On Sunday, I decided to install and test an antenna of the End Fed antenna for two ranges: 7 and 14 MHz. This is what came of it ...

Introduction

In gardening, located 50 kilometers from St. Petersburg, I do not have permanent antennas. I am there only two weeks of the year in the summer, during vacation.

The site is small: 6 acres: 30 meters long and width 20, part of the area is occupied by the house. For such dimensions, the Endfed antenna is 20 meters long, which operates in three ranges - 40, 20 and 15 meters.

The emitter of 19.8 meters with a counterweight of 1.7 meters and UNUN 64: 1 was tested in early spring in the Pine Glade Park (received a KSV <1.5 in both ranges of 7 and 14 MHz). However, to work on the air, you need to configure the antenna in the summer cottage "on the place". Also, it is necessary to connect a coaxial cable and make a shut -off throttle to cut off the current of the braid (symphaznaya current).

Antenna location on the site

In order to reduce the interference from the 220 volts network, I tried to take the antenna away from the power line and from the house in which there are electrical appliances that interfere with the reception of short waves, such as charging devices of cell phones. The 220 volt network itself is a source of interference - because The same sources of interference in the garden areas of neighbors are connected to it.

Coordination of the antenna

The coordinating device Unun 64: 1 has one output for connecting the antenna canvas, which has a high input resistance. The total length of the antenna is half the wavelength of the lowest range. The first half of the antenna is the emitter - a wire slightly smaller (1.5-2 meters) than 1/2 waves. The second half of the antenna is a segment of the cable braid to a choke balun (Choke). The Choke cuts off the further current on the cable braid. It consists of 20 turns in a mandrel with a diameter of 11 cm (empty plastic bottle). Adjusting the length of the main canvas and the cable segment between the locking throttle and unun can be achieved at the best coordination at a certain frequency. The length of the coaxial cable 50 Ohms is arbitrary, any.

UnUn - industrial manufacture, purchased on AliExpress. _ Hypers Sytnille is removed on 08/31/2023 in order to avoid violation of Federal Law No. 274 dated 06.24.2023 "On Amendments to the Code of the Russian Federation on Administrative Offenses", clause 16 of the Law (administrative liability: for failure to provide information on Internet advertising in Roskomnadzor). The law comes into force on September 1, 2023__

Photo Unun 64: 1 bright: on the case the call sign is visible BH7JYR.

Inductivity of the throttle:

The resistance of the throttle to cut off the current according to the formula

It turned out 1 kOhm at a frequency of 7 MHz and 2 kOhm at a frequency of 14 MHz.

Photo report

1. Homemade choke balun (from coaxial cable), the so-called "Ugly BalUn":
   

2. The PL-259 connectors for the RG-9 cable, which soldered to the LMR-240 cable against the background of the desktop.
   

3. Connection Unun:
   

4. The location of the antenna canvas above the site is at a low altitude of 1.5-2 meters.
   

5. Settings using the NanoVNA antenna analyzer.

The resonance of the antenna was originally lower than the range of 14 MHz

After shortening the canvas, the resonance hit the range of 20 meters (14200 kHz):

To coordinate in the 7 MHz range, it was necessary to shorten the cable segment between the Unun and the shut -off throttle, wrapping the cable on a plastic bottle.

Result:

The resonance of the antenna in the 7 MHz range was very sensitive to shortening the counterweight (cable segment 1.5-2 meters long)

I had to unwind the cable from the shut -off throttle back, leaving only one additional round of three from the three:

The final approval in the range of 7 MHz (40 meters range) is satisfactory (VSWR <1.5 in a wide lane):

In the range of 14 MHz, approval is worse, VSWR is about 1.7.

5. 5. Turning on the reception. Impulse power supply Manson SPA-8230 it practically does not make noise on short waves.
      
      

СигThe amateur radio stations in the range of 7 MHz - at 59. The noise of the broadcast is 3 points (small interference),
the crack from lightning also affects. The antenna is quite quiet, because it is located low.


The range of 14 MHz has a very clean technique. (Sound files will be posted soon).

6. The effectiveness of the End Fed antenna for transmission is in question. In the 7 MHz range, I wanted to answer, but the operator left (Qsy). I recorded only QSO other radio stations from St. Petersburg while waiting for the line.
   I tried to answer the RU6DM, which worked for a general challenge in the range of 14 MHz, he did not hear my answer, perhaps at 14 MHz the antenna is not well agreed.

Sound files (SSB 7 and 14 MHz entries)

7 MHz: QSO R4IB.
the record is completely. The signal kept at a level of 9 points in a S-meter.

14 MHz: QSO RU6DM.
pause and 2 unsuccessful calls are cut. I took RU6DM at 59, but I was poorly audible to a power of 100 watts and the correspondent did not answer. Perhaps the antenna in the 14 MHz range is not sufficiently configured (KSV 1.7) and the transceiver dropped the output power.

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