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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79 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 ...
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1answer
60 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
58 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 $\angle I_n$ ...
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4answers
317 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
101 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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1answer
68 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 ...
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2answers
396 views

How does end loops on a long wire antenna affect antenna length

I've put up a "random" length long wire antenna for HF in my yard at about 124ish feet about 15' off the ground. I got this length from an online resource. Here's my questions: How does the ...
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2answers
81 views

Destructive interference between two close antennas

let's consider this two planar biconical dipoles of total length and width each one 10mm, at a distance D = 25.6mm. They are excited with the discrete ports in the picture, which corresponds in this ...
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492 views

Receiving the ISS SSTV: dipole antenna configuration and orientation

In short I am trying to receive SSTV Images from the ISS (145.8Mhz) and I all have is a simple "bunny ears" dipole antenna. In what configuration (straight, vee shaped, upside down vee, ...) ...
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3answers
127 views

Does Kirchhoff's current law (KCL) apply to antennas?

I think I'm having a hard time understanding HF antennas because they go against everything I've been taught about analyzing circuits. If we look at a dipole antenna, there is the highest current in ...
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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 ...
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1answer
58 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 ...
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1answer
106 views

Cobra hand held 50wxst aftermarket antenna

I’d like to add an aftermarket antenna to my cobra HH50wxst to boost my range. My only concern is if I got a longer antenna, could it possibly throw off the SWR and damage the radio? I am totally new ...
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202 views

Loop Antenna Construction

I have a loop antenna. When I connect the probe from my oscilloscope, does the probe also act as an antenna? If so, how should I fix that? I read about feeding technique, but I still do not ...
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3answers
125 views

Receiving multiple signal

Maybe this is a really silly question even from me, a completely amateur... But I like to know about how's the antenna output when its receive multiple signal Is it possible different signals on ...
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249 views

Is the 1.5kW power limit per antenna? What about antenna arrays?

My son KJ7NLL just got his general, and while we don't (yet?) have plans to transmit at 1.5kW, he asks if the 1.5kW limit is per-antenna? If it is per-antenna, and you use an antenna array of 8 ...
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1answer
68 views

Signal frequency domain

Hello I am a beginner on radio and also In speaking english. I hope you will understand what I say. Let's say I have an impulse generator and the air gap breakdown. I am already able to see the ...
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79 views

do resonant antennas need to be re-tuned in the field?

i am considering a "no tune" efhw antenna: https://qrpguys.com/qrpguys-end-fed-wire-antenna i also saw one with a tuner: https://qrpguys.com/end-fed-half-wave-sota-antenna-tuner do resonant ...
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852 views

Is a magnetic loop antenna a good option for those in an apartment?

Are magnetic loops a good choice for those living in apartments or condos where a permanent installation is often not an option and the operator still wants access to the HF bands? Why or Why not? ...
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1answer
56 views

How do I connect a homebrew antenna using RX-8 to a Yaesu FT-70DR (SMA)?

I made an 2m / 70cm tape measure antenna using RG-8 coax. That part was quite a bit of fun and went fine. But when I tried to connect the coax to my Yaesu FT-70DR, the copper core of the RG-8 was too ...
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3answers
322 views

Use (TV?) Log-Periodic antenna for VHF

I found this old log periodic antenna that I assume was from a TV. Could I, or how would I, use this on the amateur radio bands? My main focus would be VHF, with UHF being secondary and HF would also ...
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2answers
279 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 ...
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3k views

Adding and subtracting dB/dBm/dBi values

I've got a question and any clarification on that would be greatly appreciated. For calculating the pathloss in wireless communication we usually use the following formula: PL = pathloss (in dB) + ...
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How to decide between Dipole and Monopole antenna for Cubesat Uplink (433 MHz)? [duplicate]

We are currently deciding between a dipole and a monopole for uplink (435MHz) , while the monopole is easier to feed, we are unsure of how effectively we'll be able to implement the ground plane, ...
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133 views

How should I go about finding the transmitter or antenna of a radio signal?

This site gets many questions about people trying to track down RFI, or interesting signals picked up on radios. Often the exact location of the transmitter or the antenna would be a valuable clue to ...
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63 views

Dual Rubber Ducky antennas

Can I use 2 identical rubber ducky antennas with a splitter on my CB HT radio to improve range?
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87 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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3answers
179 views

How do 'plumber's delight' type Yagi antennas have a bandwidth?

For Yagi antennas where the driven element is electrically connected to the boom like the parasitic elements, how can this function without diminished performance outside of the design frequency? In ...
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1answer
335 views

What is the optimum length for a random longwire on 10m?

I have all the space in the world and wish to errect a single random longwire to use on the 10 meter band only. I understand that once such a wire is very long, losses associated with the wire itself (...
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3answers
97 views

How does a smartphone FM antenna work?

My understanding is the earbuds that connect to the aux port act as the antenna. It's a long wire. The problem is that the same wire is being used to power your earbuds so you can hear the radio ...
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5answers
257 views

How can a tuner pick up a specific frequency?

The point I'm confused about is the antenna. Depending on the environment, there are tons of different frequencies passing through you (FM, AM, 4G, SAT, etc). The electrons in the wire will move as ...
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1answer
102 views

Is this "floating" output single-ended or differential and against GND or VCC?

I'm looking at a simple FM transmitter output (see picture). It is from the collector of a transistor and it goes through a DC blocking capacitor before the antenna would be connected. The entire ...
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1answer
56 views

Hatch Mount Antenna Selection - Dual Band 2m/70cm

I just bought a Diamond CP-5NMO hatch/lip mount and intend to put it on the hatchback lip of our 2018 Subaru Forester and, if it will fit, another one on our 2019 Kia Niro EV. I understand that hatch ...
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2answers
121 views

Output power from the TX/RX port of the USRP N210 decreases as the frequency increases

I am trying to build an FMCW radar using a USRP N210 with a CBX40 daughterboard. I generate a sweep from 1.5GHz to 5GHz. According to their respective datasheets, the daughterboard and the USRP should ...
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1answer
70 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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3answers
79 views

Recommendation for hobbyist flight computer radio antenna

I'm a CS college student working on the flight computer of my Rocketry Club's rocket. My flight computer has a 915MHz radio transceiver, and it needs to transmit data to my computer with another radio ...
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104 views

Anyone know what this antenna is?

Hello, what kind of antenna is this? I’ve been trying to figure it out for 14 years. None of my neighbors know. Whomever installed it either moved or passed away.
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21 views

Is this result correct ? [ impedance cavity based on emtamaterials using CST Microwave]

In the contexte of my reaserch about antenna conceptions, I'm trying to simulate using CST Microwave a cavity antenna based on metamaterial structure and a slot antenna as a GND,However I got as a ...
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1answer
125 views

Substitute a car roof with radials?

I have a K40 Plus CB antenna, which is supposed to be attached to a car roof for the ground plane. However, I would like to set this up as a base antenna. Could I instead attach the ground to separate ...
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2answers
143 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 ...
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1answer
48 views

Bidirectional motor control using MFJ-4116 with RCS-4

I have the RCS-4 with two MFJ-4116. Prior to installing my motorized HF antenna system topside, I bench-tested the core of the assembly in my shack. The MFJ-4116 near my transceiver was injected with ...
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2answers
329 views

How to use 75ohm (RG6) coax?

I know that there have been many similar threads on this, but I still need clarification. At the moment, the only thing I have is a 500' roll of RG-6 and a (very) tight budget, and I should be ...
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2answers
194 views

Troubleshooting 5BTV antenna

I have a Hustler 5BTV antenna i resurrected after a previous monopole succumbed to birds. It is giving me a world of trouble trying to get it tuned for resonance. For those not familiar with the ...
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1answer
81 views

Stacked Yagi Gain calculation

I had a quick look at a practice exam for the license in my country and had a question on stacked Yagi antenna. I have been looking around but the only thing I can find is the mention of an additional ...
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2answers
314 views

How does a 40/15m dipole with capacitance hats work?

I followed an article Antenna Here is a Dipole [PDF] by James Hearly, NJ2L to build a dual band 40/15m dipole: The antenna works more or less as expected. My 40m dipole was resonant at 7.030 MHz and ...
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91 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 ...
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2answers
134 views

Antenna phase explanation

Trying to grasp antenna phase, reading through ham.se and youtube but haven't come across a clear (enough) explanation. I understand the basics of antenna phase (i think), where E leads I that's ...
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2answers
141 views

Building a low-power simple RF frequency (433MHz or 900MHz (but not both)) detector effective at 5m with a 10mW signal

I am looking for a simple schematic for building an effective RF detector which can trigger a GPIO. The goal is to (passively?) detect a 10 mW RF signal (10% duty cycle) and have that raise voltage on ...
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4answers
973 views

Are there any antenna that can create disk like lobes?

Are there any antenna that have disk like lobes : Or are there any antenna that have very thin directivity, say lobes be no more wide than few mm.
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302 views

Loop a long wire antenna or EFHW

For a typical EFHW antenna, let's say we are in a very space-restricted environment, says a hotel room. I am thinking of the idea loop around the wire around the room, maybe even many loops. This is ...

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