Signal Propagation and DX Tips
Quick Jump: Signal Propagation | DX Tips



Signal Propagation

Please note: DXFM has a great description as to how DX happens, so I will generalize below. Please refer to DXFM's site for more detailed information.

Groundwave
Stations heard by groundwave are your local radio and TV stations, which are heard more-or-less all of the time regardless of reception conditions. Here in Virginia, these stations are usually 0-70 miles away. Signals heard from groundwave stations are strong and usually have complete RDS and HD Radio (assuming your station runs both services) and a color picture or DTV signal with TV.

Tropo / Tropspheric Ducting
This method of DXing brings in stations from nearby towns. Sometimes you will get better reception from towns within 200 miles away, but a 'duct' can form, which could bring in stations as far as 1000 miles away while excluding closer signals on the same frequency. I tend to find tropo in the 120-250 mile range on average. Signals received via this method vary from strong (like locals) to very weak and hard to listen to. It definitely helps to have good equipment so you can receive as many stations as possible. Click here to hear an example of a station received by Tropo, WGNI 102.7 Wilmngton, NC, received 322 miles away.

Sporadic E-Skip
I consider this the 'holy grail' by far for DXing. After over 70 years of research, it is exactly unknown how Es happens, but this method of propagation can bring in stations roughly 500-1500 miles away, often with clear local-like reception. Stations received by Es , although strong, usually have rapid fading, or are mixed in with other signals. Sporadic E openings tend to pop up in the late morning (~11am) and early evening (~8pm) hours in the warmer months. Click here to hear an example of an FM station received by Es, KBZI 100.7 Deerfield, MO, 946 miles away. Note the rapid fading in the signal.



DXing Tips
Quick Jump: DX Log | How to Identify Radio & TV Stations | Knowing When To DX | Advanced DX Techniques

DXFM has already perfectly described how to DX successfully, so I will refer you to his website if you are new to DXing and would like to know more about this great hobby and being a successful DXer. I am going to give you additional advice that I've found DXing this past ten years, and also relate it as the advice pertains to my reception in Northern Virginia.

DX Log
To be successful at DXing, you must become an expert about your local reception conditions. It is imperative to know what stations come in at any given time. The best way to do this is to establish a DX log. A DX log is simply a list of every radio and/or television station received at your location. The perfect way to start a DX log is to list every signal that you are receiving at the moment. You can view my DX log by clicking here.

I actually have two DX logs. One log is the main log here, complete with full information about each DX logging. My second DX log is an everyday regular notebook. This notebook is used when DX is strong to make notes of which radio stations I am logging, and it helps me sort out information prior to entering it in my real DX log, as well as pulling IDs out of recorded audio files. I recommend everybody have a temporary DX log as it helps you log more stations.

With due time, you will instantly know when the DX conditions are abnormal, usually by finding a station coming in on a frequency that you usually don't have any signals on. After nine years of DXing in the same area, I actually recognize each local station's audio processing and signal strength to the point where I notice if a different radio station is coming in on the same frequency as a local station. This is how I logged WDYL 101.1 Chester, VA (85mi) over local WWDC Washington (25mi) on 5/11/02. Both stations have a rock music format, so I would have easily mistaken WDYL for WWDC if I just scanned past 101.1 while DXing and heard rock music on 101.1. The signal strength of WDYL on 101.1 was much weaker than WWDC, which caught my ear. Upon further listening, I heard a "Y101" voiceover, which confirmed my suspicion: it wasn't WWDC.

Counting radio stations in your log - I only count radio stations one time in my DX log totals, regardless of if the station subsequently changes their calls, name, format, etc. in later loggings of the signal. I also don't count HD Radio signals as separate stations from already-received analog signals unless I only receive the HD signal, which is possible under some conditions. I do, though, count HDTV signals as separate signals from their analog counterparts as these HDTV signals are physically on their own channel, and therefore are separate signals unlike HD radio, where the HD feed of the station is broadcasted on the same frequency as the analog signal.

How To Identify Radio & TV Stations
It can be hard, at first, to know what radio stations you are listening to, especially if you didn't pay attention to stations other than your favorite(s) that you usually listen to. A good idea, before starting your DX log, is to download the radio station spreadsheets at DXFM. These spreadsheets list every FM, TV and AM radio station in North America and are a great free service to all DXers. You can use the information contained inside the spreadsheets for your DX log, and even get exact distances for all stations by entering your coordinates at the top of the file.

Identifying by audio - To identify a radio station, the easiest way is to listen to the station. Most commercial stations (above 92.1 FM) have a station name (i.e. "94.7 The Globe") that helps listeners identify the station. I'd recommend going to Radio-Locator and typing in your town, so you can get a list of stations that should be received in your area. By doing so, you will find the call letters of your local stations, and you can use that and the spreadsheets from DXFM to accurately list stations in your log. You might find additional stations being received that are not listed on Radio-Locator depending on reception conditions.

U.S. stations are required by law to say their call letters and city of license some time between 10 minutes before, and after, the top of the hour, so it also helps to listen around that time to ID mystery signals. Signals in the noncommercial band (88.1-91.9 FM), sometimes simulcast nationwide networks (such as NPR, K-Love or AFR). These stations don't always have a local identification after every song like most commercial stations, in many cases the only local ID is given once hourly at the top of the hour. Therefore, it is more difficult to ID these stations just by listening.

It is also important to listen to info such as traffic, programming and weather reports. For example, if you are in Virginia, and you are hearing a weather forecast with temperatures in Celsius, chances are you are hearing a station from Canada. Likewise, if you hear a concert promotion for a concert in Iowa, chances are the station you are hearing is from Iowa or a surrounding state.

Identifying by electronic means - Two great ways of identifying stations is with RDS and HD Radio. Both services allow a radio station to display information about their station, such as call letters and current song playing, on your radio's screen. Radio stations aren't required to use either service, and it isn't guaranteed that you will receive either even if the station you are hearing runs both, so please keep that in mind as you can't always rely on RDS or HD Radio to get a positive ID from a station. It is also a requirement to have an RDS and/or HD Radio-capable receiver to receive both services, as neither will be picked up by a regular radio. I've had many instances where the station's call letters would pop up instantly when tuned to the station, saving me time by not having to ID the station by other means, such as an audio ID.


RDS received from KIAQ 96.9 Clarion, IA, instantly upon tuning to the station. This is a definite positive ID, received on 6/4/08 via Es at 925 miles away from KIAQ's transmitter.


This is a positive HD Radio ID from WUWF 88.1 Pensacola, FL, received instantly upon tuning on 6/23/08 via Es at 794 miles.

Web simulcasts and song matches - I've had countless signals fade out (either by Es or Tr) before an ID is heard. This can be extremely frustrating, especially after a signal has been heard for 2-3 minutes clearly, only to disappear when identifying information is broadcasted. One thing you could do is check any suspected stations' website to see if they have a webcast. If you are hearing the station in question, you will hear matching audio once the webcast starts playing. Another way of identifying stations, especially below 92.1 FM, is if they are part of a public radio network, such as 'NET Radio' (Nebraska), or 'Red River Radio' (AR/LA area). For example, if you hear a 'NET Radio' ID on 90.3 FM, you are definitely hearing KMNE Bassett, NE, as there are no other NET Radio affiliates on 90.3 FM, even though they simulcast each other.

Finally, a good source of matching a station by song heard is Yes.com, however you have to be cautious as your station might be airing a syndicated program (such as Delilah), and therefore would be airing the same songs at the same time as other similarly-formatted stations on the same frequency, which lessens the chance of positively IDing the station without hearing a definite ID. Of course if you get an RDS/HD radio reading from said station, then you can claim the station as received in your DX log.

Please understand that some station networks (especially K-Love, NPR and similar networks) broadcast the same signal, with more than one station on the same frequency as possible targets, so matching a signal you hear to a webcast doesn't always give you a positive ID. Most likely, the only local ID is the station's top-of-the-hour ID. For example, I have logged three "AFR" simulcast stations on 88.1 FM, one via Tr (WRIH Richmond, VA), and two via Es (KATG Athens, TX, KAPG Bentonville, AR). It is plausible to say that WRIH might be heard locally via Tr while Es is strong into TX/AR, so you can't be quick to log an 88.1 AFR signal as KATG or KAPG unless you hear a local ID.

Knowing When To DX
It is safe to assume that, as a new DXer, any time is perfect to DX. I used to scan the dial all the time to find new signals at all hours of the day. You soon find that new signals won't always be received all the time like when you first started DXing as you get more logs. With that said, it is good to know when to DX based on the propagation mode that you are looking for.

Tropo - For me, stations received via tropo usually come in the best in the overnight hours, especially in the early morning hours between 4:00am and 9:00am. It is wise to pay attention to your local weather forecasts, as passing weather fronts in your area (in particular stalled fronts) can provide excellent DX. High pressure systems usually are the basis for good DX reception. Part of DXing by Tr definitely depends on your location. If you are close to the Gulf of Mexico, you can most likely enjoy many strong Tr openings up to 1000 miles away some nights, while those further inland just get signals 200-300 miles away. I tend to get Tr only 70-250 miles away on average due to my location in the Mid-Atlantic region.

Sporadic E-Skip - For years the best way to keep tabs on developing Es is to have an analog TV tuned into a channel on, or below, TV 6. However, with the impending US transition to DTV, this can't be as easily done. Sure, there are DTV signals on channels 2-6, and they can definitely propagate elsewhere via Es, but this would require a constant channel search by your TV to 'discover' the new channel. With this development, a good idea is to check the TV/FM Skip Log and the DX Sherlock Maps site for hints of propagation via Es. Es always starts at lower frequencies and goes up in MHz, so these sites are great future indicators of possible FM and TV Es. Of course, the best way to keep tabs on FM Es is to do a dial scan on the lower FM band every so often. Es can be tricky: it can pop up out of nowhere with top-of-the-band reception with no prior warning, either by others online or elsewhere!


Advanced DX Techniques
Now that you understand how to receive, log, and identify stations received by DX, you will definitely want to know how to log even more stations, even stations on same frequencies as your local stations. It definitely is possible to log other radio stations on the same frequency as a very strong local signal, even when your strong local signal is on the air and broadcasting. If you have a roof-mounted antenna, the easiest way is to use an phase box (more on DXFM.com about this) which nulls your local signals, allowing you to hear what is being picked up under them, however one might be very hard to obtain at the moment. There are other ways that you can get other signals over your locals, which I'll explain, among other things, below.

Logging stations with local stations off-air/on low power - This is an interesting way of DXing. While scanning the FM dial, you might find a usually strong local station off-air either due to damage or scheduled maintenance. This is rare, as most stations in the US are on-air 24/7. This can be a perfect way of DXing hard-to-get regional stations. I found local 104.1 (then WXGG) Waldorf, MD off-air on 4/6/07. With WXGG off-air, I was able to log WAEB Allentown, PA (166mi), and WNNK Harrisburg, PA (115mi), both of which are impossible to log if WXGG was on air as WXGG's signal is extremely strong in my area. It is hard to know when to check to see if stations are off-air, as I've found local stations off-air in the middle of the day, as well as in the middle of the night. All I can suggest is that you don't skip past your local signals when DXing (assuming they are operational and on-air), as you might find the station is temporarily gone. You should also read into local station sales, signal move-ins, and other technical information found online, as many of these things could result in the affected station(s) signals going off-air for a while. As you can imagine, stations don't advertise when they will be going off-air!

A perfect time to check to see if your locals are off-air is immediately after a thunderstorm comes through your area. Please take care to make sure the storm has passed before DXing, as you, as well as your equipment, could be harmed if you DX while an active storm is still happening in your area. I've found many of my local signals off-air from anywhere between 10 seconds to 10 minutes depending on the severity of the storm. This happened one time during an Es opening, which allowed me to log 93.3 WNCV Shalimar, FL (779 mi away) when local 93.3 WFLS was off-air for 30 seconds on 6/23/08.

Additionally, a storm might cause a local signal to be on low-power. According to DCRTV.com, the thunderstorm on 6/23/08, the same one which knocked 93.3 WFLS off-air, caused another local station, 98.7 WMZQ Washington, DC, to be on low power as they fix their transmitter. As I write this page on 7/5/08, the station is still on low power, which has allowed 98.7 WNOR-Norfolk (138mi) to come in over WMZQ some nights with full RDS and stereo reception.

Turning the antenna - This technique seems to be too simple, but it is very important and effective. If you have a rooftop antenna, you might find another station coming in while aimed away from your locals. On 6/26/08, during a very strong Tr opening into central NC, I picked up 101.5 WRAL Raleigh, NC (218mi) over local WBQB Fredericksburg, VA (24mi). The only way WRAL came in was with my antenna turned to the NE, which surprised me at first given both WBQB and WRAL are both south of me. WRAL only came in for about 2-3 degrees to the NE, so it was necessary for me to turn my antenna and listen for WBQB to get weak as the antenna turned, then move the antenna slightly to maximize reception from WRAL. Take care not to wear out your rotor when DXing this way.

Antenna-turning is more effective with tropo signals, at least with my antenna setup. On 105.5 FM, during any usual tropo opening, I always get WRAR Tappahannock, VA to the SE, WOJL Louisa, VA to the SW, and WDKZ Salisbury, MD to the east and northeast. Without a roof antenna, you'd probably only get the strongest of the 3 signals, which is usually WRAR. While DXing in a moving car, you'd find the three stations fighting for dominance of the frequency, much like an Es opening. I tend to find the same signals, in an Es opening, come in regardless of direction, however you might find results as dramatic as explained above with tropo signals depending on your own antenna setup.