DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, MAY 26, 2001
By Arnie Coro CO2KK
Send your comments, questions and ideas to: arnie@radiohc.org
| Hi amigos, welcome to the weekend edition of Dxers Unlimited! Solar activity is still going up, and there is a rather large and magnetically complex sunspot group that may be producing solar flares during the next two to three days... I am Arnie Coro, your friend here in Havana, and just at the start of the show, I want to run a tape I made a few days ago right here at RHC's studio 7. My good friend and five-time visitor to Cuba, Dietrich Rosenau from Berlin, Germany came in as usual to say hello... Dietrich was having a nice vacation in Varadero, but he took one day to visit Havana and the RHC studios... I asked Dietrich to say hello to many of our friends in Europe who listen to Dxers Unlimited, and of course Dietrich said he would do it... in German. So listen now to Dietrich Rosenau, long-time Short Wave Listening Enthusiast,Tropical Bands expert and writer of many articles for German Radio Hobby magazines... [tape] |
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| In today's edition: Paul's Traveler's Antenna |
Ok amigos, you have just heard my good friend and long-time Radio Havana Cuba listener Dietrich Rosenau send a salute to our German-speaking listeners, to whom we hope someday in the future to be able to broadcast in their own language... in the meantime, German-speaking amigos, keep listening to our English language Dxers Unlimited!!!
Stay tuned for more radio hobby-related information, coming to you from Havana with love. Margarita Delgado is my sound engineer and producer, I am Arnie Coro, back with you in a few seconds...
The name of the show is Dxers Unlimited, you are tuned to Radio Havana Cuba, and for those of you who enjoy late evening listening of our English Language Broadcast in Eastern North America, we have on the air our 100 kilowatts on 9550 kiloHertz. From 01:00 AM to 03:00 AM. Eastern Daylight Saving Time, you can listen to the late late edition of Dxers Unlimited there, the last rerun for the broadcast day, just after 0530 UTC, that is around one thirty in the morning EDST or thirty minutes past midnight Central... The frequency again: 9550 kiloHertz, on the air with our English programming from 05 to 07 UTC...
That's our New York Rhombic Antenna, designed by Radio Havana Cuba's founding father and my mentor Dr Jose A Valladares Ph.D., as recently rebuilt under the supervision of two other great RHC engineers, Dictinio Diaz and Hector Esperon. So if you pick up 9550 kHz in English during the late, late evening hours Eastern and Central, send me a signal report and comments about the quality of reception, something that will make 85-year-old Pepe Valladares, the designer of that antenna 40 years ago, a very happy old timer indeed...
Recycling: Recycling, amigos, is the way to go in order to obtain high quality electronic components for your experiments at practically zero cost.... Don't send those old computer plug-in cards to the dump ... Save them! Recycling older computer plug-in cards, the ones that are connected to ISA slots, is a very nice way of obtaining valuable electronic components for free... Every legacy video card has at least one quartz crystal and many other useful parts. The same holds for old floppy disk and hard drive controller cards...
My latest regenerodyne receiver, a combination of a simple crystal-controlled converter and regenerative detector, uses several crystals salvaged from old ISA slot computer cards. For example, the 1.843 kiloHertz crystals not only make a nice single tube CW transmitter for 160 meters, they also provide coverage for Tropical Reception with the regenerodyne, tuning from about 3.8 to 5.8 megaHertz when the regenerative detector tunes from 2 to 4 megaHertz. But this combination has a little problem that you will soon notice... the second harmonic of the 1.843 crystal will saturate the receiver as you tune from about 3.65 to 3.7 mhz, but that is a small price to pay for using a free crystal!!!
I have received several questions from Dxers Unlimited's listeners asking why use this frequency conversion set-up, and the answer is that your detector will always work within a limited frequency range, you can calibrate your dial, and calibration will not drift away, and last but not least, the overall receiver gain and stability is much better than when you connect a regenerative detector directly to the antenna... To that I must add that by using the Radio Frequency amplifier and mixer stages ahead of the detector, you avoid many problems that are typical of regenerative receivers when coupled directly to the antenna....
Computer plug-in cards and fried motherboards will provide you with a lot of quartz crystals to extend the tuning range of your REGENERODYNE receiver, and you can also make good use of computer clock oscillator modules, that only require a 5 volts positive DC voltage to operate!!! AND... By the way, and before I forget you can learn a lot more about regenerative receivers by requesting Arnie Coro's Regenerative Receiver INFO PACKAGE. send you request to arnie@radiohc.org, and if not yet in cyber space, then send your request via AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Want to know the best times for listening to short wave during this summer season? Here is Arnie Coro's advice, optimize your listening schedules to start just after local sunset, then again just around midnight your local time, and set your alarm clock for as early in the morning as you can....
Now more about computers and radios:
High-speed computers, the ones that run their internal clocks above the 300 megaHertz don't only work faster... they also have proven to be much quieter from the radio frequency interference point of view... Very fast clocks do not cause interference to short wave reception as do older machines using clock frequencies all the way from around 4 megaHertz to 33 megaHertz. When asked by a Dxers Unlimited listener via e-mail why his primary machine did not affect his short wave reception, while his older DOS 386 running at 16 megaHertz did, I explained to him that the newer machines do not have harmonics that impact badly on the short wave spectrum....
But there is still one big problem with operating computers and radios side by side... when you are using cathode ray tube monitors, the high power horizontal output sawtooth waveform can make reception next to impossible. That's why it is a very good idea to use a liquid crystal display machine to interconnect to your radios... Here is one nice trick: try changing your monitor's refresh rate, something that MUST be done carefully, as some computer monitors can be actually damaged if you switch to a wrong refresh rate... SO VERY CAREFULLY try changing your monitor's refresh rate and see how many of those carriers just disappear!
More about regenerative receivers: Among the very nice designs sent in by Dxers Unlimited's listeners is one using 4 field effect transistors, that seems to be very easy to reproduce... I'll have it posted at the website and in the meantime, you can request it directly via e-mail, and I will send it as an e-mail attachment. It is a nice very clever circuit, in which the designer adapted the field effect transistor's characteristics to a circuit that belongs to the vacuum tube era... not too long ago, I was talking to a very knowleadgeable radio amateur, and he was telling me that the old workhorses of field effect transistors -- the 2N3819 and the MPF102 -- could be thought of as the solid state equivalent of a 6C4 or EC92 vacuum tube triode, something that simplifies designing solid state circuits using field effect transistors.
The 4 FET regenerative receiver circuit can be requested via e-mail by sending your request to arnie@radiohc.org, and I'll be very pleased to send it to you as soon as possible, but let me then ask something from you in return: As soon as you build the 4 FET regenerative receiver, send me your comments, so that they can be shared with the rest of Dxers Unlimited's worldwide audience... OK??? I'll be waiting first for your requests, and a few days later for your comments about how the circuit worked for you!!
Paul's Traveler's Antenna
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And today those who are already subscribed to Dxers Unlimited's mailing list will receive a script with several photos of the Traveler's Antenna. Designed by my good friend Paul from Arizona, USA, the Traveler's Antenna is a very low-cost, easy-to-make yourself portable antenna that reels up after use, and that will boost short wave reception a lot as compared with the typical portable radio's telescopic whip.
If you want to subscribe to Dxers Unlimited's mailing list, send your request to majordomo@rhc.cu leave the subject line blank and in the body of the message just type the following: subscribe dxers_l. And if you happen to have any trouble with majordom, just send me an e-mail to arnie@radiohc.org and I will subscribe you manually. Dxers Unlimited's e-mail distribution list sends you an HTML format document with the script of the show and NOW also some illustrations related to the topics dealt with in that particular edition...
AND NOW, AMIGOS! As always at the end of the show, here is Arnie Coro's Dxers Unlimited's HF plus 6 meters propagation update and forecast: Solar activity will continue moving up... Solar flux will probably peak somewhere around 180 units during this solar rotation, but the perspective for next solar rotation is that it will almost certainly peak no higher than 150 units; this depending of course, on no new active regions showing up.
Six-meter band operators from Europe and South America are experiencing a very unusual post-equinoctial DX activity, which is hard to explain with such low solar flux figures as we are seeing now... For easy short wave listening during your local evenings, do keep your radios to the highest possible frequency where the programs you enjoy are available...
See you next Tuesday and Wednesday UTC days at the mid-week edition of the show, and don't forget to e-mail me your signal reports and comments about the show to arnie@radiohc.org!
Arnie Coro CO2KK
Havana, Cuba
May 26, 2001
Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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