Tag: QRS

The 5250 – 5450 kHz range

Allowed for Bulgarian radio amateurs 1 class on a secondary basis.

All classes of emission with a maximum permissible power 100 W are permitted for this frequency range, except for the 5351.5 – 5366.5 kHz band, where amateur radio stations must not exceed 15 W equivalent isotropically radiated power (EIRP). The fact that it is permitted for all classes of transmission and operating modes does not exclude the formation of certain preferences, and the table below reflects these.

The range is not permitted for class 2 amateurs, but this is a great opportunity to take the exam and win class 1 – and this is completely achievable!

Limitations

It would not be correct to comment on the 15 W equivalent isotropically radiated power (EIRP) limitation for part of the range. It was probably invented by smarter minds than me, but I will try to explain what this means. After all, radio amateurs do not necessarily have to be engineers in this field. I hope my explanation will be of help to them.

What is equivalent isotropically radiated power (EIRP)

Equivalent isotropically radiated power (EIRP) is a theoretical quantity that measures the total power radiated by an antenna in the direction of its maximum gain.

Or EIRP represents the power that would have to be fed to an ideal isotropic antenna (which spreads the signal equally in all directions) to achieve the same signal intensity that a real directional antenna achieves at its strongest point of radiation.

I try not to write formulas, but my explanation does not seem to make it much clearer. Let’s emphasize the practical with a concrete example.

To comply with the 15 W EIRP limit on a portion of the 60-meter range using a standard dipole, the output power of our transmitter must be set to approximately 9.15 W (with zero cable loss).

This is because the 15 W limit does not apply to the final power of the transceiver itself, but to the energy that is actually radiated into space. Since most antennas (even a simple dipole) concentrate energy in certain directions, they have a “gain”. EIRP takes into account this gain relative to a theoretical isotropic antenna (and it is measured in dBi). Let’s say we use a half-wave dipole for 60 m. The theoretical gain of a half-wave dipole in free space is 2.15 dBi. This means that the dipole radiates 1.64 times more in its maximum radiation direction than an isotropic antenna. To determine the allowed power at the transmitter output, we need to divide the defined power of 15 W by 1.64, which gives 9.146 𝑊. In real conditions, we also have losses in the feeder to the antenna. If they are, for example, 1 dB or 0.79 as a factor, we can slightly increase the power of the transceiver (to about 11.5 𝑊).

In short:

We, Bulgarian radio amateurs, should know that when operating on 60 m with a regular dipole, the transceiver power should not exceed 9.15 W, if there are no significant losses in the feeder. If you use an antenna with higher gain, the power should be reduced even more, and with antennas with losses (for example, shortened verticals or other compromise antennas) – the transceiver power can be increased, as long as the calculated EIRP remains within 15 W.

Why this limitation is only for the range 5351.5 – 5366.5 kHz I also cannot know, if this material is read by some knowledgeable employee of the Bulgarian Radio and Television Commission, maybe he will write some useful explanatory comments. My personal guess is that the 5351.5 – 5366.5 kHz band is the internationally agreed upon WRC-15 (World Radiocommunication Conference) frequency band, which is allocated to the amateur service on a secondary basis worldwide (Region 1). The 15W EIRP limit was adopted by the ITU to protect the fixed and mobile services (military, diplomatic, etc.), which are primary users. The rest of the band (5250-5450 kHz) is a national allocation that the Bulgarian Radio and Television Commission has specifically allowed for Bulgaria, and therefore the more liberal national rules (100W) apply there.

Of course, everyone can share their opinion in a comment! Especially if something is not as I have described it – I will be happy to make the necessary corrections.

Bibliography:

1. Communications Regulation Commission (CRC) – Rules for the use of radio frequency spectrum for radio equipment by amateur radio service, , Issued by the Communications Regulation Commission, Promulgated in the State Gazette No. 35 of May 10, 2022, amended and supplemented by the State Gazette. No. 64 of August 5, 2025.
2. IARU Region 1 – HF Manager’s Handbook, Version 9.0 – Section for the 5 MHz (60m) frequency plan.
3. ITU (International Telecommunication Union) – Final Acts WRC-15, World Radiocommunication Conference 2015, Geneva.
4. Bulgarian Amateur Radio Federation (BAFRF) – National Frequency Plan and Regulatory Framework for the 60-meter Band.
5. G4IFB, John Raydo – 60m Band Enthusiast’s Guide – (International resource for the specifics of 5 MHz operation).