Reception of the World Music Radio station on the 11m Short Wave Band - June 2021

16th June 2021: I noticed a post on my Facebook feed yesterday about a Danish station transmitting on 25800 kHz on the 11m broadcast band. I really don't have much interest in short wave stations but this one caught my attention as it is reasonably close to the 28 MHz band.

The post from the 14th of June 2021 read... "WMR (World Music Radio) is now on the air on 25800 kHz - locally audible in Aarhus, Denmark -  and sometimes by eskip og F2 propagation."

Today, I noticed I was hearing OZ7IT in Denmark on WSPR on 28 MHz via Sporadic-E propagation with a good 0dB signal. I then checked for the OZ7IGY beacon on 28.271 MHz and sure enough, it was there.

When I checked 25.800 MHz, the World Music Radio station was there on AM with a signal strength of about S '5' to '8' with a lot of fading. The distance was in the region of 1300 kms to my location.

In response to a question, they said that they were running 100-watts into a vertical antenna on top of a tall tower. Photo at the end of this post.

100w sounds like a lot but in terms of short wave broadcasting, it's very low power.

Sporadic-E propagation: If anyone wants to have a listen during the Summer Sporadic-E season (May to July), I have put together a map showing the likely range.

The signal is likely to be heard in the range of 500 kms to 2000 kms. Anything under 500 kms is in the skip zone. anything over 2000 kms is likely to be too weak.

The best spot is roughly between the two, say 900 to 1600 kms.

In conclusion: Putting a short wave transmitter on 25800 kHz near the bottom of the sunspot cycle seems like a strange choice. It will probably be a few years before there will be consistent F2 propagation at that frequency and even then, 100-watts on AM will only go so far.

The 11-metre broadcast band is an unusual band with very few stations on it and many of the typical small portable radios don't cover it.

I checked my own TecSun PL-380 and it tops out around 22 MHz.

Yet for all that, it's interesting to see if it can be heard. I'm thinking already if that nice 100-watt carrier could be used for meteor scatter tests! 😂

If you hear Danish stations on 28 MHz then have a listen and you should be able to hear it.

Links...

1) World Music Radio website

2) Their Facebook page

Calendar for F2 openings on the 11m and 10m bands

For anyone using the 27 MHz to 29 MHz part of the spectrum, propagation is an important subject especially if you want to get work stations around the world. In general, the two main modes of propagation for the 11m and 10m bands are Sporadic-E mainly during the Summer months and F2 for the rest of the year.

In this post, the charts deal just with F2 and what parts of the world are likely to be heard at certain times of the day throughout the year.

It should be noted that this is a general guide. It is highly dependent on where we are in the 11 year Solar Cycle and what the Solar flux is. Usually for stations in North-West Europe, the Solar flux needs to be about 80 or above to start getting openings. North-South paths are more likely and the East-West ones appear with higher flux levels.

The big variable in this is Sporadic-E. This occurs mainly during the Summer months but is present during most months to a certain degree. This can allow stations in the UK for example to get into the Mediterranean on Sporadic-E and then via F2 into South Africa. Expect the unexpected on 10 metres.

This map shows various parts of the World numbered and the charts are based on propagation from the UK and Ireland.

The charts below show the times of day those are might be heard at various time of the year.

Low Pass Filter for the 10m & 11m Bands

Another one from the archives :o). This is a design for a low pass filter for 29 MHz and would be suitable for anyone on the 28 MHz or 27 MHz bands who needs a filter to reduce harmonics. This is especially valid for anyone using a low powered radio to drive an external amplifier. e.g. Amplifying  4w to say 50-100w.

Coils...12 SWG wire. 6 turns. 8mm internal diameter. Coil length 19mm.

Capacitors...High Voltage ceramic or Mica. 110pf Cap is 100pf and 10pf in parallel.

A suitable enclosure might be a diecast box with the filter built on copper clad board. Note the screen which can be made from the pcb material as well. If you can live with a slightly lower performance in terms of filtering, you can omit the internal screens but make sure you put it in a metal box.