# 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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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 ...
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 ...
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 ...
63 views

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 ...
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 ...
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 ...
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) ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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&...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...
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&...
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 ...
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 ...
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 ...
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 ...
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 ...
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, ...
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. ...
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 ...
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 ...
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 ...
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 ...
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 ...
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. ...
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 ...
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 ...
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 ...
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 $\angle I_n$ ...