RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, JULY 24, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos RADIOAFICIONADOS! Welcome to your favorite radio hobby program on short wave and on the world wide web, and now also available in html format via our e-mail low traffic distribution list... I am Arnie Coro, your friend in Havana and host of this twice-weekly program devoted to the promotion and development of this wonderful hobby that you and I enjoy so much...
Start rolling your tape recorder now, here is item one: Solar coronal holes, several of them located at geoeffective positions, may disrupt high latitude radio communications during the next few days... The daily solar flux number is now near 140 units and moving down! So, the peak of this solar rotation is a thing of the past by now...
Item two: AO40, the troubled amateur radio satellite is now back in service, but the transponders so far activated are only available to very, very few radio amateurs, because they are using 70 centimeters and 23 centimeters uplinking and a 2 gigaHertz band downlink... As you may realize, just a handful of dedicated satellite operators have the appropriate equipment to access AO40 using the one and only 2 gigaHertz band downlink... More about amateur satellite communications later in today's edition of Dxers Unlimited.
Item three: lots of e-mail from listeners requesting specific advice on technical problems... something that makes me a very happy person indeed, as this shows how much you enjoy the hobby and how you see Dxers Unlimited as your friendly radio show that provides quick answers to your radio hobby-related questions... By the way, today I will be answering not one but two very interesting listeners' questions.
Stay tuned right here on this same frequency, and don't forget to set aside a little time to send me your comments about the show, QSL requests and signal reports, as well as any radio related questions to arnie@radiohc.org. Margarita Delgado is my sound engineer and producer, I am Arnie Coro in Havana, back with you in a few seconds, after this brief musical interval....
This is the mid-week edition of Dxers Unlimited, and here is item two in detail: Radio amateur satellites of the future.... without any doubt, radio amateurs have enjoyed satellite communications systems a lot. But few hams have had the appropriate equipment and acquired the know-how to be able to use those satellites. As a matter of fact, and according to a survey of sorts that I made a few years ago, it seems like the very brief communications window provided by low Earth orbit radio amateur satellites is the main factor that has kept many radio amateurs away from the regular use of those wonderful space-based relay stations.
The use of the LEOs, or low Earth orbit satellites, requires that the operators establish a contest type QSO... And the only two satellites so far capable of sustaining long contacts, OSCAR 10 and OSCAR 13, proved to be just a bit too sophisticated for the average radio amateur. OSCAR 13 burned when its orbit was so low that it actually entered the upper layers of the Earth's atmosphere, while OSCAR 10 is still active but without any control... in other words, OSCAR 10 is locked in a certain particular operating mode, and becomes available for certain periods of the year when the Sun illuminates its electricity-generating solar photovoltaic panels, making it possible for the radio equipment on board to operate.
By now I am sure that you realize that what the worldwide radio amateur community needs is an easy-to-access, geostationary orbit satellite, something that is unfortunately out of the question because of its astronomical cost... So, the second-best option should be to design starting practically from scratch, a radically new, long elliptical orbit radio amateur satellite, a bird that would stay available for several hours at a time, and that by playing with the orbital Keplerian elements, will make its access very easy to predict. Let's be optimistic, and see if the lessons learned from the AO10 satellite's problems will eventually lead to the first elliptical orbit satellite, easily accesible with low cost equipment and simple antennas.... The know-how is fortunately available, so let's all hope for the best!!!
QSL, QSL, QSL, yes amigos we do QSL here 100 percent, via AIR MAIL to your postal address, direct to your computer via INTERNET e-mail and right here, ON THE AIR... QSL ON THE AIR to our long-time listener and contributor to this show, Tim Rasch... Tim is always experimenting and surfing the World Wide Web in search of valuable radio hobby-related data... His most recent nostalgia radio project is the revival of two 1950's era automobile radios that use a very special type of vacuum tube plus one of the first-ever audio power transistors in a hybrid circuit...
Those very special tubes used 12 volts from the car's electrical system both on the filaments and on the plate and screen electrodes.... Amazing? Well, not much, if you do some interesting experiments with vacuum tubes, reducing the anode or plate voltage and watching what happens. One of my very simple vacuum tube regenerative receivers works like a champ when running 24 volts on the plate circuit, and provides still useable gain while running from 12 volts, and let me tell you that these are standard vacuum tubes designed for operation with rather high plate electrode voltages, from 100 to 250 volts DC...
QSL on the air to the many Dxers Unlimited's listeners who are now enjoying the NEW VERSION of Arnie Coro's broadband short wave receiving antenna, the TTFD-2... Yes, amigos, it's a very good compromise antenna system if you have space for only one skywire at your location... It is about 14 meters long, uses an 800 to 900 ohm terminating resistor and is fed using either open wire balanced transmission line or a 16 to 1 balun and 75 coaxial cable...
If you want to know more about the TTFD-2, an all around HF antenna for both the short wave listener and the radio amateur, just send me an e-mail to arnie@radiohc.org, and if you're not yet in cyberworld, then send an AIR MAIL postcard with your request for the TTFD-2 antenna files and graphics to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Now another very popular section of Dxers Unlimited, according to feedback from listeners around the world... here is YOU HAVE QUESTIONS, and Arnie tries to answer them!!! Two listeners' questions today amigos! Here is the first one:
Arnie, have already built the vacuum tube regenerodyne receiver from the circuit diagrams and text file you sent me... Now I want to ask you if this same high performance circuit can be, let's say, translated, into a solid state electronics version...
Well amigo from Wisconsin, USA... seems like you have telepathy... as that's exactly what we are doing right now here, with the advice of my long-time friend and professional engineer Jose Amador, radio amateur CO2JA. Professor Amador teaches at Havana's ISPJAE Technical University, and he has helped develop some very interesting circuits for radio amateurs, like the JAGUEY solid state 10 watt double side band transceiver. Following a lengthy exchange with my good friend Jose, I have just tested the solid state front end for the REGENERODYNE... and let me tell you, my friends, that it works great. So far, I have built the antenna input filter for just one amateur band, 20 meters, because it is the band that is open for DX most of the time all along the solar cycle...
Well, the new solid state version of the REGENERODYNE is now running... so, phase two of the project is going to be the hardest one to deal with, as I must be able to design and build a solid state REGENERATIVE detector that is as efficient and easy to use as the very reliable 6AK5 vacuum tube circuit that makes operation of the REGENERODYNE so nice.... It seems like I must use a dual gate MOSFET active device, together with a bipolar transistor Q multiplier. Don't worry, as soon as it is finished I'll make it available via our Dxers Unlimited website and Dxers Unlimited's mailing list! Ah... before I forget, the solid state REGENERODYNE audio module was the first one I finished, and both prototypes are working very well, providing excellent audio quality, and one of them has included a very useful and easy-to-build audio filter.
Now here is the second question that I'll be answering today here at the YOU HAVE QUESTIONS section of Dxers Unlimited... It came from a listener in Canada.... here is his question:
Arnie, have you tested a VHF version of the TTFD antenna?
ANSWER: Sure amigo, and I can assure you that it is a very nice antenna for scanner enthusiasts, although the VHF TTFD is not used in the same way as its HF counterpart. In actual practice you can install my VHF 30 to 150 mHz wideband terminated dipole in one of three different ways -- as a vertical antenna for optimizing the reception of vertically polarized signals, as a horizontal antenna for picking up horizontally polarized transmissions, or the way I use it here, at a 45 degree sloping angle, so that the antenna will be picking up both vertical and horizontally polarized radio waves. More about the VHF BROADBAND TERMINATED DIPOLE in an upcoming edition of this, your favorite radio hobby program, Radio Havana Cuba's Dxers Unlimited....
And now as always at the end of the show, in the public domain, for optimizing the enjoyment of this wonderful hobby, here is Arnie Coro's HF plus 6 meters propagation update and forecast. Solar activity will be moving downwards for the next two weeks, so we will be seeing rather low daytime maximum useable frequencies. Be aware of possible HF propagation disturbances that may occur during this week due to high-speed solar particles impacting the Earth 's magnetosphere... The number of sporadic E events will now start to go down... and when the solar activity is around 120 units and the A index, the geomagnetic disturbance indicator, is below 5 or 6 units, you may start to search for lower frequency DX after your local sunset.
See you at the weekend edition of Dxers Unlimited next Saturday and Sunday UTC days... And if you happen to be an active radio amateur, let's hope to have a nice two-way contact on 20 or 15 meters. My favorite spots for SSB QSO's are around 14.200 and 21.290 kiloHertz... See you there, amigos RADIOAFICIONADOS!!
Prepared 24-Jul-2001; transmitted 29-Jul-2001
Arnie Coro CO2KK
Havana, Cuba
July 24, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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