Radio Habana Cuba: Dxers Unlimited mid-week edition for October 10, 2000
By Arnie Coro, radio amateur CO2KK
Hi, amigos! This is the mid-week edition of your favorite, listener-oriented, full coverage, radio hobby show via short-wave, and also available at the World Wide Web in an easy-to-download text format. I am Arnie Coro, radio amateur CO2KK, and here is item one: Get ready for yet another geomagnetic disturbance, which could reach the Earth's magnetosphere early October the 12th. This one can be traced to a full halo coronal mass ejection originating from solar active region 9182, after a C7 class solar flare... Nothing out of this world, just another example of typical solar maximum behavior.
Item two: A Cuban amateur radio station is active on the RS13 low Earth Orbit satellite... if you need to work Cuba via satellite, here is a good chance to catch Martin, CO3SG, an excellent operator who has one of Cuba's best homebrew amateur radio stations. So be on the lookout for Charlie Oscar Three Sierra Gulf, Martin, from San Antonio de los Banos, a town about 45 minutes' drive South of the City of Havana!
Item three: The ever-popular YOU HAVE QUESTIONS section of Dxers Unlimited deals today with a very interesting topic, is it or is it not possible to use automatic gain control on regenerative radios....
All this and a bit more during the next 14 minutes of air time from Radio Havana Cuba. The sound engineer and producer is Margarita Delgado; I am Arnie Coro, back with you in a few seconds....
The name of this station you are tuned to is Radio Havana Cuba, the name of the show is Dxers Unlimited, our twice-weekly contribution to the development and enjoyment of this wonderful hobby, yours and mine -- RADIO.
And here is item three in detail...YES, I am working on a Frequently Asked Questions list dealing with regenerative receivers, and here is a very interesting and challenging one. It came from a listener in the USA who asks: Arnie Coro, is it possible to incorporate automatic gain control to the classical regenerative receiver?
ANSWER: Amigo from Illinois, the answer is YES and NO... The classic regenerative detector, that is the single triode or tetrode vacuum tube with a single tuned circuit, connected via a small capacitor or a variable link to the antenna, is not well suited to applying Automatic Gain Control. The reason for this is that the single tube regenerative circuit requires very critical adjustments, which will be detuned when the AGC action starts. BUT, follow me, a more sophisticated regenerative receiver, with a radio frequency amplifier stage ahead of the detector, can be made to work quite well using a combination of both manual and automatic gain control. This type of circuit uses audio-derived AGC, which feeds back to the Radio Frequency amplifier stage grid. By carefully selecting the type of vacuum tube, and its operating parameters, excellent results are obtained. So, I hope that this gives you, amigo from Illinois, a good idea about how it can be done. In other words, you will have to design and build a regenerative radio with a radio frequency amplifier stage, incorporate an audio-derived AGC circuit and that's it.
BUT, let me tell you something: I simply love to use manual gain control, as it gives the operator full command of the radio. The manual gain control of the radio frequency amplifier stage is achieved by three different circuit approaches. First, I use a resistive radio frequency attenuator at the antenna input; second, a variable antenna coupling link gives a very wide margin for adjustment of the coupling; and last but not least, I use a conventional cathode circuit gain control which allows me to change the RF stage actual gain.... Then the regenerative detector circuit shows a smooth-as-silk regeneration control, coming in and out of oscillation so swiftly that you have to hear it to believe it!
Tuesday early morning local time here in Havana, around 10:30 UTC, I was listening to the first European stations coming in on the 13 meters international broadcast band using my three-vacuum-tube regenerative receiver, to which I have never added the AGC or automatic gain control option, because the radio works very nicely with the three manual gain control options that I have available. Radio Exterior de Espana, Spanish International Broadcaster was coming in beautifully in the regenerative tuned to their 21700 kiloHertz frequency, and I could also listen to several other stations on that band with very good quality.
YES AMIGOS, MY FRIENDS, MES AMIS... regenerative receivers are simply fantastic, and they are also much easier to build than other circuits... So, if you want to learn more about this interesting circuits, just drop me an e-mail request and ask for the REGENERATIVE RECEIVERS INFO PACKAGE. Send your e-mail to arnie@radiohc.org -- very easy to remember -- and if you're not yet in cyberspace, a postcard sent via Air Mail will do the job. Send your AIR MAIL request for the Regenerative Receivers INFO PACKAGE to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Dxers Unlimited coming to you from Havana... Here is item four: QSL on the air to Glenpool, near Tulsa, Oklahoma, USA, to Jesse Hodge who sent a very nice e-mail with comments about our programming in general and Dxers Unlimited in particular; thanks, amigo Jesse, will try to keep it going the way you like it... QSL on the air to West Virginia, to our good friend K8KFJ, Garie Halstead, a really enthusiastic amateur radio operator who works a lot of 6 meters DX.... QSL on the air to all DXers Unlimited's fans who have sent for the free INFO PACKAGES dealing with the TTFD and Broomstick antennas. I have just completed sending out all the requested materials, so if for some reason or another, the INFO PACKAGES have not reached you yet via E-Mail, please resend your request, and I will gladly do it again.... Sometimes, some INTERNET connected machines seem to accept e-mail and then they don't deliver it, and the e-mail stays in a Cyberworld limbo forever!!!
Item five: "Bare wire, plastic-covered wire, or enamel-coated wire... which of the three I should use for my BROOMSTICK antenna?" asks a listener from CANADA. Well, amigo, I prefer to make my BROOMSTICKS using the low-cost, easy-to-find no.18 plastic PVC insulated wire popularly known as "bell wire." Because of the plastic insulation, the turns are separated from each other, providing a higher Q or factor of merit of the coil. If you want, you can use the so-called magnet wire or enamel-insulated wire used for winding transformers and electric motors. BUT, this wire MUST be of the highest possible quality, because the last thing you want to happen is that the enamel will peel off from two adjacent turns and short them out. SO, if you do use enameled wire, be really careful handling it, and don't forget to wind it using gloves, so that your skin's oils and fatty acids will not damage the very thin insulation. A third option: You can use bare copper wire, but then you must wind two parallel wires at the same time, and after the BROOMSTICK is finished, you must unwind one of them, in order to leave the spacing between turns, which is essential when using bare copper wire. I hope this answers your question, and let me add that a new improved version of Arnie Coro's now-famous BROOMSTICK antenna is in the works; tests are going nicely, and we will soon have it available for publication!
And now amigos, at the end of the show, as always, here is Dxers Unlimited's exclusive and NOT COPYRIGHTED, free for all, in the public domain, for the enjoyment of radio hobbysts worldwide, HF plus 6 meters propagation update and forecast! Solar activity has taken a steady downward trend during the past 7 days, with solar flux at 203 units October the third, and now just at 140 units on the tenth of the month. The next solar rotation will see a well-defined maximum between October the 18th and October the 22nd, and the peak will almost surely be above 220 solar flux units -- something that, coupled with a much lower altitude F2 layer, will provide amateur radio operators with some really nice conditions on the 15, 12, 10 and 6 meter bands.
The most immediate disturbance will be hitting the Earth in a few hours from now; it can be traced to a coronal mass ejection, and will probably generate high polar cap absorption, aurora borealis, and some abnormal F2 layer propagation. The best bands for daytime operation are going to be in the range from 15 to 25 megaHertz, with possible openings up to the 30 to 35 megaHertz segment. Nighttime reception will be best in the range from as low as 6 megaHertz to as high as 15 megaHertz, but about two hours after local sunset, signals on the 15 megaHertz band will begin to lose strength, especially along the East-to-West paths. Amateur operators will enjoy working DX on both the 40 and 30 meter bands that are now becoming less noisy as the summer static disappears.
See you on 15 meters, around 21295 and on 10 meters around 28.500 and don't forget to send your very much appreciated comments about the show to arnie@radiohc.org, or via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba!
Arnie Coro CO2KK
Havana, Cuba
October 10, 2000Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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