RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, APRIL 16, 2002
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos radioaficionados! Welcome to the mid-week edition of Dxers Unlimited! I am Arnie Coro, radio amateur CO2KK, your host here in Havana, now ready to share with you about seventeen minutes of all radio hobby related information!!!
Here is item one: Solar flux still past the 200 mark, and sure enough, a lot of nice DX on the higher frequency short wave bands and on 6 meters too...
Item two: ham radio is benefiting from more research... yes, lots of amateurs that use single side band voice for their operations are enjoying some excellent new microphone elements and audio processing equipment that gives a lot of extra punch to their station's audio... More about amateur radio audio optimization later...
Item three: Answering a question about the unique broadband discone antenna in our "You have questions and Arnie answers them"section of Dxers Unlimited, item four: a visit to my workshop to take a look about another new low cost transceiver now in the works...
Item four: more about power line isolation to protect your radios and also reduce noise levels, and as always at the end of the show, Arnie Coro's Dxers Unlimited HF plus 6 meters propagation update and forecast...
Margarita Delgado is my sound engineer and producer here at RHC studio seven, standby now for more radio hobby related information coming to you from Havana in a few seconds...
You are listening to the mid-week edition of Dxers Unlimited... and here is item two... amateur radio single side voice signals may sound a lot better than they usually do, and thus improve your chances of making better two way contacts... Audio processing, a topic long familiar to broadcast engineers, is now making headway into amateur radio, many years after the broadcast industry started to use sophisticated audio processors to improve reception. But let me tell you that processing amateur radio voice signals is quite different from what the broadcast stations do because, among other things, ham radio voice systems use a much more restricted audio bandwidth.
During the early days of amateur radio SSB voice processing, the use of audio compressors or the more sophisticated RF envelope speech processors led the way to much improved performance, IF the operators knew how to adjust those new gadgets... Then emphasis started to be made at the very input of the system, the microphone, something that broadcasters had learned from the very early days of the use of audio processors. High-performance microphone elements, specially tailored for amateur radio needs, are now replacing the original manufacturers' supplied mikes, dramatically improving the audio punch, especially with some particularly bassy voices.
The new optimized microphone elements are becoming available with specially tailored frequency response curves, so the operator may test which one best fits her or his voice.... "Its like testing a pair of shoes -- you must try one, and another and another, until you find the one that fits properly," a veteran broadcast engineer told me recently when we discussed recent developments in microphone technologies. And he added that you can't do anything to improve the audio from a poor microphone element!!!
Sure, I agree -- no audio processing is worth the effort if the microphone element does not provide a good audio quality to start with, so first things first: Never attempt to do electronic audio processing if you have not yet installed a high performance, communications optimized, mike...
Phase two of your amateur radio station transmitted audio performance improvement program is to start experimenting with simple audio processing, and after you are familiar with the more common processing, then you can proceed to experiment with sophisticated segmented band analog processors.... Finally, digital audio processing is the way to go, but that does require a lot of know-how if you want to homebrew them!!! Even the simplest, basic changes to your Single Side Band or FM voice transmitter's audio will improve reception a lot, so it is always a very worthwile effort!!!
At CO2KK, my amateur radio station, I use four different microphones -- two for single side band voice, and two for FM communications... One of each for standard everyday operation, and the other specially optimized for Dxing!!!
Yes amigos, Dxers Unlimited welcomes your QSL card requests, radio hobby related questions, new ideas for the show, and of course your comments about the program. Send them all to arnie@radiohc.org or via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Now here is item three, our popular you have questions and Arnie tries to answer them section of the show:
Question: Arnie, I want to monitor the 30 to 50 mHz band with my new scanner receiver, and also listen to the 110 to 174 megaHertz band that includes the AM mode aviation band from 108 to 136 megahertz, the two meter ham band, and all the services that use that segment of the VHF spectrum up to 174 megaHertz, can I do this with a single discone antenna, or will I need two or three of them?
Well amigo from Manitoba, Canada, I think that you will have better reception by just building one skeletal discone antenna, one that will start its coverage at 30 megaHertz; that is, the low frequency cutoff is set by design to be a bit lower than 30 megaHertz, for example at 25 megaHertz... Now this antenna will allow your nice new scanner receiver to pick up signals in the range from 30 to 300 megaHertz.... as the discone provides an excellent 10 to 1 frequency ratio!!!
BUT, when you study the VERTICAL TAKE OFF ANGLE of the discone, you will see that for this particular design, at frequencies higher than 200 megaHertz, the Take Off Angle is much higher, so reception of ground wave signals suffer.... That is why professional radio spectrum monitoring stations use not one but two or even three discone antennas with overlapping frequency coverage to explore from 30 to 300 megaHertz, a region of the radio spectrum described in textbooks as VHF, for Very High Frequencies....
By the way the skeletal discone with no less than 8 spokes to simulate the cone, and another 8 spokes to simulate the disk works very well indeed.... The length of the wires or tubing used for the cone spokes for the 30 megaHertz to 300 megaHertz antenna is 3 meters or about 10 feet, while the spokes that form the disk have a length of one meter or just near 3.3 feet... As you realize, this is not a small antenna, but it has the advantage that you can use the wires forming the cone, properly insulated as part of the mast support guy wires....
This antenna is fed directly with 50 ohm coaxial cable, connecting the center conductor to the disk, and the shield to the cone wires. It does not, and I repeat, it does not need a balun, because it is essentially an assymetrical antenna, just like the coaxial cable!!! If you want to know more about designing the broad band discone antenna, just drop me an e-mail to arnie@radiohc.org or via Air Mail, send your request to Arnie Coro, Radio Havana Cuba, Havana, Cuba. I even have a very nice little computer program that will calculate the discone antenna for you very nicely, too!!!
You are listening to the mid-week edition of Dxers Unlimited; solar flux is still just above the 200 mark, and there seems to be yet another big sunspot group on the far side of the Sun soon to be rotating into view, while a rather large sunspot now in a geoeffective position may generate M or even X class solar flares during the next 48 to 72 hours, so don't be surprised if you witness one of those very interesting radio blackouts!!!
Isolating your radio equipment from the power line is always a very good idea... As a matter of fact, the best approach is to power your radios from a pure DC power source; in other words, to use batteries instead of connecting them to the Alternating Current power lines.... BUT, this is both expensive and not always possible, especially with high power equipment, so your next-best choice is what I do here at my amateur radio and short wave listening monitoring stations... and that is using a especially designed ONE TO ONE ISOLATION TRANSFORMER, that has an additional FARADAY SCREEN winding connected to the station ground.... Of course, this transformer must have enough current-carrying capacity to power up all of your equipment, so if you have a lot of radio gear, this will need a big and heavy transformer... But, for powering radios up to about 250 watts of demand, the size is quite reasonable.
I have never found out why this very practical, easy-to-implement and rather low-cost solution has not received more attention by radio enthusiasts around the world, and now that sensitive high speed microprocessors are used by both the radios and their associated computers, well-designed and properly screened isolation transformers are certainly a really valuable asset, as the line noise entering your sets will go down a lot, while at the same time, a certain degree of protection from power line spikes is assured, too... If you want to know more about power line isolation transformers, just send an e-mail to arnie@radiohc.org or a postcard VIA AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba, and I'll send you a computer file with additional data about this topic...
And now, as always at the end of the show, here is Arnie Coro's Dxers Unlimited's HF plus 6 meter band propagation update and forecast: Well, we are now expecting another impact from high speed solar particles ejected from the Sun, and that should generate a geomagnetic field disturbance on the 17th or 18th of April... Solar flux just above 200 now, and the sunspot number is pretty high at 243, and the average sunspot number for the past six days days is an outstanding 242!!! The effective smoothed sunspot number is very near 160 and this will continue to bring very high maximum useable frequencies, especially to the North - South propagation routes... Expect possible 6 meter band openings for both TEP and F2 modes during the next 72 hours...
Hope to see you again on this same frequency during the weekend edition of Dxers Unlimited, amigos!!! And dont forget to send your comments, signals reports, QSL requests and radio hobby related questions to arnie@radiohc.org or via AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Prepared 16-Apr-2002; received by NY Transfer News 17-Apr-2002, 23:00 EST
Arnie Coro CO2KK
Havana, Cuba
April 16, 2002Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
To Arnie Coro's Dxers Unlimited
Back to NY Transfer's RHC main page