Radio Habana Cuba: Dxers Unlimited mid-week edition for March 6, 2001
By Arnie Coro, radio amateur CO2KK
Hi, amigos worldwide, welcome to the mid-week edition of your favorite radio hobby show on the air and on the web! I am Arnie Coro, radio amateur CO2KK, your friend here in Havana, and here are the headlines....
HF propagation still slightly degraded at high latitudes due to the effects of the solar wind generated by a coronal hole, but everything will be back to normal for the season and the level of solar activity by Wednesday UTC days, IF no other unusual events occur 93 million miles away from Earth, at our nearest star... the SUN. Solar flux now hovering very near 160 units, quite nice for spring equinoctial propagation conditions now available to all HF DX enthusiasts...
Item two: Antenna topic, if you happen to have but a single mast... What's the best possible antenna that can be installed using a single supporting structure? I'll answer that question in today's mid-week edition of Dxers Unlimited...
Item three: More about homebrewing radio equipment, a topic that has generated a lot of e-mail messages from our listeners, and as always, at the end of the show, be ready to tape or take notes, as I will provide you with the most up-to-date propagation update and forecast covering from the AM Medium Wave Band all the way up to the 50 megaHertz or 6 meter amateur band!!!
You are listening to Radio Havana Cuba, soon to celebrate our 40th Anniversary amigos! The name of the show is Dxers Unlimited, and here is the ever-popular ANTENNA TOPICS section of the show... Today I will be answering a question sent in by listeners in Canada, the United Kingdom, the United States and Australia... They all want to know what's the best antenna to install if you happen to have space for just one and only one antenna mast or tower....
Well, here is the answer: If there are not building codes or other restrictions that block you from installing both a mast or tower and a rotatable antenna at the top of the mast or tower, by all means, try to install a rotatable LOG PERIODIC ANTENNA, which has many advantages over any other types, as when properly designed and installed, a ROTATABLE LOG PERIODIC antenna will provide very wide band coverage, for example from 10 to 30 megaHertz for one of the most recent lightweight SPIDERWEB or TELARANA designs... The lightweight version of the log periodic array can be rotated by a not-too-expensive rotor, and will provide you with an antenna system that will be good for short wave listening and amateur radio operation.
The SPIDERWEB, made from a combination of space age materials like reinforced fiberglass spreaders, high-strength aluminium tubing and high-quality copperweld wire, will stand heavy winds, but will not be a very good option under icing conditions, and in my opinion that's its main limitation for radio hobby applications, where it is not possible to run antenna anti-icing systems...
A well-designed SPIDERWEB log periodic antenna that will cover from 10 to 30 megaHertz should be your number-one choice for the TOP OF THE MAST OR TOWER antenna, while two other lower frequency antennas will complete your single mast or single tower installation. They are a SLOPING DELTA LOOP, fed with open wire line via an antenna tuner, and a second generation TTFD or tilted terminated folded dipole... The three antennas will of course interact a bit, but when properly installed, interaction is kept to a minimum... The SLOPING OR TILTED DELTA LOOP can be made as large as possible, to provide low frequency coverage and, likewise, the TTFD version that you install can be made long enough to cover frequencies as low as between 3 and 5 megaHertz.
NOW, be aware that this is not a one weekend project; it will require a lot of planning and proper installation in order to provide good service. BUT, you can be sure that the combination of the SPIDERWEB for covering from 10 to 30 megaHertz, a one wavelength DELTA LOOP cut for the 40 or 80 meter bands, and a TTFD with a low frequency cutoff around 3 to 5 megaHertz will be about the best possible system that can be installed using a single mast or tower. By the way, both the DELTA LOOP and the TTFD do require short masts close to the ground, but those can usually be easily installed and do not require heavy guy wires. The three antenna system will require the use of three diferent feedlines, a coaxial cable for the SPIDERWEB, an open wire line for the DELTA LOOP and a coaxial cable for the TTFD... AND OF COURSE AMIGOS, I am sure that you will use the three antennas of this single mast or tower dream system feeding an antenna tuner that is connected to your receivers or amateur band transceivers...
AS YOU MAY REALIZE, this three antenna system is a compromise, as the SPIDERWEB LOG PERIODIC antenna will cover the 30, 20, 17, 15, 12 and 10 meter amateur bands, but with less gain than if you install a typical three band YAGI beam for 20, 15 and 10 meters... The advantage of the SPIDERWEB approach is that you have a SIX HAM BAND COVERAGE, plus a nice antenna for receiving international shortwave broadcasts and utility stations from 10 to 30 megaHertz!!! I hope this answers the question, and that many of you will start thinking about your first TWENTY-FIRST CENTURY optimized coverage antenna system, and remember, if you ever need any advice about antenna related topics, just drop me an e-mail to arnie@radiohc.org or via AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Listening to short wave radio is fascinating... you know it well, talking via amateur radio with an expedition to the South Pole is more than fascinating, but if you happen to do any of the above with a homebrew radio... well, that's hard to beat! YES, AMIGOS, the added pleasure of listening or communicating with radio gear that you have built is second to none; that's why homebrewing of radio equipment is becoming more and more popular. As I have said here many times, assembling one of the many now available radio receiver kits is a first step in the right direction. You will need a few hand tools, and a good high-quality soldering iron, a digital multimeter and a small stock of electronic components...
Today I'll tell you more about MODULAR construction techniques, which are ideal for assembling homebrew radio equipment. There are three basic modules that every radio hobbyist should have ready to operate at any time.... they are: a 12 to 14 volts DC power supply, capable of supplying up to 5 amperes of current, and equipped with short circuit protection; a one to three watt output audio frequency amplifier module; and a crystal oscillator module capable of generating frequencies between 2 and 20 megaHertz.
These modules can be built very easily, and they will provide you with a shortcut whenever you want to experiment with other circuits, as there will be no need to build a power supply or an audio amplifier, and test signals can be easily generated using the quartz crystal oscillator module. As a matter of fact, it is a very good idea to add to the above-mentioned three modules a fourth one: a rechargeable 12 volt nickel cadmium or nickel hydride power pack and its charger... This fourth module will be still more valuable if you make it yourself, and install take-off points for different voltages, like 3, 4, 5, 6 and 9 volts. By the way, by using a variable voltage regulator module for your 5 ampere 12 to 14 volts DC supply, it becomes a much more useful test instrument, too.
Let's now see how this works for the radio experimenter... suppose you want to build a new regenerative receiver for the kid down the street -- just assemble a rechargeable battery pack for him, identical to your module, then build the regenerative receiver but less the audio output, as you will use your workbench audio output module.... Once the receiver RF circuits are tested, the kid down the block can assemble the audio output module under your close supervision. The receiver will be extremely safe to operate, as it will be powered by the battery pack, and building a simple charger will be a logical next step. Your power supply modules, both the one that is powered from the AC power line and the battery pack will be extremely useful at your workbench... the audio amplifier module, connected to a small loudspeaker, will be always there, ready to go and test anything you build, and will also serve as the tail end of a very useful homebrew test instrument, a signal tracer.
Time spent assembling these simple modules is well worth it, as your projects can be built and tested a lot faster when you have all this test gear at the workbench. Do remember to include the test crystal oscillator, and start collecting quartz crystals at hamfests and also picking them up from discarded computer cards... For example, some of the older multi input/output controllers of 286, 386 and 486 machines have nice quartz crystals at such good reference frequencies as 8.000, 16.000, 9.600, and practically all defunct computer motherboards will provide you with one 14.318 quartz crystal, too. The crystal oscillator module will help you test homebrew receivers and even provide very useful calibration points for your homebrew radios dials.
Follow Arnie Coro's advice and build not one, not two, but three or four audio output modules on a small printed circuit board... they will save a lot of time for your next experimental electronics project!
And now amigos, my friends, mes amis, as always at the end of the show, here is Arnie Coro's HF plus 6 meters propagation update and forecast... Solar flux hovering around 160 units and the actual sunspot count Tuesday was UP to 143, although during the past six days we saw a very pronounced dip in the number of sunspots that went to the really very low figure of just 59 sunspots last Friday... Solar activity will continue to be very low to low, and the A index, or geomagnetic disturbance indicator, will now go down after the effects of the high speed solar wind are over.
Tuesday morning the ionospheric chirp oblique sounders showed maximum useable frequencies for a one-hop path of 3000 kilometers via the F2 layer of between 35 and 40 megaHertz and that was, as expected, on propagation paths from North to South.
For 6 meter operators, the Trans Equatorial DX season is now in full swing, starting at around 4 pm local time and sometimes extending until local midnight... The 10 and 12 meter bands will continue to provide good one and two hop F2 propagation, and during the early evening hours, the 20 meters amateur band will be your best option for working DX.
Short wave listeners will enjoy excellent local nighttime reception from 6 to 16 megaHertz, with a well-defined peak between 9 and 14 megaHertz. See you at the weekend edition of the show, and don't forget to send your signal reports, comments about the show and radio hobby related questions to arnie@radiohc.org!
prepared March-6-2001; transmitted March-7-2001 13:50 EST
Arnie Coro CO2KK
Havana, Cuba
March 6, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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