Re: [HCDX] Dxers Unlimited's script weekend edition 17-18 Februrary 2007

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

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition for 17-18 February 2007
By Arnie Coro
Radio amateur CO2KK

Hi amigos radioaficioanados around the world and in space, welcome to 
the weekend edition of your favorite radio hobby program , I am Arnie 
Coro in Havana, and here is item one… its related to the ongoing solar 
cycle’s minimum… When  HF propagation conditions are poor, then it’s 
time to enjoy many other aspects of the radio hobby, like homebrewing 
receivers , installing new VHF and UHF antennas, and even attempting to 
do some interesting radio astronomy experiments like listening to planet 
Jupiter’s rather easy to pick up signals on frequencies within reach of 
many short wave receivers and using very simple , easy to install 
antennas . If you happen to have an amateur’s band Yagi antenna capable 
of operating on the 15 meters or 21 megahertz ham band, then you will 
certainly be able to pick up Jupiter’s natural radio signals regularly… 
By the way, they sound like waves slowly moving over a sandy beach, and 
going back again…
Stay tuned for more radio hobby related information and know how coming 
to you from Havana. I’ll be back in just a few seconds amigos !!!
…..
Si amigos, sure, after many years of enjoying the radio hobby, I am 
still fascinated when setting the alarm clock for two o’clock or three 
o’clock in the morning and getting ready for yet another medium wave AM 
broadcast band Dxing session… Last evening was no exception, except that 
I didn’t need an alarm clock, because my little two years old baby 
Claudia likes to wake up around that time asking for her milk bottle… 
Roxana my wife woke up first and was already  changing the baby’s diaper 
when my new super-regenerodyne receiver was already picking up its first 
DX station, one that I use as a propagation beacon, because I know the 
power its delivering to the antenna and its location East of my QTH 
gives a very good idea about ionospheric absorption especially as 
sunrise approaches. It is Radio Rebelde’s 600 kiloHertz relay in San 
German, Holguin province of eastern Cuba… The signal coming in from this 
station was excellent, so I moved up to the top end of the AM broadcast 
band, but checking the local time, and making the conversion to UTC, I 
sadly realized it was already too late to try to pick up European 
stations… Maybe tomorrow, as almost ideal AM broadcast band propagation 
conditions will almost surely continue, little baby Claudia will wake up 
a little earlier, and I will be able to pick up at least one or two 
Europeans, that by the way, for your information, in case you are not 
familiar with that fact, operate on a 9 kiloHertz channel spacing, so 
their presence is many times learned by the whistling heterodynes caused 
by their carriers beating with stations in the Americas that operate on 
a 10 kiloHertz channel spacing. The new super-regenerodyne, especially 
built for the low ebb of the solar cycle, runs the regenerative detector 
in the frequency range from 100 to 500 kiloHertz, so tuning up the whole 
AM broadcast band required splitting it into3 segments, starting on 520 
kiloHertz and ending slightly above 1700 kiloHertz. Lacking the quartz 
crystals for the frequency conversion, I used a highly stable Franklyn 
type oscillator for the first conversion with excellent results. To 
receive the segment from 520 to 920 kiloHertz, the Franklyn oscillator 
works at a fixed frequency of 620 kiloHertz, something that is not a 
very nice solution because it completely blocks reception on several 
channels… The segment from 920 to 1320 kiloHertz, requires the local 
oscillator of the first conversion to operate on 1020 kiloHertz, and 
here again several channels are blocked. The third and last segment of 
the AM band , from 1320 to 1700 kiloHertz requires the local oscillator 
to operate on 1420 kiloHertz, so I have the same problem with several 
channels lost to the presence of the local oscillator signal within the 
passband of frequencies that I want to listen to… But, let me say that 
despite this design flaw, of which I was fully aware, the sensitivity 
and selectivity of this AM broadcast band receiver is simply amazing. 
The operation of a regenerative detector at frequencies as low as 20 
kiloHertz makes the control of regeneration as smooth as one can 
imagine, so you can operate the detector at its highest selectivity 
setting allowing for single side band reception, something quite useful 
when hunting for transatlantic AM band DX stations. Now that I have 
obtained such an interesting experience with this radio, a new one will 
be built, in which the AM broadcast band will be up converted to the 
frequency range from 28 to 29.2 megaHertz…, using a specially designed 
quartz crystal controlled converter and a double balanced mixer… The 
“tail end” of this up converter is going to be my single band 10 meters 
transceiver, that due to the diminishing solar activity will see little 
use to communicate during the next several years, but could play a 
useful role as yet another AM DX receiver tail end… By the way, the 
upconversion needed a single quartz crystal for the local oscillator, 
that fortunately happened to be in my junk box !!!
…….

Yesterday I made contact with two long time ham radio friends, one was 
vacationing in the Caribbean and talking to me on 17 meters from the 
balcony of his hotel room, using a helically wound antenna just 2 meters 
high… and the other was enjoying a stay with one of his daughters that 
lives in a farm and was using a real long wire antenna, no less than 400 
feet long… We had very nice QSO’s, and for those of you that are not 
familiar with that term, its an abbreviation for a two way contact used 
by the early days radio operators… I’ll have a bit more time to be on 
the air during the next 10 days or so, and expect to have many more 
opportunities of meeting with ham radio operators around the world …The 
best bands for making contacts during the winter season are, 17 and 20 
meters during local daytime hours, and 40 and 80 meters during your 
local evenings, but we may see brief openings on 15 meters  too.
…..


Now here is the very popular technical topics section of the program… 
Operating your radios from rechargeable batteries requires taking care 
of them, so that they will really last the number of expected cycles. It 
is amazing to see how expensive rechargeable batteries are sometimes 
turned into worthless units because their owners didn’t take proper care 
of them… Gaining knowledge about the characteristics of nickel cadmium, 
nickel metal hydride or lithium ion rechargeable batteries is very 
useful , because if you apply the know-how, your batteries will live a 
lot longer. My advice is that you simply forget about nickel cadmium 
batteries, and buy, from now on, nickel metal-hydride units,as they can 
provide more operating time on the same size of battery, and also don’t 
have the so called memory effect of the nickel cadmium old technology 
batteries. Recent advances in the design of chargers for the nickel 
metal hydride cells make possible a much longer useful life of those units.
And don’t forget that the lithium-ion batteries do require a special 
charger and can not be charged with any other type of charger, as they 
may be destroyed or even explode if improperly charged…
Also, let me add that I prefer to run my receivers, whenever possible, 
using batteries, as by using them, noise coming in from the power line 
is simply reduced to zero !!!

…….
Receiving here lots of nice e-mail messages, post cards and letters 
here, and also a few FAX letters too. Keep them coming amigos, is always 
nice to read your comments about the program that are full of new ideas 
to make Dxers Unlimited a bit better on every new edition.
Item three: The ultra compact dipole antenna that I talked about here 
recently edition here on Dxers Unlimited continues to bring in lots of 
questions among listeners around the world. The most frequently asked 
question about this topic, was if this could be designed as a broadband 
antenna, and the answer amigos is NO, the ultra compact dipoles designs 
are narrow band antennas, that most be built for operating on a single 
amateur radio band if you want to transmit with them, but that may be 
used for short wave listening over a much wider range of 
frequencie.Amigos Lester, Charlie and Albert, frequent Dxers Unlimited 
listeners asked thee possibility of using the compact dipole in a 
vertical configuration to obtain a lower radiation angle ... Si amigos, 
yes, you are right, the compact inductively and capacitively loaded 
dipole is ideal for installing it in a totally vertical or sloping 
configuration. As a matter of fact, I have just recently seen a 
commercial antenna design that follows that idea pretty closely...But 
personally I prefer to use this antenna as a very efficient sloper, 
because it provides a small but significant gain in the direction 
towards  which the wire is sloping.
The ideal sloping angle is between 30 and 45 degrees, in order to form 
the best possible directional pattern with the ground reflection...
……
A quick reply to a question sent to our ASK ARNIE section of the show… 
Yes amigo Craig from Toronto, Canada, you are absolutely
right in your analysis… not all compact fluorescent energy saving
light bulbs are created equal, in other words you may install new ones 
that are extremely quiet , that is they almost don’t generate radio
frequency interference at  all,while others similarly rated may wipe our 
short wave reception far away from where the energy saving light bulb is 
installed… And don’t be surprised with some commercial brands of energy 
saver fluorescent causing problems with your TV set and VCR remote 
controls too… In more than one occasion I have seen remote control 
systems that work using infra red signals go crazy when an energy saver 
light bulb was installed near the TV and VCR … Things returned back to 
normal by just turning the light OFF !!! Of course that the only cure 
for the problem is replacing the energy saver with a better quality one, 
or even better yet, try one of the new Ultra Bright Light Emitting diode 
lamps, but check that they don’t use a switched mode power supply inside 
the bulb, before buying it…

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