Ten Meter, My Favourite DX Band!

 Ever since I started using my FT-710 radio in January 2024, 10m has been my favourite band for DX work. Main reason was that the noise level was quite low on 10m and I could work quite a bit of DX on ten meter while I was struggling on 20m and hearing hardly anything on 15m. Of course, I was trying only SSB mode, though I did try CW occasionally. As of now I am not a fan of digital modes, though I do have WSJT-X installed in an old refurbished laptop. I am yet to use any digital modes in ham radio. May be when the HF propagation goes down with the waning of Solar Cycle 25, I may be forced to use digital weak signal modes. That brings us to the reason why I was very happy with 10m again. I started using 10m when solar activity was good and also in winter, both known factors in improving ten meter propagation. Fast forward to June 2024, summer doldrums reversed the excellent propagation noted during winter anomaly.

Actual word meaning of doldrums is the low pressure regions in the 10°N and 10°S latitudes where trade winds from both hemispheres converge. They are associated with extremely calm air movements. Winter anomaly of the ionosphere is noted in mid latitudes in the level of ionization of F2 layer of the ionosphere. Even though production of ions is higher in summer when the Sun shines directly over the Earth in this region, the loss of ions is also said to be higher, causing net ionization level of F2 layer to be lower in summer than in winter. This has been called as the winter anomaly. It is mentioned that it is a feature of the Northern hemisphere than the Southern hemisphere. In polar regions, winter anomaly does not occur due to the prolonged darkness in winter. 

High velocity thermospheric winds at the F2 region blow from the high temperature dayside hemisphere to the low temperature nightside hemisphere reducing the volume of neutral atomic oxygen available for ionizing the F2 region during daytime hours. This is said to be the reason for net ionization level of F2 layer being lower in summer than in winter.  Lower level of ionization of F2 layer lowers the Maximum Usable Frequency (MUF) for F2 propagation crossing the Northern hemisphere to less than 24 MHz through mid-September and less than 28 MHz through late September, explaining lower activity of 10m band in August, when I am writing this post.

Initially I was using a dedicated 10m inverted V dipole antenna without a balun at feed point. I had soldered 2.5m each of insulated copper wire to the inner conductor and shield of an RG 213 coax and it was working well. Later when I bought a 1:1 current balun, I started using it after crimping a PL 259 connector to RG 213. Later I added couple of 10m long insulated copper wires to the feed point so that it became a 40-10m combination inverted V dipole antenna, which I am using at present. The elements are not strictly perpendicular to each other because of space and mounting constraints. Still I am able to tune well to 40, 15 and 10m bands with the built-in automatic tuner of my FT-710 radio.

Unlike other HF amateur radio bands, ten meter band has a wide spread of 1.7 MHz from 28.000 - 29.700 MHz. According to VK3YE, with good conditions, SSB activity spreads from 28.300 to above 28.600 MHz. Most of my contacts on SSB mode in 10m band have been in this range, though I have not heard anyone above 28.600 MHz. He has also mentioned that most activity is between 28.400 and 28.500 MHz, with 28.450 - 28.500 MHz being most favoured. As on any other band, lower part is for CW. Ten meter being a large band, up to lower 100 kHz may be considered for CW work. Part of the 10m band above 29 MHz is the FM segment. There are 10m FM repeaters in various global locations, though there are none in our region. Some VU hams have been able to access 10m FM repeater in Australia, though I am not sure whether they could have QSOs through the repeaters as well. I have never tried that yet, mainly because I do not have directional antenna for 10m.

VK3YE has also mentioned that 28.198 - 28.300 MHz segment is meant for beacons and 29.300 - 29.500 MHz for satellites and hence we are not supposed to transmit there. But I don't think there are any active satellites which work on 10m now. I had read earlier reports of satellite 10m activity. Current amateur radio satellite activity is only on VHF, UHF and SHF, to the best of my information. 28.200 MHz is the frequency for International Beacon Project. All beacons share the one frequency and are timed so that only one transmits at a time. There are 18 beacons in the project and the nearest to our region is the beacon by Radio Society of Sri Lanka with callsign 4S7B. The page showing the schedule of transmissions also shows which beacons are active at the moment, updating every 10 seconds. International Beacon Project beacons also operate on 20, 17, 15 and 12m. One beacon operates only on one band at an instance. These beacons are useful for checking propagation. At any given point of time, only one beacon is active on any band and there are a total of five beacons active on five bands.