Network Antenna Analyzer

For 10KHz-1.5GHz MF HF VHF UHF
Measuring S parameters, voltage standing wave ratio, phase, delay, Smith chart and the like

What are S-parameters? 
S-parameters are complex matrix that show Reflection/Transmission characteristics (Amplitude/Phase) in frequency domain. This type of test equipment is called “Stimulus/Response” and applies to both Vector Network Analyzers (VNA) and Time Domain Reflectometers (TDR). A two-port device has four S-parameters. The numbering convention for S-parameters is that the first number following the “S” is the port where the signal emerges, and the second number is the port where the signal is applied. So S21 is a measure of the signal coming out port 2 relative to the RF stimulus entering port 1. When the numbers are the same (e.g., S11), in indicates a reflection measurement, as the input and output ports are the same.

2.8 TFT Touchscreen

You can move the mark point or perform a menu operation via your hand directly or multi-functional switch.You could also rotate the wheel to operate it. Pressing is confirm.Left/Right rotation to move the selection.

10kHz-1.5GHz Frequency

New Upgraded! The measurement frequency up to 1.5GHz.Based on odd harmonic extension of si5351,new upgraded version- NanoVNA-H will transmit the signal with maximum efficiency and minimum distortion. Frequency Accuracy: 0.5PPM.

USB-C to USB-C

Compare with old version NanoVNA, it supports time domain analysis function (TDR), and more convenient to connect to mobile phones. Compatible with most Android mobile phones.

Support Windows Computer Control

Output Graph

Nonresonant single-wire longwire antennas

The resonant longwire antenna is a standing wave antenna, because it is unterminated at the far end. A signal propagating from the feedpoint, toward the open end, will be reflected back toward the source when it hits the open end. The interference between the forward and reflected waves sets up stationary standing current and voltage waves along the wire.

A nonresonant longwire is terminated at the far end in a resistance equal to its characteristic impedance. Thus, the incident waves are absorbed by the resistor, rather than being reflected. Such an antenna is called a traveling wave antenna. Figure 9-8 shows a terminated longwire antenna. 

The transmitter end is like the feed system for  other longwire antennas, but the far end is grounded through a terminating resistor R1 that has a resistance R equal to the characteristic impedance Zo of the antenna (i.e., R = Zo). When the wire is 20 to 30 ft above the ground, Zo is about 500 to 600 Ω.

The radiation pattern for the terminated longwire is a unidirectional version of the multilobed pattern found on the unterminated longwires. The angles of the lobes vary with frequency, even though the pattern remains unidirectional. 

The directivity of the antenna is partially specified by the angles of the main lobes. It is interesting to note that gain rises almost linearly with nλ, while the directivity function changes rapidly at shorter lengths (above three or four wavelengths the rate of change diminishes considerably). 

Thus, when an antenna is cut for a certain low frequency, it will work at higher frequencies, but the directivity characteristic will be different at each end of the spectrum of interest.

A two-wavelength (2λ) pattern is shown in Fig. 9-7. There are four major lobes positioned at angles of ±36° from the longwire. There are also four minor lobes— the strongest of which is –5 dB down from the major lobes—at angles of ±75° from the longwire. Between all of the lobes, there are sharp nulls in which little reception is possible. 

As the wire length is made longer, the angle of the main lobes pulls in tighter (i.e., toward the wire). As the lobes pull in closer to the wire, the number of minor lobes increases. At 5λ, there are still four main lobes, but they are at angles of ±22°from the wire. Also, the number of minor lobes increases to 16. 

The minor lobes are located at ±47°, ±62°, ±72°, and ±83° with respect to the wire. The minor lobes tend to be –5 to –10 dB below the major lobes. When the longwire gets very much longer than 5λ, the four main lobes begin to converge along the length of the wire, and the antenna becomes bidirectional. This effect occurs at physical lengths greater than about 20λ.

In general, the following rules apply to longwire antennas:

• On each side of the antenna, there is at least one lobe, minor or major, for each half-wavelength of the wire element. For the overall element, there is one lobe for every quarter-wavelength.

• If there are an even number of lobes on either side of the antenna wire, then half of the total number of lobes are tilted backward, and half are tilted forward; symmetry is maintained.

• If there are an odd number of lobes on either side of the wire, then one lobe on either side will be perpendicular to the wire, with the other lobes distributed either side of the perpendicular lobe.

(source : Practical Antenna Handbook by Joseph J. Carr)

True longwire antennas

Figure 9-5 shows the true resonant longwire antenna. It is a horizontal antenna, and if properly installed, it is not simply attached to a convenient support (as is true with the random length antenna). Rather, the longwire is installed horizontally like a dipole. The ends are supported (dipole-like) from standard end insulators and rope.

The feedpoint of the longwire is one end, so we expect to see a voltage antinode where the feeder is attached. For this reason we do not use coaxial cable, but rather either parallel transmission line (also sometimes called open-air line or some such name), or 450-Ωtwin lead. The transmission line is excited from any of several types of balanced antenna tuning unit (see Fig. 9-5). Alternatively, a standard antenna tuning unit (designed for coaxial cable) can be used if a 4:1 balun transformer is used between the output of the tuner and the input of the feedline. What does “many wavelengths” mean? That depends upon just what you want the antenna to do. Figure 9-6 shows a fact about the longwire that excites many users of longwires: It has gain! Although a two-wavelength antenna only has a slight gain over a dipole; the longer the antenna, the greater the gain. In fact, it is possible to obtain gain figures greater than a three-element beam using a longwire, but only at nine or ten wavelengths.

What does this mean? One wavelength is 984/FMHz ft, so at 10 m (29 MHz) one wavelength is about 34 ft; at 75 m (3.8 MHz) one wavelength is 259 ft long. In order to meet the two-wavelength criterion a 10-m antenna need only be 68 ft long, while a 75-m antenna would be 518 ft long! For a ten-wavelength antenna, therefore, we would need 340 ft for 10 m; and for 75 m, we would need nearly 2,600 ft. Ah me, now you see why the longwire is not more popular. The physical length of a nonterminated resonant longwire is on the order of

Of course, there are always people like my buddy (now deceased) John Thorne, K4NFU. He lived near Austin, TX on a multiacre farmette that has a 1400ft property line along one side. John installed a 1300 ft longwire and found it worked excitingly well. He fed the thing with homebrew 450-Ω parallel (open-air) line and a Matchbox antenna tuner. John’s longwire had an extremely low angle of radiation, so he regularly (much to my chagrin on my small suburban lot) worked ZL, VK, and other Southeast Asia and Pacific basin DX, with only 100 W from a Kenwood transceiver.

Oddly enough, John also found a little bitty problem with the longwire that textbooks and articles rarely mention: electrostatic fields build up a high-voltage dc charge on longwire antennas! Thunderstorms as far as 20 mi away produce serious levels of electrostatic fields, and those fields can cause a buildup of electrical charge on the antenna conductor. The electric charge can cause damage to the receiver. John solved the problem by using a resistor at one end to ground. The “resistor” is composed of ten to twenty 10-MΩ resistors at 2 W each. This resistor bleeds off the charge, preventing damage to the receiver.

A common misconception about longwire antennas concerns the normal radiation pattern of these antennas. I have heard amateurs, on the air, claim that the maximum radiation for the longwire is

1. Broadside (i.e., 90°) with respect to the wire run or
2. In line with the wire run

Neither is correct, although ordinary intuition would seem to indicate one or the other. Figure 9-7 shows the approximate radiation pattern of a longwire when viewed from above. There are four main lobes of radiation from the longwire (A, B, C, and D). There are also two or more (in some cases many) minor lobes (E and F) in the antenna pattern. The radiation angle with respect to the wire run (G–H) is a function of the number of wavelengths found along the wire. Also, the number and extent of the minor lobes is also a function of the length of the wire.

Quad Beam Antennas

The quad antenna was introduced in the chapter on beams. It is, nonetheless, also emerging as a very good VHF/UHF antenna. It should go without saying that the antenna is a lot easier to construct at VHF/UHF frequencies than it is at HF frequencies! Figure 18-13 shows a modest example. 

There are several methods for building the quad antenna, and Fig. 18-13 represents only one of them. The radiator element can be any of several materials, including heavy solid wire (no. 8 to no. 12), tubing, or metal rods. The overall lengths of the elements are given by:

There are several alternatives for making the supports for the radiator. Because of the lightweight construction, almost any method can be adapted for this purpose.

 In the case shown in Fig. 18-13, the spreaders are made from either 1-in furring strips, trim strips, or (at above 2 m) even wooden paint stirring sticks. The sticks are cut to length, and then half-notched in the center (Fig. 18-13, detail B). 

The two spreaders for each element are joined together at right angles and glued (Fig. 18-13, detail C). The spreaders can be fastened to the wooden boom at points S in detail C. The usual rules regarding element spacing (0.15 to 0.31 wavelength) are followed. 

See the information on quad antennas in Chap. 12 for further details. Quads have been successfully built for all amateur bands up to 1296 MHz.

Reference : Practical Antenna Handbook - Joseph P. Carr

Halo Antennas

One of the more saintly antennas used on the VHF boards is the halo (Fig. 18-12). This antenna basically takes a half-wavelength dipole and bends it into a circle. 

The ends of the dipole are separated by a capacitor. In some cases, a transmitting-type mica “button” capacitor is used, but in others (and perhaps more commonly), the halo capacitor consists of two 3-in disks separated by a plastic dielectric. 

While air also serves as a good (and perhaps better) dielectric, the use of plastic allows mechanical rigidity to the system.

(source : Practical Antenna Handbook by Joseph J. Carr)