Radio Habana Cuba: Dxers Unlimited Weekend edition for January 20, 2001
By Arnie Coro, radio amateur CO2KK
Hi amigos, welcome to the weekend edition of Dxers Unlimited, coming to you from Havana. I am Arnaldo, Arnie, Coro radio amateur CO2KK and as always its really nice to share with you some sixteen minutes of all radio hobby-related airtime!!!
Here is item one: Sudden, unexpected, but very real DIP in solar activity... the daily sunspot number went down to the below 100 mark, and reached just 71 sunspots on Friday!!!! The daily solar flux also went down, but not as abruptly... Solar flux is now still above 150 units, but will very possibly go to near 130 before bouncing back during the next solar rotation! And as my good friend Oscar CO2OJ likes to say, what is bad for 10, 12 and 15 meter band DXers is really good news for those of us who also enjoy Dxing on 160, 80 and 40 meters... In other words, if you have good antennas, you can enjoy radio during the FULL DURATION OF THE SOLAR CYCLE!!! That is, during the high activity period of the cycle, you spend most of your operating time above 14 megaHertz, while during the much longer lasting period of lower solar activity, with good antennas you can certainly have a nice time operating on 160, 80 and 40 meters!!!!
Item two: No more news this week from the OSCAR40 satellite, except a note that was very slowly unveiling what was evidently a terrible disaster on board amateur's radio most sophisticated an expensive satellite ever built and launched... Seems like the fuel leak is not the only problem that happened after firing the engines more than a month ago. Omnidirectional antennas simply do not operate, and there are several vital on-board systems that are also not responding to ground control station commands. In other words, some very clever reprogramming most be done in order to make the best possible use of whatever facilities can be made operational on the OSCAR40, and to that I may add that the calculated lifetime of the satellite must now be changed from several years to a big question mark...
Item three: Vacuum tubes do work with low voltages, SURE, once the electrons leave the cathode, they can be accelerated and made to work for us using low anode voltages... More about low-voltage vacuum tube experiments here at your favorite listener-oriented radio hobby show via shortwave. Stay tuned right on this same frequency... Margarita Delgado is at the mixer board in studio 7, and I am Arnie Coro broadcasting today from my shack!!! Back with you in a few seconds...
The name of the station is Radio Havana Cuba, the name of the show is Dxers Unlimited and yes, amigos, we do answer all you radio hobby-related questions, on the air, via e-mail and also via Air Mail if you sent them via POST to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
And here is once again, the very popular section of the show... YOU have Questions and Arnie Answers them... Today's question: Arnie Coro, an oldtimer at my radio club -- yes I followed your advice and joined a local club, Arnie -- well an old timer at my club was telling us during the last meeting about some vacuum tubes that are capable of operating while using very low plate voltages. He added that when he was a teenager his dad's car radio used a set of vacuum tubes that ran on 12 volts for both the filaments and the plates, and the radio used an output transistor for the audio output. Arnie, please tell me more about this very interesting topic. Signed, Jonathan from Missouri USA.
Well amigo Jonathan, the old timer has a good memory indeed, YES, he is right, there were several car radios that used 12 volts tubes, vacuum tubes which were especially designed so that the clumsy and unreliable vibrator DC power supply could be forgotten!!! Car radios from the very early days to the late 'fifties needed a high voltage supply for the vacuum tube anodes, which was made using a mechanical switching device known as a VIBRATOR, which caused a lot of trouble to radio repairmen. So, when the new 12 volts on the plate tubes appeared, and the first germanium power transistors became available in quantitities, the hybrid car radio was born. it had no vibrator power supply, BUT... the high power output transistors were still in their infant days, and they did fail a lot. So, the HYBRID radios quickly gave way to full solid-state receivers, using much more modern devices. In other words, the life of the HYBRID car radios was a really short one!!!
Nevertheless we can learn a lot from the past, and now that some types of vacuum tubes are easily available at low cost, because no one can find any use for them, it is only natural that experimenters have started to play with them... The results are, as always when amateurs get into something, simply outstanding!!! The best example is an almost unbelievable regenerative receiver that uses a single vacuum tube, running with 12 volts both on the filament and the plate. Actually, there are two vacuum tubes in one single envelope; one is a radio frequency pentode, and the other a triode. I started experimenting with this receiver, and quickly added another dual vacuum tube, so now the 12 volts vacuum tube receiver has a radio frequency amplifier stage, the regenerative detector, and audio pre-amplifier stage and an audio output. Amazing as this may seem, it works beautifully, and because I run DC on the filaments too, the radio has a remarkably low noise level!!!
I have the original circuit design available in Adobe Acrobat PDF type computer files, so if you wish to see the article, just send me an e-mail to arnie@radiohc.org and do include in your request for the 12 volts vacuum tube radio article, your postal mailing address, so that I can send you our QSL card, and now that I talk about QSL cards, just got a very angry e-mail from a listener, something that is really unusual, he has not received our QSL card, so I went to the correspondence department to check, and sure they have mailed him not one, but three Radio Havana Cuba's verification of reception QSL cards... Obviously something is wrong with the postal service , so we will not only try again amigo, but also I will give you QSL on the air a little later today too... See, it's not my fault that the postal service to some countries is not good!!!! BUT I CAN ASSURE you that radio waves will certainly reach your receiver tonight, as propagation conditions are pretty good for the 6 megaHertz, 9 megaHertz, 11 megaHertz and 13 megaHertz bands that we use for broadcasting to North America !!!!
As I am writing the script for this show, at around 1730 UTC, that's 30 minutes past local noon here in Havana, Saturday, a cold front is moving in with a lot of rain... This meteorological event reminds me about VHF propagation, and how it is so well linked to weather events... For example, after the heavy rains from the cold front impacting the local moist and hot air over the island are over, the high pressure area will move in, with low temperature and low humidity air, exactly what is needed for VHF DX conditions to settle in... If you want to learn more about VHF propagation via ground wave, start matching your weather maps with DX conditions, and very soon you will learn how to relate weather events with VHF radio and TV Dx conditions!!!
And now amigos, QSL on the air -- a very special one to angry James W White from Hudson, Florida. Jim K1EXE has tried to obtain his DXCC, that is one hundred countries confirmed for a loooong time, without success, and he now describes Radio Havana Cuba as not a good QSL station, to my surprise... And I say to my surprise and very possibly to the surprise of many of you listening too, because Radio Havana Cuba, from the very first experimental broadcasts made during February of 1961, almost 40 years ago, has really devoted a lot of attention to QSLing to its worldwide audience!!! So, amigo Jim K1EXE, we will try again to send you another nice QSL card, and this QSL on the air, a very special one, is intended to reduce your anger for not receiving a physical hard copy QSL card yet!!! Keep enjoying your regenerative homebrew receiver, relax, and although I cannot do anything to improve your amateur's QSL cards rate of return, let me give you a bit of advice... Find out about ham stations that have QSL managers, I have found out that QSLing via QSL managers works great for me, and YES, I do have more than one hundred countries confirmed on 10 meters, my second favorite ham band... but on 6 meters, my real top favorite band, I have yet to work a few more and confirm them before applying for DXCC!!!
And now, just before going QRT here is Arnie Coro's exclusive and not copyrighted HF propagation update and forecast... Solar activity is oscillating between low and moderate, the actual sunspot count registered a minimum of just 71 on Friday, but a new active region with more spots is now rotating into full view, and this will increase both the actual sunspot count and the daily solar flux figures. The next solar rotation's maximum is expected to reach a peak of between 170 and 180 units, but we must still wait a bit more and see in order to tell for sure that solar maximum is a thing of the past now.
You and I can enjoy the excellent DX conditions that will prevail during the local evening hours on the 40 meter amateur band, the 41 meters international broadcast band and also on the 30 and 31 meter bands... Daytime DX will continue to be available on 10, 12 and 15 meters, but the number of hours that those bands will be open is not going to be as it was during the two previous solar rotations. AM medium wave band DX condtions are going to be good too, especially two hours before sunrise local time and until just a few minutes before the actual local sunrise.
See you on 40 meters, I will be operating between 7050 and 7060 kiloHertz, and listening on the same transmitting frequency and also between 7160 and 7200 for split frequency contacts... Enjoy radio, and join your local radio club too!!!
Arnie Coro CO2KK
Havana, Cuba
January 20, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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