Dxers Unlimited  weekend edition for Sunday 3 February 2019

By Arnie Coro
radio amateur CO2KK

Hello amigos…. this is the  the weekend edition of Dxers Unlimited coming to you from Radio Havana Cuba just as we continue to travel along the present solar minimum of cycle 24. Do not expect geomagnetic field disturbances that may produce Aurora Borealis displays as well as poor short wave propagation due to the effects of high speed solar particles impacting on the Earth’s magnetosphere. No they won’t be happening, because solar flux levels have barely reached 75 units for many consecutive months and solar wind speeds remain at low levels

I am your host here in La Habana , Cuba where last Sunday we had to deal with an extremely powerful category ET Four tornado that caused lots of damages to our city.  Once again, amateur radio operators proved how they could handle emergency traffic during the severe weather event, when the 2G and 3G mobile cellular phone systems collapsed due to damages to the base relay sites and the excessive traffic generated by the event.

Using the Havana Metropolitan Area main repeater on 145.190, stations with handheld FM transceiver could keep in touch from even the most difficult places in the affected areas comprising the municipalities of Regla, San Miguel del Padron, Habana del Este and 10 de Octubre. Damage to buildings and individual homes was substantial as well as breakdowns in the electricity distributions systems,  and both wired and wireless telephone communications.

A second two meters band FM repeater located within the affected area of the 10 de Octubre municipality proved to be very useful to handle traffic with the health care system, firefighters and the government officials in charge of handling the emergency that already caused 4 deaths and more than two hundred persons wounded.

By the way, after the recent breakdown of my HF transceiver’s power supply, I was able to be back on the air by adapting an old PC switched mode power supply that is working very well…. The unmodified power supply provides very near to 12 volts DC at about 15 amperes peak current, and I am also using it on my 2 meters FM 25 Watts power rig. As my mentor CM2DK , used to say, ham radio is a hobby where creativity and ingenuity in finding solutions will make you enjoy it a lot more…

Ignacio Rafael Diaz Perez CM2DK was my neighbor that I picked up using my first crystal diode radio receiver…  way back in 1954. He gave another radio amateur his street address during a 40 meters band contact, Victoria Street number 9, apartament 3, between 41 and 33, and a few minutes later I was knocking at his door… I was just 12 years old, and that was the event that opened the door of the radio hobby for me…

Diaz Perez as he was known, was a veterinarian that had learned about radio and TV by means of an American correspondence school course that made him also an excellent radio technician.  He was a very  kind person, that helped all newcomers to the radio hobby, providing his know how and patiently explaining the most complex topics in such a way that they could be understood… He helped me to build my first amateur radio station that went on the air years later, using the callsign CM2DL  that was my first amateur radio experience….

Si amigos, yes my friends, oui mes amis, it is always nice to remember those radio amateurs that devoted a lot of time to helping others to be on the air and enjoy this wonderful hobby….

Item three: The digital modes now in use by amateur radio operators around the world are growing in number and complexity as time goes by…. In my opinion the easiest one of them all is the PSK31 in its different flavors…. As a matter of fact PSK31 is very user friendly and the existence of a worldwide community of amateur radio operators that regularly monitor certain specific frequencies within the ham bands, makes possible to make contacts even under very poor propagation conditions….

Any single side band capable rig will operate on PSK31, and you can use an old computer plus the very well written FLDigi software package that is freeware and can be downloaded from several Internet sites absolutely free of charge, because FLDigi is freeware…. More about digital communications by amateur radio stations coming up in a few seconds after a short break for a station ID… I will be back with more amigos !!!!

This is Radio Havana Cuba , the name of the show is Dxers Unlimited and here is more about the use of digital communications modes by amateur radio operators around the world….

Recently I had to repeat a demonstration on how you can go on the air using the PSK31 digital mode by using a very simple transceiver to computer acoustic interface… I applied my long standing principle of keeping technical matters as simple as possible, and here is what I did …

Two home built with easy to find materials and parts acoustic couplers totally isolated the computer from the transceiver…. making possible to receive and transmit several digital modes with them.  They are made using a small length of twenty five millimeters , that is one inch diameter thick wall PVC pipe where you place a microphone element and a small diameter loudspeaker at each end of the 100 millimeters or four inches long tube….

For transmitting , you simple connect the output of one of the computer loudspeakers to the small one in the digital modes adapter… just put them in parallel, and solder the connections … then connect the microphone to the input of your transceiver ….

For HF bands operation you must use a transceiver that has a voice activation circuit, known as VOX…. Once you set up the FL Digi software package and select the BPSK31 mode, simply call CQ and carefully set the VOX control so that the rig will start to transmit as soon as the signal from the computer starts… and disconnects after a short time when signals are not fed from the computer digital software program.

The receiving set up is made using the same type of acoustic coupler…. and it is even simpler !!! Consisting of a microphone element that is placed in front of the transceiver’s loudspeaker and connected to the computer’s sound card input…. For a fast demonstration  at the radio club I simply place a standard PC computer microphone in front of the transceiver’s loudspeaker and just carefully regulate the level while observing how the FLDigi decodes a strong signal that can be seen on the screen….

It is a quite remarkable and impacting demonstration that shows how the digital modes can be easily implemented in practice using the simple acoustic couplers that also provide total electrical isolation between the transceiver and the computer….

Running 10 Watts on the 20 meters band PSK31 parking spot, 14070, I have made hundreds of two way contacts using my ultra simple acoustic couplers set up… The cost of making them was essentially zero, because I already had a standby computer microphone that could be removed from its stand, another dynamic computer microphone element from an old rig, and a small one inch, or twenty five millimeters loudspeaker from a defunct transistor radio. Now, late in the evening when everyone at my home QTH is sleeping, I connect my digital communications modes interface , and enjoy working many stations on both 20 meters when it is open at night, and on 40 meters at anytime with excellent results, and of course that this is a totally silent operation mode….

that by the way can be a very attractive way of making hard of hearing or totally deaf persons to enjoy amateur radio …. Si amigos, you would not need an expensive digital modes interface to start enjoying the keyboard to keyboard communications modes… but as time goes by, perhaps you may want to build or buy a more sophisticated interface that will provide a trigger signal to activate the rig in addition to the audio feed to the microphone input.

Send your signal reports and comments to arnie at rhc dot cu. Or VIA AIR MAIL, to Arnie Coro, Radio Havana Cuba, see you all at the mid-week edition of Dxers Unlimited heard just after the top of the hour RHC English language program.

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