Let’s face it: The HF bands haven’t been that great for a while.
Trying to enjoy Ham Radio during the bottom of the 11-year solar cycle can be tough. The maximum usable frequency (MUF) rarely gets above 14 MHz, meaning QSOs on 17, 15, 12, and 10 meters are hard to come by. And the summer months see an increase in noise on the HF bands, which only deepens the suffering.
However, for many Hams, the summer months are the most exciting time to be on the air. These are VHFers, Hams who enjoy making QSOs on 50 MHz and up. To them, mid-May to mid-August on the “ultra-highs” offers exciting propagation modes whose openings have nothing to do with the 11-year solar cycle. With a bit of change in perspective, you could be enjoying Ham Radio when others have pulled the big switch and found alternative things to do. And if you’re a Technician, these tips can help you do more with your license, because you have full privileges on all frequencies above 50 MHz. Many Hams have HF all-mode radios that include 6 meters, and some of the “DC-to-daylight” rigs have 2 meters and 70 centimeters as well. If you haven’t explored these additional bands, you are leaving some QSOs on the table during a time of low sunspot activity!
There are three major forms of propagation that VHFers use to their advantage: sporadic-E, tropospheric ducting, and aurora. Here’s a brief description of how these propagation modes work.
Sporadic- E
Sporadic-E, sometimes called E-skip, is so named because it occurs in the E-layer of the ionosphere, and because it’s… well, sporadic. During the summer months, ionized particles in the E-layer can clump together, becoming dense enough to reflect radio signals back to earth. 10 meters sees quite a bit of sporadic-E activity in the summer months. However, when the clouds get dense enough, 6 meters will also open. On rare occasions, even 2 meters can be affected. QSOs from 800-1,000 miles are common on a single “hop.” If two clouds appear at the same time and line up just right, “double-hop” QSOs are possible up to around 1,600 miles. Multi-hop openings to Europe and Central/South America occur on occasion. Lots of contacts can be made on SSB, CW, and FT8.
The downsides: First, because this is a naturally-occurring phenomenon, it’s nearly impossible to predict when a sporadic-E opening will happen. It is possible to go weeks without hearing a signal, though that is a rare occurrence during the summer months. Second, the opening can be very selective. You may see 6 meters open, but Hams a hundred miles away may hear nothing but static.
Depending on the size, position and density of the ionized clouds, the areas you hear may be very selective. For example, you may only hear stations from a particular state. Other times, the band is wide open, and you will hear stations from an entire region of the country. Openings can last from just a few minutes to several hours, depending on the density of the ionized clouds. Check out this video of VE3EN in Ontario working a 6 meter pileup on sporadic-E.
Tropospheric Ducting
Tropospheric ducting, or tropo, openings occur during stable weather periods of high pressure. While tropo can occur any time of year, it is most common during the summer and autumn. Typical conditions are warm, cloudless days with little or no wind. If a large layer of cold air encounters a large body of warm air, a temperature inversion, or duct, can be created. If it occurs on a larger scale, 2 meter signals can travel hundreds of miles. In extreme cases, tropo openings can extend all the way up to 1.2 GHz. Here’s a video of Larry, WD0AKX, talking us through a 2 meter FM tropo opening in Minnesota in 2015.
Aurora
HF operators cringe when they hear the words “solar flare” or “coronal mass ejection.” They know that a large burst of charged particles is going to hit the ionosphere and disrupt their bands, oftentimes generating the Northern Lights. What many Hams don’t know is that these flares can create fascinating opportunities for QSOs on 6 and 2 meters, and even 70 centimeters in extreme cases.
The key to working an aurora opening is to point your antenna to the north. The northern lights are an indicator as to how far the ionization is occurring at the poles; the larger the flare, the greater the disturbance, and the farther away from the poles aurora openings will occur. By pointing your antennas north, you are using the edge of the aurora as a reflector of your radio signal.
Here’s the catch: the surface of the aurora isn’t smooth. As a result, your transmitted signal hits the surface of the aurora and scatters in several directions simultaneously, more or less back toward you. This results in a very distorted signal. On 6 meters, you can usually understand an SSB signal enough to make a QSO. On 2 meters, the distortion is so severe that voice QSOs are impossible. CW is the most effective mode for aurora QSOs on 2 meters and up. Even then, the distortion is so pronounced that a pure CW tone, which normally sounds like a “BEEP,” will be almost whisper-like, sounding more like a “PFFFT.” However, openings of hundreds of miles are possible under these conditions.
Here’s what 6 meter SSB sounds like on aurora (https://www.youtube.com/watch?v=Cg1Qxo7PUPo), and here’s what CW sounds like during a 2 meter aurora.
Equipment Needed
Most radios will have enough power to successfully make QSOs on the VHF+ bands during these types of openings. Sporadic-E QSOs can be made with very little transmit power, if the opening is strong. As far as antennas, while bigger is always better, smaller antennas can have excellent results during good openings. A dipole for 6 meters is only 9’ 4” long; you can make it out of wire and hang it from a tree, or construct one using aluminum tubing, a mast plate and a feedpoint connector. Use hose clamps to tighten down the tubing, and adjust the length for best SWR. For domestic QSOs, a 6-meter antenna doesn’t have to be very high; good results can be had with antennas only 15-20 feet above ground.
For tropo, strong openings can be worked on FM using a good vertical antenna. A small beam will do better, of course. Don’t forget on the VHF+ bands, FM contacts use vertically-polarized antennas, while SSB and CW contacts use horizontally-polarized antennas. If you’re using the incorrect polarization, received signals could be affected by as much as 20 dB.
For aurora openings, as you will be using either SSB or CW, use a horizontally-polarized beam pointed north.
About Grid Squares
On VHF, Hams exchange geographic units called Maidenhead Grid Squares, or grids for short. These are squares 2 degrees of longitude wide by 1 degree of latitude tall. VHF+ operators collect grids, just like HF Hams collect DXCC entities, states and counties. There are 488 grid squares in the continental United States, and over 36,000 worldwide. They are lumped together in groups of 100 called grid fields. Grid fields are identified by a two-letter combination, and squares are numbered 00-99. Here’s a CQmaps grid square map available from DX Engineering. For example, most of Connecticut is in grid square FN31, while DX Engineering is in grid square EN91.
ARRL offers an award for working and confirming 100 grid squares on any single band above 50 MHz, called the VHF/UHF Century Club, or VUCC. Click here for details on this award.
How to Tell When the Bands Are Open
With these forms of propagation being intermittent, you need to pay a bit more attention to catch an opening. There are several ways to do this.
- DXMaps has a series of maps for 6 and 2 meters showing QSOs made within the last hour. You can select maps by band and continent.
- Tropo openings on 2 meters can be monitored at aprs.mennolink.org. The site uses APRS beacons to indicate probable tropo openings.
- You can get a forecast of expected tropo conditions at www.dxinfocentre.com/tropo.
- Auroral openings can be monitored at www.solarham.net. Keep an eye on this site whenever a solar flare or coronal mass ejection is taking place.
- Both 6 and 2 meters have low-powered CW beacon stations that are active 24/7 and can be monitored to detect band openings. These beacons constantly repeat their callsign and grid in CW. 6 meter U.S. beacons are found between 50.050 and 50.080 MHz; 2 meter beacons are found between 144.270 and 144.300 MHz. A worldwide list of 6 meter beacons is found here; a list of U.S. 2 meter beacons can be found here.
You can also monitor the 6 meter and 2 meter calling frequencies for any openings.
6 Meter calling frequencies: SSB – 50.125 MHz. FM – 52.525 Mhz. FT8: 50.313 Mhz.
Note: between 50.100 and 50.125 MHZ is the 6 meter “DX Window,” an area that is reserved for DX QSOs. Please do not make US to US QSOs in the DX window.
2 Meter calling frequencies: SSB/CW – 144.200 MHz; FM – 146.520 MHz.
Calling frequencies are places where people can call to make a QSO to see if the band is open. If a station calls on the calling frequency and gets a reply, move off the calling frequency to continue the QSO. It is bad practice to monopolize the calling frequency. To monitor, simply tune your radio to the desired frequency and engage your squelch just enough to silence the static. If the band opens, a signal will break the squelch; that means it’s time to get on the radio!
Contests
There are several VHF contests during the summer months that will enable you to take advantage of the enhanced conditions on the VHF+ bands. The most popular is the ARRL June VHF Contest (www.arrl.org/june-vhf), which is the second full weekend of June every year. For 2019, it will be the weekend of June 8-9. There is also the Six Meter International Radio Klub (SMIRK) contest June 15-16, and the CQ Worldwide VHF Contest July 20-21. All these events see an increase in VHF operating activity, and use your grid square as the contest exchange.
Try It – You’ll Like It!
As you can see, there’s a lot going on in the VHF portion of the band during the summer months! I encourage you to get an antenna and try making some QSOs on these bands; summertime doesn’t have to be dead air time! I hope to work you this season on 6 or 2 meters!
