Radio Havana Cuba
Dxers Unlimited
By Arnie Coro CO2KK
Hi amigos radioaficionados, welcome to the mid week edition of Dxers Unlimited at a moment when the 2750 megaHertz solar flux is very near to the lowest ever recorded levels since 1947, when Professor Arthur Covington of Canada started to monitor the Sun at microwave frequencies on a daily basis. Solar flux was at 65 units , a value very close to the minimum ever recorded. So, as may realize the daytime maximum useable frequency curve is showing a very slow build up, and is peaking at extremely low values, with the typical highest possible frequency propagating via the F2 layer not reaching higher than about 20 to 24 megaHertz and that´s for very short periods of time.
More about the very low solar activity and how it may be actually enhancing sporadic E layer propagation at the end of the program.
Item Two: Handling the daily influx of e-mail sent by Dxers Unlimited listeners around the world is quite a task amigos ! But I do enjoy it a lot, because some very interesting topics are suggested, questions asked allow me to provide useful answers not only for the person or persons who sent the question, but also for many other listeners of the program… You can send your signal reports , QSL requests for station verification of reception radio hobby related questions , and comments about the show. Send them to inforhc at enet.cu, again inforhc at enet.cu... Or VIA AIR MAIL, send your postcards and letters to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Now here is
Item Three of the mid week edition for Tuesday June 17 and Wednesday June 18th UTC days…Software defined radios are now becoming more and more both builder and user friendly… Several kits now available provide prospective homebrewers with a much faster way of assembling a software defined radio than what may be possible by attempting to buy or ask for all the required electronic components to make a Software Defined receiver or transceiver… For advanced radio hobbysts familiar with assembling electronic projects, I think that experimenting with software defined radios will provide a lot of very interesting results, and open up new ways of enjoying our hobby.
Item Four: Indoor antennas are useful when there is bad weather and you do need to communicate. More about indoor antennas for emergency communications in just a few seconds, when Dxers Unlimited´s mid week edition continues after a station ID.
I am Arnie Coro, radio amateur CO2KK in Havana…
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Si amigos ! You are listening to the mid week edition of your favorite radio hobby program, Dxers Unlimited with yours truly Arnie Coro … Here is now our technical topics section on indoor antennas for emergency communications .
Indoor antennas are no match to well installed outdoor ones, but under some very special circumstances, your only option for providing the antenna required by your radios may be to carefully select the best location inside a building and proceed to install an indoor antenna system.
I have seen extremely well designed indoor antennas that provide those who use them with very effective reception and transmission. In order to make this description a bit more flexible, my concept of an indoors antenna system includes those that are installed in balconies and attached to balcony rails.
At CO2KK , my amateur radio station, there are not one, but five different indoor antennas that see almost constant daily use.
Let me describe them for you in detail:
Number One :The telescopic whips used on my three portable multi-band receivers…
Number Two: A dual band 2 meters and seventy centimeters vertical monopole antenna that is used for monitoring the two local 2 meters FM repeaters, and also to make local contacts on that band and on 70 centimeters.
The number Three indoor antenna is a MOXON rectangle for the two meters band that is installed , when needed, on a camera tripod so that it can be aimed in the direction of the station or repeater I want to contact.
Number Four indoor antenna is a one meter diameter 19 millimeters tubing copper loop…Yes, it is tuneable magnetic loop that covers from 10 to 30 megaHertz for reception and that allows transmission on the 30, 20, 17,15 , 12 and 10 meters band, so this is in my opinion the most compact six band antenna that one can imagine. It is manually tuned, and YES, you have to retune it everytime that you need to shift frequency by even a few kiloHertz , but it allows me to be on the air , especially on 10 meters when the band is open and I don´t want to connect the outdoor beam because the presence of thunder clouds in the sky.
Finally my Fifth but not less important indoor antenna is another magnetic loop optimized for the 6 meters or 50 megaHertz band and that is kept close to a picture window. I use this smaller loop to monitor for possible 6 meters DX during the sporadic E season, that here in Cuba happens to coincide with the peak of the summer thunderstorm season….
An interesting fact about the use of indoor antennas is that their performance is very much related to the type of material used for building your home. An antenna located inside an attic that is high above the ground and has no metal elements inside its walls, will show a much better performance than an identical system that is installed inside a room of a house built with brick walls and a reinforced concrete roof. Signals , both the ones to be received and those transmitted will suffer from severe attenuation , reaching values of many decibels as compared with an identcial antenna inside the wooden wall and roof attic !!!
Please remember that just a small antenna is better than a telescopic whip or a rubber duck helically loaded whip… something that applies for both short wave and VHF operation.
Even a short length of hookup wire attached to your portable radio´s antenna and placed as near as possible to a window, or even just dropped from the window or balcony will make quite a difference , although careful placement of the indoor or semi-indoor antenna is necessary in order to reduce the pick up of interference from home appliances of all types…
If you need advice on installing an indoor antenna , just drop me an e-mail and I´ll try to provide you with advice according to
the frequencies involved and the type of building .
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This is Dxers Unlimited´s mid week edition and now here is ASK ARNIE, la numero UNO, the number one most popular section of the program… Listener Gabriel from Atlanta , Georgia, USA, wants to know what´s the best time or times of the day to pick up Sporadic E skip signals… He says in his e-mail: Arnie, I agree with you that HF , that is short wave propagation is worst than ever… Having listened to international broadcasts for the past 30 years, I have never before experienced such poor propagation conditions. Recently I became interested in FM broadcast band Dxing, one of those 84 ways of enjoying the radio hobby that you have described. And Gabe continues his e-mail describing his nice vintage Scott FM tuner that has an ECC88 cascode RF amplifier and outperforms his two other solid state FM receivers in a very significant way… Gabe says that he is using two antennas for FM Dxing, one is a commercial log periodic fed with 300 ohms low loss foam dielectric line, and the other antenna was built following instructions provided in one of my articles about the TTFD published by CQ-VHF Magazine many years ago.
Gabe ends his nice e-mail message with the question that I repeat now ¨¨ Arnie, what are the best times for Sporadic E summer DX ¨¨… Well amigo Gabriel,or Gabe as you like to be called, it is an interesting fact that Sporadic E propagation events can happen at anytime of the day, but they do show ,during the summer months a much higher probability of happening from about 9 in the morning or a little earlier local time, to about an hour before noon, and again, there is another period of higher probability of E skip from about three to four o´clock in the afternoon to just after sunset, again, I am talking about local time…
But be aware that in my more than 50 years of Dxing via sporadic E skip, I have made two way contacts on the 10 and 6 meter bands at two or three o´clock in the morning, as well as at one o´clock in the afternoon, when normally you don´t see E skip happening… By the way , we may soon be loosing one of the best sources of early warning of Sporadic E skip events , at least here in the Caribbean, and the USA, when next year the analog TV stations in the United States of America will shut down, and be replaced by digital technology signals !!! so for those Dxers, both TV and amateur radio VHF enthusiasts that don´t have bought a digital TV or a converter box, the familiar pattern of venetian blinds atop a fringe area TV channel two or even a local powerhouse when the band is really open will be a thing of the past…
That´s why amigo Gabe, amateur radio 10 and 6 meter band beacons will become much more important for us to learn when E skip is present !!! I hope that this reply answers your question and congratulations on your nice FM broadcast band Dxing setup amigo !!!
FM broadcast band Dxing is quite a challenge for people living in metropolitan areas where cross modulation problems are a tremendous problem… but those of you living away from the big cities and having a good receiver or FM tuner can still enjoy FM broadcast band DX events both via tropospheric ducting or Sporadic E.
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Technical Tips, yes Technical Tips here at Dxers Unlimited´s mid week edition… For your radio hobby enjoyment… Here is the first one: Whenever you buy or get a free piece of old equipment, be it full of vacuum tubes or solid state devices… NEVER, , again NEVER connect it to the power line if it is an AC operated radio, before making a very detailed visual inspection INSIDE… Look for electrolytic capacitors that may be leaking , signs of overheated transformers, and in the case of equipment in long storage signs of mildew and humidity damage.
After the visual inspection, if no signs of those typical problems are found, then phase two of a start up procedure for gear in long term storage will be to carefully test all the electrolytic capacitors using an Equivalent Series Resistance or ESR meter… go one by one, be patient and you will be rewarded usually with the detection of one or more capacitors that will need to be replaced… Proceed to replace them, and when powering up the equipment use a variable voltage autotransformer to carefully provide AC to the radio… I usually start with 25 volts and leave it there for a number of hours… jump then to 50 volts and monitor the AC current drawn by the radio under the revival process…after about a day at 50 volts, it will be usually safe to raise the voltage o 100 volts and watch for any signs of overheating or excessive current drawn from the variable
voltage transformer …Just before I forget… in older vacuum tube radios, it will always a good idea to replace all the paper dielectric bypass capacitors too… a time consuming procedure, but one that will save you from having to replace much more expensive and hard to find components !!!...
And now as always at the end of the show, here is Arnie Coro´s Dxers Unlimited´s HF plus low band VHF propagation update and forecast…. Bottom low solar activity, extremely low F2 layer maximum useable frequencies, while plenty of E skip events are happening over North America, the Caribbean, Central America and Europe with some unique DX on 6 meters from half way around the world coming to the surprise of long time operators on the so called MAGIC BAND---The effective sunspot number at 15 hours UTC Tuesday was an extremely low ZERO TWO <… A close look at the Sun shows we still have the remains of old sunspot 998, but we have are seeing a sunspot group, 999. This one is almost on the sun's equator and like 998 has a a clear cycle 23 magnetic signature. The flux has dropped to a bottom low level of 65 units and the K index was lower at just 4, units at around 14 UTC Tuesday with the solar wind well over 700 kilometers per second but it's unlikely we'll have auroral conditions in the near future. Due to the higher solar wind there may be some disturbance from minor geomagnetic storming especially towards the poles.
One final note that is causing concern among solar scientists..
Unfortunately it looks like we have a lot further to go before we can be certain that we have actually reached the minimum of cycle 23 yet !!!
(Arnie Coro)
