For a long time, there were no VHF beacons in the 144 and 432 MHz ranges on the air in St. Petersburg and the Leningrad region.
This made it difficult to determine the tropospheric passage. But in 2021 the situation has changed.

In February 2021, in the city of Priozersk in the north of the Karelian Isthmus, a beacon with the call sign RB1CA was turned on, with a power of 5 W on the frequency 144420 kHz.
By observing the signal level of which we can conclude that refraction has improved, that is, the bending of radio waves around the horizon. With increased refraction, the so-called “passage” is observed - long-distance tropospheric propagation of radio waves, with the help of which radio amateurs carry out VHF radio communications with correspondents who are located beyond the horizon.

The lighthouse has been assigned a call sign RB1CA, author and owner Boris UA1CCB. The transmitter is registered with Roskomnadzor (Federal Service for Supervision of Communications, Information Technologies and Mass Communications).
Installation height - 24 meters above sea level and 35 above ground level, square QTH Locator -KP51BA.

What is the exact installation location for the RB1CA beacon?

The beacon is installed on the mast of a radio broadcast tower. The radio mast for the FM radio station is located in Priozersk, but its position could not be determined. The lighthouse is located somewhere in square KP51BA 😁

Recording the operation of the RB1CA beacon

РадThe beacon operates alternately in three modes, one of which is the increasingly popular machine-generated mode (MGM) called PI4. This mode is interesting because it allows you to receive a signal with a low signal-to-noise ratio. I wanted to establish the fact of the beacon's operation and record it in WAV / MP3 format and, if possible, photograph the antenna.

On the day off, Saturday March 13, 2021, I went to Priozersk. I offer a trip report and my little research on the CW / PI4 Beacon topic.

The operation of the RB1CA beacon at 144.420 MHz was recorded using an RTL-SDR receiver (FC00013 tuner is not a good replacement for the R820T) and a laptop with the program SDR# version 1700.

The transmission duty cycle is 100% and cycles every minute. The transmission consists of 3 parts:

• PI4 modulation 25 seconds long,

• call sign with QTH locator lasting 15 seconds

• unmodulated carrier - 20 seconds.

Digital mode PI4 on "waterfall"

The PI4 signal consists of 4 tones.

The decoding of symbols is given in description of PI4 mode(PDF).

Configuring the receiver for a radio beacon

The radio station should be tuned 800 Hz below the beacon frequency. That is, if the frequency is 144820.00 kHz, you need to tune to 144819.200 in USB mode. Tuning in USB mode can be done by ear (when the tone of the beacon approximately corresponds to the telegraph tone frequency 800 Hz). The minimum frequency tuning accuracy is ±50 Hz.

For more precise tuning, which compensates for the frequency deviation of the transceiver master oscillator, you can use "zero beat" method(The term "zero beat" means tuning with a 0 Hz tone).

1. Enable CW mode,
2. disable the electronic key (KEY) and transmission mode (BK).
3. Press the key. A continuous tone will be heard with a tuning generator tone frequency of 800 Hz (the tone frequency is set in the transceiver menu).
4. Tune close to the frequency 144.820, and by rotating the frequency tuning knob until the pitch of the beacon matches the frequency of the tone generator.
5. If the two frequencies exactly match, no beats will be noticeable to the ear, which means that the transceiver frequency adjustment is complete.
6. Also, in the FT-857/FT-897, when fine-tuning the frequency in CW mode, the blue LED at the top of the front panel starts to light.

If you are using a receiver (rather than a transceiver), you can use the 800 Hz tone sample by playing it back on your smartphone, for example. The sine wave tuning signal with a frequency of 800 Hz is shown below.

PI4 Decoding

There are programs for Windows for decoding Pi4RX or MSHV.

Beacon operating range

If you drive a car along the A-121 Sortavala highway towards Priozersk, the noise suppressor begins to open at the turn to Sosnovo - a distance of 55 km to Priozersk. Then the signal disappears and appears again. It reaches its maximum strength at the entrance to Priozersk, in the area of ​​the bridge over the Vuoksa River.

It should be taken into account that the polarization of the transmitter and receiver antennas is different - for a lighthouse it is horizontal, and for a car antenna it is vertical. Therefore, when using horizontally polarized antennas, the range can be greater.

Calculation of the lighthouse coverage map

In the Radio Mobile program I calculated the routes for receiving the beacon. Antennas with a gain of 7 dbi, omnidirectional (Omni), are selected on both sides. The installation height of the beacon antenna was taken into account in the calculation. The height of the receiving antenna was 2 meters - a low mast for transportation in the trunk of a car.

1. For normal distribution conditions (no tropos) - 95% of the time - 346 days a year.

   

2. For improved tropospheric passage (presence of weak tropo) - 33% of the time - 120 days a year.
   

The calculation of RB1CA coverage maps was performed for horizontal polarization in conditional S-scores of the signal level. In addition to the terrain, the program includes vegetation and a temperate continental climate.

The most profitable QTHs for receiving a beacon

Performed several calculations of routes for the outskirts of St. Petersburg for good driving conditions (probability of acceptance 70% of the time of year).

1. Orekhovo railway station
   
   Signal/noise 18 dB.

2. Bolshaya Izhora on the southern shore of the Gulf of Finland (on the mountain h=15 meters)

   
   Signal/noise 5 dB.

3. St. Petersburg from the roof of a 9-story building (h=20 meters), there are no local obstacles.
   
   Signal/noise 7 dB.

4. St. Petersburg from square KO96CU from the ground
   
   Signal/noise 0 dB.

5. Mountain near the village of Kaporskoye, near Annino (h=100m).
   
   Signal/noise 10 dB.

In the absence of transmission (i.e., the probability of reception is 98% of the time), the signal strength is much worse - 0 points in St. Petersburg. For example, during precipitation and cyclone, strong wind. In such weather conditions, reception is guaranteed no further than Orekhovo - Sosnovo (at a distance of 55-60 km from the transmitter). In the case of a higher sensitivity of the receiver (low noise amplifier near the antenna - LNA) and antenna arrays of Yagi antennas 5-8 meters long, the reception range increases, but much depends on the terrain in the north direction.

Summary table of VHF beacons

Azimuths and distances are given relative to the center of St. Petersburg, KO59DX.

Location, power and gain of radio beacon antennas

All beacons have horizontal polarization of radio wave radiation.

Useful links:
https://ua1zfgsite.wordpress.com/pi4-mode/
https://automatic.sral.fi/index.php?p=list&stype=beacon&repstatus=QRV
https://cubesat.hammania.net/
http://forum.vhfdx.ru/mayaki/majak-rb1ca-(beacon-pi4cwcarrier)-na-144-420-mgc/

Last change: 04/22/2025

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