1350 khz Mid Downs Radio Haywards Heath
I can add a bit to this – Mid Downs Radio [1350 kHz] really is rather precisely, 1 Watt EMRP.
Stig is correct that these use a 50 watt (carrier power) transmitter with a 10 m tall toploaded monopole.
The ground system is also very minimal, else the Q would be too high and sidebands would unhelpfully be reflected back to the transmitter, rather than be radiated – this means the efficiency is not great. In more than 60 installations, radiation efficiency averaged about 4 or 5%, so even if someone naughty tampered with the transmitter power setting, they’d get ~2 watts EMRP max.
Years ago, I worked with the supplier and we managed to squeeze 4 watts EMRP out of couple of these installations for special use cases, but it wasn’t that easy.
We enlarged the hat radials and removed a series resistor usually fitted to minimise the extremes of wet or dry ground conditions and also fat wood pigeons (about 5 pF each 😉 landing on the capacity hat radials.
I am again working out of the same unit as the company now so I know that MDR recently had the antenna relocated and the (corroded) feeder cable replaced.
The fellow that did this work is meticulous and would have set the aerial current to be spot on for the licensed power level – not a dB more or less!
I have also attached a picture of the actual antenna at MDR, but this is from the MB21 website and was not taken by me. The ATU is located in the steel enclosure at the base of the antenna.
Best regards, Rash to mwcircle iog (2023-02-28)