of successful exam candidates who did not even hear an explosion in an adjacent room! I really believe that that is the level of concentration which you have to strive for! You must train yourself to only hear the Morse Signal and nothing else! That's why headphones are important when you're listening to the practice tapes! Hi! Hi!

There's not much more I can say, that isn't in the attached notes so...


Alan Simpson. VK4AAE

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VHF digital mode activity

Australia's top VHF stations are increasingly turning to digital modes to make contacts not possible on SSB or CW. Modes such as WSJT are making long-distance and Moon-bounce communication available to a whole group of amateurs using quite modest antennas.

If you are a listener, or just a curious amateur, how do you monitor these 
contacts?

Mike VK2FLR says that the first step is to have a suitable (SSB capable) receiver, interface, computer, and the suitable software which can be downloaded from various websites.

FSK441 activity in VK is on 144.230 on Saturday and Sunday mornings from 7 to 8 AM AES Summer time, plus during the week by arrangement. There is significant activity from VK2, 3 and 5, but not much from VK4 at the moment.

JT44 in VK is supposed to be on 144.225 but Michael has never heard anyone on that frequency.

There are a number of VK3 and VK5 stations active on 225 on Thursday evenings around 8pm. His only JT44 contacts have been via the Moon in the band 144.120 to 144.160 MHz.
Countries as far away as Germany have been worked via this mode.

To run JT44 you need accurate timing. Most people use clock correction programs that link to atomic clocks via the internet. This implies that you need to be online when operating JT44.

This is in fact very convenient because many operators use the JT44 logger at http://www.chris.org/cgi-bin/jt44eme to line up contacts.

With a single yagi you should be able to see EME signals from the bigger stations. Point your antenna to the rising or setting Moon and check the logger to see who is on and where they are.

And that was an account on digital mode activity in VK, written by Mike VK2FLR for the VK-VHF mailing list.

(apcnews December 4 2002)

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VHF Propagation explained

How do you know if the extended range VHF/UHF contacts we enjoy at this time of year is due to sporadic-E, tropospheric ducting or meteor scatter?  Sometimes the answer is not obvious.  However usually it is possible to identify the propagation mode by considering clues such as the band used, signal strengths, time of day, and distance covered.  

Ron Cook VK3AFW has provided the following handy tips for the summer VHFer who is prepared to do more than just speculate. 

Ron suggests reading an authoritative book such as the RSGB's VHF/UHF DX Handbook.   If you don't want to buy one, ask your local library or library extension service to get a copy for you to borrow for two weeks while you read the "Propagation" chapter.

For those that can't wait, here is some very general guidance.  Please note that the distances are approximate and it all is based my understanding of what happens. 

The most common propagation enhancement is one of the "tropo" modes, which are useable for distances between 100 and 3,000 km.  The enhanced propagation can be linked to weather patterns.  Certain combinations of pressure, pressure gradients, temperature, temperature lapse rate, relative humidity and its gradient all are involved.  The Hepburn index is an easy way of checking if "troppo" conditions are likely to be different from normal.  It is available on the Web at http://www.iprimus.ca/~hepburnw/tropo.html.

Sporadic-E (or E's) propagation results from ionisation in the E layer, distances worked are determined by geometry and intensity of ionisation, meaning contacts are usually in the range 400 km to 2,300 km.  Distances of around 3,000 km may have been worked by double hop
E's but this sort of occurrence is not common and needs some evidence of there being two clouds of E ionisation at the right places.

F mode propagation uses a higher layer and has a single hop range of around 3000 km.  There are reasons why F layer propagation tends to give wider coverage and multiple hop propagation and E's generally does not and this behaviour helps differentiate between the two.  
Also the ionosound records show where the ionisation was and how intense it was. Go to the Web site of the IPS Australia, http://www.ips.gov.au/ and check out the ionosound
data.

Trans-equatorial propagation (or TEP) requires specific geographic relationships for both stations.  This means roughly equal spacing north and south of the magnetic equator and for the stations to be aligned within a limited arc.  Contacts between Northern Australia and Japan on two metres use this mode.
 
Auroral modes are characterised by the distortion of the signals and the need to point the beam South rather than at the station.  Distances worked in VK are usually in the range 100 to 1,000 km.

Most propagation modes that are seen on six metres are seen on ten and two metres, generally at the same time.  Thus tropo contacts are often made on six, two and higher frequencies all via the same enhanced conditions between the same stations.  Ron has never experienced tropo enhancement on ten metres or non TEP F modes on two metres, but maybe they do happen.

More than one mode can occur at the same time, with mode linking being suggested as the means of some extended range contacts.  This may be so, but I would always look for the simplest explanation first.

And that was a summary on VHF propagation, prepared by Ron VK3AFW for the VHF/UHF internet mailing list.   For the average station, sporadic-E is most common on 28 and 50 megahertz, while tropospheric propagation is dominant on 144, 432 and higher frequencies.  Both modes will become most prevalent over the next three months or so.

VK3AFW/VK-VHF

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