In the article I give the dimensions of the Gossamer antenna for the FM and VHF bands.

Introduction

The Gossamer antenna was widely used in 1960-1990 for receiving television in the meter wavelength range, since this antenna is very broadband. It was believed that it covered all 12 “meter” channels.

Description of the "Gossamer" antenna

Another advantage is the possibility of making it from scrap materials - two flexible rods and any wire.
The antenna is a variant of a zigzag antenna, but round in shape.

In recent years, the antenna has been forgotten, so for long-distance reception of FM radio, a dipole - split or loop - is sufficient.
Dipoles covering the frequency range 64-108 MHz do not exist. The dipole for the range 87-108 MHz is described in the article "FM radio antennas 87-108 MHz".

Here, in this article, I have given the dimensions of the Gossamer antenna,developed by engineer Konstantin Kharchenko, converted to FM and VHF radio bands.

The “gossamer” antenna can be used in a summer cottage as an antenna placed in the attic to connect to a stereo or VHF radio.
A 75 Ohm low attenuation television cable (SAT-703 and similar) is connected to the power points in the center of the antenna. With horizontal polarization, it is traditionally carried first sideways, then secured along the rim and lowered down near the mast. This antenna has not previously been used for vertical polarization. I believe that the cable with vertical polarization should have a shut-off choke (5-6 turns of cable on a base with a diameter of 50 mm) near the feed point.

Antenna "Gossamer" for the range 87-108 MHz (FM)

The perimeter of a circle of 4272 mm is divided into equal 24 sectors of 178 mm each. A pair of lower and upper sectors are jumpers.
The diameter of the circle is not very critical, in the model it is 1360 mm, tolerances of plus or minus 50 millimeters are possible.

The matching graph with a 75 Ohm cable is shown below. The SWR varies from 1.4 to 1.7.

The radiation pattern when installing an antenna for horizontal polarization (feed points in the horizontal plane) is a figure of eight.

The radiation pattern when installing an antenna for vertical polarization (feed points in the vertical plane) is the average between an oval and a circle.

Antenna "Gossamer" for the range 65-108 MHz (VHF + FM)

If you need to cover the 65-108 MHz range, the dimensions of the above “gossamer” antenna for the FM range must be increased by 1.4 times.
Then the antenna covers both the “Soviet” VHF band OIRT 65-74 MHz and the “Western” VHF CCIR 87.5-108 MHz.

The perimeter of a circle of 5980 mm is divided into equal 24 sectors of 250 mm. A pair of lower and upper sectors are jumpers.
The diameter of the circle is 1909 mm, with a tolerance of plus or minus 50 mm.

Agreement in the CCIR range 87.5-108 will be slightly higher, SWR=2.3.

The gain of this antenna is G=3...4 dbi.

The radiation pattern when placing power points in the horizontal plane (H-polarization) is a figure eight.

Modification of the "gossamer" antenna for receiving VHF FM broadcasts

For the broadcasting band 87.5-108 MHz, the antenna can be simplified by removing almost the entire grid, which saves material and simplifies manufacturing. This antenna is similar to a double triangle - a variant of the Kharchenko zigzag antenna.

The gain of such an antenna is 3.5 dbi (1.36 dbd).
SWR (standing wave ratio) graph for a cable with a characteristic impedance of 75 Ohms.

The bandwidth for SWR<2 level is 85.5 - 108 MHz.
Antenna dimensions with horizontal polarization: width 1146, height 1442 mm.
Antenna dimensions with vertical polarization: width 1442, height 1146 mm.

To cut off the parasitic common-mode current along the cable braid, you need a cable shut-off choke. Or you need to move the cable to the side. This is especially true when installing an antenna to receive radio stations broadcasting in vertical polarization.

Models of the "Gossamer" antenna for the MMANA program

• original "Web" paut.zip
• modified "Gossamer" (87-108 MHz)paut-mod.zip- 2 options.

To obtain vertical polarization (V), rotate the antenna model (menu "Edit" - "Rotate") around the X axis by 90 degrees.

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