Dxers Unlimited
Dxers Unlimited's weekend edition for October 4-5 2003

By Arnie Coro

Radio amateur CO2KK




Hi amigos radioaficionados !, this is the weekend edition of your favorite listener oriented and
technically minded radio hobby program, the one and only that answers as fast as you can think your
radio hobby questions !, and no, we don't bore you with long lists of stations that maybe can be
heard at the specific location of someone attempting to put on the air a short wave listeners
program... As Dxers Unlimited's fans are fully aware, HF propagation conditions change a lot, and
one of their most important parameters is related to your specific geographical and geomagnetic
location... So, in other words, those lists of stations that you may pick up are only valid as an
indicator , and you may actually never hear some of them at all ! Item one: We continue now into the
equinoctial DX season, and for the past week or so HF propagation has provided nice and sometimes
not so nice time slots open for Dxing... Friday we even saw a K index of 5 at one time of the day,
an indicator of disturbed geomagnetic conditions at higher latitudes... But for all of us fortunate
to live at lower geographical and geomagnetic latitudes, the almost uniform illumination of Planet
Earth provided by the Sun at this time of the year has certainly help the higher frequency bands,
especially between 18 and 30 megaHertz to make what could best be described as a wonderful comeback
, after what many experts described as the worst summer propagation conditions of several solar
cycles !!!. Item two: When the HF bands just don't open up... what to do ?, well among other things
you can explore the VHF and UHF regions of the radio spectrum, you can learn more about satellite
communications, or you can also spend time assembling a nice new kit, or gathering the parts to
build another homebrew project... More about VHF bands scanning later in today's program. Item
three: YOU HAVE QUESTIONS, will answer a listener from California that wants to know more about
amateur radio satellites, and I will also be answering a question sent by a Dxers Unlimited fan
regarding the VBTTFD antenna, a low cost, easy to build VHF omnidirectional antenna that will allow
you to explore the range between 30 megaHertz and 150 megaHertz with MODEL ONE, and the range
between 75 and 300 megaHertz with MODEL TWO... AND, as always at the end of the program, you must
have your tape recorder at hand, or if not the notepad ready to copy our exclusive and not
copyrighted, in the public domain HF plus low band VHF propagation update and forecast. Margarita
Delgado is my sound engineer and producer... I hope you will enjoy today's menu, that will continue
in just a few seconds...




.......

Si amigos, this is the weekend edition of Dxers Unlimited coming to you from Havana... Take a look
at this very likely to happen scenario at this phase of the solar cycle... The K index goes above 5,
the HF bands are practically dead, to such an extent that even with your best antenna and more
sensitive receiver you are only able to pick up a few super high power international broadcast
stations... Immediately you are able to realice that a geomagnetic storm is in progress, and there
is not much you can do about that... Then, here is the right moment to start exploring the
fascinating world of VHF and UHF signals that surround you... You will need at least one VHF
receiver and a simple broadband antenna. The receiver can be a VHF-UHF scanner, or if you are a
radio amateur, then it is likely that your handheld FM transceiver, your VHF handie talkie may also
have extended receiving range. Now is the time to explore VHF and UHF... have your notepad at hand
and start scanning from 40 megaHertz to 50 megaHertz, using at least a vertical wire antenna that
can be improvised in a few minutes with household wire. If your radio can't tune to the 40 to 50
megaHertz region, maybe it is able to tune from 140 megaHertz to about 174 megaHertz, and you can
certainly start exploring the very interesting area between 140 and 144 megaHertz, the lower limit
of the amateur two meter band, a region of the spectrum very often overlooked by scanner fans. Of
course that the region between 148 and 174 megaHertz will be full of stations , especially in areas
of high population density... Lots of very interesting signals can be picked up between 148 and 174
megaHertz, even while using a scanner's rubber duck antenna. A homebrew VBTTFD antenna designed to
operate between 100 and 300 megaHertz can be built in a couple of hours and will bring lots of
stations even while operating indoors.

If you have never before picked up amateur radio VHF signals, try the frequency range between 145
and 148 megaHertz, tuning in 5 kiloHertz steps... you will discover local and semi-local repeaters ,
special stations usually located at mountain tops of high rise buildings or maybe one of those
super-tall TV towers. Ham radio 2 meter band repeaters allow operators using hand-held FM
transceivers, the popular handie-talkies , to communicate from very far away distances using the
strategically located repeater stations ... Write down the frequencies where you pick up more
activity, as those will be the ones that your local radio clubs will activate in case of
emergencies... And don't forget that joining a local radio club will bring in lots of new friends,
and the possibility of learning a lot more about the radio hobby from experienced operators ! Si
amigos, yes my friends, oui mes amis... when the HF bands are in poor shape, you can certainly have
a nice time listening or operating on the VHF and UHF frequencies... A low cost scanner, or a second
hand ham 2 meter band transceiver with extra receive frequencies coverage is all you will need to
start enjoying this interesting aspect of our hobby, one of the more than 70 ways that you and I can
have a really nice time with our radios !

........

You are listening to Radio Havana Cuba, and we continue to operate our new 11760 kiloHertz
transmitter from 05 to 07 UTC with our English language program... we are also using 11760 kiloHertz
starting at 21 hours UTC,and yes we are receiving nice reports from Africa during the 21 hours UTC
time slot... Now amigos here is our very popular you have QUESTIONS, and Arnie tries to answer
them... section of Dxers Unlimited that is now competing for the most popular of them all position
with our HF plus low band VHF propagation update and forecast..Here is todays number one question;
amigo Paul from Los Angeles wants to know more about amateur radio satellites... Well my friend, ham
radio satellites that are now active with easy to access features are not as many as we had a number
of years ago. The popular Russian Radio Sports 10, 12 and 13 are sadly no longer operational, and
the OSCAR 40 , the most sophisticated ham satellite ever built and launched into orbit had lots of
problems during its early days, leaving it without the most popular and easy to access amateur
bands. OSCAR 40 is working , that's true, but accessing it is not easy because the transponders that
could be recovered after the explosion that ripped up part of the satellite happened, operate on the
70 centimeters and the 13 centimeters bands and higher frequencies. 70 centimeters is rather common
regarding equipment, but the 13 centimeters microwave band does require rather special equipment,
including antennas... At this moment amigo Paul , the easiest to access satellite is the AO27 , with
an uplink on two meters FM and a downlink on 70 centimeters also FM... It uses what is known as a
parrot repeater, because it is very much like a terrestrial FM ham repeater system, except for the
fact that it switches the received two meter band signal to the 70 centimeter downlink. The AO27
provides very short operating periods, that's true, and the reason for this is that it is a low
Earth orbit satellite...But again, it is rather easy to access using very simple equipment, a dual
band 2 meters and 70 centimeters handie-talkie and a homebrew antenna is all you will need to start
communicating using the AO27...It is hoped that in the not too distant future more easy to reach
HF -VHF satellites will go into orbit !.

QUESTION number two: Arnie, I want to know more about the VBTTFD, the VHF broadband tilted
terminated folded dipole...signed Larry, callsign K7SQT... OK amigo Larry, the VBTTFD antennas I
designed a few years ago , were intended as low cost monitoring antennas, one for the range between
30 and 150 megaHertz and the other one for the range between 100 and 500 megaHertz. Both antennas
are easy to homebrew, won't cost you a lot of money, and although they are unity gain or slightly
above unity gain, they will provide you with much better reception than what the scanner's factory
antenna is able to bring in. Just for your information, the 30 to 150 megaHertz VBTTFD antenna is
just three meters and thirty centimeters long, approximately 10 feet overall length, and it can be
installed from a single mast... The 100 to 500 megaHertz version is very compact indeed, just 1
meter or a bit more than 3 feet overall length...The terminating resistors required for both
antennas MUST BE non inductive carbon type, and the best value tested here has proven to be between
800 and 900 ohms. Both antennas can be used for transmitting , but then your terminating resistors
must be capable of dissipating at least one third of the transmitter power. My 30 to 150 megaHertz
VBTTFD has ten 2 watt 9100 ohms resistors connected in pararell, to make a 20 Watt , 910 ohms non
inductive resistor. I have used the antenna a lot to transmit on the upper end of 10 meters, the
whole 6 meters band and also on 2 meters , so this single antenna gives me receiving coverage from
less than 30 megaHertz all the way up to 150 megaHertz, PLUS the possibility of transmitting on
three ham bands, 10, 6 and 2 meters... The 100 to 500 megaHertz version of the antenna provides
transmit coverage of three amateur bands also, two meters, one and a quarter meters and seventy
centimeters, plus wideband reception of the 400 megaHertz span between 100 and 500 megaHertz...
These are not high gain antennas amigo Paul, but I have worked some nice DX on 10 and 6 meters with
them... and the low band VHF antenna has provided very valuable hints regarding possible 6 meter
openings by letting me monitor some specific frequencies that are kept active all day long, as some
background music services from Chile that operate between 40 and 45 megaHertz !. Complete and
detailed building instructions for both versions of the VBTTFD are available here, so you can send
your requests to arnie@rhc.cu , again arnie@rhc.cu, and I will send you the data files with the
graphics and everything !

And now as always at the end of the program here is our exclusive and not copyrighted HF plus low
band VHF propagation update and forecast...