Radio Habana Cuba: Dxers Unlimited weekend edition for October 7, 2000
By Arnie Coro, radio amateur CO2KK
Hi amigos! Welcome to the weekend edition of your favorite radio hobby show. I am Arnie Coro, here in Havana, and here is Item one: What an interesting week propagation-wise my friends... several geomagnetic disturbances caused some really interesting phenomena, from 6 meter band openings that included backscatter propagation to lots of aurora borealis signal paths. Now it is all over, but we may see yet another disturbance hitting us by Monday. I'll provide you with the complete HF plus 6 meters propagation update and forecast, as always at the end of the show.
Item two: The magic tape antenna topic brought a lot of feedback from listeners, but unfortunately I caught the flu and could not keep up with the e-mail traffic, I am feeling better this Saturday morning, so before the weekend is over, answers to all the questions asked about the Magic Tape Antenna and the requests for the INFO PACKAGES will be travelling in cyberspace to their happy recipients.
Item three: Torrential rains in the Caribbean reminded many radio amateurs and short wave listeners that modern radios do not like high humidity at all. Many of those participating in emergency nets had to keep light bulbs and fans blowing hot air into their radios to be able to read the liquid crystal displays!!! And yes, that's the way to go: keep the radio as far away as possible from aerosols and blow hot air into the cabinet to remove the humidity that causes the problems. Then, keep the radio on all the time if that is possible to avoid further condensation. Humidity is a real big enemy of electronic equipment, especially where high voltages or very closely located circuit board patterns are used.
Stay tuned for more radio hobby-related information coming to you directly and from the source--Radio Havana Cuba's Dxers Unlimited! Margarita Delgado is my sound engineer and producer, I am Arnie Coro, radio amateur CO2KK, back with you in just a few seconds after a brief musical interval.
You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, and YES, this is a program devoted to both beginners and experts, and dealing with topics related to the more than 50 ways that you and I can enjoy this wonderful hobby... RADIO!
Here is item four: From Switzerland, an e-mail requesting the Regenerative Receivers INFO Package, that came with some interesting notes about experiments with this fascinating circuit. And, YES, amigo, I do insist: building a regenerative receiver is a once-in-a-lifetime experience. Even the ultra-simple circuit with a very low parts count will give you the pleasure of listening not only to the your local AM broadcast band stations, but also the possibility of picking up some nice DX. There are two secrets to building regenerative radios that can't be forgotten: Build them like a battleship, and experiment with the bandspread tuning. My two-vacuum-tube regenerative radio has an excellent bandspread on both the 80 and 40 meter bands, something that allows me to tune DX stations easily. Selectivity wise, the regenerative is hard to beat, especially when you are able to very carefully take the circuit very close to the point of oscillation. Among my latest DX stations on 40 meters picked up using the 2-vacuum-tube regenerative are several Pacific Islands, India, and Middle East Stations, using a 10 feet or about 3 meters long wire antenna which drops down the window!!!
AH... the vacuum tubes, before I forget, they are a 12AT7 or ECC81 that acts as grounded grid radio frequency amplifier and regenerative detector, and a triode pentode removed from an old TV set, the ECL85, that provides ear-shattering or room-filling volume, depending pn whether you are using headphones or a loudspeaker. The power supply uses a one-to-one AC power line isolation transfomer, and provides about 150 volts DC to the vacuum tube anodes, and I wound an extra secondary to provide 6.3 volts for the filaments. This little radio is a wonderful motive to promote interest in amateur radio and short wave listening among friends... and parts for it can be found at very low cost or sometimes just by recycling old radio and electronic equipment that may be gathering dust somewhere. INTERESTED??? SURE!!! Then e-mail your request for Arnie Coro's REGENERATIVE RECEIVERS INFO PACKAGE. Send your request to arnie@radiohc.org and if not yet in Cyberspace, it will just take a little longer: Send your request via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Well, the MAGIC STEEL TAPE antenna brought, as I said at the beginning of the show, a lot of requests for additional information, something that I had already expected, as it is a bit difficult to describe in words. So, I will be working on a graphic presentation that can be sent via e-mail and posted on the Dxers Unlimited website for downloading.
Anyway, here are two answers to the questions sent in by Ben Luscombe from Australia... Ben wants to know how to make a one-to-one ferrite balun, and amigo Benjamin, I am afraid you must visit your library and borrow one of the popular Amateur Radio Handbooks, look at the index, and take notes about the way one-to-one baluns are made. Please notice that I used a ferrite core in the MAGIC TAPE ANTENNA to save space, as this antenna was designed primarily for portable and emergency use.
Now, as for your other question, about where to solder the balun terminals to the tape... ANSWER: To the first 25 millimeters or first inch of the tape. You will have to sand the measuring tape's paint with emery cloth, then apply solder to tin the surface. Phase two is to drill a hole small enough so that it will not weaken the tape, but big enough for a small bolt to which a terminal is attached. Use star washers on both sides of the tape, and that's it! I connected the tape to the balun using a length of flattened coaxial cable shield or braid, which is pretty flexible.
To install the antenna, just extend the two measuring tapes away from each other, and carefully mark the length you want to achieve tentative resonance by the standard formula 143 divided by the frequency in megaHertz. That will be perfect for receiving, but if you want to transmit, there is one more step to follow, and that is to trim the antenna length for minimum standing wave ratio. The MAGIC TAPE ANTENNA can be installed in three different ways: As a standard half wave horizontal dipole, between two masts of the same height; as an inverted V supported at the center with the tapes sloping down to each side; and you can also make a wonderful DX catcher by installing your MAGIC TAPE ANTENNA as a sloper. Again, a reminder: Look for the highest possible quality steel measuring tapes, and keep in mind that this is a portable and emergency antenna, which is not designed for permanent use. Don't worry about the steel tape's conductivity; you won't be able to measure the difference between the MAGIC TAPE ANTENNA and a conventional copper wire dipole!!!
Any more doubts? No problem. Just e-mail me at arnie@radiohc.org and I'll be very happy to answer your questions about the MAGIC TAPE ANTENNA or any other radio hobby-related topic. This is a unique DXERS UNLIMITED's service to our worldwide audience which is provided as soon as possible and absolutely free of charge! AH... and don't forget to include not only your e-mail address, but also check that you have included your postal mailing address so that Irma Veitia from our correspondence department can confirm your reception report with our nice QSLs.
This is Radio Havana Cuba's Dxers Unlimited, the one and only radio hobby program with the most up-to-date HF plus 6 meters propagation updates and forecasts. Even if you listen to our late late show on the Pacific Coast of North America and beyond, the propagation forecast is never more than 12 hours old.
Now amigos, let's take a very short visit to Arnie's workshop, just to remind you about something Arnie Jr. learned this Saturday... Arnie Jr, my eldest son, is assembling a computer, and he came to pick up some components I had for him. He asked why I had included so many split ferrite cores in the box. "The reason, Arnie Jr, Arnaldito (or little Arnie)," I told him, "is that you are going to use your new machine with your ham radio station, and it is good engineering practice to include as many split ferrite cores as possible on all cables that enter and exit the computer's case." Keep that in mind -- the more RF-stopping split ferrite cores you add, the better... and don't forget to install additional ones on the cables going to the monitor, too!
And now amigos, as always at the end of the show, here is Arnie Coro's HF plus 6 meters propagation update and forecast. No less than 6 active solar sunspot regions could be seen Saturday morning here from my optical observation post here in Havana, but not one of them has really complex magnetic configuration. The official sunspot count is a bit less than 130 and it is moving down. If you need to run propagation forecasting software for a particular path, then use 120 sunspots as the number provided to the program to make the calculations.
Trans equatorial propagation will continue to be good, both between the Mediterranean and Africa and between the Caribbean and South America, with the possibility of the TEP extending a bit more to the North. The best all-around band under this low solar activity conditions is the region between 10 and 16 megaHertz, but you will notice that both the 20 meter amateur band and the 19 meter broadcast band will fade away and close around mid-evening local time. Both the 31 and 25 meter broadcast bands from 9 to 12 megaHertz are the best ones for nighttime reception. Enjoy the quiet geomagnetic conditions during the weekend and be ready for yet another disturbance that may start at anytime during Monday UTC day... if it does happen, then 6 meter operators should monitor the band for possible long range F2 propagation.
Remember how important it is for me to receive feeback from you with your radio hobby-related questions and comments about the show. They sure help making Dxers Unlimited more appealing to you and others, too! Send your e-mail to arnie@radiohc.org, or via Air Mail write to Arnie Coro, Radio Havana Cuba, Havana Cuba. See you next Tuesday and Wednesday UTC days for the mid-week edition of the show!!!
Arnie Coro CO2KK
Havana, Cuba
October 7, 2000Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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