Dxers Unlimited
Dxers Unlimited's mid week edition for April 8 - 9 2003

By Arnie Coro

radio amateur CO2KK




Hi mis amigos aficionados !!! You love radio and I do to... Have you ever thought of a hobby that
could be enjoyed in so many ways, have you ever thought what other hobby gives you the unique
possibility of making friends all around the world ? Well the radio hobby is capable of providing
unique moments, like when in the middle of a hurricane your amateur radio station is the only link
connecting your town with a those that can make the emergency resources reach your fellow citizens
!!! And radio is also capable of providing you and your family with the most up to date information
on what's happening around the world, direct and from the source where the news events are happening
... yes short wave broadcast listening is one of the most rewarding and interesting aspects of the
radio hobby. Yes, radio is a lot of fun, and it's still more fun when you start homebrewing your own
equipment... even a simple crystal set, a receiver that does not require any external power source
will provide that unique pleasure of listening with a radio that came out of your own hands... Item
one: Long range forecast for the last phase of the solar cycle ... according to recent analysis done
by several solar physicists, the cycle may be ending earlier than expected, but other collegues
disagree, and they are advocates or a rather swift ending solar cycle 23 that will reach a period of
extremely low activity between the years 2006 and 2007, but that's not all, there are still other
scientists that , after reviewing the most recent solar data gathered by several satellites, believe
that the solar cycle will have , now listen to this, they believe that there is going to be a third
solar activity peak, making this cycle a rather unique one indeed. Whichever way solar activity
goes, they all agree that around 2006 we should see a period of very low solar activity, and that
amigos means that we must all get our long wire antennas ready, as the higher bands are going to be
in really poor shape starting in about a year from now. Item two: Radio hobby related questions keep
coming in from all over the world, the equinoctial propagation conditions are responsible for really
long range reception of our Radio Havana Cuba signals, especially ou 9820 kiloHertz transmitter that
is used from 23 hours UTC all the way up to 0700 UTC. By the way, the first hour of the 9820 kHz
broadcast is in Spanish, and it is beamed to Central North America, so if you really want to
practice your Spanish, here is a good opportunity for those of you that live in the Central USA and
Canada. As I said radio hobby questions are coming from all over the world, and its nice to see how
many people are once again listening to short wave broadcasts to learn about world events . Todays
two questions have to do with power supplies, and I am sure many of you will take notes, as one of
the answers will help you reduce the noise level that your receivers pick up. Item three: Another
antenna topics section of Dxers Unlimited, explaining details about the INVERTED L, one of the most
well known and less understood antennas ... And why Arnie Coro's INVERTED L with tuned counterpoise
works so well, especially if you can make the vertical section no less than 5 meters in length and
the horizontal section of no less than 7 or even better yet 10 meters. And as always at the end of
the show , you will be able to listen to our exclusive and not copyrighted HF plus 6 meters
propagation update and forecast. This is Radio Havana Cuba, and the name of the show is Dxers
Unlimited, coming to you twice weekly amigos. Margarita Delgado is my sound engineer and producer, I
am Arnie Coro back with you in a few seconds:

......

Well amigos, two radio hobby related questions will be answered right now.. Both are power supply
related... Number one, a listener from Ohio asks, Arnie you talked about placing disk ceramic
capacitors across the diode rectifiers ,does that advise also applies to vacuum tube rectifiers...
Well amigo, Jules, the answer to your question is YES, if you are using vacuum tube rectifiers for
your antique radios, like the classic type 80 , or the more modern 5Y3, 5U4 , 5R4 or 6X5 among
others, it is a very good idea to place high voltage disk ceramic capacitors of a value of .01
microfarads or 10 nanofarads between the high vacuum diode's

cathode and plate. Be sure that the capacitors are rated at no less than 1 kilovolt for the common
receiver power supply's voltages. Installing those capacitors , will reduce the modulated AC hum
noise that may be present in many old receivers, and all that I can say that even if you don't seem
to notice any difference, they will certainly do no harm at all. Regarding solid state rectifiers,
the same value of capacitance applies, .01 microfarads , which is equivalent to 10 nanofarads
capacity will certainly reduce the noise level, especially when you are using regenerative
detectors... Now question number two, from a listener in Quebec City, Canada, Arnie Coro , amigo,
why do you talk so much about regenerative receivers, aren't they an obsolete technology ? Signed :
Your friend Marcus in Quebec City.. Well amigo Marcus, all I can say that the regenerative
detectors, when properly built are simply fantastic receivers !!! If you combine the best of both
world, using frequency conversion with a crystal controlled oscillator and a variable tuned low
frequency regenerative detector, you come out with a unique receiver known as the REGENERODYNE...
that although it is relatively easy to build and operate, will provide features like AM, PM, FM, SSB
and CW reception at very low cost... Now let me add that the regenerative receiver is not a totally
forgotten concept by today's radio design engineers, many of those car key locks that connect and
disconnect the alarms and lock the car by means of radio waves use, you guessed right !!! A
regenerative receiver operating on a UHF frequency !!! And for your information, I have built a
library of regenerative receiver's circuit diagrams that is growing day by day... Perhaps amigo
Marcus you may want to see the circuit diagram of the cascode regenerative radio, that uses just two
common dual triodes, type 12AT7 equivalent to the European ECC81and works extremely well from
frequencies below the broadcast band up to the 10 meters or 28 megaHertz amateur band.

.........

This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes, we do QSL here one
hundred percent. Irma Veitia at our correspondence department keeps record of all the correspondence
that we receive at the station, andif your signal report and program content description are OK, we
will send you an RHC QSL card, absolutely free... for you to add to your QSL card collection... NOw
our antenna topics section is on the air; The L antenna , a wire with a vertical section followed by
a horizontal section, is according to radio manuals of the early 20th Century as old as radio
itself, and it happens to work very well, when properly designed, built and installed. The INVERTED
L as it is known among experts is an excellent general purpose antenna system, that when
complemented with a ground counterpoise system, can provide very effective reception, and it is also
a nice transmitting antenna too. BUT, now listen to this, the INVERTED L, according to my extensive
experiments seems to have minimum critical dimensions... they are no less than 5 meters for the
vertical section and no less than 7 meters, or better yet 10 meters length for the horizontal
section of the antenna. An INVERTED L with those minimum dimensions will operate nicely from
frequencies as low as 6 megaHertz and all the way up to 30 megaHertz, when used with a PI network
antenna tuner, and don't forget that an INVERTED L antenna without a ground system will show very
poor performances on frequencies below 10 megaHertz. Installing a set of ground radials below the
INVERTED L, will provide a much more effective radiating system. That's why I always recommend
installing the INVERTED L with no less than five radial ground wires that are connected to the
antenna tuner ground using heavy wire or better yet a copper strap of no less than an inch or 25
millimeters width. For a long time I had an INVERTED L that was 8 meters high and about 37 meters
long. With that antenna equipped with five 39 meters long radial ground wires, I was able to work a
lot of 160 meters amateur band DX during the low ebb of the last solar cycle. Yes, the INVERTED L is
both easy to build and to install, but you must ALWAYS keep in mind that it does need a ground
system, as otherwise the antenna will show a rather poor performance, and it will be also difficult
to tune to whatever frequency you want to listen or transmit.

You can feed an INVERTED L with an assymetric transmission line of between 50 and 150 ohms, and then
tune it with a PI network antenna tuner, something that will give you not a broadband antenna, but a
really flexible , tuneable antenna system with a rather broad frequency range.

.....

Si amigos ! Yes my friends, the two vacuum tube regenerative receiver using the cascode detector is
available to all Dxers Unlimited's listeners that have an e-mail account and may be able to receive
attachments... Send your request for the two tube regenerative circuit diagram to arnie@rhc.cu,
again, it is easy to remember, arnie@rhc.cu and you will receive the circuit diagram of that easy to
build radio, that is capable of operating from frequencies as low as 200 kiloHertz, and as high as
the 10 meters or 28 megaHertz amateur band... And now , as always at the end of the show here is
Arnie Coro's Dxers Unlimited's exclusive , but not copyrighted HF propagation update and forecast...
Solar activity is expected to be low for the next several days, and the sunspot count has gone down
now to 94 , after several days of way above the 100 hundred level , the effective sunspot number was
66 on Tuesday at around 18 hours UTC and the effects of yet another coronal hole were starting when
I was writing the script of the show. Expect disturbed propagation at latitudes higher than 40
degrees North. See you at the upcoming weekend edition of Dxers Unliimited , next Saturday and
Sunday UTC days amigos