Radio Habana Cuba: Dxers Unlimited Weekend edition for June 3, 2000
By Arnie Coro, radio amateur CO2KK
Hi, my friends around the world!!! Welcome to the weekend edition of your favorite radio hobby show on short wave. I am Arnie Coro, radio amateur CO2KK, your friend here in Havana and host of this program which is entirely devoted to the promotion and development of our wonderful hobby, yours and mine... RADIO!!!
Here is item one: solar rotation downward swing is now over, and from now until the next expected peak, solar activity will increase on an almost daily basis. Expect the next peak to happen around June 12 to 15, reaching more than 250 solar flux units.
Item two: QSL on the air today will answer a nice e-mail sent from Canada, by a short wave listener and amateur radio operator that came back to ham radio after listening to Dxers Unlimited, amigos... That's good news indeed. I will answer Barry Bogart's questions a little later in today's show...
Item three of this weekend edition of Dxers Unlimited: Be on the lookout for CATV distribution cable. YES, get in touch with your local cable TV technicians as they may have surplus lengths of excellent quality low-loss coaxial cables that in many cases is simply given away to radio amateurs. OK, it is 75 ohm impedance cable, but I must tell you that it works wonderfully in any applications that you can think of.
Item four: More about the super crystal radios. Well, I got an e-mail from a listener who told me about his extraordinary success with medium wave DXing when he built a crystal-controlled up converter in which he uses the special high Q coils that he learned about when he received the e-mail with the detailed building instructions and circuit diagrams for assembling a super sensitive crystal diode radio receiver. Now, please stand by for a few seconds, I'll be back with more radio hobby related information after this brief musical interval... Margarita Delgado is my sound engineer and producer, I am Arnie Coro in Havana.
QSL on the air amigos, YES, this is the very popular QSL on the air section of Dxers Unlimited. Today I'll be answering an e-mail sent by a Canadian Short Wave Listener and Amateur Radio Operator, Barry Bogart VE7VIE, that is in phonetics Victor Echo Seven Victor India Echo... Let me now read Barry's e-mail:
TOPIC: 'new' hamI was a ham in '57 (at the age of 13), but I let it lapse. I have been a SWLer ever since, though, and listen to you regularly. I got interested in operating again, thanks partly to your broadcasts.
I took the Basic Qualifaction exam in Canada which is similar to the US Tech class. I have a dual-band HT but recently got a MFJ-9406 6m SSB rig. I am tempted to try some real QRP DX if the MUF moves up a little (or a lot)! I just put up a centre fed 6m dipole (running East/West) until I can get up a yagi, and I have the MFJ-906 Ant. tuner/SWR meter. So I was very interested in your two antenna suggestions on the weekend. But I have some questions.
What is the advantage of the 1/4-3/4 split? I was tempted to fold my dipole but never heard of a 1/4-3/4 design.
And your roll-back-the-braid one - would it be any better than a J-pole on 6m? And I am even more interested in your final mention of a 6m converter.
I also have a 7600GS (One of the most underrated receivers around!) and would love to be able to use it to scan 6m for some activity!
Fantastic idea! Do you have any documentation of the design available?
Thanks and 73
Barry, VE7VIEI am really very happy that you took your amateur radio test and are now on the air with your own station, also, it seems that you have just started on the 6 meter band right on target to enjoy this summer's sporadic E season, and a little later -- starting in late August or early September -- what could be described as the best F2 propagation season in many years! Now to answer your questions, the one quarter wave and three quarter wave antenna is about the lowest cost skywire that can give you actual directivity and gain. Try it, and remember to point the long leg of the antenna to the area that you want to cover. I use one of these antennas here at CO2KK keeping it beaming to South America, and results obtained are excellent.
Now second question, the coaxial dipole made from the same feeder coaxial transmission line... Its gain is exactly the same as a standard reference half wave dipole which, by the way, is about 2 dB below the gain of a standard J pole, which most authors describe as having roughly two dB gain over a standard reference half wave dipole...
Finally, amigo Barry in Canada, I will scan the circuit diagram of the easy-to-build, low-cost 6 meter band converter and e-mail the file to you. This easy-to-build converter uses a 40 megaHertz quartz crystal oscillator module to generate the local mixing signal, so your receiver tunes the first five hundred kiloHertz of the SIX METER band from 10 dot zero zero zero megaHertz up to ten dot five zero zero zero megaHertz which, according to what I monitor on 6, is the part of the band that is populated with CW, SSB, PSK31 and RTTY. The converter is a rather straightforward circuit using a well-designed, computer-optimized input filter, a single-stage RF amplifier, a double-balanced mixer and the above-mentioned quartz crystal oscillator module. Dxers Unlimited's worldwide audience includes many highly talented persons. One good day I will start publishing at our new website at least part of the very interesting mail that I receive here at Radio Havana Cuba regarding topics dealt with here at this show. Here is a good example: A medium wave band Dxer heard the show in which I mentioned the super crystal set circuit diagrams and technical information files; he requested them inmediately, and instead of just building the radio, he came up with what is certainly a bright idea. He tells me in another e-mail, "Arnie, why not use the super high Q coils as part of the input filter of an AM Medium Wave Band up converter?" In other words, he rightly thought that an up converter that will require tuning between 28 and 30 megaHertz, equipped with a set of super high Q coils at the input filter, could provide very interesting results when hunting for those elusive, weak, really weak AM DX signals. The input filter will have, as an additional feature, a well-calibrated signal attenuator, something that one would not need with the crystal set, and the absorption type additional L C tuned circuits will be there too, to help clear those adjacent channel stations that make loggings so difficult in many cases. I think that this is an excellent summer project, which can be designed, tested breadboard fashion and built as a prototype during the summer slow AM Band DX season, in order to have it ready for the autumn equinoctial DX weeks.
So, there you are -- once again, Dxers Unlimited is proving to be interactive too. And, you guessed right, I'm already collecting the parts to build one of these up converters too. Once again, this fascinating aspect of the radio hobby, adapting other's designs, proves to be really useful. My version of this converter will have a 27.5 megaHertz crystal oscillator, so that the receiver will tune starting at 28 megaHertz with 500 kiloHertz. The first channel of the AM medium wave band here in Region II will then be heard on 28.540 kiloHertz and the reception quality will depend a lot on what kind of receiver is used. I'll do all my experiments with an HTX-100, a Ten Meter Band amateur transceiver that I have used for similar projects in the past... So amigos, if you have not yet obtained the Super Crystal Radio circuit diagrams and data file, they are available via e-mail by sending your request to inforhc@ip.etecsa.cu and I'll e-mail them to you really fast. Also, don't forget to include a signal report and comments about this show and the station's programming too; and last, but not least, do include your postal mailing address so that Irma can send you our beautiful QSL card, verifying your reception report.
And now amigos, as always at the end of the show, here is Arnie Coro's exclusive HF Plus 6 meters propagation update and forecast: Solar activity has just reached the minimum for this rotation; from now on, you will see the daily solar flux figure move slowly up, until by June 12 to June 16 it will reach a peak of near 250 solar flux units. As more solar active regions develop, we may also see increased flare activity -- something that, as usual, may result in coronal mass ejections. Those, in turn -- if coming towards the Earth's magnetosphere -- will generate geomagnetic disturbances. As we advance into the summer solstice, daytime HF propagation gets worse... so, my advice is to go as high in frequency as you can during the daytime to enjoy best reception. During the evening hours your local time, reception in the segment from about 9 to up to even 18 and on some days even 22 megaHertz, is going to be excellent, and that's why I tell my amateur radio friends to stay up late and enjoy the nice DX conditions on the 30, 20, and some days also on the 17 and even 15 meter bands, well after 10 pm local time. AM medium wave band DX is poor, to say the least, and the same holds for the ever-popular 80 and 40 meter amateur bands. It's summertime here in the Northern Hemisphere, and solar cycle 23 continues to move towards its now-delayed peak, expected to take place at the end of this year or even later!
See you on 6 meters... I'll be monitoring the band scanning from 50.080 up to 50.200 when at home, and during the very early morning here in Havana, that's around 0900 Hours UTC, I'll be looking for DX on 20 meters, too!!! Don't forget to send your Air Mail reports to Arnie Coro, Radio Havana Cuba, Havana, Cuba. We QSL here 100 percent, amigos!!!
Arnie Coro CO2KK
Havana, Cuba
3 June, 2000Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba
PO Box 6240, Havana, CUBA 10600
phone: 53-7-814243
phone res: 53-7-301794
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