Re: [HCDX] Dxers Unlimited's weekend edition for 25-26 August 2007

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

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition for 25-26 August 2007
By Arnie Coro
Radio amateur CO2KK

Hi amigos radioaficionados around the world and in orbiting planet 
Earth…welcome to the weekend edition of your favorite radio hobby 
program that you are picking up under rather difficult propagation 
conditions due to a combination of very low solar activity and the 
effects of a disturbing high speed solar wind impacting into the Earth’s 
magnetosphere… But, if you stay up late, your lack of sleep will be 
rewarded by much better propagation conditions than those prevailing 
during your local daylight hours, as we are still in the summer, when 
that happens due to the high temperatures reached by the ionosphere in 
the sunlit hemisphere… Item two: Despite the poor propagation there are 
small windows when somewhat better HF conditions make possible picking 
up DX stations. For example, Friday morning, while testing my new fan 
dipole that was provisionally installed at just 3 meters, that’s about 
10 feet above my reinforced concrete roof, I tried to check in on the 
14245 kilohertz DX net, and despite the high noise level, and also high 
ionospheric absorption about an hour before local noon, I was able to 
work a station in California and another one in Arizona, where it was 
much earlier in the morning, so their reception of my signals was much 
better.
The twenty meter band was open for short skip from Havana to Northern 
Florida, possibly via a sporadic E cloud and to the west coast of North 
America via typical F2 layer propagation. The fan dipole is showing a 
1.8 to 1 standing wave ratio, possibly due to its close proximity to 
ground… The antenna is fed with 50 ohms coaxial cable using a one to one 
balun, or balanced to unbalanced broadband transformer at the feed 
point. I would had preferred to feed this antenna with a 350 to 400 ohms 
impedance open wire balanced line, but this wasn’t possible because the 
way the open wire line had to be routed into the shack… Tests at the low 
height above the roof show that the antenna works between 10 megaHertz 
and 29.6 megaHertz, something that was expected after modeling the 
antenna using the Japanese freeware MMANA antenna modeling software… 
This antenna is also a good performer for listening to international 
short wave broadcast stations operating on the 31, 25, 22, 19, 16, 13 
and 11 meter bands. So my new coaxial cable fed fan dipole provides nice 
reception on seven of the international shortwave broadcast bands, and 
the possibility of transmitting and receiving on the 30, 20, 17, 15, 12 
and 10 meter amateur bands. Efficiency on 30 meters is down by about 
maybe 2 dB from a reference dipole, while on the 10 meters band it is up 
by almost the same 2dB as compared to a half wave dipole cut for the 10 
meters band.
This antenna is used with my wide range PI network antenna coupler or 
tuning unit, which provides a one to one standing wave ratio all over 
the antenna’s operating range.
Of course those losses are higher with the coaxial cable down lead than 
with the open wire line, but in actual practice it is difficult to tell 
the difference between the two feed lines.
The antenna is made using six wires of identical length, each
exactly 5 meters long… one of them is placed horizontally and the other 
two spread upwards and downwards from the feed point, so that when they 
reach the end, they are separated by 1 and a quarter meters from the 
center horizontal wire…
The name of the antenna is a FAN BROADBAND DIPOLE, and ideally it should 
be fed with an optimized 350 to 400 ohms open wire transmission line…It 
is a nice general purpose antenna for amateur radio and short wave 
listening that can be built at low cost and can be installed when only 
about 12 meters or horizontal space is available, and even less if you 
install it as a sloper, that is with the antenna tilted at an angle 
between 20 and 45 degrees.
…..

Si amigos, yes my friends, oui mes amis, you are listening to the 
weekend edition of Radio Havana Cuba’s Dxers Unlimited. I am Arnie Coro, 
radio amateur CO2KK and here is item three of today’s program…more radio 
experiments with the parts recycled from inside discarded compact 
fluorescent light bulbs. I have just successfully tested two of the 
power transistors removed from a lamp that broke down when a friend was 
cleaning it… Both transistors tested OK and I already used one to 
replace the series pass power transistor in an old power supply that was 
built many years ago. It is used now to power an ancient laptop computer 
that no longer runs from its battery, and the power transistor was 
damaged when the two output terminal wires touched with each other 
causing a short circuit, something that in the case of this very old 
design of simple DC regulated power supply was not taken into 
consideration… So, I thought that maybe the transistor removed from the 
damaged lamp could work there, and sure, it works quite well, as both 
its voltage and current ratings are well above the requirements of the 
circuit. Now I have two other similar transistors ready to replace the 
audio output pair of a friend’s amplifier that was destroyed also by a 
short circuit of the output terminals!!!
Another possible application of the recycled power transistors removed 
from the small printed circuit boards inside the compact fluorescent 
energy saver lamps is as radio frequency amplifiers for low frequency 
amateur radio transmitters, maybe up to the 80 meters band, but not 
higher because the transition frequency, that is the frequency at which 
amplification by the device equals to one, for these transistors is no 
higher than 20 megaHertz or so…The typical accepted ratio for RF 
amplifier transistors is that they should have a transition frequency of 
at least ten times the frequency that they are going to operate as an 
amplifier .
Sure my friends, just by recycling electronics equipment you will be 
able to have a nice stock of parts that will cost you nothing and 
provide a lot of options for building new circuits.
……
You are listening to Radio Havana Cuba, the name of the show is Dxers 
Unlimited and I invite you to send your signal reports and comments 
about this and other Radio Havana Cuba programs to my e-mail address: 
arnie@xxxxxx and VIA AIR MAIL, send your postcards and letters to Arnie 
Coro, Radio Havana Cuba, and Havana, Cuba… Now here is our next item… 
its la numero uno, the most popular section of Dxers Unlimited… YOU HAVE 
QUESTIONS, and Arnie answers them… Today’s question was sent by listener 
Randolph from Vancouver, Canada. Randy as he signs his e-mail tells me 
that he listens to our 6000 kilohertz program from 05 to 07 hours UTC, 
but he says that he is also able to pick our 11760 kilohertz English 
broadcast during his local early afternoon hours. Randy wants to know if 
would be possible to make a compact antenna for the 6000 kilohertz 
frequency because he calculated the size of a half wave dipole and came 
up with a total length of 23.83 meters that is a bit more than 78 feet, 
and he says that there is not enough space available for such a long 
antenna at his QTH. Well amigo Randy, you can make a much shorter 
antenna and still have it resonate on 6.000 megaHertz, something easily 
achieved with the use of two loading coils that are inserted at points 
halfway between each leg of the dipole. I have already sent you a very 
easy to work with computer program that will allow you to calculate how 
to build your two coils, using easily available materials. Many radio 
amateurs around the world use such compact inductively loaded antennas, 
especially popular among the designers of Yagi type beam antennas 
capable of working on the three most popular higher frequency ham bands, 
20, 15 and 10 meters. Those Yagi beam antennas use four coils on each 
element, that are part of wave traps used to isolate part of the antenna 
so that it will operate on three bands. Amigo Randy, you can also add 
another pair of wire element in pararell with the main six megaHertz 
band antenna, so a nice combination dual band or tri band antenna can be 
built at very low cost, and let me tell you that these antennas are 
pretty effective.
AH… before I forget… if you want to resonate the antenna exactly to a 
center operating frequency, then you will need at least an instrument 
known as a grid dip meter , in order to be able to actually measure the 
frequency at which the antenna resonates, after you install the two 
loading coils. My experience with the software program I use to 
calculate the coils is that it produces very accurate results, but if 
you really want to have the antenna tuned to an exact frequency of 
resonance, then the use of at least a grid dip meter is essential.

…..
This is the weekend edition of Dxers Unlimited and here is item five … 
DX tips for radio amateurs, that can make very good use of them if you 
happen to live in North America and the Caribbean and do stay awake well 
into the late evening… Yes, these tips are particularly effective 
starting at around midnight your local time, I repeat if you live 
anywhere in North America and the Caribbean…Propagation along the 
darkness path to your west and southwest will provide some nice contacts 
for radio amateurs and possibilities of monitoring for short wave 
listeners into Australia, New Zealand, Japan and many of the Pacific 
islands. Several high power broadcast transmitting stations will provide 
nice “beacons” to tell you how the band conditions are behaving at any 
given moment. Transmitters in the Philippines, Australia, New Zealand, 
Japan, South Korea equipped with big antennas will be the first ones to 
be heard and the last ones to fade out, while lower power amateur radio 
stations will be start to be heard when the opening improves and 
disappear when propagation starts to drop… At this time of the year and 
stage of the solar cycle, it is certainly nice to stay up late, because 
your chances of working or hearing DX increase many times as compared to 
daytime operation.
And now amigos as always at the end of the show, here is Arnie Coro’s 
Dxers Unlimited’s propagation update and forecast… Just one sunspot 
group and it is certainly a small and of simple structure, so the daily 
sunspot number is the rock bottom 12, a bit higher than during the 
previous several days with zero sunspot count. The proton density of the 
solar wind has increased quite a bit, and that may trigger geomagnetic 
disturbances at high latitudes. The general description for short wave 
propagation conditions can be resumed with one single word: POOR, 
because of the combination of very low solar activity and the incoming 
high speed solar wind with high proton density… Don’t expect Sporadic E 
openings, because the season has now, for all practical purposes arrived 
to its end… Tune in for the mid week edition of Dxers Unlimited next 
Tuesday and Wednesday UTC days amigos, and don’t forget to send your 
signal reports, comments about the show and radio hobby related 
questions to arnie@xxxxxx or VIA AIR MAIL to Arnie Coro, Radio Havana 
Cuba, Havana, Cuba.

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