My low power LF radio signal is received in Germany

🔘 Almost 11 years 🗓 have passed since I last used my low-power transmitter power amplifier ( see 08.05.2013 ) based on the TDA2030 class AB audio 🔉 amplifier i.c. ( see 22.02.2013 ). Since then several data 💾 transmission modes, e.g., FST4W,  have become popular among radio amateurs who are active transmitting on the LF 2190m/136KHz 〰 ( longwave ) 📻 band. I also have high power transmitting equipment for that frequency band. However I wanted to conduct a simple test by transmitting a very low power beacon signal using FST4W to determine at what distance it might be received.

My setup for the test was the phasing exciter ( see 02.11.2017 ) as the signal source driving the low power amplifier. The antenna 🗼 was my usual one for the 2190m band; a 47m  long x 13.5m tall base and end-loaded inverted 'L' ( Ꞁ ) ;  see 19.02.2010 et al.  The transmit frequency ∿ was 136.13KHz, transmitter output power only 3.5 watts, ( similar to the power consumption of a small LED lamp 💡 ), and beacon transmission, consisting of my callsign, location and power level, sent at 5 minute intervals.

Equipment used for the low power test on 2190m band

I began sending beacon transmissions during the evening of  21.01.2024. Previously, during the tests on 8 May 2013, ( albeit using a different mode ), the reception distance had been only 17 kms. I was doubtful if anyone beyond that range would receive my signal. So I was very surprised, when, at 2120 utc 🕤, a reception report was posted 📮 on wspr rocks  ☁ that my beacon signal had been received 📶  near Chemnitz in Germany, at a distance of 582 kms. Incredible and amazing 😀 !

 

LF = Low Frequency.

135.7-137.8KHz ( 2190m band ) is the lowest frequency band allocated to radio amateurs.   

3-D Printed Holders, Clips & Formers

🔘I've designed and printed a selection of parts some of which are intended for use in the transmitter power amplifier I am currently building for the 472KHz∿/630m wavelength radio 📻 band. So far I've made holders for some large foil capacitors, mounting clips for toroidal cores and coil formers ➿. Both PETG (grey) & PLA (blue or yellow) plastic filaments were used

Toroidal core clips, coil formers & capacitor holders

The toroidal core clip is for a T150-26 core which has an external diameter of 1.5". The coil fomers are ribbed for a close-spaced winding with 1.6mm diameter enameled copper wire. One side of the capacitor holder is open so that the value and voltage rating are visible. Where required, the parts can be panel-mounted using M2.5 nuts and bolts 🔩.

One benefit is that all dimensions and the style can be customised for a 'tailor-made' solution. I am no longer restricted to using PVC tube or pipe fixings for example, in only a few sizes bought from the shop.