Wednesday, January 26, 2011
DXers Unlimited January 25-26
Radio Havana Cuba
Dxers Unlimited's mid week edition for Tuesday-Wednesday January 25-26 2011
By Arnie Coro, CO2KK
Hi amigos radioaficionados... listening via short wave and also by means of our streaming audio from www.radiohc.cu. I am your host Arnie Coro, radio amateur CO2KK now ready to start the mid week edition of your favorite radio hobby program...
Here is item one... solar activity at low levels once again, and the daily solar flux figures moving down from a very weak peak of 88 units ... as anyone monitoring the HF bands will easily find out, the low solar activity continues to limit the chances of short wave propagation on frequencies above 20 megaHertz, even during the best times of the day at any given location.
Solar cycle 24 continues to show very weak activity .
Item two: You have questions and I do my best to answer them... Yes amigos, every day the e'mail brings in most interesting questions from listeners all around the world... Like for example the one sent by amiga Alice from Edinburgh , Scotland.
Alice is a newcomer to short wave listening who started to play with her brother's new digital portable radio... discovering that she could pick up stations from all over Europe, Africa and Asia, but very few stations from the Americas... Alice asks in her e'mail why it is not possible for her in Scotland to pick up stations from other countries in the America besides Cuba, Brazil and Colombia and Venezuela.
Well amiga Alice, first of all, let me tell you that at this moment when you pick up Radio Nacional of Venezuela's Canal Internacional , you are actually listening to a short wave transmission originating in Venezuela, but that is been broadcast from Cuba, by means of a relay station agreement between the two countries.
Venezuela is now in the process of installing its first international broadcasting transmitting station , from where it will be originating programs also in the near future. Relaying international programs is a well established practice, that nowadays makes use of both satellite and submarine fiber optic cables to send the signals from the studios of the originating station to the remote transmitter site located in another country.
The relay transmissions amiga Alice, will reach the target audience with much better signals due to the proximity of the remote transmitters site... For example, Radio China International sends its signals via satellite to Cuba, where Radio Cuba transmitters relay them to North and South America as well as to the Caribbean...
Now I am sure that you will understand more about relay stations, and to answer the other part of your question, I will be back in a few seconds after a short break for station ID. I am your host Arnie Coro in sunny Havana, Cuba...
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes amigos, we do QSL, we do send QSL cards to listeners that report our programs, and this is done absolutely free of charge... Now part two of the answer to amiga Alice of Edingburgh, Scotland in the UK...
Besides Radio Havana Cuba, and Radio Nacional of Venezuela , using a rather simple short wave receiving antenna, you may be able also to pick up several stations from Brazil, as well as Argentina and Chile. Other South American countries are also on the air , especially on the 60 and 49 meters bands, but the stations are using low power and simple low cost antenna systems because they are intended to provide local or regional coverage.
When HF bands propagation conditions are good, you may pick up several of those low power stations from Peru, Bolivia , Ecuador , Colombia and Mexico... reception of those low power short wave broadcasts , mainly on the 60 and 49 meters band, but also at times on 31 meters this will usually take place very late in the evening your local time.
Item three: Answering another question sent by listener Mark from Toronto, Canada... Mark found a radio related device that is marked outside as a PRESELECTOR, and he Asks Arnie in his e-mail, if that piece of equipment is of any useful value.
Mark tells me that the preselector has a band switch and a dial, just like a short wave radio, but when he lifted the hinged top lid, he found that there are only two vacuum tubes inside, one is a rectifier, Mark also tells me, d the other one is a 7 pin miniature tube stamped on the glass with the markings 6AK5 , dash 5654 ...
Well amigo Mark, let me tell you that the PRESELECTOR that you now own, after the buy at the yard sale, is a piece of radio equipment that was popular in the early days of the radio hobby, when low cost receivers didn't had enough radio frequency amplification.
Adding the preselector between the antenna and the receiver, boosted the reception more or less significantly... the increase in signal strength was much more noticeable above 15 megaHertz , so radio amateurs on a tight budget will add a preselector to their receivers when they wanted to improve the performance on the 15 and 10 meter bands.
For all practical purposes, your well preserved preselector will not improve the performance of a modern table top receiver, but it could boost the reception and also clean the presence of image signals when connected between the antenna and a low cost portable solid state receiver ...
Now item four of the mid week edition of Dxers Unlimited amigos !
Amateur radio enthusiasts here in Cuba will be participating in a nationwide contest to be held on the 27th and 28th of this month of January to pay homage to Cuban national hero Jose Martí, whose 158 birthday will be celebrated on the 28th.
The contest will take place on the 160, 80 and 40 meter bands, and stations of the three categories of licenses are going to participate. This national contests are used also as a practice drill for emergency communications , as a large number of portable stations are deployed at historical sites. Those portable stations provide the contest participants with extra points, so everyone tries to work them, both on
SSB voice and on CW, as this contest encourages the use of both voice and Morse code radiotelegraphy communications.
The winners in each of the categories will receive diplomas and also several prizes that will be awarded by the Cuban Federation of Radio Amateurs.
Amigos your are listening to the mid week edition of Dxers Unlimited, that is on the air just after the half hour news segment of our daily programs. Our weekend edition is on the air Sundays and Mondays UTC days, just after the top of the hour newscast. Here is now more radio hobby related information coming to you from Radio Havana Cuba...
For both short wave listeners and amateur radio operators the installation of an adequate antenna for obtaining best results within the frequency range from 3.5 to 29.7 megaHertz is quite a challenge to say the least. City dwelllers, and especially those who live in apartment building face a great challenge when trying to listen or to operate, in the case of amateur radio hobby enthusiasts, because of the severe restrictions regarding the installation of external antennas.
High rise apartment buildings are an ideal location for VHF, UHF and Microwave operation if you happen to be living at one of the top floors, but are quite useless for that purpose if your apartment is located close to the ground requiring the installation of a very long length of transmission line.
Even the best coaxial cables available have very high losses on the frequencies above 50 megaHertz !
But, despite all those difficulties, I very often come across a ham radio operator that with a lot of ingenuity manages to operate, for example, on the 20, 17 and 15 meters bands, using different types of antennas.
Do notice that I don't even mention the 12 and 10 meters HF bands because the size of antennas for those bands is small enough to make them fit across a balcony ... But 20 , 17 and 15 meters are certainly the most popular DX bands when propagation conditions are let's say, normal or slightly above normal, and that is why people living in housing facilities with severe restrictions as regards to the installation of external antennas, try , in the first place to put up an antenna system that can be tuned to 20, 17 and 15 meters.
One of the regular Dxers Unlimited's listeners , who is also an avid ham radio operator asked about what could be done to install an antenna for the 20, 17 and 15 meters band that could fit into his apartment's balcony that measured from one end to the other roughly 5 meters or about sixteen and a half feet. He was already succesfully operating on the 6 meters band with a half wave dipole, and also on 2 meters using a homebrew DK7ZB 5 element Yagi ... on the 70 centimeters band his DK7ZB
Yagi also allowed him to access a repeater located very far away.
His 10 meters half wave dipole brought some local contacts, and also some DX when the band is open, but as everyone now is fully aware, the 10 meter band openings via the F2 layer are very rare indeed due to the lack of solar activity.
So, here is what I advised him to do...
Number one: Start learning about magnetic loop antennas, in order to be able to make one in the near future... The magnetic loop will require the use of expensive copper tubing , buying also expensive variable capacitors and finding someone capable of doing a very good soldering using silver solder to complete the antenna. So I told amigo Bob to begin learning about the magnetic loop as it may be a very good near
future option, but in the meantime, he could build a compact short dipole antenna that will make possible to operate on the 20, 17 and 15 meters bands with rather good efficiency, and also on the 30 meters band with somewhat reduced performance.
The antenna I suggested fits perfectly into a slightly less than 15 feet horizontal space, and when fed via homebrew one to one balun and using a wide range antenna tuner has proven to provide excellent performance. One good advantage of this antenna is that it can be installed in a couple of minutes when you want to operate or listen to the radio, and likewise it can be taken down and placed in storage at a corner of the balcony !!! The good efficiency of this antenna design despite its
short length, is due to the use of two carefully built end loading spiders, that act as an effective capacitive load.
The two loading spiders are built using eight wires that are carefully soldered to a circle made of 6 millimeters or about a quarter of an inch copper tubing. Each leg of the antenna is just two and a quarter meters long and they end up connecting to the end loading spiders ... The center insulator supports a one to one balun transformer, and the antenna is fed with a short length of RG213 or RG8X coaxial cable that connects it to the antenna tuner.
Please notice that this antenna uses no loading coils, although it you want to experiment , maybe it would be interesting to insert midway at each leg a small loading coil. But so far, all our experiments with this antenna have proven that it will work quite well with a simple antenna tuner, making possible to operate on the 20, 17 and 15 meters bands, as well as on the 12, 10 and 6 meters band too. The fact that the antenna is located inside a balcony, places some limitations as regards to both the overall coverage and also limits its use to power levels not to exceed 25 watts.
But let me add that running 25 Watts to this antenna on 20 meters even under quite normal band conditions it is possible to work DX stations especially when using CW and digital keyboard to keyboard modes. If you want to learn more about this compact antenna system, especially designed for apartment dwellers, just drop me an e'mail to inforhc at enet dot cu, again inforhc at enet dot cu.
And now as always at the end of the show, here is Arnie Coro's Dxers Unlimited 's HF propagation update and forecast. Do not expect sporadic E openings until about 8 weeks or even more from now, solar activity continues to be low, and the daytime maximum useable frequencies are correspondingly low too... The night time maximum useable frequency curve continues to exhibit its usual very sharp drop just after sunset, typical of the northern hemisphere winter season.
Don't forget to send your signal reports and comments about this and other RHC programs to inforhc at enet dot cu ...
(Arnie Coro/Radio Havana Cuba)
at 6:18 PM