Dxers Unlimited

Dxers Unlimited's weekend edition for 18 and 19 October 2003

By Arnie Coro

radio amateur CO2KK




Hi amigos radioaficionados, with our now classic welcome to all radio hobby enthusiasts around the
world this is the weekend edition of your favorite listeners oriented and technically minded
program, Dxers Unlimited with yours truly Arnie Coro at the microphone.. And here is item one...
geomagnetic storming on Thursday and Friday, continuing at lower levels on Saturday UTC days , has
brought very interesting DX to many listeners around the world... Many of you remembered what I
stated here recently that high planetary geomagnetic disturbance indicators were not a reliable
indicator of lack of DX, and as a matter of fact, some really rare DX stations did appear during the
stormy radio weather. K indexes a middle latitudes reaching the 5 level have proved my point quite
well during the past three days amigos ... Item two: A lot of interest on the fast scan low
resolution television standard was generated by a recent edition of Dxers Unlimited, and as always,
listeners to the show have found new and very interesting ways of using new amateur radio software.
Although the 30 horizontal scan lines standard is now becoming popular on the 10 meters amateur
band, it seems like it will also soon be popular on the 2 meters and 70 centimeters band for local
and semi-local work, and ham radio software writers are now talking about another step in the fast
scan TV standards, that will be a sort of intermediate between the classic 525 and 625 horizontal
lines professional transmission standards and the recent 30 horizontal lines amateur fast scan
mode... Considering bandwith limitations imposed by the

faster scan modes, it seems likely that a new amateur TV mode using a 120 fast scan standard will
become a de-facto way of transmitting and receiving TV using sound cards and computers on the 2
meters and 70 centimeters bands... The 120 line fast scan mode will not be apt for the lower bands
because it will require more bandwidth than what is presently allowed

even on the 28 megaHertz or 10 meter band... Si amigos, you have just heard it here, amateur radio
operators continue to develop the hobby using a clever combination of the ICT, information and
communications technologies and classic radio !!! Item three: Spanish space explorer soon to be on
the air from the International Space Station if all goes well with his flight towards the orbiting
spacecraft. His amateur radio call will be ED4ISS and plans are in the works to demonstrate to
school children in Spain how space communications work. Item four: Letters and e-mail messages
continue to reach me here at a very high weekly rate, and practically all if not all of them bring
in more and more radio hobby related questions, from requests for advise on how to add a simple
antenna to a portable radio in order to improve reception to questions related to sophisticated
communications equipment repairs... Yes, I do try to answer them all as fast as I can, but at this
moment there is a backlog, that I hope to clear during the next few days, so if your radio hobby
related question is still waiting for an answer, my apologies, and I do hope you understand that it
does take time to answer each e-mail, postcard or letter ... What I have done in the past and still
do is to sort the questions and try to answer on the air those questions that have a higher
probability of been of interest to many listeners like the ones I selected for today...

After you have questions is over, and as always Dxers Unlimited will be presenting our exclusive and
not copyrighted HF plus low band VHF propagation update and forecast...

My sound engineer today is Jose Costa Pupo, I am Arnie Coro in Havana, back with you in a few
seconds...

.....

Si amigos, its nice to see that so many people, young and old are becoming interested and try to
learn more about radio... For example, a listener in Canada, from Regina, asks in his letter how he
can build a simple short wave receiver using the electronic components that he has obtained from
recycled electronic equipment... He sent me a very extensive list of parts that he had patiently
removed from circuit boards and equipment, and then tested using a digital multimeter and an
inductance, capacitance and resistance bridge... Amigo Karl , from Regina , Canada, what you have
done is a very well thought first step in order to start homebrewing radio equipment... Recycling
components is a win-win achievement, as your parts will not pollute the Earth when they are re-used,
and at the same time homebrewers of radio gear save a lot of money by using, and please listen to
this carefully, recycled and fully tested parts, as amigo Karl has done. I have had some frustrating
experiences that have happened when recycled parts were installed on a new homebrew project, without
first testing them... About five or maybe six years ago, while building a classic three vacuum tube
regenerative receiver that had always started to work nicely when plugged into the power supply ,I
was surprised to get absolutely no audio output.... testing the radio from the loudspeaker
backwards, as it should be done when fault finding, I came across a defective component, it was a
totally open polyester capacitor... that was supposed to couple the audio from the regenerative
detector's plate to the grid of the first audio preamplifier stage via a volume control
potentiometer... The capacitor measured ZERO CAPACITANCE when tested on the capacitance bridge, and
when I opened it up, the reason for the open circuit was found... one of the two connecting leads
had become loose from the foil that made one side of the capacitor ....So , there was no capacitor
there at all, and the radio provided no audio output whatsoever. Soldering another recycled
capacitor that was fully tested and found to be in like new condition solved the problem... So amigo
Karl, there is a lesson to learn from your careful recycling of electronic components, because fully
testing each and everyone of them is the only way to assure that your projects will work, and now
let me add that is it also a very good radio projects construction practice to test brand new parts
too, as I have had my fair share of new from the box parts that were defective ....

Now another letter to Dxers Unlimited, from listener Sam in Georgia , USA, Sam wants to know if
using the expensive plastic guy wires made of a material known as PHYLISSTRAN will help him to
obtain a better radiation pattern from his wire antennas supported from a 20 meters high tower...
Amigo Sam , you should take a look at the price tag of the very expensive PHYLISSTRAN plastic rope
for radio antennas guy wires... Some AM broadcast stations have use it for their complex directional
antenna arrays, in order to remove the presence of the steel rope guy wires. But , I must tell you
amigo Sam that breaking the guy wires with high quality ceramic insulators will be a lot less
expensive than using PHYLLISTRAN, and results are going to be almost identical. The trick is to
calculate the lengths of the segments of the guy wires, in order to break the resonances away from
the amateur bands... You don't want a guy wire to be , for example, a quarter wave parasitic antenna
supporting your mast or tower.

In other words it is important to carefully calculate the lengths at which the special ceramic
strain insulators will be positioned in order to avoid resonances... All I can say is that it is not
that difficult to do it, and that you will have excellent results and save a lot of money ...

Question number three of today's ASK ARNIE will follow in a few seconds after this brief musical
intercut

......

You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited and YES; we do QSL ,
we do reply to our listeners correspondence, including your requests for more radio hobby
information, and we do it while enjoying it too... Of course that our QSL cards and verification
letters are sent absolutely free of charge to the listener that writes to us, as we consider QSLing
not only a courtesy , which it is, but also part of running an international short wave broadcast
station. Send your QSL requests, signal reports, comments about our programs and radio hobby related
questions to arnie@rhc.cu, again, arnie@rhc.cu, and VIA AIR MAIL , we do have a very easy to
remember postal address too... send VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
and now Dxers Unlimited's YOU HAVE QUESTIONS section of the program continues... third radio hobby
related question came in from a listener right here in Cuba, from Guantanamo province, where Eduardo
tells me that he can pick up the 6000 kiloHertz broadcast to North America pretty well. Eduardo
wrote to me in Spanish, and he wanted to know if he could cascade several operational amplifiers to
make an improved audio filter. Well I have already sent him the circuit diagram of a very nice dual
audio filter, that at the flip of a switch provides both very sharp for CW and rather broad for SSB
selectivity. The audio filter is easy to make, has no critical parts, and tests done here show that
it improves the quality of reception significantly. The dual CW and SSB audio filter circuit diagram
is already in digital format, so you can send an e-mail to request your copy...I do want to repeat
that the electronic components used for Arnie Coro's DUAL CW and SSB audio filter are standard
values, so that it can be easily built. The filter requires no adjustment and is powered from a 9
volts battery. You can send for the circuit diagram via e-mail, send mail to arnie@rhc.cu and don't
forget to include the sentence: request for audio filter in the text of the message... Well designed
audio filters enhance the performance of radios in a surprising way, making copy much easier and
sometimes making possible to copy stations that simply can not be heard without the filter
connected.

And now amigos, as always at the end of the program, here is Arnie Coro´s Dxers Unlimited HF plus
low band VHF propagation update and forecast. Solar activity is certainly at the very low level,
while at the same time the solar wind is still impacting the Earth's magnetosphere. Both low solar
activiy and a disturbed magnetic field are certainly not a very nice combination for the HF bands
!!!

Solar flux and sunspot numbers were lower this past week, and the
planetary A index was higher. Generally we like to see the reverse
for HF propagation.October 14 and 15 conditions were quite stormy. This is
because a coronal hole on the sun was spewing a strong solar wind,
and the interplanetary magnetic field pointed south, leaving earth
vulnerable. The planetary A index was 48 and 42 on October 14 and
15, and Alaska's high latitude College A index was 65 and 71.
The sunspot count dipped really low to 24 on October 14, this was the lowest sunspot number since
May 10 of this year, when it was 22. We should be expecting more days like this, with very low
sunspot counts as the solar cycle declines.
The good news is that,over the next few days, we should see sunspot numbers and solar flux rising,
with solar flux values peaking around October 25 at 130.
Solar wind over the next few days should cause more geomagnetic
upset, with the October 17-22 planetary A index pegged at 25, 20,
15, 15, 30 and 25., all way above the A indexes of between zero and

about 10 units that provide the best overall HF propagation conditions.

See you all at the mid week edition of Dxers Unlimited next Tuesday and Wednesday, and don't forget
to send your signal reports and comments to arnie@rhc.cu, or VIA AIR MAIL to Arnie Coro, Radio
Havana Cuba, Havana , Cuba.