What gives DX transmissions their distance is the practice of refracting the signal off of the ionosphere, sometimes several times in one transmission. This gives the broadcast much more range, but makes it more dependent on conditions. The weather, time of day, the eleven-year sun spot calendar, and even solar storms can greatly affect the success of these transmissions. They must also be sent using low frequencies typically under 50 MHz.
DXing equipment can consist of an elaborate system costing thousands of dollars, or it can be conducted using a cheap portable receiver. Just by using an AM radio at night you can listen to stations that are broadcasting from hundreds of miles away. If you wish to listen to broadcasts from several different countries during daytime hours, a cheap shortwave radio can accomplish this. It is only when the distance gets extreme that you need fine-tuned equipment.
Many serious DXers purchase or build equipment to better fit their needs. Their receivers are often specifically designed for long range transmissions and their antennas are often built for a specific frequency. In all reality the inexpensive setups will pick up just as many transmissions as the expensive setups. The difference is the quality of the transmission. With better equipment you can deal with adverse broadcast conditions better. The additional filtering options and interference blockers give you clearer reception.
Another common practice in recent years is called diversity reception. This is when a DXer connects multiple receivers or antennas to a computer. It allows them to make an ‘apples to apples’ comparison on a specific frequency to help them determine which combination of antennas and receivers picks up the best signal. The process allows them to take fine tuning to a whole new level.
AM radio listeners in the 50’s and 60’s often would make their own crystal sets with long wire antennas. Top 40 music was very popular at that time, but many of the AM stations had a limited range. For some people the only way to receive these signals was to fine tune their equipment to receive from longer distances. Many of these stations were not allowed to broadcast at night, so listeners turned to DXing during those hours to pick up their music. The need for this has faded with the use of FM stations for music.
VHF DXing has not been nearly as popular. These signals can be skipped for hundreds or even thousands of miles. Often emergency services will broadcast using VHF and these signals will travel great distances. The vast majority of listeners for this type of broadcast are local, so it is surprising that these signals are sent out over great distances. One of the biggest challenges of DXing over VHF is that broadcasters are not required to identify themselves, so determining the source can be difficult. This may have lead to the limited use of this medium.
Shortwave DXing started as a way to broadcast internationally during wartime. With the advent of streaming audio through computers, the use of shortwave for DXing has greatly diminished. However, missionaries still use shortwave heavily to reach third world countries whose people often cannot afford computers. Many of these broadcasts are sent out in single band mode so specific equipment is needed to receive it.
Amateur radio is the most popular medium for DXing. Many of these hobbyists will pursue awards from DX clubs and organizations. For example, awards are given out for the number of “entities” that have are confirmed to have been contacted. Entities are used instead of countries because territories and island chains are often treated separately from their mainland countries.
The confirmation system is the key to the entire DXing community. When somebody listens to a DX broadcast, they then complete a SINPO report. SINPO stands for:
S – Signal strength
I – Interference with other stations or broadcasters
N – Noise ratio in the received signal
P – Propagation (ups and downs of the reception)
O – Overall merit
The report rates each one of these categories on a scale of 1 to 5 with 5 being the best quality. The frequency on which the broadcast was heard is listed along with the type of equipment used, a description of the program, and any suggestions the listener wants to list. It is then labeled with longitude and latitude coordinates for the location received and either mailed or emailed to the broadcaster.
The other side of this transaction is the broadcaster sending back verification that they made the broadcast described. This is called a QSL form and typically has the broadcast information on one side and a picture on the other. These are the real collector’s items for the DXing community, so the pictures often show the landscape or culture of the area from which they came. Both parties have to take the initiative to do their part for this process to work properly. This relationship between broadcaster and recipient allows both parties to get better at sending and receiving signals over long distances.
So besides being interesting and fun, why is this practice important? Many people consider DXing to be a backup system for long distance communication when satellite communication goes down. This scenario could be caused by hackers taking control of our satellite systems. It could also be caused by solar storms or debris doing mechanical damage to the satellites themselves. In any of these situations, long distance communication could remain to be essential.
The importance of this form of communication extends to several potential SHTF scenarios. There are plenty of ways that cellular and internet communications could be shut down. Most cellular towers require a power source. That means that communications could be down even if you have a generator to keep your phone charged. Flooding like we saw with hurricane Katrina or Sandy could wipe out communication. During Katrina the majority of people who were able to communicate were using HAM radios.
The fact that DXing can allow you to receive transmissions from other countries is key to its importance. If the US was attacked, it is likely that communications would be shut down. By receiving foreign transmissions DXers may be able to keep up with the news. Any information you can get in a situation like that would be absolutely vital.
Another benefit of this type of communication is that the equipment can be built. One of the ways we could be attacked would be an EMP (electromagnetic pulse) blast which would wipe out almost all electronic devices. Cell towers would be destroyed, so any way to communicate would have to be built. With just a quick stop at a radio shack or digging through your garage you could build a device to send or receive long distance transmissions.
In the end, any alternative form of communication is a good idea. The fact that this form can span hundreds or even thousands of miles makes it that much more valuable. DXing is a simple yet challenging form of radio transmission that does not require a license. Anybody on any budget can participate and hone their skills. There is also a strong DXing community, so learning from others is quite easy. If you want to get into radio communication as a hobby, this may be a good way to get your feet wet.