Author Topic: The LPAM Medium Wave Antenna  (Read 53 times)


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The LPAM Medium Wave Antenna
« on: January 13, 2022, 10:27:32 pm »
Here's a basic design for building a 30FT / 10 Meter LPAM Medium Wave Antenna.

This antenna is basically comprised of a vertical radiating element which at it's base is a loading coil to overcome the reduced length of the radiating element. At higher frequencies this coil is usually not all that large in inductance.

In essense the antenna is basically just an end fed 1mm core wire strapped to a telescopic fiber glass pole. You could also use aluminum tube sections put together at a maximum height of 32 feet. Note this can also help reduce the required inductance of the loading coil as you increase the diameter of the radiating element.

It's important to note that ground radials are required too. These can be omitted, but performance is drastically reduced if you do choose not to use them. Even if you have more radials at shorter lengths is better than less at longer lengths.

Here's an example of the vertical monopole with ground radials.

These antennas are usually regarding as being called a "Compromise Antenna", however this type of design is very close to the commercially availble antennas used for Long Term RSL / LPAM Radio stations all over the UK. The only difference is the lack of a "Top Hat" or "Capacitive Hat" section. These are used to help reduce the loading inductance and can also help move the radiating lobe higher up the driven element to overcome trees / nearby objects and buildings etc.

Example of loading coil

You can further reduced the loading coil size by either, increasing the diameter or the radiating element, or adding a capacitive hat at the top. If you do decided to use this type of antenna which is very similar to the commercial type available, all-be-it minus the capacitive hat. The loading inductance @ the lower end of the band will be very large.

UK LPAM Frequencies

Dutch Pirate Frequencies

« Last Edit: January 13, 2022, 10:53:11 pm by 26AM081 »

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