Radio Habana Cuba: Dxers Unlimited Weekend edition for July 1, 2000
By Arnie Coro, radio amateur CO2KK
Hi! Welcome to the weekend edition of Dxers Unlimited, your favorite radio hobby program on short-wave... the one and only with the wide scope coverage every radio hobbyist deserves. I am Arnie Coro, radio amateur CO2KK in Havana, and here is our menu for today: YES, you already have noticed...HF propagation conditions are very good, considering that we are in the middle of the summer season... Solar flux data shows 160 units, and the forecast calls for a nice jump to 180 solar flux units in no more than three days. Saturday morning my local time here brought a nice mixture of Sporadic E and F2 propagation, with 21 megaHertz the best option for DXing during the daylight hours. Item two: our technnical topics section will tell you how to install an ultra-simple protection circuit to avoid damage to your receivers and transceivers in case they are fed with the wrong polarity, something that is sadly a quite frequent event, especially when out in the field. Item three: PSK31 tests using 2 meters FM continued here, and they were very, very succesful... both stations used a one kiloHertz tone, and perfect copy was possible even when intentionally reducing power to a few milliwatts. Item four: FM band Dxing is now at the peak of the summer season, and several of my local FM enthusiasts have now logged their first double hop stations, and they are very happy about their luck this year. All this and maybe a little more, if I can squeeze more information units per second while on the air. Now stay tuned for more radio hobby related information coming to you from Havana with love... My sound engineer is Margarita Delgado, I am Arnie Coro...back with you in a few seconds...
Now, Dxers Unlimited's technical topics section, today providing you with something that should be done to every piece of battery-operated radio equipment. Reverse polarity protection, YES!!! Slowly... reverse polarity protection: this means that you install a device or devices that will protect your battery-operated radio gear from accidental connection with the wrong polarity... in other words, that terrible event that consists of accidentally connecting the minus Direct Current lead to the plus terminal at your radio's input connector and the plus lead from the battery to the minus terminal on the radio... and that mistake, that terrible mistake, is often irreversible. I have seen lots of radios just destroyed by this simple mistake... BUT let me tell you that there are several ways to avoid this, and the simplest of them all is what I do to ALL MY RADIOS. That is installing a reverse polarity protection diode.
There are two easy ways to install a reverse polarity protection diode to any piece of electronic equipment. One is just to add a series-connected diode between the battery plus terminal and the radio's plus terminal. This is, as I have just said, the simplest approach, and it works quite well for low and medium power applications. The series diode does drop about 700 milliwolts from the battery's voltage, something that can be tolerated in most cases; that's a very small price to pay for complete reverse polarity protection... as I have just told you, including a typical 100 volts at one ampere silicon diode in series with the B plus line, will save your radios from a disaster. The series-connected polarity reversal protection diode can be located very easily inside most radios. Any radio that is equipped with an external battery input connector should be reverse polarity protected using this ultra-simple circuit.
For radios that use more than about 1 ampere of DC current, I use another quite different approach, which involves a heavy current carrying capacity diode connected in such a way that it will blow the DC fuse in case the wrong polarity is applied. In this case, the diode does not introduce any voltage drop at all, it is there doing its watchdog duty, conducting heavily for a very short time if reverse polarity is accidentally applied to the rig... but this DOES REQUIRE the use of a carefully selected power diode and DC fuses.
By the way, here is a little extra Arnie Coro's technical topics advice: Always use two fuses on your Direct Current powered radios, YES... include a properly rated fuse in both the PLUS and the MINUS DC power leads...
So now, amigos, you have a little project at hand... check all your DC powered equipment, and start to include reverse polarity protection on all of them... it won't take much time, won't cost a lot of money, and will save your equipment from reverse polarity damage, that as I said a while ago, in some cases can prove to be irreversible... If you have any questions about how to protect your radios for accidental reverse polarity, e-mail them to me at arnie@radiohc.org, and I'll be sending you a reply as soon as possible with an analysis of your particular problem. Writing to arnie@radiohc.org is also good for sending QSL requests and signal reports, plus comments about the show!!!
This is the weekend edition of Dxers Unlimited, and here is item three: PSK31 keyboard to keyboard digital communications system tested here in Havana on the 2 meter band, using the FM voice mode channel... Results... absolutely outstanding. Setting the PSK31 program to work at one kiloHertz at both ends, there is no possible drift, as the audio carrier stays right on frequency all the time. And even when we reduced power so that the received signal was very weak, reception of the PSK31 signals provided perfect on screen copy. These tests open up the possibility of using PSK31 on FM for emergency communications, when solid copy, reliable text, is important for those handling the emergency.
You can search the world wide web for the PSK31 software, or download the latest version 1.08 right here from our website. Then, install a very simple audio cable from your radio to your computer's sound card, following the easy instructions provided by the PSK31 software, and start receiving this wonderful mode on the 20 meter amateur band, around 14.070 kiloHertz. Again, the center frequency from which to start your search for the PSK31 stations is 14.070 kiloHertz... on 10 meters, when it is open, the frequency is 28.120 kiloHertz, 28.120 kiloHertz.
You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, and our postal mailing address is Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Here is item four: FM band Dxing summer season is now at its peak... and FM Dxers are having a good time logging a lot of new stations, some of them via double hop sporadic E, a propagation mode that extends the range of FM DX quite a bit. For double hop skip to happen, one should be so lucky as to catch two sporadic E clouds with high enough free electron concentration to bounce back to Earth signals on the FM broadcast band -- something that is pretty rare, to say the least, but it does happen, and when the two clouds are active, then you can pick up double hop FM signals at distances that are really amazing. Imagine, here in Havana, listening to an FM station in Los Angeles, California, or in Seattle, Washington, or maybe in Quito, Ecuador. Amazing, YES, but absolutely possible during the peak of the FM band DX sporadic E skip season which we are going through right at this very moment!!!
Now some comments about the present solar rotation... it seems like we are going to see a peak of not much more than 200 solar flux units, something that scientists are really watching very carefully, as it may or may not be a warning that we have just gone through a much-lower-then-expected peak for solar cycle 23. The next three solar rotations -- in other words, the next 81 days -- will prove to be decisive. If the next two solar rotations don't move much above 200 units. or go lower than 200, then we might have seen a rather poor cycle. On the contrary, if solar activity starts moving back up again, then the peak may come by the end of the year, some six to nine months later than expected.
And now, just before going QRT, as always in the public domain, here is Arnie Coro's exclusive and not copyrighted HF plus 6 meters propagation update and forecast: Solar activity should start to move up, as the present solar rotation bottomed at 160 solar flux units on Friday. Expect rather nice and quiet geomagnetic conditions for the next 3 to 5 days, but that may change after Thursday UTC day. Best bands for daytime Dxing: from 18 megaHertz up to the limit of the MUF or maximum useable frequency for a given path. Ionospheric absorption is not too high, and you may see some nice sporadic E openings happening at any time of the day, so do monitor from 28 megaHertz up during your local evening, as you may be pleasently surprised by some nice DX on 10 and 6 meters. For short wave listeners, nighttime reception on the 25, 22 and 19 meter bands is excellent, so give our 11705 kiloHertz single side band transmission a try, and don't forget to send your QSL request, signal reports and comments about Dxers Unlimited to arnie@radiohc.org, or via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Arnie Coro CO2KK
Havana, Cuba
1 July, 2000Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba
PO Box 6240, Havana, CUBA 10600
phone: 53-7-814243
phone res: 53-7-301794
e-mail: arnie@radiohc.org
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