Re: [HCDX] Dxers Unlimited's mid week edition Sept 18 -19 2007

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

Dxers Unlimited
Dxers Unlimited's weekend edition for Sept 18-19 2007
By Arnie Coro
radio amateur CO2KK

Hi mis amigos radioaficionados around the world and in space !!! This is 
the midweek edition of your favorite , listener oriented and technically 
minded radio hobby program, coming to you via shortwave and also via 
streaming audio on the World Wide Web from http://rhc.cu our new fast 
track world wide web address, I am Arnie Coro, radio amateur CO2KK, your 
friend in sunny, beautiful Havana, where we have enjoyed excellent 
tropospheric ducting propagation on the VHF, UHF and Microwave bands... 
Way out there, 93 million miles away, our nearest STAR, amigo SOL, is 
now taking a break, and the actual sunspot count has gone down ZERO for 
many, many days one after the other...No active sunspot regions in 
sightand I expect a very low sunspot count and a diminishing solar 
microwave energy flux to continue during the next seven to ten days... 
More about HF, VHF, UHF and Microwave propagation later, at the end of 
the program... Item two: Listeners letters provide instant feedback 
about the show's content, new ideas, and very interesting radio hobby 
related questions that keep yours truly really busy the whole week, and 
be aware that Dxers Unlimited, Breakthrough the science show,  and our 
Spanish language daily science technology and the enviroment at Radio 
Havana Cuba are not my only duties... I do spend a lot of time every 
week teaching, and that amigos, is a very rewarding activity, as you do 
learn a lot while preparing your lessons !!! Listeners from all around 
the world write to Radio Havana Cuba's Dxers Unlimited and recently I 
decided to make a poll of the show's most listened sections... As 
expected ASK ARNIE was once again LA NUMERO UNO... the most popular 
section of Dxers Unlimited , closely followed by our exclusive and not 
copyrighted HF PLUS propagation update and forecasts that according to 
the e-mail messages, postcards and letters, really helps you all to 
catch nice DX sometimes, to optimize your band plans for a contest, or 
to simply stay away from the radio and homebrew some more equipment when 
propagation conditions take a turn for the worst !!! Item three: ASK 
ARNIE, today will be answering two questions, then it will be followed 
by TIPS and TECHNNIQUES, a  Dxers Unlimited's section that is winning 
listeners at a fast pace, and as always at the end of the program the 
propagation information that today will be of a more general nature, and 
for those of you that have asked, YES, I do have to work ALL SATURDAYS 
amigos,so that the weekend edition will feature the most up to date HF 
propagation forecast... !!! Stay tuned for more radio hobby related 
information, coming to you , with love, from Havana...
I'll be back in a few seconds , after a short musical intercut
....
The name of the station is Radio Havana Cuba, we are on the air since 
1961, providing to our listeners the best possible programs about Cuba 
and the world amigos... Here is now ASK ARNIE for today... The first 
radio hobby related question came from a country where Dxers Unlimited 
has a massive audience, according to the e-mail messages, postacards and 
letters that I receive here every week... Yes , its Canada, where the 
short wave listening hobby seems to have many followers... The question 
was sent by Dxers Unlimited's listener Mark, from Toronto... He ASKS 
ARNIE... what is a TUNIPOLE antenna ... because he recently visited an 
AM broadcast station, where the chief engineer told him that they had 
recently changed their antenna system to a TUNIPOLE... Mark then adds 
that he sees exactly the same tower that has been there for years... 
Well amigo Mark, sure, the tower is the same, but the antenna system was 
changed by the station's engineers to a very different configuration. 
The TUNIPOLE is a commercial name for what is known in radio engineering 
as a GROUNDED FOLDED MONOPOLE antenna... And the main reason the station 
you visited changed their antenna configuration is that they almost 
surely had to upgrade to a new solid state transmitter. The TUNIPOLE or 
more properly speaking GROUNDED FOLDED MONOPOLE ANTENNA, provides 
additional protection against lightnning that is badly needed by today's 
third generation solid state transmitters... The traditional vacuum tube 
power amplifier transmitters were much more tolerant to voltage spikes 
generated by lightnning than their solid state equivalents of today... I 
have seen a very nice second generation pulse duration modulation AM 
broadcast transmitter go off the air with all its power modules dying 
instantly after a the series fed antenna took a direct hit from 
lightnning... YES, sure, solid state transmitters are the way to go, no 
doubt, they save a lot of energy and replacement parts are available at 
very low prices, but so far no one has found how to really protect them 
from lightnning when they are connected to an insulated tower... So 
amigo Mark, that's part one of my answer, now part two... the AM 
broadcast station you visited will also benefit from converting their 
series fed insulated base antenna to a GROUNDED FOLDED MONOPOLE , 
because from now on they can rent tower space to other users of the 
radio frequency spectrum, a source of extra income to the station that 
will help AM broadcasters to balance their budgets. It's no secret that 
in many countries AM broadcasting stations are loosing audience to FM 
stations, so by renting their grounded towers to cellphone operators, 
for example, they can keep themselves on the air !!! A typical 100 
meters high AM station tower makes an excellent support for cellphone 
and other commercial communications systems that can then save money by 
renting space on an existing site, rather than having to make a 
completely new installation from scratch... Amigo Mark, radio is a very 
complicated business, and tower space renting is becoming more and more 
important at a worldwide scale, by the way, many high tower operators 
graciously provide tower space for amateur radio repeaters in what could 
best be described as a very good public relations act. Now question 
number two.. it came from South Africa, where we are building up an 
audience according to the correspondence department here... Listener 
Mumbele from Cape Town, tells me that he is picking up ou 6000 kiloHertz 
broadcast for just a few minutes every day, on what seems to be a very 
short band opening... Mumbele wants to know if this has something to do 
with what is known as GRAY LINE or TERMINATOR LINE propagation... Well 
amigo Mumbele, I will have to take a look at the time of the day here in 
Havana, and the time of the day in Cape Town that this is happening... 
GRAY LINE or TERMINATOR LINE propagation happens when two points of the 
Earth are touched roughly at the same time by the line that separates 
day and night... and YES, it does enhance propagation a lot... As a 
matter of fact, many radio amateurs used terminator line propagation in 
a routine fashion to work DX... By the way amigo Mumbele, you may want 
to give a try to our streaming audio from 05 to 07 UTC provided at 
http://rhc.cu..
.....
This is the midweeke edition of Dxers Unlimited, coming to you from 
Radio Havana Cuba, and let me reiterate that solar activity is at very , 
very low levels, and that is having a very negative impact on short wave 
propagation conditions ... I think that according to the present state 
of solar activity the probability of a large solar flare happening is 
very , very low... Now here is our TIPS AND TECHNNIQUES section of the 
show, one that is becoming really popular with all of you according to 
the most recently received correspondence amigos... Several listeners 
wrote telling me about their success with the homebrew microphones, and 
that they were really pleased with the audio quality obtained from 
them... Gary from Indiana , USA, says in his e-mail that he is now 
collecting broken cellphones in order to be able to make several more of 
the homebrew microphones for three of his other transceivers... He 
tested a microphone element from a NOKIA cellphone that was damaged when 
it was actually crushed by the tires of a car, that by miracle left the 
microphone undamaged... Gary tells me that his two meters mobile FM 
transceiver sounds much better now, and that what he actually did was to 
remove the microphone capsule from his rig's mike and replace it with 
the NOKIA cellphone microphone element, leaving everything else 
untouched ... Si amigos, yes my friends, out mes amis, as you all know, 
radio is hobby that can be enjoyed on a shoestring budget and that also 
helps to keep the environment clean by recycling !!! Second part of TIPS 
and TECHNNIQUES... when a radio receiver has not operated for a long 
time... don't just plug it in to the AC power line... Bring it back to 
life slowly , by using one of the two following techniques... Connect 
the radio that was in long storage to a variable voltage transformer, 
also known as a VARIAC, and set the transformer for 25 volts AC 
output... keep the radio operating at that voltage for about 24 hours, 
then go to 50 volts, and keep it there for 12 hours, step three is 
taking the operating voltage to 75 volts AC and keeping it there for 6 
hours... Then you run the radio from 100 volts and see what happens... 
It is likely that it will make a nice comeback into useful life if there 
are no damaged components... You can benefit by monitoring the AC power 
line current that the radio is taking by means of a digital multimeter 
set for AC current measurement... This step by step method has proven to 
be very effective for me, and has helped to detect bad electrolytic 
capacitors before they really go up in smoke... By the way, if you are 
doing this procedure to an old vacuum tube radio, it is a very good idea 
to do a total , comprehensive visual inspection of the receiver , clean 
the dust and accumulated debris, and then proceed to  replace ALL THE 
ELECTROLYTIC and PAPER BYPASS CAPACITORS, before plugging in the radio 
to the AC power line !!!
More recently built solid state receivers of the so called first 
generation, dating back to some 35 to 40 years ago will usually come 
back to useful life too, but replacing the electrolytic capacitors will 
not be as easy as with the older vacuum tube receivers because of the 
use of a very compact layout of the printed circuit boards...
TIP NUMBER THREE for today... If you want to use a loudspeaker instead 
of headphones for listening to CW Morse Code signals, use a small 
speaker, one between two and three inches will be ideal, and then follow 
Arnie Coro's advice and paint the paper loudspeaker cone with nailpolish 
to raise its low frequency resonance.. The modified small louspeaker 
will operate as a mechanical audio filter or sorts that has proven to be 
very effective and of course will cost you practically nothing.. There 
is yet another nice way of optimizing a small louspeaker for CW Morse 
Code reception , that I will leave it for an upcoming program... in the 
meantime try this one and tell me how it worked for you... send mail to 
arnie@xxxxxx, or send me an AIR MAIL postcard to Arnie Coro, Radio 
Havana Cuba, Havana, Cuba...
....
Si amigos, Dxers Unlimited comes to you twice weekly, on Tuesdays and 
Wednesdays UTC day we have the mid week edition and on Saturdays and 
Sundays UTC days we provide you with our weekend edition... They are two 
completely different shows, especially written usually on the same day 
they go on the air for the first time... Now as always at the end of the 
show  here is our HF plus VHF, UHF and Microwaves propagation update and 
forecast... Solar activity is VERY LOW, and very probably it will 
continue at extremely low levels for the next seven to 10 days... 
Sunspot numbers of ZERO or near ZERO are expected during this period, 
and the microwave solar flux should bottom at figures around 65 to 70 
units for the rest of this solar rotation. . Hope to have you joining me 
for the weekend edition of Dxers Unlimited next Saturday and Sunday, and 
please don't forget that your e-mail messages, postcards and letters do 
help to make this radio hobby program better for YOU AMIGOS !!! Send 
them to arnie@xxxxxx or VIA AIR MAIL TO:  Arnie Coro, Radio Havana Cuba, 
Havana, Cuba
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