Re: [HCDX] Dxers Unlimited´s weekend edition 23-24 February 2008

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

Radio Havana Cuba

Dxers Unlimited weekend edition for 23-24 February 2008

By Arnie Coro

Radio amateur CO2KK

Hi amigos radioaficionados, welcome to your favorite radio hobby 
program... Dxers Unlimited with your's truly Arnie Coro at the 
microphone. Here is now item one... I recently repeated an experiment 
here at CO2KK, my ham radio station , for the benefit of several new 
comers to the amateur radio hobby that visited me... the experiment 
consisted in running a step by step power output test, and it was done 
on the two meters band, and the results showed, once again, that with a 
good antenna, QRP or very low power operation is really possible. I took 
my 2 meters band station trough a power test that went down to 100 
milliWatts or a tenth of a Watt while using a 6 dB gain antenna, 
effectively radiating when running the 100 milliWatts about 350 
milliWatts, taking into consideration feedline losses. Groundwave 
contacts with stations up to one hundred miles away were possible when 
tropospheric ducting conditions existed, and with absolutely flat 
conditions, the 350 milliWatts effective radiated power could be heard 
regularly at stations 50 to 60 miles away if the other station was using 
a good antenna. But as you may guess to assure a good quieting of the FM 
receiver's noise, running 10 dB more power , that is about 3.5 Watts was 
more than enough to keep very stable two way long conversations with 
stations in the 50 to 60 miles from Havana perimeter even when they were 
using just a half wave vertical dipole antenna at not more than 3 or 4 
meters above the average terrain...

More about power output and antenna gain, in a few seconds , when Dxers 
Unlimited continues, after a short break for station ID... I am Arnie 
Coro in Havana...
.................


This is Radio Havana Cuba, the name of the show is Dxers Unlimited 
amigos, and here now I am ready to continue discussing the topic, power 
output and antenna gain... For two meters band operation , an 
omnidirectional antenna with 6 dB gain will be a quite logical addition 
to your station , as it will provide around the compass coverage if your 
station is located out in the clear with no local obstructions that will 
stop or deviate the radio waves. A 6 dB antenna gain is not too 
difficult to achieve on the two meters band, and a lot easier to reach 
on the 70 centimeters band. On lower frequency bands, 6db antenna 
omnidirectional gain is much more difficult and expensive to achieve, 
and that's why the use of directional antennas is the way to go on the 
lower frequency bands..

For those of you not familiar with decibels, let me say that 3dB means 
doubling the power, 6 dB is quadrupling the power, and a 10 dB gain is 
multiplying the power ten times. Something that can not be forgotten is 
that antenna gain is good for transmitting as well as for receiving too...


So amigos, all efforts to install better antennas are worth every minute 
and every single cent spent on them !!!........

Dxers Unlimited continues now with our popular Arnie's workshop section 
of the show, Here at the workshop the most recent version of the hybrid 
REGENERODYNE receiver is still under test. Here is now an update of the 
latest results... The tests with the computer clock TTL crystal 
controlled modules that are being used to provide local oscillator 
injection to the front end of the REGENERODYNE, have proven to be both 
reliable and , as expected , very, very stable.

They are fed with 5 volts regulated DC, and are easy to install. 
Switching frequencies is done by providing the selected module with the 
5 volts output , as their output is connected to the broadband mixer in 
parallel in this first experimental setup, but I am planning to add a 
diode switching system in the next few days.

This prototype receiver has two local oscillators systems, one using the 
above mentioned computer crystal oscillator modules that deliver a 
square wave output that is ideal for feeding the four diode balanced 
mixer, and a second local oscillator using a standard NPN transistor and 
quartz crystals.

As explained during a previous edition of Dxers Unlimited , this 
receiver is a hybrid, an attempt to use the best features of both solid 
state and vacuum tubes, and also to put to good use a lot of recycled 
components that were in perfectly good shape, just waiting to be 
soldered to a new project.

The front end is now working very well, and the tuneable bandpass filter 
at the input was added as a second option because it does help to 
increase the front end selectivity, as compared to what is achieved with 
a single tuned circuit antenna input circuit..

Don't worry amigos, I am always keeping you all pretty well informed 
about the evolution of this design that so far has surpassed by highest 
expectations.... Just to give you an idea, using the experimental hybrid 
Regenerodyne or EHR receiver on the 40 meters amateur band, in 
comparative tests with my excellent Kenwood TS820 transceiver receiver, 
one of the best analog radios ever built, I have yet to find a 
difference between the two sets sensititivity to weak signals, absence 
of spurious responses, images and overload... BUT, as expected the 
TS820's receiver can not be matched regarding its selectivity while 
picking up single side band stations, due to the shape of the IF 
filter's passband, something that the regenerative detector can not 
achieve for obvious reasons... Nevertheless when receiving CW signals, 
the two radios are producing almost identical results with extremely 
weak signals...

More about Arnie Coro's EHR , Experimental Hybrid Regenerodyne receiver 
in upcoming editions of your favorite radio program, the one you are 
listening to at this moment DXers Unlimited, from Radio Havana Cuba

........


QSL , QSL, yes QSL on the air to the many Dxers Unlimited listeners that 
keep sending reports about our station... And this is something that I 
want you all to know... Short wave broadcasts are targeted to specific 
zones, and although they sometimes may be heard in other areas of the 
world, even at very far away distances from the selected target areas, 
frequency planning does not contemplate providing service to zones 
outside the ones selected by the station to be the primary target 
areas...Just to clarify, let me give you an example... Radio Havana Cuba 
is beaming to the East Coast of North America on 6000 kiloHertz from 00 
to 05 hours UTC... From 00 to 01 we broadcast in Spanish, and from 01 to 
05 in English to North America from approximately northern Florida, all 
the way up to the north of the Canadian Maritime provinces and 
Newfoundland... BUT, you can certainly pick up our 6000 kiloHertz signal 
in Chicago, or Toronto, although the antenna beam is not in that 
specific direction, so this explains why listeners in Central North 
America should listen to our English language programming between 01 and 
05 hours UTC on 6180 kiloHertz, the frequency that is beamed into that 
specific direction ...

Many times , while opening up my e-mail just after waking up and having 
a cup of nice Cuban black expresso coffee, I receive reports of Dxers 
Unlimited coming from New Zealand, Australia, Argentina or maybe South 
Africa or Greece... and that's to be expected too, because every antenna 
system has minor radiation lobes into other directions than the main 
beam of the array, and when propagation conditions are good, our station 
can be heard all around the world, by an Antarctic expedition scientist 
or maybe by the operator of an air traffic control radar station in an 
isolated region of Norway...

Si amigos, yes my friends, short wave propagation is always full of 
surprises, even when going trough solar minimum as it is happening right 
now !!!

........



This is Dxers Unlimited's and here is now another popular section of the 
program... Antenna topics, that today will be devoted to indoor 
antennas, an option that is sometimes the only one at hand for many of 
this program listeners that live in apartment buildings or in areas of a 
city or town where outside antennas are forbidden by zoning 
regulations... Indoor antenna systems can improve performance over the 
typical portable radio's telescopic whip in a very significant way...

You will notice less fading, and higher signal levels when adding a 
length of insulated wire to your telescopic whip, and fixing the wire 
with plastic tape to a window, or just taping it to a balcony rail... 
Yes, I am talking about a lot of difference... many decibels amigos.. 
Just to prove this point I ran two tests at my home QTH using the small 
analog Grundig FR 200 receiver...

……………………..

// <http://www.radiohc.cu/ingles/dxers/dxersmenu2006.htm>//And now 
amigos , as always at the end of the show , when I am here in Havana, 
and can make both the optical and radio observations of solar activity 
and its incidence on the Earth´s ionosphere, here is Arnie Coro´s 
exclusive and not copyrighted HF plus low band VHF propagation update 
and forecast. Solar flux continues at bottom low levels, with the daily 
solar sunspot count at ZERO for many, many days now. Solar scientists 
have issued, once again , a so called solar quiet alert, something that 
is done to help researchers , so that they will perform certain 
experiments that should be done when a totally quiet Sun is keeping both 
the solar flux and the solar wind speed at very low levels. Despite this 
end of solar cycle 23 very low activity, radio amateurs continue to 
report some rare openings of the 10 meters band, that seem to defy 
theoretical analysis that exclude such openings when solar flux stay 
around 70 units for many days. February is coming to an end now, and 
with it, the transition from winter to spring propagation conditions, so 
be prepared for the much better equinoctial propagation that should be 
starting to be felt by the second week of March. In the meantime 
everyone is still waiting for yet another sunspot group from new solar 
cycle 24 to show up, something that according to several of my friends 
that study the Sun for a living , should had happened several weeks ago. 
So, we must continue to wait and in the meantime the best periods for 
low frequency Dxing continue to be from about an hour before local 
sunset to between one and two hours after the Sun sets at your location, 
and you may also pick up some DX stations on frequencies below 10 
megaHertz around midnight your local time, when stations located East of 
you will be seeing the Sun rise … I hope to be able to work some of 
Dxers Unlimited´s listeners that are also amateur radio operators on 40 
meters during my now almost daily operation on 40 meters using PSK31 and 
MFSK16 digital modes… see you around 7035 and 7070 kiloHertz amigos !!!


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