RADIO HABANA CUBA
DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, JULY 28, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos radioaficionados!!! Welcome to the weekend edition of your favorite radio hobby program, on shortwave and on the WEB! I am Arnie Coro, radio amateur CO2KK, your friend here in Havana and host of this twice weekly show devoted to our wonderful hobby, the one and only you and I enjoy so much: RADIO!!!
Here is item one: NEW AMATEUR RADIO METEOR SCATTER RECORD.... heard it!!! A new record, and it was set by Cuban radio amateur operator Oscar Morales Jr. CO2OJ, Charlie Oscar 2 Oscar Juliet... stay tuned to learn more this record-breaking QSO that was made using computer software specifically designed to optimize meteor scatter communications...
Item two: The Sun is very, very quiet, and the number of sunspots is steadily declining... latest sunspot count Saturday was 96, down from 115 on Friday... But, the very low to low solar activity has not stopped hams from having a nice time on the 15 meter band, the 21 megaHertz amateur band, working the Islands on the Air Contest... Lots of European stations worked and heard here in Havana Saturday morning at CO2KK, my ham radio station...
Item three: A very interesting thread going on at the GLOWBUGS vacuum tube enthusiasts e-mail list... It has to do with the use of low plate voltages and how radios still work when using much lower voltages than they originally used....
And, as always at the end of the show, you will be able to pick up Arnie Coro's HF plus 6 meter band propagation update and forecast...
Margarita Delgado is my sound engineer and producer, here at RHC's studio 7... I am Arnie Coro, stay tuned...
The name of the show is Dxers Unlimited, you are tuned to Radio Havana Cuba, and here is Item one in detail, amigos!!! NEW Meteor Scatter Amateur Radio Record.... CO2OJ, my good friend Oscar Morales Jr. the son of my ham radio mentor and Elmer, CO2OM, Cuba's topmost Dxer ever, followed his dad's achievements by implanting a new meteor scatter record this Saturday!!!
Oscar used a very new software that sends and receives very short bursts, so that the chances of the signals finding an ionized meteor trail are increased substantially... The two meter amateur band signals from Oscar's station were sent using a 100-watt power amplifier working into a homebrew 9 element Yagi.
The record-breaking contact was made with Russ K2TXB, and the distance between the two stations is 1233 miles, or 1984 kilometers -- almost at the theoretical limit for a meteor scatter contact, if one considers the altitude of the ionized trail to be located within the E layer of the ionosphere... The contact was made on a typical amateur radio meteor scatter schedule; it started at 0400 UTC July 28th, and ended almost one hour and a half later, at 0523 UTC.
The technique used is known as HSMS; that stands for High Speed Meteor Scatter, and uses a special recently developed software that goes by the name of WSJT. Oscar and Russ used the WSJT frequency shift option, and it proved to be very effective, even though there certainly was no meteor shower in progress. I guess that when the upcoming Perseids Meteor shower comes, many new meteor scatter records will be made using this very special computer program, WSJT, which is capable of sending and receiving very short bursts in order to use even the smallest meteor's trails to communicate...
Congratulations Russ and Oscar for your outstanding achievement, amigos!!! K2TXB in the United States of America and CO2OJ in Cuba are now the North America and the Caribbean record-holders for meteor scatter communications, one of the more than 50 ways that YOU can enjoy the radio hobby!!!
arnie@radiohc.org, that's the e-mail address to send your signal reports and comments about the show and the easiest way to get in touch if you already have access to an e-mail system... Via Air Mail, send a postcard to Arnie Coro, Radio Havana Cuba, Havana Cuba, and don't forget to include your return postal address!!!
Now here is item two: The Sun is very quiet, solar activity now oscillating between very low and low, but according to experts, this may change in a few weeks, just in time to give all of us a nice equinoctial DX season... The daily sunspot count Saturday morning here in Havana was just above 95, and the solar flux was at 120 units, barely enough to keep the 21 megaHertz or 13 meters international broadcast band, and the amateur 15 meter band open for a few hours... No more signs of coronal holes, so expect very good AM medium wave band DX conditions during the next three to five days... something unusual at this stage of the solar cycle and time of the year...
There are several very interesting radio hobby mailing lists; one of them goes by the name of the GLOW BUGS, in clear reference to the light emitted by vacuum tube filaments when operating... The list has many experienced electronic hobby enthusiasts among its members, and guess... sure, I am also a member of the GLOW BUGS mailing list!!! One of the most recent threads has proven to be very interesting. It has dealt with vacuum tube anode and screen electrodes operating voltages, and how they may be reduced and still obtain not only good but actually better performance from the radio receivers that use them.
I tried this approach on a very nice Chinese-made R403 Communications Receiver, made in the People's Republic of China in 1963... It was used by Cuban Coastal Communications stations before it was retired from service about 10 years ago... The R403 is certainly a collectors item!!! It is a very straightforward superheterodyne single conversion receiver, and the vacuum tubes run at about 225 volts DC on the plates... After following the thread about lower plate voltages going on at GLOW BUGS, I decided to reduce the plate and screen voltages of all except the final audio amplifier beam tetrode, a rough equivalent of a EL84, 6BQ5... and here are the results: The receiver gain changed practically NOTHING, but two other parameters did change, and took a turn for the better -- frequency stability increased signficantly, due to the lower amount of heat generated when the tubes were powered from a 30 volts DC supply, and the receiver's noise level also went down dramatically. So, now I am going to modify the R403 receiver by feeding all the vacuum tubes except the audio output stage with between 30 and 50 volts from a variable voltage electronically regulated power supply.
In order to preserve the receiver's collector's value, I will do it in such a way that the modification may be reversed at any time... The extra power supply is going to be an outboard one, using solid state, up-to-date technology!!! and that's something that I should not be talking about among the old receivers enthusiasts...
Anyway, the experiment proved to be a very interesting one indeed, and it was really very easy to implement... The current taken by the tubes when operated from the plus 30 to 50 volts DC power supply is actually less than the power they use when fed from the radio's built-in 225 volts DC supply, so I will be able to build a rather lightweight unit... Guess than no more than about 200 milliamps is going to be more than enough, so even a single LM317 voltage regulator will take care of all the power needed by the vacuum tubes anodes and screen electrodes. The LM317 variable voltage regulator and its equivalents handle between around 1.5 volts and 37 volts at a typical 1 ampere current rating...
Yes, I am already looking for all the parts needed for this project that is now my top priority for the rest of the weekend, a weekend that I will have to split between the workbench and the amateur radio operating position, because the Islands on the Air Contest is now also in progress, and many contest stations need to work Cuba, North America 15 IOTA designator, that CO2KK can provide!!! If you happen to be the happy owner of one of those old vacuum tube communications receivers, reducing the plate and screen voltages to the tubes in the signal path may not only improve your radio's performance but actually extend the useful life of its tubes and other electronic components!!!
Now item four: YOU HAVE QUESTIONS, and yes Arnie tries to answers them FAST!!! Today's question came from a listener in the United Kingdom:
Arnie, I have just heard about an antenna with a very funny name... Its name is the HEN-TENNA... have you heard about it?
Well, amigo Grant from the UK, yes the HEN-TENNA is a japanese-designed LOOP ANTENNA, and the HEN part of the name has nothing to do with the rooster's nightmare... HEN in Japanese, they tell me, means something like marvelous or marvel.... so HEN-TENNA stands for marvel antenna!!! By the way, I do use it here for TV reception of our VHF TV channels... My local TV stations operate on channels 8 and 10 in the range from 174 to 216 megaHertz, and I found out that a HEN-TENNA cut for the center frequency between the two TV stations works very well with my ATEC, Advanced Technology Cuban-built TV set. The HEN-TENNA is very easy to match with transmission lines in the range from 50 to 90 ohms. Here I use standard TV-type 75 ohm cable downlead, and reception is really nice with a single element LOOP HEN-TENNA!!!
And now amigos, as always at the end of the show, here is Arnie Coro's HF plus 6 meters propagation update and forecast: Solar activity is moving DOWN, and I expect this solar rotation to reach very low values of solar flux and sunspot count... Solar flux will move down from the present 120 to just around 100 by Friday. BUT, as always, be on the alert, as a new sunspot group can start growing at any time!!! The lower solar activity has reduced the number of hours of 15 meter amateur band and 13 meter broadcast band openings... and 10 meters is only open to the South for a brief period during your local afternoon. Sporadic E events may still happen, but their number and frequency is now certainly much less than during previous weeks. AM medium wave band Dxing should be good between around 2 o'clock in the morning and a few minutes before sunrise your local time...
See you at the mid week edition of Dxers Unlimited, next Tuesday and Wednesday UTC days, and don't forget to send your signal reports and comments about the show to arnie@radiohc.org, amigos! And if you are participating in the IOTA contest, look for CO2KK North America 15 between 21.280 and 21.300 Sunday, starting at 1200 UTC!!!
Prepared 28-Jul-2001; transmitted 29-Jul-2001, EDT
Arnie Coro CO2KK
Havana, Cuba
July 28, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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