Questions tagged [antenna]

Questions about the design, selection, building, testing, mounting, or properties of antennas. See also specific tags: [antenna-theory], [antenna-construction], [dipole], etc.

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3answers
78 views

Can ham radio antennas interfere with RING devices, causing them to produce high-pitched noise? [closed]

Can a HUGE ham radio antenna on a house with an array of RING devices (5 in total) cause interference and high-frequency reverberation? The attached shows one of these devices (there's 2 under the ...
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0answers
109 views

Hardened UHF Antennas

Minuteman missile silos used an interesting hardened UHF antenna. What kind of antenna is this? Does anyone have a drawing with a cross section? Edit: Jay Moore added a picture to a different type of ...
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1answer
78 views

When to use air dielectric cables for antenna installation

I'm putting up antennas on a tower, and have a couple of 7/8" cables style on hand. One is Hj5-50 air dielectric cable and the other AVA5-50 "Virtual Air" cable. I notice that the HJ5 ...
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2answers
63 views

Isolated linearly loaded antenna?

Is there a name or common descriptive term for a linearly loaded dipole or end-fed, where a (near) parallel loading element or elements are not connected (galvanically isolated) to the fed element or ...
2
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2answers
68 views

How to compute the efficency of an omnidirectional antenna from its gain?

Some antennas have very limited specifications with no stated efficiency. For example, this antenna has the following specifications: Frequency Band 902-928 MHz VSWR <2.0:1 Impedance 50 Ω Gain ...
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1answer
51 views

How does a loopstick antenna actually receive signal?

Around 1970, I acquired a little transistor radio (powered by 4xAA cells, 6V) that had no external antenna. Inside the back panel (which opened to allow replacing the battery cells) one could see the ...
4
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3answers
483 views

Measurement of antenna with VNA does not match its specs

I have a NanoVNA V2 Plus (50kHz - 3GHz) and decided to test my LoRa antennas: an unknown antenna delivered with a LoRaWAN gateway (RAK831) a 868Mhz antenna from Linx Technologies (ANT-868-OC-LG-RPS) ...
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2answers
131 views

What do radials really do for a vertical antenna?

I have read everything I can find about monopole (vertical antenna) radials, and also watched many YouTube videos that touch on the topic. I see conflicting information about what they do, where a ...
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2answers
104 views

Can a smartphone with single antenna receive signals modulated by different schemes

I am working on a system whereby a smartphone may receive signals simultaneously from different sources. As we know, the fading and pathloss will make the transmitters send their traffic with ...
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2answers
64 views

At near-QRP levels should I include a balun/unun in the antenna system? [duplicate]

To my comprehension a BALUN/UNUN is an RF Transformer. If this is correct and since a BALUN/UNUN is part of the antenna system ... how much power does one expect to lose there? Specifically, how much ...
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1answer
81 views

Yagi antenna isolation from other Yagi antennas

I have multiple Yagi antennas horizontally polarized. They are all placed in closed proximity at the same height horizontally and operating in a similar frequency. The yagis are 2.45GHz, bluetooth ...
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2answers
67 views

Ground plane reflects RF or brings it to ground

I'm still confused with the purpose of a ground plane purpose in an antenna. My understanding is this. If an antenna is perfectly balanced, there will be no common-mode currents going to ground. If an ...
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2answers
104 views

How much dB gain do you need from an LNA in front of an antenna for great low-signal reception from satellites in the 2m and 70cm bands?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. This LNA we are considering (Qorvo QPL9547) provides about 22dB gain in the 2m and about 27dB in the ...
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4answers
128 views

3D Printed yagi antenna

I'm trying to produce a Yagi antenna for the 2.45 GHz band using a 3D dual extruder printer. The idea is to print the antenna elements using a metal filament and encasing it all in plastic. The ...
2
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1answer
69 views

What might a “split-ring on a printed-circuit board” antenna for 144 MHz on a downward-looking Space Shuttle window look like? How big would it be?

This excellent answer to First Ham Radio contact from space; what frequency, what kind of antenna, and how did they route the coax out the window? in Space Exploration SE contains the block-quoted ...
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2answers
78 views

Antenna suggestions for SDRPlay RSP1A

Looking for suggestions for a portable antenna for use with a SDRPlay RSP1A. I notice that most other SDRs come with a few antennas, but not the RSP1A. I have a 2m/70cm HT, so I own a Nagoya NA-771R ...
2
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0answers
35 views

How might various conductive mast mounting configurations affect an electrically isolated rhombic antenna?

Assuming a rhombic antenna is: terminated for directionality electrically isolated at its mount point mounted to a metal mast partway up vs top of mast horizontally oriented (elements parallel to ...
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2answers
75 views

Tuning two antennas using wire length

I've heard that in the early spark-gap wireless telegraphy era people would use kites with a wire acting as antennas and if the receiving side had a wire length that was an even division or multiple ...
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2answers
97 views

Interpreting (noise) signals from a small untuned shielded loop

This a follow up from this question: QRN: How to chase down a solid S9 noise floor on 40m only Focusing on how to interpret the signals received with an electrically small, untuned "shielded loop&...
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2answers
80 views

Tuning wire with SWR LED

I have a QRP rig (Mountain Topper) and a variable capacitor QRP end fed half wave antenna with an SWR LED indicator. The LED doesn't go fully out in all configurations but there is always a local ...
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2answers
63 views

Hang wire antenna on TV antenna?

I have a TV antenna on the top of my house that I don't use. It is the highest point around so I would like to hang a wire antenna (for HF) on it. Is an inactive antenna going to cause any ...
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3answers
131 views

When a dipole antenna is fed via coax, what powers the ground-side of the dipole?

I've been trying to understand how dipole antennas work, and I believe I understand the basics when they're fed via a balanced feed line. In fact, every dipole physics YouTube video and web page I can ...
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3answers
108 views

Why do we need special geometry for telecommunication antennas?

In many youtube videos about building low power radio transmeters , I have seen a piece of regular wire or extension cord used as a antenna. But , it seems like telecommunication antennas have ...
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0answers
25 views

Magnetic and Electric Wall in HFSS

I'm new to RF engineering and I want to ask how to draw magnetic and electric wall in HFSS software? I know magnetic Wall means open circuit in circuit model and electric wall means short circuit, but ...
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1answer
61 views

Replacing a N-connector with SMA, easy?

I purchased a cell phone booster for the cottage that came with an external yagi. Since its important to get the antenna as far away as possible from the indoor omni, the yagi has about 25 meters of ...
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1answer
282 views

Boosting Mobile Phone Reception

Yes, I know, this could very well be a controversial topic, so feel free to close this off if you feel it's not a good fit for this site. That said, I'm posting it here because hams (and as a ...
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2answers
85 views

what is main reason for formation of side lobes in directional antennas?

I would like to know why are side lobes formed along with main beam in an antenna. I asked one of my colleague and he explained me that its due to radiation of frequencies near to the required center ...
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1answer
80 views

Is a MagLoop antenna better than my 50ft end fed di-pole for 20-80 meters?

I'm restricted to putting antennas in my attic which is 50 feet long and peaks at about 8 feet. I'm currently using the Nelson UJM-150-50 end-fed dipole 80-10 meter antenna. The attic is about 25 feet ...
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1answer
56 views

What type of omnidirectional antenna gives the most gain for a frequency of 2.4 GHz?

I have a 2.4 GHz transceiver that outputs 4.5 DBm. I wish to amplify the signal using a 15.5 DBi antenna so that the signal reaches 20 DB, the maximum legal limit. Preferably, the antenna would be of ...
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1answer
123 views

How to compute the required length and turns for an air-cored antenna

I'm experimenting with RF reception in the 433MHz band and have made the most simple "whip" monopole antenna with 17.6 centimeters of wire. Out of curiosity, I tried various designs for the ...
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2answers
117 views

1/8 wave 3-element 2m beam antenna

Here's what I am working on, and someone please tell me if I'm doing this right or wrong, but be kind and gentle. Center frequency 146.520MHz Driven element is 1/8 wave 10.25" long set at 6.125&...
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3answers
153 views

Antenna options

I am considering a new ham station in a relatively urban environment on the South coast of England, and would like like some ideas / feedback on antenna options. Aim is to get reasonable performance ...
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2answers
144 views

Using a parabolic dish for working the 70cm band - Am I missing something?

I have read a lot of times in this forum that C-Band TV dishes are not suitable for operating 70cm. However: Suppose that we have a 2,4m dish. By assuming a global efficiency of a 60%, our total gain ...
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1answer
76 views

Antenna Tuner Range

I have a Kenwood TS-480S and a Kenwood TS-870S both with built in antenna tuners. On the TS-870S I have a ZS6BKW multiband antenna and on the TS-480S I have a vertical whip with two counterpoise lines ...
4
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1answer
100 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 ...
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2answers
101 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 ...
2
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2answers
113 views

Coupling 2 Antennas to one line?

Imagine two dipole (or Yagi) antennas as might be used to create a circularly polarized combination antenna. The two are physically oriented (rotated) by 90 deg, and if in the same receiving plane, ...
5
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1answer
70 views

can the adhesive used in thru-glass antenna couplers be replaced?

I recently bought a pair of self-adhesive thru-glass antenna couplers for my mobile radios and erred in mounting both of them, which required me to peel them off the side window glass in my minivan. ...
3
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2answers
173 views

Dual Polarization Yagi Antenna for 10 m

Imagine that someone has built a 4 element horizontal yagi antenna for 28 MHz with elements insulated from the boom, and with the driven element not split in the middle and using a gamma match to set ...
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2answers
699 views

What is the appropriate length of an antenna for a handheld on 2 meters?

I want to upgrade the stock antenna on my Baofeng uv-5r for which I mostly use the 2 meter band. The quarter wavelength for this band is about 19.2 inches, but when I look for antennas, they are ...
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0answers
56 views

Biconical antennas - bandwidth and installation

I am posting this question (and its related question) here because of the unique expertise that Ham Radio Operators have as it relates to antennas. I'm a newish Ham and really appreciate your help ...
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2answers
170 views

Trying to identify and understand this antenna design - ground independent dual band vertical

This is the insides of a common dual band antenna 2m/70cm, made by diamond or nagoya. its generally labelled as: 1/2 wave radialless (144MHz), 2 x 5/8 wave radialless (430MHz) Its meant to be ground ...
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3answers
104 views

Constructing a ground level antenna array to monitor radio frequencies using SDR

New to this community and also a newish Ham. Hello everyone. This question could easily have been posted under 'Astronomy', but I thought I would start here since Hams tend to be quite knowledgeable ...
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3answers
101 views

High-Z RF amplifier for magloop RX vs Q-factor

I've noticed that increasing load on magloop reduces it's Q-factor, it becomes less selective. Traditional way to approach this is reducing size of pickup loop, or alternatively, using transformer. ...
4
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3answers
96 views

antenna coax feed-thru for a car roof

Newbie here, with a 2 meter mobile rig and a magnet-mount antenna. I am currently routing the coax out an almost-closed window and am tired of having rain water enter the car through it. Is there such ...
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1answer
63 views

I have a 433MHz LoRa Dipole antenna mounted on a rocket. I am looking for a suitable Antenna to receive data from this. Any Suggestions?

The idea was to send GPS data from the rocket to the ground station at 433 MHz using a Lo Ra transmitter - mainly to help locate it once it lands and also to provide in-flight telemetry. I have a ...
2
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1answer
58 views

Identical HF Horizonal Dipoles Operating in Close Proximity

I'm planning to use a multiwave horizontal dipole oriented to work comms toward Alaska from Colorado. That ends up being awkwardly oriented to work east coast and Europe. If I placed a second ...
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1answer
45 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 $\angle I_n$ ...
4
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3answers
222 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 ...
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1answer
73 views

Troubleshooting the MFJ 1982 EFHW

I am a beginner with not much experience in HF. My shack consists of a Xiegu G90 connected with 20ft of RG-8x to an MFJ 1982 end fed half wave antenna. There is a small coil of coax next to the ...

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