Dxers Unlimited

28-29 october 2003
 

HI mis amigos radioaficionados, my radio amateur friends around the world... welcome to the mid week edition of your favorite radio hobby program.

I am Arnie Coro, radio amateur CO2KK, and today, item one, once again , at the request of many listeners , today I will be presenting our special technical topics section featuring a piece titled... Antenna Tuners, are they really so important ?, that I hope will help you to realice how important an antenna tuner is to increase the performance of your radio monitoring post or amateur radio station.

Item two will be devoted to our most popular section , ASK ARNIE, and always at the end of the program, our HF plus low band VHF propagation update and forecast...

Margarita Delgado is my sound engineer and producer, I'll be back with you in just a few seconds amigos !!!

This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and here is our Special Dxers Unlimited's technical topics section, the titleAntenna Tuners, are they really so important ?
SEND YOUR COMMENTS, QUESTIONS AND IDEAS DIRECTLY TO ME AT: arnie@rhc.cu, again arnie@rhc.cu

Antenna Tuners , are they really so important ?
YES, THEY ARE.... as my first grade English teacher made the whole class repeat after her...
So.. repeat after me... YES Antenna tuners are important. As a matter of fact, a well-designed antenna tuner is my number one choice for the second item to be bought by a newcomer to the hobby, after the HEADPHONES!!!

Now, how can someone who is just starting to learn about shortwave propagation, how to QSL, how to fight the high noise levels causing interference etc., tell what a "well-designed antenna tuner" is?
FOLLOW ME... and you will be able to either select a nice tuner from the many high quality, well built units now available in many countries... or, perhaps you may want to build your own following an article soon to appear here at this WEBSITE...

Let's say you want to buy yourself an antenna tuner. Then you should ask some questions about the future of your radio hobby activities...

In many cases, when consulted, I recommend buying an antenna tuner that may be used for transmitting too... as it is not too rare to have someone starting in the Short Wave Listening hobby to end up with an amateur radio license too...

And... tuners built for the typical 100 watt class ham transceivers usually have higher quality, more rugged components than tuners intended for the SWL 's.
One thing you will want when buying an antenna tuner is to be really sure it has a really wide matching capability... avoid tuners that have very few taps on their coils, and those that have taps marked only for the ham bands...

Today's typical antenna tuner uses a circuit which, honestly, I don't like at all.... It may be very convenient for manufacturers,it may match to reasonable loads... but the T, yes the letter T, network tuners are not as good as other types from an engineering point of view.

Now, this doesn't mean that they are not going to be extremely useful in most cases... BUT, the fact is that a PI network, form the Greek Letter PI (the famous 3.1416...) is a much better approach.

Antenna tuners using ROLLER COASTER variable coils are better than those using fixed coils with TAPS selected by a switch... BUT, once again, a ROLLER COASTER tuner will be much more expensive than the simpler tapped coil type.

For your first antenna tuner, your friend Arnie Coro will recommend a tuning range of from 6 to 25 megahertz... That will take care of 99 percent of your listening, leaving only the segment from 1.6 to 6.0 megaHertz without coverage.

A standard T network tuner for the amateur bands MAY or MAY NOT work on the international shortwave broadcast bands.. It will depend on the taps of the coil and the maximum and minimum capacity of the two tuning capacitors used in that circuit.

SO... you may look around for a commercial ANTENNA TUNER that will offer full range coverage from 3 to 30 megaHertz, or in a somewhat smaller range from 6 to 30 megaHertz.

CONNECTORS AND CABLES: VITAL TO TUNER OPERATION

Once you have your antenna tuner, then you must install it between your receiver and the antenna system.
This is done with coaxial cables and connectors in practically all cases. Some single wire antennas like the Inverted L, connect to a single terminal at the tuner's input, but do require a GROUND CONNECTION to be made.

A coaxial cable fed TTFD, Dipole, Vertical, or any other type of antenna, connects to the tuner via a coaxial cable, so you must prepare the cable's end to use the same connector used by the tuner's input. From the tuner's output to the radio, you must also run a coaxial cable, making sure that both the center conductor and the shield or braid are properly soldered...

If you don't do things properly, the antenna tuner's performance may be downgraded significantly. SO... be sure that the interfacing between ANTENNA and TUNER and between TUNE and RECEIVER is done properly.
For receive-only installations you can use the very easy to work with RG58U cable to go from the tuner to the receiver. For the antenna downlead, you may can use RG58U or RG59U for runs of about 30 meters (100 feet), and the heavier and less lossy RG213 or RG11U for longer runs.

HOW TO USE THE ANTENNA TUNER

You must learn how to operate the tuner... something that for the typical RECEIVE-ONLY installation is not very difficult at all...

The PI network tuner has three controls, the input capacitor, the coil (either tapped or roller coaster) and the output capacitor... All you need to do is play with the three controls for best possible reception... which can be done in several different ways...

For example you may tune the receiver to an empty frequency, then select a coil tap or roller coaster position according to the frequency, and then play with the two capacitors to obtain MAXIMUM NOISE at the receiver...
You may also try this other way... look for a WEAK station, a really weak one, and play with the controls to obtain better reception... don't try this approach with a STRONG signal, as the subtle changes will not be noticeable.
Then, there is a much more "scientific" way of TUNING THE TUNER... which is only applicable to the amateur bands... You simply transmit a signal on the ham frequency and tune the tuner for minimum standing wave ratio, as indicated by an SWR bridge.

My experience shows that even the simplest of PI network tuners will help shortwave reception quite a bit, helping to reduce and sometimes eliminate out of band signals from getting into the receiver's input circuits (the cause of some very upstetting crossmodulation problems ).

Antenna tuners may be designed for asymmetric input only... in which case, when you want to use a balanced feedline, a BALUN must be used. This means that the BALUN must be installed between the balanced antenna and the unbalanced antenna tuner input.

For the beginner's first antenna installation, I don't recommend using an open wire balanced line, do use coaxial cables and keep things simple.
Medium sized digital readout portables seem to benefit a lot when an antenna tuner is connected ahead of them... between the antenna and the radio... Receivers like the SONY ICF2010, the Grundig Satellit 700, Realistic DX440 and similar types show a significant improvement when even a very simple tuner is used. And the improvement is much more dramatic with still smaller and lower cost shortwave receivers... As a matter of fact, a simple PI network tuner will allow you to use one of those extremely low cost radios with amazing results.
So follow your friend's Arnie Coro advice, and homebrew or buy an antenna tuner, then test it, and after you are convinced of the many advantages provided by the antenna tuner, then install it permanently....

Si amigos, yes my friends, oui mes amis, here is now our popular YOU HAVE QUESTIONS section of the program... today I will be answering a question sent by a listener in Jamaica, who tells me about his FM Dxing adventures... Here is what he says in his e-mail... Dear Arnie, I need your advise in order to install more
Antennas for FM band Dxing , signed Percy in Kingston.... Well, dear amigo Percy, for FM band Dxing a combination of three antennas is about optimum.... A TTFD broadband dipole is ideal for detecting the first signs of Sporadic E skip, a 4 to 6 element YAGI, cut for the part of the 20 megaHertz wide FM broadcast band is an excellent choice ... for example, you can cut the antenna for the lower 5 megaHertz of the band, from 88 to 93 megaHertz, with the center frequency at around 90 megaHertz, and then the third antenna that you will really find extremely useful is a well designed log periodic, with no less than 9 elements, and better yet from 11 to 13 elements and covering from 88 to 108 megaHertz. Both the YAGI and the LOG PERIODIC will need a rotor, and if you amigo Percy are so involved with FM broadcast band dxing, then my advice is for you to install the YAGI and the LOG PERIODIC using two different masts or towers and antenna rotors... You may also want to complete the FM antenna farm with several assymetric sloping dipoles or ASD antennas, each beaming into a particular direction where many FM stations may be found....

FM broadcast band Dxing is one of the more than 70 ways you can enjoy this wonderful hobby, but let me warn you that this one requires a lot of patience on the part of the dxer, and you must keep a constant watch on the weather patterns as well as on signs of low band channels TV DX that will indicate possible FM broadcast band openings !

And now amigos , as always at the end of the program, here is la numero dos, the second most popular section of Dxers Unlimited, Arnie Coro's HF plus low band VHF propagation update and forecast.... Imagine an effective sunspot number of 322 UNITS, no that was not a mistake when I read it on the air, and it was not a misprint... the sudden fantastic upswing in solar activity brought the SSN index way above the 300 mark on Monday UTC day, and the daily solar flux was well past the 250 units mark during early Tuesday UTC day... And this amigos means that when the present period of high and very high solar activity comes to an end and the solar flux starts to move downwards, we are going to enjoy what in my opinion is going to be one of the best periods of short wave propagation conditions in a long , long time... So be ready , as they may start happening very soon, during the very early days of November with possible 6 meter band world wide openings, the 10 meter band open even during the local evening hours, and other phenomena characteristic of periods of peak solar activity. See you all at the weekend edition of the program, and don't forget to take a little time and send your signal reports and comments, radio hobby related questions and QSL requests to Arnie Coro,
Radio Havana Cuba, Havana , Cuba, and via e-mail to arnie@rhc.cu .