By Arnie Coro
Hola amigos… more reasons for the very poor propagation
conditions on the MF and HF bands.
Geomagnetic conditions have reached moderate storm levels
on a planetary level (NOAA Kp 6 for the 6-9UT period today, 11 September 2018).
The storm is due to the enhanced solar wind parameters associated with a
coronal hole high speed stream, while the solar wind speed gradually increased
from 370 km/s at noon 10 September to values near 610 km/s at 10UT today.
DXCC COUNTRY/ENTITY REPORT
According to the AR-Cluster Network for the week of
Sunday, September 2-9, they were 206 DX
countries or entities on the air on the monitored amateur bands.
I am Arnaldo, Arnie, Coro your host here at the middle of
the week edition of Dxers Unlimited. Now our next news item...
A number of hand-held FM transceivers capable of
transmitting on frequencies beyond the 2 meters and 70 centimeters band are
being banned by several frequency management authorities around the world. The
usually very low-cost dual band FM handie talkies are considered a menace
because they can easily be reprogrammed to operate on the public services
frequencies. Banning those radios is achieved by placing them in black lists
kept by Customs on the countries were they are no longer allowed to be
imported.
QSL on the air to Dxers Unlimited's. Listeners that have
asked to keep the HF bands propagation updates at the end of the show on every
program. Don't worry, from now on whenever possible Arnie Coro's HF plus low
band, HF propagation update will be on the air at the end of the show.
Next News Item: Sponsored by the International
Telecommunications Union, ITU, the specialized oldest United Nations agency, a
worldwide research project that is measuring the radio frequency spectrum noise
levels will provide valuable information about this severe problem that has a
negative impact on the use of radio telecommunications systems that are vital
in today's world.
By the way some of the worst radio broadband noise levels
measured at several megalopolis, like Mexico City, New York, London, Shanghai,
Tokio, Moscow and Paris are showing that the AM broadcast band services are becoming
useless at the present transmitting stations power levels. The actual effective
service area originally planned for many AM broadcast stations since 1959 have
proven to be practically useless due to the poor signal to noise ratios prevailing
on the 530 to 1700 kHz frequency range.
Hurricane Florence now is in an almost fixed track, and
is going to impact the US East Coast as a category 4 or even category 5 storm.
The most powerful storm to reach that part of the continental United States, in
more than 60 years.
Amateur radio operators located in the affected areas as
well as others around the first skip HF coverage area are already deploying
their emergency communications stations.
It is expected that the record-breaking winds will
produce considerable damage to the telecommunications and broadcasting
facilities. As it happened last year in Texas, the cellphones networks went
down before the full blast of hurricane Harvey had hit the area, making the use
of amateur radio emergency systems essential for responding to live saving
operations requiring air evacuations from flooded isolated areas.
Number 94 is here. Yes amigos, the number 94 way of
enjoying our spare time by means of our radio and television hobby is
here: It is known as amateur digital television, capable of high definition
transmissions.
For delivery of television signals, there are several
methods in use that include: cable (C), satellite (S), terrestrial (T),
internet streaming (www), DVD, etc.
Each delivery system has its own advantages and
disadvantages. As a result, different digital encoding mechanisms are used for
each method. The cable, satellite and terrestrial all use RF carriers, while
satellite and terrestrial are truly over the air rf paths. As radio amateurs,
we use over the air rf transmission paths.
In the early days of DTV (early 2000s), some DTV hams
were experimenting with using satellite TV equipment, mainly due to the low cost
(? $25) of free-to-air (FTA) satellite, L-band (1-2GHz) receivers. Their work
was primarily on the 23cm (1.2GHz) band.
Other early adopter, DTV hams experimented using cable TV
equipment for the same lowcost reasons. The normal amateur radio environment is
really the over the air, terrestrial, rf transmission with radio waves being
transmitted horizontally over the surface of the earth.
The major issues encountered with such radio waves is the
presence of multi-path, RFI and weak signals. Multi-path refers to multiple rf
signals bouncing off of various reflectors, such as hills, buildings, etc. and
arriving at the receiving antenna with various time delays. In the days of
analog TV, this was readily evidenced by the presence of "ghost"
signals on the TV screen.
DTV transmission in a cable TV environment is rf transmission
in an almost perfect environment. It
is almost a perfect, echo free environment due to the efforts made to maintain
very low VSWR in the cable TV system. Signal strengths can also be
kept up to relatively high levels. Thus, the digital modulation method for
cable TV does not need to make many corrections for its good environment.
DTV transmission from broadcast TV satellites, is again in
a relatively clean rf environment. Because
of the high gain and directivity of the receive antennas, there is essentially
no multi-path to contend with from satellites. The main issue for
satellite rf signals is very low signal strength at the receive antennas. Terrestrial
rf transmission is the worst possible rf environment. It must deal with
multi-path, RFI, and weak signals and still deliver a perfect DTV picture.
Here in Cuba our national television uses the highly
efficient DTMB'T that has proven to be more reliable than the ATSC systems
variants used in the USA. So far, Cuban radio amateurs have used analog television
transmissions using several slow scan TV modes that proved to be very effective
sending still photos of hurricane affected areas to the Civil Defense command
posts using both 2 meters FM and HF single side band transmissions.
This is Radio Havana Cuba, the name of the show is Dxers
Unlimited. I am your host Arnaldo, Arnie Coro and here is our next radio hobby
related item for today...it is about the really amazing results achieved by
minimalist amateur radio stations, using minimum parts counts receivers and
transmitters.
Starting with a dual triode tubes in a glass envelope the
regenerative receiver was designed to work on the 40 meters amateur band, using
high impedance headphones.
The first triode is the detector and the second one works
as an audio amplifier. The radio tunes from 7000 to 7150 kHz only. It has good
sensitivity and uses very common electronic parts that you can find by
recycling equipment. It uses a low voltage power supply that is also easy to
build.
The transmitter first option uses quartz crystal control
and a single power tetrode or pentode vacuum tube, that when fed from a voltage
doubler power supply will easily provide between two and five watts into the
simple half wave coaxial fed dipole antenna.
When a local amateur that is a QRP low power radios
enthusiast saw the minimalist station he said and I agreed with him that it a
simplified version of the famous World War II Paraset !!! He took the circuit
diagrams and photos to duplicate the set.
And now at the end of the show.... Arnie Coro's HF
propagation update.... Zero sunspots ... a blank solar disc with very low solar
activity ...AND A GEOMAGNETIC STORM IN PROGRESS: As predicted, a moderately
strong G2-class geomagnetic storm was underway on Sept. 11th as a stream of
high-speed solar wind buffets Earth's magnetic field. This morning in Alaska,
"amazing auroras covered all of the sky," reports Ayumi Bakken from
just outside Fairbanks:
Send your signal reports and comments about this program
to
inforhc@enet.cu or postal mail to: Arnie
Coro , Radio Havana Cuba, Havana, Cuba.
(Arnie Coro/R Havana Cuba)
