Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's mid week for 1-2 November 2005
By Arnie Coro
radio amateur CO2KK
Hi amigos radioaficionados ! You are now listening or reading the script of
Dxers Unlimited's mid week edition. I am Arnaldo, Arnie, Coro, radio amateur
CO2KK, your host here in Havana, now ready to bring you about seventeen
minutes of on the air and on the world wide web streaming audio radio hobby
related information. Here is now item one: CQ Radio Amateur Magazine
worldwide Single Side Band contest took place during the weekend, and I have
received lots of complaints from CW Morse Code operators because lots of
phone stations went down to the very low edge of the 40 meters or 7
megaHertz band , causing a lot of harmful interference to ongoing two way CW
contacts... Reviewing the radio rules and regulations of several countries
regarding amateur radio, I have not found a single sentence saying that
phone operation is forbidden below a certain frequency on 40 meters, except
on the very carefully reviewed recently Cuban Amateur Radio Regulations,
that specifically sets aside the first 25 kiloHertz of 40 meters as an
exclusive segment for CW A1A transmission mode...My personal opinion about
this topic is that contest rules must be written in such a way so as to
disqualify participants that cause harmful and deliberate interference to
other stations, something that unfortunately happened during this weekend as
the maximum useable frequency curve dropped dramatically due to the very low
solar activity and lots of contest stations had no other choice but to move
down to 40 meters in order to be able to obtain more contest points and
multipliers !
Item two: Nicaraguan and Hondurean radio amateurs operated their stations
during the hurricane BETA emergency, and received support from stations in
Cuba and Mexico when they required relays due to short skip propagation
related problems. International Amateur Radio Union Emergency Communications
coordinations worked very well, with Areas C and D of IARU Region II
cooperating very well. One of the problems that we observed during this and
previous hurricane WILMA, was the harmful interference to the emergency nets
by the automatic WINLINK PACTOR digital stations, that in my opinion should
not be allowed to operate between 7.025 and 7.100 kiloHertz because of the
technical characteristics of that system, that does not check if the
frequency is or is not in use before starting endless loops of automatic
calls... By the way, again in my opinion the very nature of the WINLINK
PACTOR II and III systems operating inside the amateur bands must be
reviewed as they are used more and more as substitutes for commercial
traffic handling, especially by maritime operators that want to save money
by using such a system instead of the satellite systems especifically
designed for that purpose like INMARSAT...
Item three: Crank up radios worked very well during the Hurricane WILMA
emergency here in Cuba, providing people with up to date weather reports and
other vitally important information like evacuation procedures. Cuba has
bought a substantial number of such radio receivers that are powered by a
crank up generator, can charge the batteries with a small solar panel or
from the electricity network and can also operate with a wal wart AC to DC
adapter...
More radio hobby related information will be following in a few seconds as
Dxers Unlimited's mid week edition continues after a short break
......
You are listening to Radio Havana Cuba, the name of the show is Dxers
Unlimited
and SI AMIGOS, we do QSL, we do confirm reception reports, and I enjoy a lot
reading your e-mail messages, letters, postcards and FAX messages too. Our
FAX number is 53-7-8776531, that is manually operated, requiring you to ask
for the FAX machine tone.
My e-mail address is arnie@rhc.cu, again very easy to remember , arnie@rhc
cu, Now here is item four to today's program...
Yet another 2 meters amateur band simple wire antenna captured my attention
this past week, as I was once again operating an emergency communications
station during Hurricane WILMA's approach to Cuba... This antenna is very
simple to homebrew, has a good gain figure, and costs almost nothing ... It
uses four half wave dipoles fed in phase, that are very easily matched to a
50 ohms coaxial line by means of the well known quarter wave pararell like
transformer made from aluminum or copper tubing. The antenna can be taped to
a PVC plastic mast or you can simply hang it from a mast or tower by using
two insulating spreaders made of PVC or hardwood dowels.
The phasing transformers are easy to reproduce from a mechanical point of
view, and it you are careful measuring the lengths of the different wire
sections, the antenna will work very well.
My guess estimate of this antenna's gain figure is that it should be near 6
decibels over a reference half wave dipole , but in actual practice,
apparent gain may be higher due to the lowering of the vertical take off
angle as compared with a standard reference half wave dipole. This is a
truly portable, two meters band vertically polarized gain antenna, that can
be built easily in a couple of hours, and it makes an ideal radio club
project, because your club may organize an emergency antennas building
meeting, where everyone attending goes back home with a nice antenna, ready
for action if an emergency comes up...
If you want more information about this antenna , including graphics and
photos of two different but similar designs, just send me an e-mail to
arnie@rhc.cu, again, arnie@rhc.cu, and I will have them e-mailed back to you
as files attached to the reply message .
Item five: DRM, Digital Radio Mondiale transmissions continue to generate
interference well away from the assigned 10 kiloHertz short wave broadcast
channels, and this is causing many listener's anger. There is no reason to
operate DRM broadcasts with such a greater than required bandwidth, and as a
matter of fact, I think that DRM short wave broadcasts must be assigned a
number of sub-bands, so that they don't continue to cause such harmful
interference to stations using the standard AM broadcast double side band
plus carrier system with five kiloHertz audio bandwidth that uses , when
properly adjusted, 10 kiloHertz of spectrum space for each station. In
actual practice, an audio filter with a steep slope above 4.3 kiloHertz
actually improves the reception of an AM shortwave broadcast, and using a
filter with a similar fast slope that will reduce the bass frequency
response below 100 Hertz is also a very good idea to put in practice ...
.......
QSL on the air, QSL on the air, to listeners in Belgium, England, Canada,
the USA , Nigeria and Australia that have requested more information DRM ,
Digital Radio Mondiale broadcasts and the problems that they are causing to
stations operating on the standard AM , amplitude modulation mode... As you
have just heard amigos, the concept of isolating the DRM stations into
sub-bands of the existing short wave international broadcast bands , or even
assign new bands for them to broadcast , is now advancing among several
telecommunications administrations, and already I am keeping a watchful eye
on several DRM broadcasts that are on the air on frequencies that are far
away from the 6 megaHertz band assignment, as they may be signalling the
begining of a trend...
QSL on the air , QSL on the air number two today, to listeners that have
sent e-mail messages to arnie@rhc.cu, requesting more information about the
non inductive resistors mentioned here recently ... Amigos, let me tell you
that some of these resistors are still manufactured , while others have just
vannished from the production runs of all resistor manufacturers. The
wirewound non inductive resistors achieve that unique property by placing
opposing windings in such away that the inductances just vannish... but the
more common so called sandbar high power non inductive resistors achieve the
non inductive characteristics by means of using materials that have a high
specific resistance per unit length and high power handling properties. All
high power transmitters use a lot of these resistors to stop possible VHF
frequency oscillations that do happen when medium or high power vacuum tubes
are used as Class B, Class C, D or E radio frequency amplifier stages, and
they are also used in high level class B modulators to stop the vacuum tubes
or valves from generating vhf band parasitic oscillations.
A unique source of the non inductive medium or high power resistors are
retired AM Broadcast band transmitters in the one to 50 kiloWatt output
power class. Many AM broadcast stations are phasing out their vacuum tube
transmitters,and some are having problems moving the old transmitters out to
the junk yard because they use dangerous PCB oil filled capacitors. When
these old transmitters are retired from service, they can usually be
cannibalized by a group of radio amateurs, under the strict supervision of
the station's chief engineer , who in many cases is also a radio amateur too
When you look for the 300 to 900 ohms non inductive resistors as the old
transmitter is taken apart, don't forget to use the opportunity to take back
home a high voltage plate transformer , a filter choke, and the filament
transformer for the mercury vapor rectifiers... The typical 10 to 50
kiloWatt AM transmitter uses about
2.5 to 3.3 kilovolts to power up the RF driver stage and the AM high level
plate modulator, making it ideal for powering a high power linear power
amplifier !
And now amigos, just before going QRT, here is the latest HF plus low band
VHF propagation update and forecast.. Solar activity has moved up a bit,
just a little bit, so don't expect sensational DX on the segment between 20
and 30 megaHertz amigos !
A spotless Sun for several days in a row, sends the daily maximum useable
frequency curve way down, but fortunately there are many ways in which you
and I can benefit from these propagation events...Solar flux was still below
80 units..Spots: 29 as of 10/31/2005 :: Flux: 78 | Ap: 11 | Kp: 3 (25 nT)
Solar Wind: 444 km/s at 4.8 protons/cm3 :: [ Other Kp graphs ]