Re: [HCDX] Dxers Unlimited's weekend edition for 22-23 Sept FEEDBACK ON THE E-MAIL DISTRIBUTION WILL BE APPRECIATED ....

["Prof.Arnaldo Coro Antich" <coro@xxxxxxx>]

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition for 22-23 Sept 2007
By Arnie Coro
Radio amateur CO2KK

Hi amigos radioaficionados anywhere were you are ! Maybe participating 
in a radio amateur DX expedition at a remote island , or perhaps 
listening to my show with your kitchen radio as amigo Craig in Ottawa 
often does… Or you may be soldering the last two or three connections to 
your brand new regenerative receiver, that in a few seconds will start 
picking up, hopefully, many short wave stations. You may be one of the 
very few radio amateur operators that have ever called CQ from a space 
ship… or one that has experienced the brute force of a hurricane when 
trying to fix up an antenna in the middle of a storm… Radioaficionados 
around the world enjoy this hobby in many different ways, and your 
budget may be big or small, but as you all know well, radio is a very 
enjoyable hobby , an excellent way of spending whatever little spare 
time we may have…
Join me for the next sixteen minutes, at this edition of Dxers Unlimited 
that will provide you just now with an update about solar cycle 23, the 
one that has really defied all forecasts and keeps on moving along at 
zero sunspot count for many days … Yes amigos, scientists will now have 
to face the reality that solar minimum is still very much with us, and 
that March and April of 2007 were not the two months of minimum solar 
activity for the present cycle… Item three: imagine a receiver that is 
powered from a single 1.5 volts battery… now , imagine still further 
that this receiver uses very, but very little current… and despite those 
two solid facts, the receiver is capable of picking up amateur radio 
stations at least two or three thousand miles away. Add to that the fact 
that the circuit is extremely simple, and that in the still experimental 
prototype, just four rather common transistors are used… The cross 
coupled regenerative detector circuit in a Wheatstone bridge balanced 
configuration is the proper name for this circuit, that has already 
stirred up a lot of building activity among the very enthusiastic 
membership of the YAHOO Regenerative Receivers list…
The circuit of this receiver is still under development , but results 
achieved so far have proven to be really amazing…
Two transistors connected in a cross coupled Wheatstone bridge balanced 
regenerative detector are provided with a well designed antenna input 
filter and a very smooth acting regenerating control.
Of course that some precautions must be followed regarding the circuit 
actual layout… For example the coil used in the tuned circuit must be 
wound symetrically and the coupling coil from the input bandpass filter 
must be placed exactly at the center of the two windings into which the 
coil is split to give way for the input coupling.
If you really are looking for optimum results from this circuit then my 
advice is that you spending some time matching the two silicon 
transistors used bo build the detector is a worthwhile effort. 
Transistors can be matched for direct current gain quite easily , 
because you don’t need to know the actual current gain of the devices, 
because what we are looking for are two transistors that have almost 
identical gain.
As regards to the audio amplifier section, it can be built with just two 
transistors, or you can add a third stage to further boost the audio 
output… So you end up with a receiver that has a two transistors 
regenerative detector and a two or three transistors audio amplifier 
that feeds a pair of low impedance headphones.
This type of receiver is a lot easier to assemble by a beginner than 
even the simplest of direct conversion or
Superheterodyne receivers…The parts count is pretty low, so assembling 
this little radio won’t cause financial problems to your pocketbook !!! 
  Stay tuned for more radio hobby related items coming up in just a few 
seconds when Dxers Unlimited’s weekend edition continues…

………
Si amigos , yes my friends, oui mes amis , you are listening to Radio 
Havana Cuba , and here is our solar update, that for the first time in 
many, many years shows that during fifteen consecutive days optical 
observations done by the world’s most important observatories have 
registered absolutely no sunspots… In other words, for the past two 
weeks the sunspot count was ZERO, and it is expected to remain at that 
level for a few more days. Together with the zero sunspot count , we are 
receiving information about microwave radiation from the Sun, that is at 
the minimum possible level ever registered at the 10.7 centimeters 
wavelength… With zero sunspots and solar flux between 65 and 70 units, 
the daily maximum useable frequency curve moves up very slowly after 
local sunset, and it never reaches frequencies above 25 megaHertz, while 
at the same time the highest possible frequencies that do propagate for 
a few hours every day, rarely if ever move above 18 or 19 megaHertz… As 
a good friend of mine that has lived through solar cycles 19, 20, 21, 22 
and now 23, has told me this week, this extremely low number of sunspots 
is an unprecedented event… “ Arnie, - he said – ever since I started to 
listen to short wave stations when I was a teenager way back in 1956, 
never before HF propagation conditions have been so poor “, and yes 
amigos, I fully agree with my friend, as yours truly also started to 
listen to the short wave bands during the mid nineteen fifties …
Now here is our technical topics section, that is becoming more and more 
popular according to the e-mails sent to arnie@xxxxxxxxx Today this part 
of the program will be devoted to the switched mode power supplies that 
are becoming now so popular for both amateur radio transceivers and all 
types of computers that require to be powered from the AC mains, or that 
need the batteries to be recharged periodically.  The big problem with 
switched mode power supplies is that they can be designed and assembled 
according to very different criteria, that cause them to be very useful 
in some instances and terrible for radio applications in others. 
Switched mode power supplies when properly designed and built provide 
excellent voltage regulation, and they also have built in protection 
against high voltages and current overloads… They weight a lot less than 
the typical linear transformer powered units, and that’s one of the main 
reasons of their widespread use. But, be aware when buying or building a 
switched mode power supply… You can end up with a useless power supply 
because the unit may generate such high level of radio frequency noise 
as to make your reception impossible on some bands, and very difficult 
in others… The most recent switched mode power supply designs , 
especially aimed at using them for radio applications, provide extensive 
shielding and radio frequency filtering… that can be so good as to be 
practically impossible to detect the presence of noise from the 
extremely low frequencies all the way up to the high VHF band that is 
considered to be the top frequency range where the switched mode 
supplies can still generate annoying noise that will interfere with 
radio reception.
A well designed and built switched mode power supply will be more 
expensive, will be enclosed inside a steel box, and will have radio 
frequency filtering at the power line input and also at the direct 
current output . By using higher quality components and higher switching 
frequencies, interference caused by these power supplies can be 
minimized, making them a very attractive option for radio amateurs 
traveling with their transceivers…and the same criteria are true for 
laptop and notebook computers that nowadays are considered to be 
essential for the operation of any DX expedition…
……
Yes, we do QSL, we do verify reception reports sent to arnie@xxxxxx, or 
VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba , and now 
here is our antenna topics section here at the weekend edition of Dxers 
Unlimited…The two meters amateur band is by far the most popular one 
worldwide, and this is due to the existence of relatively low cost, 
compact and energy efficient portable and mobile FM transceivers… In 
many instances, commercial equipment can be adapted for amateur radio 
use, making possible to buy a very nice FM multi-channels transceiver at 
very low cost. But, those radios either come with a very simple 
helically wound short antenna for the handie-talkies, or with no antenna 
at all in the case of mobile or desktop transceivers. That’s why 
amateurs can save a lot of money and learn also a lot about antennas by 
homebrewing them for the 2 meters FM band. You can make a much more 
efficient antenna for your handheld FM transceiver using readily 
available materials, and some of the more popular directional antenna 
systems for base stations are also easy to build and to adjust. There 
are even some antenna designs that , if built to exact specifications 
won’t need any additional adjustment, that’s the case of a two element 
YAGI system than , as I have just said , if built exactly as explained 
by its designer, will produce a very clean radiation pattern and the 
impedance at the feedpoint will be very near 50 ohms, so there is no 
need for any matching systems that require adjustments with the use of a 
VHF standing wave ratio meter. The other antenna that shows a feedpoint 
impedance very near 50 ohms if built following the design formula is the 
so called MOXON Rectangle, a compact two element parasitic array, that 
is becoming a favorite among not only two meter band users, but also as 
an excellent beam antenna for other bands… You can calculate the MOXON 
antenna dimensions with a very easy to use computer program that allows 
you to design it with whatever materials are available locally… Si 
amigos, sure my friends, the two meters ham band is the world’s most 
popular one, and you can enjoy it much more by adding external high gain 
antennas to handheld, mobile or fixed stations.
And now just before going QRT,  to underscore, solar activity at rock 
bottom levels for the past two weeks , with zero sunspot count and solar 
flux all the time below 70 units, something that scientists expect to 
continue for at least one more week, when maybe, and I repeat, maybe a 
new sunspot active region may signal an end to this extremely long 
period of no activity… VHF low band propagation will improve for areas 
where transequatorial signals are usually heard at this time in the 
Northern Hemisphere… Hope to have you listening to our midweek edition 
next Tuesday and Wednesday UTC … and don’t forget to send your signal 
reports and comments about this program to arnie@xxxxxx 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
Hard-Core-DX@xxxxxxxxxxxxxxxx
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