Questions tagged [antenna-theory]
Designing antennas, selecting antennas for specific applications, properties of a given antenna design.
253
questions
2
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0answers
28 views
Gain of Yagi turnstile?
I am currently working on a system to communicate with amateur CubeSats. I have decided to use the turnstile crossed-dipole style yagi because it is relatively easy to construct and uses circular ...
0
votes
1answer
31 views
Can you measure how much radials you are lacking for HF vertical?
I have tried mount ham sticks on SUV and a convertible use trunk lid mount, especially on 40m on the convertible I notice the SWR changes from opening the door and close the door.
Now I am quite ...
0
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1answer
50 views
Inverted L Feedpoint Height
I have this antenna EFHW 40-10 from Maple Leaf Studios. My current configuration: Inverted L with feed point 3m above ground, with "L" at 9m. I have 45 20-foot in-ground radials just below the feed ...
2
votes
1answer
42 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. ...
0
votes
1answer
63 views
Can i use an anaolgue IC switch to change a 10 m yagi's directivity by somehow combining received signals with different variable phase?
Can i use an analogue IC switch being triggered at the same frequency I am receiving on to change a 10 m yagi's directivity by somehow combining received signals with different variable phase either ...
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4answers
76 views
Which 10 m antenna will give the most rejection in one direction for received signals which are vertically polarized?
I want to null out a particular direction so that i can't receive some vertically polarized interference on 10 m coming from that direction.
Which 10 m antenna will give the most rejection in one ...
-1
votes
1answer
62 views
How would I calculate aperture efficiency for an antenna?
How to calculate aperture efficiency for an antenna with the following parameters:
Big reflector diameter= 24 mm
Gain= 9.265 dbi
Frequency= 11.60 GHz
4
votes
3answers
1k views
Vertical Yagi spun at 1000 RPM: gain properties?
If I were to mount my 10 m vertical Yagi on a pole with a motor attached at the bottom with the appropriate fastening and coax mounted via electrical brushes, if the Yagi is spun at say 1000 RPM would ...
2
votes
2answers
49 views
Will ferrite rings around a metal pole hide it in an RF sense from my vertical 10 m Yagi?
If i mount my vertical 10 m 4 element yagi directly on a metal pole so that the pole is between the elements and so messes up the radiation pattern and input impedance, if i put lots of type 43 ...
2
votes
1answer
180 views
When I am told that a dipole must have a determined length, does that include the space between both elements?
I am trying to build an antenna for receiving NOAA satellites and I need to build two 137,5MHz dipoles. When I enter the frequency and width of the wires in a calculator, I obtain that $λ/2=1.09\,\...
4
votes
2answers
65 views
Basic antenna matching theory?
I'm fairly new to antenna matching, other than having built a base loaded vertical.
I'm also new to EZNEC and I tried to simulate an horizontal loop. I arbitrarily chose a 10x10M loop, so I added 4 ...
2
votes
2answers
54 views
How to estimate a dipole feedpoint impedance?
An ideal dipole, at resonance, will have an impedance around 73 ohms. A folded dipole, around 280 ohms.
How can I calculate the impedances when not at resonance? Let's assume I have a span of 15M in ...
0
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2answers
54 views
Can I make signal transmitter without decoder?
I'm sorry if my title seems weird but I just started to learn about signal transmitting and I don't know where to start
I'm searching about simple ways to make diy radio but I can't really ...
5
votes
1answer
79 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, ...
4
votes
1answer
48 views
Voltages in a beam antenna's passive elements?
This question has good answers for the voltages reached in portions of a dipole antenna during transmit.
In a beam (Yagi or Yagi-Uda) antenna, do points along passive or parasitic elements (...
2
votes
1answer
60 views
What sort of antenna would use a bicone or lozenge-like arrangement of vertical wires?
In another QA here, there's a picture of an antenna I identified as a "discone": What are these antennas used for?
One commenter noticed that antenna was actually a "Discone, but no disc, just the ...
2
votes
2answers
106 views
Will using a 1:1 balun at the feedpoint of a center feed dipole result in no common mode current on the outside of the coax?
Will using a 1:1 balun at the feedpoint of a center-fed dipole when using coax result in no common mode current on the outside of the coax ?
0
votes
1answer
66 views
Passive antenna system as a Wi-Fi repeater [duplicate]
I want to extend WiFi signal using a passive repeater between two isolated boxes (have to make both box wireless).
Transmitter antenna from box A is placed in the gap between box A and B.
In the same ...
5
votes
3answers
169 views
ARRL handbook as a reference for all your radio learning needs?
Looking to take up learning understanding everything from basic electronics to how today's wideband radios work, so that I can build my own radio systems (not just ham radios), and talk radio concepts ...
2
votes
2answers
66 views
resonance vs resonator in antenna
Resonance in electronic means: reactance of zero. (maybe wrongly/correctly someone's calling the minimum VSWR, the resonance of antenna! and this cause confusion)
I've heard in Antenna Design for ...
4
votes
4answers
163 views
Why does an RF Amplifier fail when the SWR is high?
Exactly why does an RF output transistor fail if the SWR is bad ?
Is it A because the impedance mismatch between the transmission line and the antenna results in maximum power not being transferred ...
3
votes
0answers
36 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 ...
3
votes
4answers
146 views
How does the thickness of the radiator affect an antenna
Another question (Metal for antenna construction?) covered some aspected of this question, but the answers didn't exactly answer it, so I'll make it specific.
Given 2 dipole antennas, resonant at the ...
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vote
3answers
130 views
How to calculate impedance in antenna design's practice?
I would like to make a match half wave length (λ) dipole antenna (or probably a short dipole antenna). So I would like to make it by measure using LCR meter.
What I am still confuse is about what is ...
2
votes
4answers
160 views
What is the maximum and minimum of antenna gap of dipole antenna?
Consider the picture below is design of half wave length (λ) dipole antenna. I read some explanations saying that it is the best design to get the optimum transmit power. Half wave length (λ) is from ...
4
votes
0answers
63 views
Dipole loading coil winding directions?
A single inductive loading coil in a vertical or a pair of loading coils in a dipole are commonly used to match a given total antenna length parameter to a given frequency wavelength (where the ratio ...
3
votes
1answer
75 views
How do I design a dual band LPDA antenna?
Im not sure if this is the best place to ask a question like this but its the best place i could find.
My goal is to build a dual band antenna similar to this one. That covers ...
3
votes
1answer
88 views
What type of antenna is this?
I have very little knowledge about antennas (I just read about simple dipoles and monopoles recently) and I need to buy a directional antenna for my wireless device. I have found a cheap antenna (I ...
5
votes
2answers
710 views
Why is my calculation for added length of coax for a double cross antenna different to everyone else's?
I'm an amateur amateur radio enthusiast finally building my own antenna, and have decided on a double cross antenna, with the goal of pulling data from NOAA satellites.
Four coax cables, two of ...
1
vote
2answers
189 views
Will transmitting on this antenna cause problems?
Inspired by this discussion, I wanted to check if this is something I can get away with.
I've got an old FM Broadcast antenna that came with a home stereo receiver -- it's 75 ohm flat cable, in a T ...
5
votes
3answers
90 views
Why does no one use a Buddipole as an Inverted V?
I have been looking at the Buddipole, and I've seen the most popular configuration is as a standard dipole with the arms parallel to the ground. I've also seen it configured as an upright V, as well ...
9
votes
5answers
1k views
Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?
I haven't seen this done, (which, after more than a century of amateur and professional radio development, is probably a bad sign), but I had an idea the other day for simplifying the setup and feed ...
1
vote
1answer
94 views
Colinear Vhf antenna
Textbook colinear vertical antenna designs show coax cable with alternating braid to centre configuration. Commercial whips seem to utilise a single wire as the radiating element with .66 velocity ...
2
votes
3answers
101 views
Add capacitor to unload antenna?
So add inductor coil(loading coil) is to cancel out capacitive reactance to make the antenna electrically longer. But what if a capacitor is placed on the antenna, to make the antenna electrically ...
1
vote
1answer
91 views
Mounting antenna on a metal structure? Tower/Antenna insulator?
If an antenna needs to be mounted on a metal structure what would be needed to avoid interference? Are there just some specific length to avoid or it is better to be separated by some insulator?
As I ...
1
vote
1answer
64 views
SWR characteristic changes when lifting coax off the ground?
I was at Anaheim HRO and few guys there were talking about an MFJ all band vertical antenna that does not need radials. I forget what model number it is but it is one of those "wife pleasing antennae" ...
7
votes
3answers
185 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 ...
3
votes
2answers
265 views
How do I listen to the amateur radio satellites?
I'm new to amateur radio, and I would like to listen to those satellites in the orbit.
Where do I start?
What types of amateur radio satellites exist?
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0answers
36 views
Looking for a formula used by VE6YP trap calculator
I wonder whether the source code of VE6YP (Tony Field) coaxtrap design program (link 1, link 2) was ever published or described. As a Mac user I'm having little difficulties using this software and I ...
5
votes
3answers
412 views
What is the proper way to electrically wire in a loading coil to a vertical antenna?
I am trying to put together a vertical pole style antenna with a loading coil housed at the base using a plan very similar to the one described in this ARRL article. I am trying to understand how to ...
2
votes
1answer
53 views
Measurements in far field for radar cross section
I have to measure the S parameter for a rectangular sample with an antenna that works from 2 to 18 GHz. I need to measure a large band from 5 to 15 GHz and I have a problem with the known F.F. (Far ...
3
votes
3answers
163 views
Give vertical antenna directional gain?
So here is a strange thought.
If a vertical electrically speaking is a half dipole with the other half as a ground plane to balance out. Perhaps there are ways to make equivalent director and ...
2
votes
1answer
74 views
Why SWR significantly changes with adding 10-30 meters of coax in presence of RFI choke?
I've build a verical for 40M band using a fishing rod as a mast, 6 radials and an RFI choke (FT240-31 ring, 8 turns of RG58, W1JR winding according to the article by Steve Hunt).
When I measure SWR ...
2
votes
2answers
134 views
Beamwidth of omni-directional antenna with gain
I am looking to buy a wifi antenna for a boat to connect to shore based wireless hotspots that may be "far" away. Due to the waves, I am assuming that the antenna mast sways +-15° from vertical. The ...
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vote
2answers
144 views
What are Smart Antennas?
What are smart antennas? How are they used in amateur radio, and how might they better than conventional antennas?
5
votes
2answers
95 views
Does a loop antenna have less susceptibility to atmospheric noise than an open ended antenna?
I always get the feeling that an antenna which has a loop for the driven element such as a folded dipole or quad will pick up less static or 'high impedance' noise than an antenna that has free ends ...
2
votes
3answers
113 views
Are standing waves on a transmission line RF or DC?
I am very confused about Standing Waves on transmission lines.
Wikipedia says "a standing wave, also known as a stationary wave, is a wave which oscillates in time but whose peak amplitude profile ...
3
votes
4answers
117 views
Is there a way to explain antenna radiation patterns on receive without reciprocity?
I don't consider myself an expert, but I have a fairly decent understanding of radio. I belong to a club that includes a number of people who have less theoretical background.
I understand that ...
5
votes
3answers
326 views
Determining Impedance With An Antenna Analyzer
I need some help interpreting some information from my antenna analyzer (RigExpert AA-35). I want to use the information to impedance match my AM receiving antenna system to AM radios. No ...
0
votes
4answers
115 views
Cell tower identifier antenna isolator cannon
There are several cell towers on the hills around me.
Usually I just walk around their base in a circle with
one of the many CellID apps
to get their ID. Then I can impress my friends, "That's tower ...
