Dxers Unlimited weekend edition for 20-21 June

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 20-21 June
By Arnie Coro
radio amateur CO2KK

Amigos !! please report back to inforhc@enet.cu , when you read this posting !!!
Happy Father's Day for those of you living in countries where Father's Day
is celebrated during the third Sunday of June, like here in Cuba
73 and DX
Arnie

Hi amigos radioaficionados around the world !
Welcome to the weekend edition of Dxers Unlimited that is reaching you as we approach the summer solstice here in the northern hemisphere, while those of you “down under” are going to pass right trough the winter solstice.

By the way, reports received from listeners in Australia, New Zealand, Japan, India and Bangladesh describe really excellent winter propagation conditions that are happening even under the extremely low prevailing solar activity.

Item two: News from scientists... it seems like the solar physicists are now very near or have already found out why solar cycle 24 has had such a slow start. Using advanced heliosysmic technologies that look more like science fiction than anything else, heliophysicists have now learned that the slow moving cycle is a consequence of complex phenomena happening some seven thousand kilometers deep below the Sun's surface.

The good news is that they believe cycle 24 will soon be showing up a much larger number of sunspots on a more regular basis.

Item three: Nice to hear from you amigos... lots of e-mail messages, postcards and letters, as well as comments about Dxers Unlimited during two way ham radio contacts are really encouraging and provide many good ideas for including new sections of the show... Practically all listeners reports keep telling me that ASK ARNIE , our questions and answers column is the number one most popular, and in recent messages it was very interesting to read how ASK ARNIE replies had helped many Dxers Unlimited's fans to improve their receivers, antennas and accesories.

Item four: Recently read, a wonderful book edited by the Radio Society of Great Britain... the author is Pat Hawker, and the title is Technical Topics Scrapbook all 50 years. Yes, the same name , Technical Topics as a regular feature of Dxers Unlimited.... The book also brings a CD with it, and I must say that it makes really nice reading... Pat Hawker wrote a regular monthly column since 1958 that was published by the Radio Society of Great Britain's monthly magazine . Technical Topics really helped many amateurs to start experimenting with antennas, transmitters, receivers, station accesories, and also opened up some very interesting discussions that helped to learn more about radio wave propagation.

Stay on this same short wave frequency, or via our world wide web Internet streaming audio that is active in English from 05 to 07 UTC from www.rhc.cu

I am Arnie Coro in Havana, back with you in just a few seconds amigos.

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You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited,and it is on the air twice weekly to help promote our wonderful hobby , yours and mine ... radio !!!

Now here is item five of this weekend edition... Intense sporadic events are happening now all across the Northern Hemisphere, with European stations reaching North America and the Caribbean on the 6 meters or 50 megaHertz amateur band.

I am receiving some very interesting TV DX reports from TV DX fans telling me that they are picking up using the analog TV sets, signals from Mexican, Central American and Caribbean stations via sporadic E layer propagation , as well as the first catches of the ATSC digital standard signals .

The comments include comparisons between the characteristics of the NTSC analog standard and the ATSC digital standard right at the peak of the summer sporadic E season. To say it in a few words, all the observations coincide as regards to how fragile the digital TV broadcasts are... something that we all expected to happen... frequent pixelation, images frozen and vannishing happen because of the inherent characteristics of the digital standard...

For those TV Dxers used to watch even complete programs via sporadic E propagation, I must say that this will no longer be possible... You may be lucky and catch the ID of the digital stations, but chances of enjoying long duration events to watch programs are next to zero...

Item six: ASK ARNIE, confirmed as the most popular section of this program will today be answering a question sent by several listeners who are having lots of trouble picking up not DX, but their regular local TV stations after it has switched to the digital ATSC standards, a move that in many cases was complicated by the shift from one channel to another one.

The worst possible scenario for regular TV viewers in the United States of America has happened in those cities and rural areas where one of several of the stations that normally served that region has not only phased out the analog TV broadcasts but has also moved from a UHF or a VHF hi band to a low band.

So, those who bought the so called Digital TV antennas, that are designed for receiving the UHF TV signals ended up by seeing nothing at all.
Digital TV broadcasts on the VHF LOW band ,channels 2 to 6 require a large size antenna to pick them up... as a matter of fact the TV channel frequencies were kept unchanged, so , just to give you an example, a half wave dipole antenna for TV channel 2 that spans from 54 to 60 megaHertz , approximately 5 meters wavelength needs to be two and half meters or eight feet long ... then you must add at least a reflector and a director to the antenna, and just figure out the size of what has to be installed in order to pick up a good signal from a digital ATSC standard TV station operating on channel 2 !!!

The analog blackout , done in the USA on June 12 has demonstrated to other nations many of the “ how not to do it ” most relevant mistakes , that will serve to improve the future switchovers by other nations from analog to digital TV.
For TV Dxers the rule of the game is to install the best possible antennas , and in the case of the UHF band, to use a masthead preamplifier and a very low loss and obviously expensive coaxial cable downlead !!!

If you study the characteristics of the ATSC digital TV transmission standard in detail you will soon learn that it is a much bigger challenge for the broadcasters to deliver a high quality signal.The old analog standard has many drawback, especially its low definition and the lack of color reproducing reliability that gave way for the funny description by engineers that said it was not National Television Standards Committee what standed for NTSC, but Never Twice the Same Color .. but , a TV transmitter broadcasting an NTSC standard M or N signal provides much better coverage than a digital one...
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Item seven : Another all quiet solar alert is now in progress, and this may contribute to more Sporadic E layer events to be happening right at the peak of the summer E skip season. Several very well documented research papers show an inverse correlation between solar activity and the number and duration of summer sporadic E propagation events...

Item eight : Join me now for a short trip across the room to the workbench, where the overcrowded two tables have to be wiped clean soon... At the largest workbench I have now the huge Marconi signal generator, that is so powerful that it can trigger the local Havana 145.190 repeater when connected to an indoor antenna... The purpose of transporting the signal generator from its storage place in the closet to the workbench is to measure the sensitivity of the new direct conversion receiver .... so that I can test different arrangements of the input bandpass tuned filter and radio frequency amplifier modules. The options available for the radio frequency amplifier stage are a bipolar transistor grounded base stage , that works very well and is unconditionally stable, a two transistors cascode stage that also works very well and responds nicely to automatic gain control voltage, then I will also be testing a single N channel field effect transistor amplifier, a dual gate, and the last configuration to be tested will be using a dual gate MOSFET N channel device. The purpose of the comprehensive test is to provide prospective builders of the direct conversion receiver module that forms part of a transceiver project is to provide different options that can be built according to the components that may be locally available. So far I have completed the test procedure for the first two modules,and there is really very little if any difference between them...

This approach forms part of a more far reaching project that aims at providing a “cookbook” of well tested , fully documented circuit modules that can be built without having to be involved in electronic design work. Imagine a young Cuban ham operator living in a small town , who has access to electronic components recycled from the energy saving fluorescent lightbulbs, old TV sets and some brand new parts that he can buy at reduced price from the local radio club. Instead having to loose a lot of time experimenting , he can homebrew a nice rig using the “cookbook modules” , that don't require sophisticated test instruments to be tested and aligned...

The Cuban Federation of Radio Amateurs has a nationwide membership of some five thousand five hundred radio enthusiasts that start their ham radio careers operating on 2 meters and 160 meters...

Once they take the second class license test, operation is allowed on the HF bands, and this is the time when they start to ask for circuit diagrams plus advice on how to build a simple, yet reliable HF transceiver that doesn't use “ rare , hard to find or unobtanium electronic components”....

Nowadays you can hear many of those rigs on 40 meters, using double sideband for voice and CW ... The Islander, Jaguey, Huracan and other similar designs have proven that amateur radio enthusiasts that devote their efforts to homebrew those rigs are rewarded with that unique and very special pleasure that is only possible when you make a nice two way DX contact using a transceiver , receiver or transmitter built with your own hands !
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And now amigos, as always at the end of the program, here is Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast...

And all quiet solar alert is in progress, solar flux at rock bottom level of 68 units, with the A index at also very low values...

Expect that the maximum useable freq will be showing a very interesting upward swing just around sunset your local time, so that , for example the 20 meters band will stay open well into the night. Sporadic E events will be both frequent and of long duration during the next few days. Don't forget to send your signal reports, comments about the program and radio hobby related questions to inforhc at enet dot cu or Via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba...