Questions tagged [antenna-system]
The system composed of an antenna and a feed line, and possibly also an RF ground connection, antenna tuner, balun, phasing device, et cetera.
113
questions
4
votes
1answer
90 views
Frequency selective surfaces working principle
I've seen that sometimes frequency selective surfaces are used to load a certain impedance to a certain antenna (for instance for input matching purposes).
These surfaces act like a filter on the ...
2
votes
2answers
86 views
Selecting antenna for rocket telemetry system
I'm currently in a rocket team and we are building a rocket that can reach 3000m (10.000 feet). I am responsible to find an antenna for the telemetry system. I was searching on the net to find the ...
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6answers
178 views
If receive performance doesn't depend on SWR, then how can I tune my manual HF antenna tuner by band noise?
The popular question "What is the relationship between SWR and receive performance?" asks if a receiver with a well-matched antenna (low SWR) beats a receiver with a poorly-matched antenna, ...
1
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1answer
35 views
Excitation coefficient of a linear phased array
it's well known that in a linear and equispaced antenna array, the array factor is equal to:
The array is then called uniform if $|I_n| = I$ is the same for all elements. The phase terms $\angle I_n$ ...
3
votes
3answers
181 views
Is an antenna always matched to free space impedance?
In this thesis the following model for an antenna is proposed:
It is seen as a 2 port network, in which only port 1 is accessible (port 2 is an imaginary connection between the antenna and the free ...
2
votes
1answer
45 views
Total radiation pattern in antenna arrays
let's consider a simple linear uniform spaced array:
We know that, from elementary array theory, the total pattern (for instance in terms of E-field) may be evaluated, in case no phase shift is ...
3
votes
0answers
36 views
Printed Dipole Transmission Line Equivalent Model
let's consider a printed dipole on a substrate with a GND plane:
I've seen many times an equivalent model which uses transmission lines like this (reference):
This model is useful to understand the ...
3
votes
1answer
52 views
Phase shifts in antenna arrays
Let's consider a simple antenna array. For instance, this three-elements equispaced dipole array:
Each dipole is connected to a signal voltage source. It's well known that it's possible to choose the ...
0
votes
1answer
84 views
How did SMA connector size become standard?
I'm working on a project in microfluidics and it has become apparent that a significant challenge to overcome is a lack of consensus in connector design.
I have been thinking about my time working ...
3
votes
2answers
113 views
horizontal EFHW antenna attached to gutter
I'm brainstorming methods of mounting an EFHW. Unfortunately, I have no trees, so I'm considering a horizontal gutter mount which would afford me about 70 feet. Is this workable or should I consider a ...
0
votes
2answers
60 views
Is there an instance where you can directly feed a half wave dipole with coaxial cable without having to worry about balanced to unbalance?
Like the question says, can you feed a dipole with coax with no ill effects? Nothing else in the system, just the antenna and the cable.
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0answers
30 views
J Pole, what is the best way to deal with Common Mode Current? [duplicate]
I am planning on utilising a ferrite choke on a J Pole antenna for CMC. Placement directly on the feedpoint poses possible mechanical restraints. Is it okay to place it a quarter wave down the coaxial ...
1
vote
1answer
51 views
What lengths of coaxial feed lines should you avoid?
Are there lengths of feed line to avoid or ones that may cause problems with an antenna system? For single band use.
Appendix: The run of coaxial will be for the 10 metre band. I would imagine this ...
0
votes
1answer
33 views
How lossy are gamma matches?
What are the real losses associated with a typical gamma match at a set frequency? Furthermore, are there good designs or dimensions to minimise these losses?
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3answers
99 views
Why is outer coax usually grounded?
I'm building a simple ground plane antenna for VHF, and I'm doing some research on grounding in case I want to permanently install it. I keep hearing that the ground rod is connected to the outer coax ...
1
vote
1answer
34 views
How to calculate of shielded loop antenna correction factor without extra antenna measurements
A lot of article about 60 cm shielded loop antennas and how to measure antenna factor using antennas with already known antenna factor.
But for example if I have one shielded loop antenna (...
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vote
2answers
89 views
How many turns of wire inside 60 cm shielded loop antenna (9kHz - 30 MHz). How can I find this number without destroying the antenna?
Lots of information about shielded loop antennas is available on the internet. However, antenna manufacturers do not indicate the number of turns. How can I find the number of turns of a manufactured ...
0
votes
1answer
58 views
60cm 9 kHz 30 MHz Shielded loop antenna behavior as a transmitting antenna
I know how shielded loop antenna work as a receiver antenna. (How behave electric and magnetic field).
But I can not understand how shielded loop antenna works as a transmitter.
Will it produce only ...
2
votes
1answer
68 views
Looking for criticisms on my VNA-like SWR meter I am designing
I am in the process of building a SWR meter with VNA-like features. I'd be really interested to hear from fellow hams any input, suggestions, or tips they have regarding this before I go get it mass ...
3
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0answers
166 views
DIY Triplexer for HF (low), 6m (med), and 2m/440 (high)
I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas ...
2
votes
1answer
202 views
Should I bother with a doublet if I can't go straight to the tuner with open wire?
I have two trees about 135 feet apart and about 55 to 65 feet tall. I have been trying to determine which kind of wire antenna to put up there.
Initially I was considering either a fan dipole or ...
0
votes
2answers
85 views
Relative disadvantages of impedance mismatch vs. non-resonant length wire antenna
So given a choice between a non-resonant length of wire antenna center fed by 50 Ohm coax, or a resonant length of wire fed highly off-center by 50 Ohm coax, or a resonant length of wire fed by high ...
3
votes
1answer
75 views
impedance matching with window twinlead
Question from new ham here, regarding ways of matching impedances between a feedline and an antenna.
Is it possible to fashion a broadband HF impedance matcher from a length of windowed twinlead, in ...
6
votes
4answers
538 views
Any reason not to choose a discone antenna over a Wide/ MultiBand mobile antenna for TX/RX operations
We are setting up a all-band radio in an emergency com center that's intended most for amateur band use, but since its' for emergency use will also be used in the public safety bands; (150-170)MHz, (...
0
votes
2answers
240 views
Antenna Basics - Open/Short Circuit & Half-Duplex/Full-Duplex
I am beginner in the Antenna theory and I have a few basic questions.
Please help me to clarify my understandings related to the basics which I have read.
And this question has 3 basic questions. ...
0
votes
1answer
54 views
What Are Some of the Most Important Characteristics Applying to the Radiation of Monopole Antenna Systems?
Such characteristics are described in Answer 1 below, as sourced in a study of antenna engineering textbooks, and by generating NEC4.2 studies.
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votes
4answers
152 views
Why do we talk about common mode current from an antenna, but not from a transmitter?
There's a lot of information available about how to block common mode current originating at the antenna end of a coax cable. But, I haven't seen any reference to common mode current originating at ...
1
vote
1answer
54 views
Vertical Hustler - do I need any radials?
I'm planning on installing a Hustler 4-BTV vertical by the house. There's already a 12 ft. steel pole mounted in cement, so I'm going to mount it on that pole about 10 feet up (sort of small mini ...
1
vote
1answer
89 views
How should I stack these folded dipoles?
Looking to stack these 8 folded dipoles on my 100ft tower.
I can not find any information whatsoever on these. I have 4 consecutive serial numbered boxes.
Bluewave Marathon
BME139FN1H0
138 - ...
2
votes
3answers
1k views
Ideal Doublet Size 160-10 Meters
Is there considered an ideal / optimum length for a doublet for use on 160-10 meters when fed with open-wire feedline and a balanced tuner in the shack?
0
votes
1answer
40 views
How can I design a microstrip patch rectenna that can power up 1W of payload?
I know the major components of rectenna should be
Receiving antenna - Patch Antenna
Matching circuit
Low pass filter
Rectifier - Schottky diode
but I could not visualize how can we put all ...
4
votes
2answers
310 views
Actual Impedance of a folded dipole at resonance
I am using a Folded Dipole which I bought when I first got my General License. It was advertised as an all band antenna. My results with it were less than the claims made by the makers to say the ...
2
votes
2answers
95 views
Does RF go through thin corrosion better than DC?
I might have a bit of a problem with my groundplane, but I am unsure.
I am using a ground screen instead of radials. The problem is the ground screen is made of galvanized metal, but I can see that a ...
0
votes
2answers
140 views
ISOTRON 80m 75m Antenna Position
I know, a dipole is the way to go, but cannot fit one, only a
'birdhouse' antenna like the 75m 80m Isotron antenna.
Is it better to put at 15 feet Above Ground Level outside, or 20 feet AGL ...
3
votes
2answers
89 views
Using two VHF antennas vs one because of a large obstruction
We have a VHF Omni directional antenna, 2.5 W and 119 MHZ (approximate) mounted on top of a commercial hanger. Access to the antenna is out of the question because of the lack of fall protection. ...
5
votes
6answers
680 views
How to match low impedance of NVIS Dipole?
I want to match a 50-ohm coax feed wire to a 40-meter NVIS half-wave dipole. NVIS antenna examples I've found are usually based on a regular dipole (72 ohms in free air). However the impedance drops ...
6
votes
1answer
170 views
Counterpoise wire voltages?
One practice which seems common when operating temporary or portable QRP, SOTA, etc., is to throw a counterpoise wire out on the park lawn or shrubbery, mountaintop or hillside or parking lot ground, ...
2
votes
2answers
93 views
Grounding of a portable setup
I am occasionally using an extremely simple shortwave portable setup consisting of a battery, the transceiver, a short coax feedline and a vertical half-wavelength vertical antenna with a transforming ...
1
vote
3answers
359 views
How does the Maximum Power Transfer Theorem relate to RF power amplifiers?
The Maximum Power Transfer Theorem says that maximum power transfer occurs when the source impedance equals the load impedance, when the power transferred to the load is 50%, the other 50% being ...
4
votes
1answer
209 views
How does a higher antenna reduce rain static on a lower antenna?
I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
4
votes
1answer
94 views
How to simulate two antennas in 4nec2
I need to simulate 2 helix antennae placed side by side, and see the resultant radiation pattern. But after adding the second antenna with a separate and when I try to simulate 4nec2, only simulated ...
4
votes
1answer
48 views
Antenna system components in the rain
An antenna system often consists of more than the feedline and radiating wires: such as fixed or tapped loading coils, LC traps, baluns, toroids, air variable capacitors, roller inductors, feed horns, ...
1
vote
1answer
91 views
Is this antenna “system” really work? [closed]
I posted yesterday asking how can I have signal inside my house which my house is obstructed by a hill from direct signal from the cellular's operator' Base Transceiver System (BTS). The schema of the ...
0
votes
2answers
969 views
Understanding RG6-75 ohm Cable Impedance
Here is my measurement to a piece of RG6 cable. It is around 30cm cable. On the shield is written COAXIAL CABLE 5C-2V 75 ohm. From my measurement I got data as below:
From that table, we can see that ...
2
votes
4answers
801 views
What is the maximum and minimum of antenna gap of dipole antenna?
Consider the picture below is design of half wave length (Ī») dipole antenna. I read some explanations saying that it is the best design to get the optimum transmit power. Half wave length (Ī») is from ...
1
vote
1answer
120 views
What happens when you directly couple the transmitter antenna to the receiver antenna?
I was wondering what happens when you directly electrically couple the transmitter antenna to the receiver antenna? Particularly Iād like to know what happens for FM radio broadcast.
Since I donāt ...
3
votes
3answers
559 views
Why have knife switch storm grounds for antennas vanished?
Long ago, it was fairly standard to provide lightning protection for outdoor radio antennas by installing a large double-throw knife switch -- antenna leads to the center, radio on one side, ground on ...
2
votes
3answers
843 views
VHF 50 Ī© Antenna Over 75 Ī© TV Coax
I have a 50 Ī© VHF airband antenna which Iām planning to install in my loft, for use with a RaspberryPi-based RTLSDR scanner/receiver.
I already have a UK-standard UHF/Freeview antenna using standard ...
4
votes
3answers
6k views
Using 75 Ī© instead of 50 Ī© coax feed
Can I replace my old 50 Ī© coax with RG6? It's cheaper and less loss at VHF/UHF. I would match by L/2 multiples of coax to repeat input and output impedance or L/C matching networks at each end.
Is ...
7
votes
3answers
258 views
Passively reducing ground loss?
Would a disconnected wire or conductive mat below a low height antenna reduce ground losses?
A tuned length of wire under a wire antenna might be suitable for NVIS gain. But would a bunch of space ...
