Radio Habana Cuba: Dxers Unlimited mid-week edition for November 28, 2000
By Arnie Coro, radio amateur CO2KK
Hi amigos, maybe you hear me well, maybe not, but if you have a difficult time picking up Dxers Unlimited today, this is due to the unusual solar activity of the last several days. As a matter of fact the solar fireworks started November 24th, and there are still at least two active solar regions that may produce more flares.... At least one of the flares was an X4 type, and we did had several X2 class flares.
The Earth's magnetic field is now subjected to the impact of charged particles ejected from the Sun by the coronal mass ejections associated with the solar flares. SO... if you are located at a high enough latitude and visual observations conditions are OK, you may watch some nice AURORA BOREALIS, and on the radio, the auroral curtain will send back to Earth signals on the VHF and even UHF range of frequencies... This is all part of the peak of solar cycle 23, which according to recent revisions is now scheduled to happen some time next year ....
Item two: High solar activity and geomagnetic storms do generate some very interesting propagation phenomena... for example, I was tuning around the 6 meter band at around noon my local time Tuesday here in Havana, and suddenly I heard stations from Costa Rica, Panama, California and the Grand Cayman island. California was a clear, by-the-book path for a single hop F2, but the other three stations were coming in via the rather unusual F2 backscatter mode!!!!
Item three: YOU have questions and send them to Dxers Unlimited... then I try to answer them. Today's two questions have to do with antennas, one of every Dxers Unlimited listener's favorite topics. Margarita Delgado is my sound engineer here at RHC's Studio number 7, I am Arnie Coro in Havana... stay tuned...
ARNIE GETTING READY FOR THE NEW OSCAR 40 SATELLITE
Arnie has just completed building a 15-element, high-gain YAGI
for 70 centimeters to uplink to the OSCAR 40 (ex PHASE IIID) amateur radio
satellite, now in orbit and soon to be available for ham radio
use!
Stay right on this same short wave frequency for more radio hobby-related information, and again, if you notice some reception difficulties -- no, it is not your radio and our transmitters are OK -- it is just anomalous short wave propagation caused by a geomagnetic storm !!!
You are listening to the mid-week edition of your favorite radio hobby show via short wave.
Here is item three in detail... Question number one: Arnie, I happen to follow your advice and when I bought my second tabletop receiver, I kept the small portable with which I started short wave listening two years ago. NOW, Arnie, is there a way I can connect my one and only external antenna two both receivers at the same time?
Well amigo, congratulations for your new nice radio, nd also congratulations for keeping your nice portable, which is an excellent receiver, too. NOW, what you want to do is quite logical and not too difficult to implement. You say you have a nice TTFD external antenna up about 15 meters at the high end... that's about 50 feet, so it must pick up a lot of stations for you in the range from 6 to 30 megaHertz. now, you happen to have two radios, a nice new tabletop digital receiver and your portable, so this is how you can connect both to the same antenna: All it will take is a very simple signal splitter, which is easily made using a few carbon resistors. The splitter will attenuate the signals a little bit, but will at the same time isolate both radios from each other. The easiest splitter to build is the one used by many TV distribution systems, known in techno jargon as a resistive splitter, and you can even save time by buying one from an electronics supply store. BUT be aware of the kind of signal splitter you want to buy; the one needed is the type that has only resistors inside -- no coils, no ferrite rings -- just resistors. As a matter of fact, those are usually the cheapest ones to buy and, as they are not frequency sensitive at all, they will work very well from the medium wave band all the way up to the VHF frequencies. If you cannot find them ready=built, then you can make them yourself with several carbon resistors, following a simple circuit diagram, which you can obtain from any radio handbook that your local library may have. Remember to connect the antenna to the center of the signal splitter, and to connect each radio via a short length of coaxial cable. For all practical purposes, you can use either 50 ohm or 75 ohm coaxial cables... AND, keep in mind that short wave signals are normally so powerful that the very slight loss from the splitter will not be significant at all.
I have two such splitters in my shack, one connected to my TTFD antenna feeds, a Russian-built communications receiver, the nice R250M, and a National HRO-60 receiver. Both operate very well using the same antenna, and interaction is practically zero. So, I hope this answers question number one asked by a listener in the state of Maine, USA.
Now question number two, also antenna related; here is how it was formulated in the e-mail sent to arnie@radiohc.org:
Dear Arnie, I want to know how small I can make a 10 meter band antenna and still make it work OK. See, this is something I was discussing with some friends at the radio club, and I told them that some time ago, I heard you on Dxers Unlimited talking about very short vertical antennas... So, please tell me how short a 10 meter band vertical can be made and still be reasonably efficient.
Well, amigo from Alberta, Canada, that's a good question. Let's do some numbers together... follow me: We want a vertical antenna for the center of ten meters, say 28.5 megaHertz to work both CW and SSB phone. There, a half-wavelength is exactly 5 meters long, so a one-quarter wavelength vertical will be 2.5 meters high. OK... now a quarter of a wavelength is 90 electrical degrees, and you can make a vertical antenna work with as short a radiator as 45 electrical degrees. in other words, that will be 1.25 meters high or just 4 feet high. Of course, this will require a loading coil, and it would not be 100 percent efficient, but you will be amazed to see how well this antenna works when used with an adequate ground plane. You can make it even smaller, say 30 electrical degrees or some 83 centimeters high and again, to your amazement, it will work too.
I use a combination of capacity hat loading and a coil placed at the top of the aluminium mast that is the actual radiator... One nice trick is to use a large diameter pipe, like say 2 inches or 50 mm in diameter... BUT, do remember to include no less than 4 radials of one quarter wavelength long each... YES amigo from Alberta, you can build really short, yet useful and rather efficient, low-profile vertical antennas for ham radio work, especially for the 15, 12 and 10 meter bands. IF you need more information about my KK-9 shorty vertical for 10 meters, just drop me an e-mail to arnie@radiohc.org or send an air mail postcard requesting the information about the very short vertical antenna for 10 meters. I am sure that you will be able to reproduce it with very simple tools.
You are listening to the mid-week edition of Dxers Unlimited, and again, if you notice any reception difficulty, this is due to the abnormal propagation conditions caused by the solar disturbances that have disrupted radio communications worldwide for the past several days....
NOW here is item 4: More about my KK ONE single-band, easy-to-build, modular amateur radio transceiver. Well, the project is going quite well; now I am making the final PC board layouts, after a lot of experimenting. I am getting the help of Arnie Jr. CM2KW, and we will soon complete two of the four printed circuit boards that are needed for a KK ONE. Why 4 PC boards instead of one or two? Well, for a very good reason: We are leaving a lot of space between components, so that builders can use resistors, capacitors, transistors, of any available size... So if you happen to need a 27 K resistor that is specified at a half-watt rating in the diagram, our board has enough space to allow you to use a 1 watt resistor. We also thought about easy soldering, so that beginners can assemble their own printed circuit boards under the supervision of a more experienced radio amateur. In the past, we've seen that circuit boards designed with very tight spacing between components ended in disaster when newcomers to the hobby tried to assemble them, even when an expert was right in front of them !!! SO, the KK ONE boards are larger than they are supposed to be, but that will make the radio easier to build and easier to repair, too!!! As soon as the whole project is finished, I will upload the KK ONE manual, building instructions, circuit diagrams and pictorials, plus some photos, to the Dxers Unlimited website for all of you to enjoy, and download to your computer if you want to build one, too.
And now amigos, as always at the end of the show , here is Arnie Coro's Dxers Unlimited HF plus 6 meters propagation update and forecast. This is a very difficult job today, as the SUN is very unstable, to say the least! There are two solar active regions that may generate more solar flares during the next 72 hours, and if this happens then we may see some more disturbances during the next several days... My HF propagation forecast up to the 10 megaHertz band calls for rather poor conditions, due to increased ionospheric absorption. Frequencies in the range from 15 to 30 megaHertz will show good propagation, and you may even find them open well after sunset.... on the 10 meter ham band tune to the 28.200 worldwide beacon network... you will be happily surprised to hear those beacons coming in, even late into the local evening these days. For 6 meter band operators, this is the time to be permanently not only listening but also calling CQ as often as possible. You may be also surprised to learn that the band is actually open, although when you start to call CQ nothing is heard... So, learn this nice lesson about the higher frequency bands ... from 21 megaHertz open, many times they are wide open to a part of the world with very little amateur radio activity, so calling CQ on what you think may be a dead band may bring in the surprise of your life when a real DX station comes back to your call.
AND don't forget to look for me on the 10 meter band, I will be on 28.5 zero zero, plus or minus 5 kiloHertz, and also when 6 meters is open, I monitor the 28.885 international 6 meter band coordination frequency.
See you on the amateur bands, and if you have not yet obtained your ham radio license, don't wait one more second... the HF band conditions are going to be very good for the next two years for you and me to enjoy ... and a new amateur satellite OSCAR 40 is now in orbit too about to be operational in a few weeks for the first tests!
Arnie Coro CO2KK
Havana, Cuba
November 28, 2000
Postal address:
Arnie Coro, "Dxers
Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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