The essence of the experiment: find out which antenna will create the maximum field strength at a distance of 5 km.

The essence of the problem

To work, both through a relay and in a direct channel with correspondents, it is necessary to provide a lot of field strength as much as possible. There are two options - to raise the antenna to the roof and put up with losses in the cable and on the connectors or put the antenna on the balcony or attach it near the window. In the case of placing the antenna in the transmitter, the losses in the cable do not exceed 1 dB.

Description of the experiment

Antenna No. 1 - two elements per 144 MHz, directly at the transmitter, is installed at an altitude of 4 meters, an amplification coefficient of the antenna of 6 DBI, loss of less than 1 dB (RG58 3 meters long - losses 0.2 dB).

The dimensions of the two -element antenna:

Antenna No. 2 -COMET GP3 установлена на высоте 14 метров, усиление 5/8 - 2дБи потери 3 дБи (кабель длиной 25 метров).

The signal level in DB was measured on Websdr (http://websdr.78dx.ru:8901/) 5 km from my house.

The first antenna has a resonance at a frequency of 145.100 MHz - checked by the Nanovna device, while KSV = 1.2, RVX = 60 Ohms.
The second antenna on the roof is configured at the plant to the range of 144-146 MHz.

Losses in the cable - Antenna No. 1 (on the roof) - a feeder of two segments: 4 meters RG8X for passing through the frame and 25 meters analogue RG213 to the antenna. The RG8X cable has 11 dB/100 m, in RG213, I take the chassel attenuation 8DB/100 m. I take losses equal to 5 *11/100+25 *8/100 6DB = 3DB. They need to add a signal attenuation on the connectors - 2 connections of 1 dB total total losses of 5 dB.

Antenna No. 2 - one segment of the RG -58 cable 1.5 meters with PL connectors, there are practically no losses.

The choice of antennas No. 1 and No. 2 using an antenna industrial -type switch.

comparison of the transmission power to the remote WEBSDR receiver

At a distance of 5 km to the receiver, the antenna located at a lower height can win a higher one.

With a short cable, if the antenna outside the window, you need to pay attention to the KSV-at 1.3-1.5, the transmitter seems to reduce (“throw it away”) power, with a KSV 1.0-1.2 this does not happen and the power of power is complete. Thus, you need to rebuild the antenna No. 1 higher.

Interference with the admission on the antenna installed outside the window. Comparison of the quality of the reception

If the antenna is installed outside the window, it accepts the "Electric Smil" from electrical appliances in the house. At the same time, the size of the interference depends on the type of wiring - the old houses have a wiring with an isolated neutral without a grounding wire, the interference is significant up to 8 points. The houses of new series - grounding are given more attention, interference on KV and VHF much weaker.

Although the antenna at an altitude of 4 meters creates high field strength, in reception it significantly (more than 5 points) loses the antenna on the roof. For example, on the scale of a S -meter of an interference type "harmonic 50 Hz" on a low antenna - up to 8 points, while on the roof - noise 2-3 points. Also, the cleanliness of the reception is higher on the antenna installed on top of the building. The long -range R1 relay (145.625) is not accepted on the first antenna at an altitude of 4 meters from the opposite side of the house (only presence), while the antenna No. 2 in the center of the roof is 8 points with a slight white noise.

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