RADIO HABANA CUBA
DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, APRIL 14, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi amigos, welcome to the weekend edition of your favorite radio hobby show on shortwave and on the web! I am Arnie Coro, radio amateur CO2KK, your friend here in Havana and host of this twice weekly program entirely devoted to our wonderful hobby... RADIO!!!! Here are the headlines, amigos....
Yet another geomagnetic storm in progress, started on Friday and it did kill DX on the ham bands for many hours both Friday and Saturday UTC days.... Now solar active region 9415 has moved farther from a geoeffective position, so, if any new powerful flares are generated there, chances are they will not produce further geomagnetic disturbances here on Earth....
Item two: More and more amateur radio operators are enjoying the challenge of very low power and ultra low power operation, especially on the HF bands from 80 meters to 10 meters. Low power ham radio transmitters are very compatible with city environments, that is they do not generate high level radio frequency energy that may overload the front end of receivers, or that will breakthrough audio and video amplifier's input circuits...Another useful biproduct of QRP or low power amateur radio operation is that hams are finding that using very low and extremely low power can provide long distance contacts... a good example was the recent two way QSO between an amateur radio station in India, and another one in Maryland USA, in which the indian station went down a just one miliwatt output.... Yes, you heard it right, the power was cranked down to one thousandth of a watt, and signal level was still enough to give almost perfect copy .... Yes another outstanding achievement by amateur radio operators...
Now item three: Several listeners asked why I advocated for the wideband fan dipole instead of the TTFD or Tilted Terminated Folded Dipole for transmitting.... So, now stay tuned, right on this same frequency, to listen to Dxers Unlimited's antenna section, that will be on the air just after a brief musical interval... Margarita Delgado is my sound engineer and producer, I am Arnie Coro in Havana.
You are listening to Dxers Unlimited's weekend edition, here is item three in detail...Our very popular ANTENNA TOPICS section... Answering questions sent by several Dxers Unlimited's listeners, here is why I advocate the use of the version of the FAN DIPOLE that is 13.4 meters or 44 feet long, if you are planning to use this antenna for transmitting. The FAN DIPOLE ANTENNA will prove to be much better for transmitting in the frequency range from 7 to 30 megaHertz when compared with the TTFD 14 meter long or almost 46 feet long antenna.
As you will realize, both antennas are of almost identical length.... BUT, there is a vital element that you must take into consideration when deciding which of the two antennas to install.... and that element is that the TTFD, when used for transmitting, will show losses, even rather high losses, at some particular frequencies, even when you use an excellent antenna tuner.... If your interests are to install a receive only antenna, then by all means go ahead and start gathering the materials to make your homebrew Tilted Terminated Folded Dipole, following the diagrams and building instructions available right here at the Dxers Unlimited website....
Building homebrew equipment is a lot of fun, and there are many simple projects that can be put together in just a few hours, like the simple KK-UP receiving converter... This KK-UP receiving converter was my practical approach to use a very nice 10 meter band only ham radio transceiver with digital frequency readout, during the many hours of each day that ten meters is closed for DX....
As many of you regular Dxers Unlimited's listeners know, the 10 meter ham band is very dependent on a rather high level of solar activity, and usually it is only available for ground wave contacts during the local evening hours... So my nice little HTX100 10 meter band only transceiver is now performing as the tail end of what has become an excellent AM medium wave DX receiver. The KK-UP receiving converter has a dual tuned bandpass input filter, a variable radio frequency attenuator, a homebrew four diode double balanced mixer and a quartz crystal oscillator that is tuned to 27 megaHertz, using a surplus citizen band crystal that is marked 27.005, but that can be tuned to exactly 27 dot zero zero zero... So, the AM band loop antenna is connected to the input of the KK-UP converter, and the AM broadcast band is converted to the frequency range from 27.550 to 28.7 megaHertz, with the added bonus that you can tune also to the low frequency aircraft non directional band by tuning the HTX100 ten meter band radio from 27.200 to 27.450 kiloHertz... So the KK-UP simple UP CONVERTER will actually cover both the low frequency aircraft beacon band and the full AM broadcast band that spans from 540 to 1700 kiloHertz....
When using the KK-UP converter, which by the way is powered from either a single 9 volt battery, or by borrowing DC from the HTX 100 transceiver, you set the frequency that you want to listen two by just forgetting the first two digits of the digital frequency display on the HTX100.... In other words, when you read 27.540 kiloHertz, you are actually tuned to the first channel of the AM broadcast band in ITU region II, if you want to pick up a station on say 890 kiloHertz, you only need to set the HTX100 transceiver's frequency to 27.890 kiloHertz...
By the way this KK-UP up converter will work with any ham radio transceiver that tunes to the 10 meter band, but its main use is to be connected to a single band 10 meter transceiver, turning it into a very sensitive and effective receiver which will make AM band DXing possible, using all the features of the 10 meter band transceiver, like the narrowband SSB filter and digital readout...
Again, the KK-UP up converter uses a very simple circuit, just a double tuned bandpass input filter, a resistive input radio frequency attenuator, a double balanced four diode mixer, and a single bipolar transistor quartz crystal oscillator... Coupling to the HTX100 or whatever single band 10 meter transceiver is via a short length of RG58U coaxial cable... and in order to avoid the possible destruction of the diodes in the mixer, you must always REMOVE THE MICROPHONE from the transceiver, so that while you are using the KK-UP converter, you will not push the transmit push to talk switch on the microphone....
AND YES... I did destroy one set of 4 mixer diodes..... so now when I connect the KK-UP Low frequency and AM broadcast band converter to the HTX100 10 meter band transceiver, I always remember to remove the microphone, and later, I added a safety miniature switch that blocks the push to talk line, so that the rig can not be keyed when that switch is in the OFF position...
If you want to know more about the KK-UP simple UP converter for the frequency range from 200 kiloHertz all the way up to 1.7 megaHertz, just send me an e-mail, or an Air Mail postcard, and I will be very happy to send you a file with all the data needed to homebrew your own KK-UP converter that once built will make good use of your 10 meter single band transceiver when 10 meters is closed!!!
You are listening to the weekend edition of Dxers Unlimited, coming to you from Havana; send your QSL requests via e-mail to arnie@radiohc.org and Via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
And now here is item four: Digital Short Wave Broadcasts will eventually replace present day AM signals, but that is a process that will span over many years, according to several experts who are working on the implementation of a worldwide digital standard for radio broadcasting that, among other features, may use present-day transmitters.... But, receivers are another completely different story.... present-day receivers will not be compatible with the digital radio broadcasts, so eventually they will end up in museums, junkyards, scrap piles and recycling plants... Again, this is not going to happen in the immediate future; the transition from standard AM short wave broadcasting to DIGITAL will require the adoption of a worldwide standard, and then, that receiver manufacturers will flood the market with low-cost radios that consumers may acquire easily to replace present-day short wave radios....
Digital short wave broadcast tests from at least one of the consortiums involved in the development of such a system are now in progress, but if you do not own one of the very few experimental digital receivers, then tuning to the test frequencies will only produce noise coming out of your loudspeaker or headphones...
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 is now moving down, as solar active region 9415 -- the most active one on the solar disk -- is now moving out of a geoeffective position, meaning that if it produces high power solar flares, the Xrays and ultraviolet rays will not reach the Earth, and the same will happen with the stream of solar particles that form the associated coronal mass ejection that usually follows a flare. Solar data monitored around 1700 UTC on Saturday showed an effective sunspot number of 91, and the A index moving down and reaching around 25 units, indicating still a rather active geomagnetic field...
For all practical purposes the 10 and 15 meters amateur bands were in pretty bad shape Saturday morning here in Havana, but the conditions may improve by early Sunday. We still may see some interesting 6 meter band openings via the classical trans-equatorial path.
Short wave listeners will enjoy best reception during local evening hours on the 31 and 25 meter bands, with the 22 and 19 meter bands closing up earlier than during the previous two weeks... Will see you on 28.5 if 10 meters is open!
Arnie Coro CO2KK
Havana, Cuba
April 14, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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