DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, JUNE 12, 2001
By Arnie Coro CO2KK
Send your comments, questions and ideas to: arnie@radiohc.org
Hi amigos! Welcome to the mid-week edition of your favorite listener-oriented radio hobby program, on the air and on Dxers Unlimited website, and now also available via our exclusive free subscriptions to Dxers Unlimited's mailing list...
Item one: Typical summer propagation prevailing in the whole Northern Hemisphere... lots of interesting Sporadic E layer openings happening even at 5 o'clock in the morning local time, according to our good friends Bob Chandler VE3SRE and Oscar Morales CO2OJ, that spent a lot of time hunting for rare DX during this past weekend's VHF contests...
F layer long range HF propagation is certainly peaking after local sunset, as expected due to the daytime thermal expansion of the ionosphere... More about the characteristics of summer season propagation later in today's edition of Dxers Unlimited...
Item two: Harold Cheney, another radio amateur, homebrewer and faithful listener to this show sent in a very interesting question... Listen to it:
Arnie... the 6 meter band is opening up a lot these days, and people are working a lot of interesting DX, here is my question... how would a REGENERODYNE receiver perform on the 50 megaHertz, or 6 meter band?
Well amigo Hal, I am happy to be able to answer your question here today, I am also sure you are listening, so stay right here on this frequency to learn about how the REGENERODYNE is performing on VHF frequencies....
Item three: QSL on the air to the UK Six Meter
Group... Just received the May
2001 issue of their excellent magazine, "SIX NEWS."
You can see the UKSMG
website by going to www.uksmg.org, where
you can learn how to become a member of that international radio amateurs
and listeners club that is devoted to the promotion of the use of the MAGIC
BAND, SIX METERS, on a worldwide scale... And soon you are going to be able
to read an article that I wrote especially for "SIX NEWS," too...
Margarita Delgado is my sound engineer and producer, I am Arnie Coro, radio amateur CO2KK in Havana, back with you in a few seconds, amigos!
You are listening to the mid-week edition of Dxers Unlimited, this is Radio Havana Cuba, and for those of you with receivers capable of tuning to Single Side Band signals, we do operate on SSB too.. 13660, 11705 and 9830 kHz are the three frequencies that we are presently using on SSB... The 11705 kiloHertz transmitter is on the air from 0100 to 0500 UTC with one of our curtain arrays that is beaming due North from Havana, providing excellent service via the one hop F layer mode above 30 degrees North Latitude and all the way up to the North Pole...
Now, as promised, here is a special report... answering FAQ's -- frequently asked questions -- about summer season propagation...
Question number one: Why does the ionosphere show lower daytime maximum frequencies during the summer? Answer: Because of thermal expansion... Yes, you heard it right -- during the summer the ionosphere expands due to the thermal input from the Sun's radiation... and for that very easy-to-understand reason, electrons are farther apart from each other. If you ask scientists, they will tell you that the number of free electrons per cubic centimeter is much lower at all altitudes during the summer season and, as expected, a lower number of free electrons provide much lower maximum useable frequencies....
Question number two: What's the best period of the day to hunt for DX signals during the summer season? Answer: No doubt, after the SUN SETS at your location, because the ionosphere will start to contract and the number of free electrons per cubic centimeter will increase... So here is the paradox... AFTER the SUN sets, we are able to work more DX, because the maximum useable frequencies actually are HIGHER during the period that starts roughly after your local SUNSET...
Question number three: When is the best time period for Sporadic E skip signals? Answer: Well, as I said at the start of today's program, Sporadic E can happen almost at anytime during the 24 hours of each day... BUT, we usually see a greater number of sporadic E events during three well-defined time periods... from about 7 am to 11 am local time, from about 3 pm to 7 pm local time, and there seems to be another period of frequent sporadic E openings that starts around 10 pm local time and will usually last until about 2 AM... This last period is not well documented yet, but the increased use of the amateur 6 meter band is making it clear now that there is certainly a higher probability of sporadic E events from 10 pm to 2 am in the morning local time. So again, we seem to be able to witness sporadic E events from 7 am to 11 am local time, from 3 to 7 pm local time and from 10 pm to 2 am local time... AND, I must add that sporadic E events do happen at anytime during the summer months with a clear peak happening precisely right now, during the month of June, around the summer solstice, and a smaller peak also happens during December in the Northern Hemisphere. Those of you who happen to live in the Southern Hemisphere will see that the Sporadic E season "down under" is all the way around, with the peak happening during December's southern hemisphere summer solstice.... FM band and TV Dxers make very good use of Sporadic E events to add new stations to their logs, too!!!
Send your QSL requests, signal reports and comments, plus your radio hobby related questions via e-mail directly to me: send mail to: arnie@radiohc.org and if not yet in cyberspace, send a postcard VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba. No need for more -- my friends at Correos de Cuba, the Cuban Postal Service will place your postcard or letter in our mailbox when they see Radio Havana Cuba there....
Now item two... Answering our good friend Hal's question... YES amigo, the REGENERODYNE receiver is a good VHF radio indeed... My VHF version of the REGENERODYNE is a hybrid radio, using both solid state devices and vacuum tubes. Here is a brief description of the VHF version of the REGENERODYNE: This receiver is still very experimental in nature, and the regenerative detector was first set to operate from 5 to 10 megaHertz, in order to be able to use the radio for exploring the frequency range from 30 to 80 megaHertz by selecting appropriate quartz crystals for the front end...
BUT, I soon found out that the IF feedthrough -- that is, the signals that were leaking past the front end into the regenerative detector -- made reception of VHF signals very confusing to say the least. SO, I decided to move the Regenerative detector's frequency way up to avoid the IF feedthrough problem. The detector is now working from 16 to 21 megaHertz, and is much better shielded now. The number of signals that leak through from the antenna into the detector's range is much lower, and the regenerative detector can be operated as a straight AM receiver, taken near to the oscillation point to receive SSB and CW signals and, by operating the detector in the super-regenerative mode, I can receive narrow and wide band FM signals, too, with rather good quality....
BUT amigo Hal Cheney, operating the regenerative detector of the REGENERODYNE from 16 to 21 megaHertz has required the use of very sophisticated shielding, and battleship-like construction... The front end of the receiver is rather conventional, using a MOSFET Radio frequency amplifier, a diode ring mixer and a bipolar transistor crystal oscillator... The 6 meter band is tuned by using a crystal that I found on an old computer card that is marked 34 megaHertz -- a rare frequency indeed. Doing some simple mathematics will tell you that 50 megaHertz minus 34 megaHertz produces 16 megaHertz, so the first 500 kiloHertz of the 6 meter band are tuned from 16 to 16.5 megaHertz with the regenerative detector. AND just for your information, I tested the front end of the Regenerodyne with my Russian built R-250M2, a professional triple conversion receiver, tuned from 16 to 16.5 megaHertz... I then compared reception using the R-250M2 and the Regenerodyne using a very weak signal, actually a birdie from our local channel 2 station, and found out that the REGENERODYNE's sensitivity compared very favorable with the professional receiver using the same front end.
You are listening to the mid-week edition of Dxers Unlimited, coming to you from Radio Havana Cuba... and here is item three, this one for short wave listeners... Amigos, you will be able to pick very nice signals from Australia, Japan and New Zealand if you happen to live in Eastern North America, by setting your alarm clocks for an early morning hour... During the summer season, signals from "down under" come in very well on the 31 meter band from about 0900 UTC to even after 12 hours UTC... and their signal level is a very good indicator of how the propagation path is behaving, very useful information for amateur radio operators too!
Prepared 12-Jun-2001; transmitted 17-Jun-2001, 22:58 EDT
Arnie Coro CO2KK
Havana, Cuba
June 12, 2001
Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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