Here is today's script of Dxers Unlimited Radio Havana Cuba
Dxers Unlimited Dxers Unlimited's mid week edition for 26-27 December 2006 By Arnie Coro radio amateur CO2KK Hi amigos radioaficionados... Seasons Greetings and a Happy New Year 2007 to you all... I am Arnie Coro, radio amateur CO2KK, your friend in Havana and host of this twice weekly radio hobby program that tries to deal with every aspect of our wonderful way of enjoy our spare time... from winding a modulation transformer required to restore an antique transmitter, to the how to improve your 2 meter band handie talkie coverage during an emergency using readily available materials... from learning how to make your own HF propagation forecasts to teaching newcomers to the hobby the basics of radio communications technologies... YES AMIGOS, Dxers Unlimited's success is based not only in its coverage of a really widespread number of issues, but also by providing critical analysis of radio developments, like what we have been doing recently regarding the controversial DRM transmissions, that I agree with many listeners that wrote to me, can also be extended to the IBOC or In Band On Channel transmission system for the AM broadcast band too... About IBOC for FM I won't comment yet, as it does require a very comprehensive study of such a system in order to be able to voice a well documented opinion. As regards to the short wave DRM technology now in use , my opinion can be summarized in two aspects: One, the transmitters used for broadcasting DRM short wave signals are evidently not well suited for operating on that mode, and Two: the lack of receivers in general, and of at least medium priced receivers in particular is making DRM a quite useless effort, and for station managers a real waste of their budgets .... More radio hobby related topics in a few seconds, when Dxers Unlimited's mid week edition continues... I am Arnie Coro in Havana ....... Happy hams all along the Cuban archipelago, because the number of people that passed the amateur radio license test during the weekend was really impressive. One of the reasons of the very high number of high marks has to do with the excellent textbook that was written and printed after the last National Convention of the Cuban Radio Amateurs Federation and the creation at each Radio Club of a teaching committee that took the task of giving classes to the newcomers to the hobby, so that they will be able to succesfully pass the test. For third class licensees, the Morse Code test is now non excluding as it used to be... it just adds or subtracts a few points to the overall test mark... For all class of licenses the top speed required now is just 5 words per minute, and my personal impression is that in the near future the ham radio exams will simply drop the Morse code, and ask you more digital computer modes related questions... Item four: Low sunspot count doesn't mean good AM broadcast band propagation as some people may think... You may be seeing an almost zero sunspot count while a high speed solar wind stream is impacting the Earth, producing a lot of ionospheric noise and even a magnetic storm... Item five: Just fixed a defective Kenwood FM 2 meter band transceiver... and I don't really know yet where the problem was located... The "fix" consisted in going trough each and every soldering point of the rig with high quality low melting point solder and a lot of patience... The "repair" was suggested by a website that provides information about the repair of amateur radio equipment... So, if you find a broken down Kenwood FM 2 meter band transceiver of between 1990 and the year 2000, chances are that its defect may be identical, poor soldering connections especially at the ones that link one side of the printed circuit board to the other side...After the soldering session that took more than an hour and a half, the rig came back to like with excellent sensitivity , and also with full power output... so far, after two weeks have passed, the radio continues to work nicely, so it was obvious that no component was actually damaged or out of parameters, just poor quality control at the factory that allowed those units to escape despite a soldering machine problem... ..... Si amigos, we do QSL, and we do reply your radio hobby related questions, no matter how difficult that may seem to you and to us too... ASK Arnie is the section of Dxers Unlimited, devoted to answering your questions , like this one sent by listener David from the Upper Michigan Peninsula... Dave asks Arnie what can be done to remove the static electricity that accumulates on his wire antenna , especially during very dry and windy days... Well amigo David, if your antenna is just used for receiving, it's very easy to solve the problem by installing two carbon resistors of about two thousand ohms each in parallel, and then connecting them between the antenna and ground... The resistors will act as a permanent path to ground that will bleed off the static so that it will never reach a high voltage... If your antenna is used for transmitting then it is another different story, because you will need a special device that is installed between the transmitter and the antenna, and is also connected to ground. This device has the property of ionizing the gas inside it after a certain critical voltage level is reached, so you must use the proper one according to your transmitter 's output power... I prefer to use a carefully calibrated spark gap between the antenna and ground... Because that one I can monitor easily , something that can't be done with the gas discharge protection devices... For all practical purposes there are two approaches when dealing with static electricity building up... One is to keep the antenna permanently connected to a ground systemwhen not in use, and the other is to when the antenna is in use, keep discharge resistors of gas discharge devices connected to ground. Not too long ago I was asked by a local radio amateur to take a look at his HF transceiver that had loosed a lot of sensitivity.... and all we found was a dead MOS FET input amplifying device, possible due to a local thundertorm, as my friend recalls that after the storm the radio had lost it usually very good ears !!! It took about an hour to change the radio frequency amplifier and readjust the front end a bit... By the way there are many somewhat old, but certainly still in good condition to restore back to full operational capabilities hanging around all around the world, as the "art" of fixing electronic equipment is now something of a lost thing of the past, as no one even attempts anymore to fix those radios because the extremely high cost of specialized labor... After a four or five hours long repair job, you may be charged for labor more than the actual cost of a new rig !!! And amigos, I am not kidding !!! I have received many e-mail message and letters asking what to do with broken down receivers and transceivers in need of repair, as th cost seems to be astronomical... .... Antenna, antennas, without antennas, radio won't exist, and every day someone seems to come out with a new idea on how to design a new antenna system... Some of those ideas are esoteric and meaningless, like the now ill fated CFA or Crossed Field Antenna, that seems to be more of a scam than anything else. But also from time to time someone comes out with a good idea, or a modification to an already existing antenna... One of the best examples is the FOLDED GROUNDED MONOPOLE,that is so succesfully used nowadays by AM broadcast band stations to replace the series fed isolated from ground vertical radiators. Using the folded grounded monopole has many advantages for the AM stations, among the the fact that damages from lightning strikes are much less , and also that they can now rent tower space to other users of the radio frequency spectrum , like cell phone systems and microwave relays. Radio amateurs have been very slow in picking up the idea of the folded grounded monopole vertical, despite the fact that it is very easy to implement, and provides nice bandwidth. As a matter of fact, AM stations have converted existing antennas to the folded monopole with very little investment and in a very short time. Here in Cuba many AM broadcast stations are succesfully using the folded grounded vertical monopole antenna and some of them are operating with diplexers, feedin two transmitters on different frequencies to the same antenna system, something that saves a lot of resources. ...... Dxers Unlimited's mid week edition continues now with more comments from listeners about the terrible effects of poorly adjusted DRM transmissions... According to several reports received here, signals up to thirty, yes you heard it right, thirty , three zero kiloHertz wide have been reported on some of the DRM transmissions, making reception of stations located up to thirty five kilohertz away from the poorly adjusted DRM broadcast very difficult indeed. I think it is up to the telecommunications authorities of the nations where the affected stations are located to file up the corresponding complaints to the offending broadcaster's telecomms administration, so that approppriate action can be taken. Discussing this excessive bandwidth problem with one of Cuba's top most broadcasting engineers, he told me that , in his opinion, had to do with the fact that the DRM technology requires that the transmitter be capable of a very high degree of linearity, and at the same time be able to manage a very wide margin of peak to average power ratio. He then added that old transmitters used for standard AM type broadcasting are certainly not capable of handling the DRM requirements... If you , as a regular listener of short wave broadcasts hear a rush type noise that seems to blanket your favorite station reception, be almost sure that a DRM transmission is taking place nearby without due regard and respect for your station from the broadcaster using DRM. If you notice this kind of problem, send an e-mail to [EMAIL PROTECTED] Now, as always at the end of the program, here is Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast ... Solar activity at very low level, but two small sunspot are now in sight, after days with a spotless Sun, solar flux hovering around 75 units, and the A index has moved down now... after the solar wind speed has diminished. Good chances for VHF E skip openings during the next two weeks , so keep watch on the low band TV channels where they are available, and on the amateur bands, watch for very short skip on twenty meters, as both are good indicators of ongoing Sporadic E openings... Send me your signal reports and comments about the program to [EMAIL PROTECTED] or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba Havana, Cuba ---[Start Commercial]--------------------- Preorder your WRTH 2007: http://www.hard-core-dx.com/redirect2.php?id=wrth2007 ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed and/or modified under the conditions set down in the Design Science License published by Michael Stutz at http://www.gnu.org/licenses/dsl.html
