Re: [HCDX] Dxers Unlimited's weekend edition for 3-4 February 2007

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

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition for February 3-4 2007-
By Arnie Coro
Radio amateur CO2KK

Hi amigos radioaficionados wherever you are now located listening to 
Dxers Unlimited’s weekend edition… maybe you are sailing happily around 
the Caribbean, or looking at a snow covered landscape from your picture 
window, perhaps you are reading the script of the program from one of 
the Internet mailing lists that make it available to the worldwide radio 
community ,or let’s see, you are just sitting right next to the small 
portable radio with just the telescopic whip extended , reading a radio 
magazine and enjoying one of your favority hobbies… short wave 
listening… Yes amigos, Dxers Unlimited’s listeners around the world keep 
surprising me every day, like when I received a report from a senior 
airline captain that told me that his HF Single Side Band transceiver 
was able to pick up our 6180 kiloHertz frequency while he was flying the 
right seat of a ferry flight taking an aircraft to the scheduled 
maintenance . Si amigos, yes my friends, you can pick up our show or 
read our scripts almost anywhere, and you can also contribute with your 
ideas on how to make it a better program for the benefit of the world’s 
radio hobby enthusiasts, send your e-mail messages to arnie@xxxxxx or 
send me a post card or letter to the following address Arnie Coro, Radio 
Havana Cuba, Havana, Cuba… And now here is item one hang gliding 
enthusiasts are becoming more and more involved in amateur radio and it 
is expected that after the Morse Code test is no longer required to 
obtain an amateur radio license in many countries, more hand gliders 
will be equipped with 2 meters and 70 centimeters FM communications 
equipment… I have heard already of many instances when the use of 
amateur radio gear by the hang glider pilots has helped them to warn 
others of sudden bad weather conditions, and also to call rescue teams 
to pick them up when due to air currents they have drifter far away from 
the projected landing sites. Using already existing 2 meters or 70 
centimeters repeaters the hang glider and also the standard gliders 
pilots have found a nice way to enjoy two hobbies at the same time: 
aviation and amateur radio …
Item two , coming up in a few seconds, when the weekend edition of your 
favorite radio hobby program continues ….
I am Arnie Coro, radio amateur CO2KK, in Havana.

…….
This is Radio Havana Cuba, and in a few days on the 24th of February we 
will be celebrating the 46th anniversary of our first experimental 
broadcasts from the Bauta transmitter site west of Havana. I was a very 
young radio technician at that time, attending engineering school, and 
enjoying the unique experience for anyone that loves this hobby of 
helping to install our first transmitters and antennas… I still remember 
very well how we went to the lumber yard of the electricity utility to 
ask them for the longest wooden poles available, so that we could 
install the first full wave dipole antenna for our one and only one 
kiloWatt Gates transmitter, that used a 4-1000 A final amplifier and two 
833ª’s triodes as high level modulators. For those of you that enjoy 
radio history, yes, we had used that transmitter earlier from a downtown 
Havana location, and it was later moved to a small construction’s 
workers shelter in Bauta. The operating frequency was fixed with the 
only quartz crystal that we had at hand… 6000 kiloHertz, yes, the same 
6000 kiloHertz frequency that we have been using for broadcasting our 
programs for many years now… In an upcoming edition of Dxers Unlimited, 
I will tell you more about our first antenna and how it went up with the 
help of a crew from the Empresa Electrica, the electrical utility that 
helped us to install the three masts required for the antenna.
Item three: ASK ARNIE , as popular as ever, according to your e-mail 
messages, letters and postcards, as well as when I have the nice 
opportunity of talking to Dxers Unlimited’s listeners on the amateur 
short wave bands…
Here is ASK ARNIE for today: Listener Mario from Sicily, wants to know 
more about how to improve the front end filtering of his receiving set 
up, because he has heard from fellow short wave listeners using Arnie 
Coro’s optimized bandpass filter and signal attenuator with good results.
Well amigo Mario, while reviewing a few years ago the design criteria 
for HF , that is short wave radio receivers that operate in the 
frequency range from about 2 megaHertz all the way up to 30 megaHertz, I 
realized that designers of the most sophisticated and also more 
effective receivers, those that are sold only to professional 
organizations due to their high cost, do devote a lot of engineering 
know how to the handling of the signal from the antenna and until it 
reaches the receiver’s first active device, that is, from the antenna 
input to the input of the radio frequency amplifier stage. Radios that 
may cost tens of thousands of dollars or Euros are used by professional 
monitoring stations, also by sophisticated communications centers used 
for long range contacts with aircraft flying the oceanic routes, that 
are out of reach of the VHF and UHF almost line of sight communications 
. Those receivers include many features that you won’t normally find in 
less expensive equipment, but that can be easily included , and at low 
cost, in any homebrew radio , even in the simplest ones.
For example, adding a step by step resistive signal attenuator at the 
antenna input to any existing radio will improve the way it may deal 
with high intensity signals and reduce the chances of cross modulation, 
one of the worst things that happens when cheap radios are connected to 
a large size external antenna. In a similar fashion, the use of several 
sophisticated filters between the antenna and the receiver’s front end, 
will improve reception too. After many years of designing and 
experimenting with short wave receivers, I do have a number of working 
modules that are included on every new radio built, and the integrated 
signal attenuator , low pass, high pass and tuneable band pass filters 
box is now considered by yours truly as an essential part of any really 
serious project. As a matter of fact even a streamlined or simplified 
version of this module will improve your reception dramatically in many 
cases. The cut off frequencies for the low pass and high pass filters 
are very easy to determine… for example, in my most recent Regenerodyne 
hibrid radio, I have included a filter that has a rather steep cut off 
for signals below 2 megaHertz, in order to remove the presence of a 
powerful AM broadcast station less than three miles away from my home, 
another filter has a cut off above 35 megaHertz, to reduce the possible 
impact of the TV and FM transmitters that are also not far away from 
home… Then the dual tuned bandpass input filter provides a rather narrow 
range of frequencies to the radio frequency amplifier stage, that in 
this particular receiver is used only to compensate for the losses 
introduced by the input filters…The step attenuator can be switched from 
0 dB, that is bypassed, to minus 3 , minus 6, minus 10, minus 20 and 
minus 30 dB, a scale that has proven to be very effective and that helps 
to give the operator a good idea about propagation conditions when you 
tune to short wave stations that come in regularly. So amigo Mario, in 
Italy, I hope that his answers your question, and I have also already 
sent via e-mail the complete, detailed circuit diagram of the input 
module used in my latest REGENERODYNE, a very nice radio that any 
advanced electronics and radio experimenter can easily duplicate… NO, I 
won’t recommend it for beginners, because among other things, it uses a 
plus 180 volts direct current supply for powering the vacuum tube 
stages, and you must really be very careful when working with such voltages…
……
Amigos, you are listening to the weekend edition of Dxers Unlimited, and 
now here is our technical topics section , that today will deal with 
antenna insulators… According to what may best be described as radio 
tradition, glazed ceramic ribbed insulators are among the best to 
install wire antennas… If there is a lot of tension applied to the wire, 
then ceramic compression type insulators, the so called EGG insulators 
must be used, but then you will be forced to use several of them because 
the separation between the antenna wire and the supporting wire is very 
small when you use EGG type insulators. The availability of new 
materials has brought a new family of plastic insulators with excellent 
electrical and mechanical properties, like for example the fluoride 
based plastic insulators, which are typically made from 
poly-tetra-fluoro-ethylene, plastic, better known by its most common 
trade name TEFLON… and also in Europe it is known as FLUORO PLASTIC… 
Teflon insulators are also excellent at much higher frequencies , so 
they are used for VHF-UHF and MICROWAVE antenna systems. High density 
polyethilene is also a very good insulator, and I have used sections of 
the inner insulator of large diameter coaxial cables, like RG17 and 
RG19, to make by own ZERO COST antenna insulators with excellent results.
When installing very thin wire antennas , like the ones many people have 
to use when visible antennas are out of the questions because of 
landlords or zoning restrictions, you can even use plastic cloth buttons 
as excellent end insulators… Choose dark colored ones so that your 
stealth antenna will be a lot more difficult to spot… By the way, number 
24 or number 26 black or dark blue Teflon insulated wire is extremely 
resistant from a mechanical point of view, and it won’t stretch as much 
as enameled copper wire, so keep this in mind when you do need to 
install your next stealth antenna for short wave listening or your 
amateur radio station. It is surprising to see that even a 30 to 60 feet 
long, that is 10 to 20 meters overall length wire stealth antenna built 
using such a thin radiator, provides an excellent match when using a 
well designed antenna tuner…
And now amigos, as always at the end of the show , here is Arnie Coro’s 
Dxers Unlimited’s not copyrighted, in the public domain , HF plus low 
band VHF propagation update and forecast… PREDICTIONS Sunday February 
the 4th 10CM FLUX: 088 / and the planetary geomagnectic indicator at a 
nice and low: 003
PREDICTIONS FOR Monday 05 Feb 2007 UTC day  10CM FLUX: 087 / and the 
geomagnetic field at a still nice and lowAP: 005 Solar activity was 
extremely low during the Friday UTC day. No significant flaring activity 
is expected for the next 72 hours. Geomagnetic activity was very low 
during the last 48 hours. The solar wind speed measured by the ACE 
spacecraft is about 400 km/s. Quiet conditions are expected for the next 
72 hours .The probability of sporadic E events is practically zero for 
the whole of next week.
I invite you to listen to the mid week edition of Dxers Unlimited next 
Tuesday and Wednesday UTC days amigos…


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