Dxers Unlimited's mid week edition 26-27 May 2009

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition for 26 -27 May 2009
By Arnie Coro
radio amateur CO2KK


Hi amigos radioaficionados worldwide !

Welcome to the mid week edition of Dxers Unlimite coming to you from sunny Havana, where afternoon and early evening thunderstorms are now happening on a day by day basis, and those storms are very important for one special type of radio wave propagation mechanism known as Sporadic E skip .

Scientist have done a lot of research about the cause or causes of the sporadic patches at the height of the normal E layer that sometimes are capable of sending back to Earth signals on frequencies as high as 200 megaHertz... Yes , you heard it right, amateur radio operators and TV Dxers have documented many Sporadic E propagation events when the maximum useable frequency went up past the little used 222 megaHertz ham band, or the TV channel 13 stations .

Photos of TV 13 stations from a thousand miles away show that a particular very intense E skip event that took place during the 1963 summer sporadic E season form part of the many treasures that radio hobby enthusiasts have contributed to the science of propagation research.

We are now well into this year's summer sporadic E skip season, as many devoted 10 meters and 6 meters bands radio amateur operators know very well... Here in Havana , the 10 meters band beacons sub-band is the best indicator about a band opening.

Ham radio beacons are low power stations that automatically send out Morse Code signal identifier that provides information of its callsign and location ... So if you for example slowly tune your ten meters band transceiver starting at 28.2 megaHertz , and pick up a CW automatic transmission on 28.247 kiloHertz , you can be absolutely sure that the band is open if there is no local beacon operating on that frequency. A few seconds later you are able to pick the callsign of the beacon, and its grid square locator... so you are then sure of the exact location of the automatic beacon, and can start calling CQ DX higher up the band on phone, or in the lower edge of the band CW sub band...

Keeping a record of the beacons and their locations is very useful, because you can turn your rotatable beam antenna into the area where the beacon is located to increase your signal strength and also to get better signals from the ham stations .

But , let me add a very important fact... in many occasions when 10 meters is open via Sporadic E propagation, signals may be of such high intensity that using low power and a simple half wave dipole or a quarter wave ground plane vertical antenna will make possible to make many two way contacts...

Sporadic E propagation is extremely difficult to forecast, so the best you can do to enjoy it is to keep monitoring the 10 and 6 meter amateur bands, and also to keep a TV set tuned to analog channel 2... But soon, many of the analog channel 2 stations will go off the air , so in order to learn about an opening by monitoring the low band TV channels, you must install a set top box to convert the digital over the air signal so that it can be seen on the analog TV set...

Si amigos, yes my friends , oui mes amis... Sporadic E Dx is one of the more than 85 ways that you and I can enjoy this wonderful hobby, and let me add that radio amateurs have made very important contributions to propagation research by keeping records of Sporadic E events for many years.
Stay tuned on this frequency, as Dxers Unlimited's mid week edition will continue in just a few seconds, I will be back after a station ID coming up now..

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You are listening to Radio Havana Cuba , the name of the show is Dxers Unlimited , and here is item two of our program today.

Homebrewing a 10 meters band antenna for enjoying the summer Sporadic E skip season is a nice , low cost and easy to implement project for the weekend.

June and July are the two peak months for E skip event, and according to well documented research, the third week of June is usually the one that brings in the largest number of DX events, and they too have a tendency to last longer... In order to enjoy the presence of DX stations, you can homebrew and install a sloping half way dipole cut for the lower segment of the 10 meters band.

You will need to make three antenna insulators, of which two will be about 15 centimeters or 6 inches long, and one is about seven and a half centimeters or 3 inches long. The two long insulators are for supporting the ends of the antenna, and the short one is the center insulator of the dipole antenna.

You will need about 6 meters of household PVC insulated number 14 or number 12 wire, and enough RG58 or RG213 coaxial cable to connect the antenna to your ham radio transceiver...

The antenna is just a half wave dipole, with each leg of it cut to a length of about two and a half meters or a bit longer, and you will need to have access to a standing wave ratio meter in order to optimize the antenna's length for minimum SWR at 28.5 megaHertz.

With a tall single mast available, the antenna is installed sloping down at an angle of 45 degrees in the direction that you want to work the DX. Trimming the antenna for minimum standing wave ratio will require a few trips to roof or the garden but once it is adjusted , the SWR won't change much, even when it is raining or snowing.

Connecting this simple sloping dipole to a ham radio transceiver will make possible working lots of Dx stations whenever the Sporadic E clouds traveling at high speeds about 105 kilometers above the Earth are present.

Now if you want to optimize your 10 meters band station, it is very easy to make two or three or even four sloping dipoles and aim them in different directions... Connecting them to your ham radio rig with a switch, it is very easy to pick up signals from the main areas where stations are located.

For example, here in Havana, I keep two 10 meters band slopers up... One is beaming into central North America, and it provides good coverage of parts of Mexico, the USA and Canada, while the other antenna is beaming down South, with the lower side aiming at 150 degrees.

This second SOUTH sloper brings up DX signals from the Caribbean with Sporadic E openings events, and also, it brings nice signals whenever the band opens up for the F2 layer Trans Equatorial Propagation that makes possible to pick up stations from Brazil, Argentina, Uruguay , Bolivia and Chile during the two yearly equinoctial DX seasons that peak in March and September every year and that is quite indepedent of solar activity !!!

Your three antenna insulators are very easy to make using white PVC plumbers pipe... and connecting the coaxial cable to the antenna can be done using four cable clamps that can be bought at hardware stores in the electricians supplies area.

By using the high quality copper cable clamps you avoid the need to solder the coaxial cable to the antenna wires, and if you tighten the clamps real high and protect the area with high quality electricians PVC tape.

The coaxial cable downlead must leave the antenna at a 90 degrees angle , in order to make the sloper dipole work properly.
Yes, in about two or three hours time , and at very low cost, you can homebrew and adjust this easy to make antenna system that will provide a lot of nice two way contacts all along the summer sporadic E skip season and later on too...

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Well , I am sure that you will like to read the text of the script of this Dxers Unlimited's edition , and review the details and see a diagram of the 10 meters band sloping dipole , something that can be easily done by visiting Dxers Unlimited blog site, just type dxersunlimited at blogspot dot com,and enjoy !!!

Now here is item three: The most popular section of Dxers Unlimited is here amigos... ASK ARNIE, answering your radio hobby related questions in an easy to understand way..

Today's question came from Sweden, where listener Bjorn is able to pick up our 6000 kiloHertz transmitter very late in the evening his local time all along the summer months. Bjorn asked about the long range forecast for solar cycle 24, that is very slowly starting up.

Well amigo Bjorn, the latest consensus among solar researchers seem to be clustered around the idea that cycle 24 will not, and I repeat will not be as active as any of the previous 4 solar cycles.

As a matter of fact the forecasts that are now available from different sources coincide in a peak activity not to exceen one hundred average sunspots for the peak month or months of cycle 24.

Notice that I wrote peak month or months, because the last two solar cycles, 22 and 23 had not one , but two very clearly noticed peaks of sunspot activity .

If the present forecast turns into reality amigo Bjorn, the chances for worldwide 6 meters band F2 layer openings will be much lower ... so this is bad news for 6 meters band ham radio operators around the world !!!

Item four: Also a very popular section of Dxers Unlimited, it's our Technical Topics segment, that will be presenting more information about very simple, yet effective radio receivers....

A recent Plaza radio club meeting came to an end with an agreement among participants to organize a simple radio building event for the next time that the club will be holding a meeting at the place that is kindly lent to our club by the local community center.

The project is now in the parts gathering phase,as we already decided that we will be assembling and adjusting a Polyakov direct conversion receiver for the 40 meters amateur band. The radio uses two common silicon transistors recycled from TV sets for the VFO or variable frequency oscillator, which is the most critical part of the circuit, and that will require the attention of the three members of our club that are more technically minded.

The audio amplifier module will be using one low noise NPN bipolar transistor and three transistors recycled from compact electronic flourescent light bulbs .... Finally the two diodes for the Polyakov harmonic detector are already at hand for the fifteen radios we are planning to build. They came from a local TV and radio repair shop that provided them at very low cost to us...

This little radio receiver uses a very well designed and effective bandpass dual tuned input filter, and its two coils are wound on short lengths of PVC pipe, so there is no need to look for the hard to find iron powder or ferrite toroid rings that are often required by other receiver designs.

The prototype of the KK;40 dash two single band direct conversion receiver will soon be ready for testing at my home workshop and once it is given the OK by the three members technical committee of our radio club, then we will proceed to prepare the fifteen first kits of parts that will be taken to the club meeting where they will be assembled and tested.

We expect that this unique effort will end up by providing each and every one of our club's members with a nice 40 meters band receiver that can be used running from battery power , so it can be kept ready for any emergencies that may come up. This is part of an ongoing effort by our Radio Club to enhance the emergency preparadness as the tropical hurricane season is about to start on the first day of June.

And now here is our HF plus low band VHF propagation update ... solar activity once again at very low level after a very short showing up of sunspot region 1018, that vanished from the solar disc after just one day ... daytime maximum useable frequencies are going to be below 18 megaHertz , but we will be enjoying some very nice sporadic E openings that may send the Maximum Useable Frequencies well above the 108 megaHertz top end of the FM broadcast band !!!

Send your signal reports, radio hobby questions and comments about this edition of Dxers Unlimited via e-mail to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.


Note: Sorry for posting this one day late !

I had a lot of work to catch up with, especially now that we are ending here
the academic year !!!

The script was a bit too long for the on the air, slot, so I had to edit the digital
audio file in order to make it fit into the half hour segment.
So you will thus read here a bit more of what went on the air !
Please send any comments about this blog, especially if you find it a useful way
of learning more about the radio hobby.
Send mail to inforhc@enet.cu
TNX
73 and DX
Arnie