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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64 views

Receiving medium - low frequency CPU signal

I'm trying to listen to the CPU freq's my PC produces (kinda similar to what was done here: https://github.com/fulldecent/system-bus-radio) I do see a clear signal that comes from the CPU (I know ...
2
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3answers
504 views

SWR, overall, is too high

This is a sort of follow-on question from my tuners in series question. The problem I am ultimately trying to solve is this: I am using a manufactured end-fed, half-wave 40m antenna. The ...
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4answers
742 views

CB Ground Plane on fiberglass RV

The CB ground plane on my 43' fiberglass motorhome stinks. Has never worked correctly. If I install a piece of sheetmetal around the antenna on the roof would that help the ground plane at all? A flat ...
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3answers
641 views

Tiger Tail + capacitive coupling… what's the interaction?

I've been working on a 2m setup for hiking. My goal is to have the best possible antenna that can be used while walking, and that won't get damaged if I walk under a low branch or some other forest ...
2
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1answer
249 views

75Ω Wire FM antenna

I was recently given an older, but really nice broadcast FM receiver (88-108Mhz) by neighbor, but I am confused by the antenna connector and labeling. for the FM antenna connection, there are two ...
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5answers
964 views

What kind of 2 meter antenna is this?

At first glance this appears to be a simple ground plane but there is far more going on. The ham who built this back in the '80s is now SK and I can't find anything else like this anywhere. The ...
2
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2answers
422 views

Satelite dish modified for Wi-Fi (Signal Elevation Question)

I am doing a project where I will be re-purposing an old TV satellite dish as a directional Wi-Fi antenna. The dish is circular in shape, not oval. The dish has an arm coming from the bottom that ...
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3answers
1k views

Can I test a base station CB radio with a magnetic mobile antenna?

I am looking at a base station and want to test it before purchasing can I use a magnetic mobile antenna to see if it transmits and receives without damaging it?
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1answer
493 views

What is pinout for headphone FM radio antenna?

My Android phone (as many others) have FM radio receiver on-board. But apparently, it has no internal VHF antenna at all, since there is no signal at all w/o headphones plugged in and sound quality ...
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3answers
310 views

Is cheap Chinese coax wire ok to use as an antenna?

So I've been following this guide on how to build an antenna for a High altitude balloon: link In the guide they say to use RG174 wire, which is why I bough some cheap RG174 wire off Ebay. I guessed ...
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2answers
825 views

Does a receiving antenna need radials?

I am very new to radio and am using two 433MHz 1/4 wavelength monopole antennas to send and receive data. On the transmitting antenna I'm going to add radials (as it is the standard in my application)...
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1answer
1k views

What frequency to set trap on?

I plan to build trapped multiband dipole so I read lots of documentation I found. There is one thing that confuses me: various authors recommend setting resonant trap frequency differently: some say ...
2
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1answer
211 views

Yaesu FTM-3200dr Antenna

I am looking to upgrade my station soon by buying a Yaesu FTM-3200dr mobile 2m radio. I am limited on funds for radio and I don't want to get the wrong type of antenna connector and wast a bunch of ...
2
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1answer
659 views

What material is best to design a dipole antenna working at VHF frequency? [duplicate]

I need to design an antenna using the tool FEKO. The antenna is supposed to work in VHF frequency and has a gain of around 2.2 dB. What is the best material to use and what are the specifications of ...
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3answers
716 views

What is the point of high gain antenna with respect to the maximum EIRP

OFCOM states that the maximum EIRP within the UK for 2.4 GHz is 100mW. Simply put, what is the point in being able to buy 2.4 GHz high gain antennas which can say do 24dBi, which already puts the ...
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1answer
181 views

Transition Point Between Fan and Cage Dipoles

A fan dipole is a dipole with multiple active elements, either for different frequencies or different directions (see turnstile antenna) while a cage dipole emulates a larger conductive by having ...
1
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1answer
491 views

Why Coaxial Collinear Antenna Gives Strange Graph of Frequency Sweep vs SWR?

Antenna Analyzer gives a understandable results for a Quad Antenna (photos 1, 2 & 3), but gives strange results for Coaxial Collinear Antenna (photo 4) Photo 1 of 4: Test setup for Quad Antenna ...
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2answers
762 views

Optimal antenna orientation for High altitude balloon?

(First of all, I hope this is the right subform, please correct me if I'm wrong) I am using a 433 Mhz LoRa Radio to communicate with a high altitude balloon and am using an antenna like in this guide ...
2
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2answers
2k views

What is the purpose of having multiple bays for a bowtie antenna?

What would be the difference between a two-bay antenna designed like this: and a four-bay antenna designed like this: Assuming that everything about these two antennas are identical aside from the ...
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2answers
215 views

Reciprocity for loopstick antennas?

What is the reason a small loop-stick antenna ( typically used for AM reception) does not have reciprocal characteristics for both reception and transmission. ( AM reception works great on those ...
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3answers
527 views

Packet Radio at 100 miles [closed]

I am wanting to assemble a Packet Radio solution that will allow for packet radio transmission with a range of about 100 miles or better. I am not sure what band to use, what radio to use, what ...
5
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2answers
1k views

What ways are there to extend an antenna?

I am using an arduino micro controller with a LoRa radio module to communicate. The shield has 2 ways of connecting an antenna: either a SMA jack or a hole for soldering. Now my problem is this: I ...
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2answers
173 views

Amplified antenna & typical boombox radio

Can an amplified antenna be connected to a typical boombox radio with a telescoping antenna without damaging the radio?
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3answers
1k views

What do you connect antenna Radials to?

I am trying to communicate between two arduino microcontrollers using radio. For this purpose I am building a whip antenna with 4 ¼ wave radials. I've done a bit of reading and have got most of it, ...
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2answers
1k views

Field Strength calculations with known antennas

I can receive a calibrated decibel milliwatt signal level from the output of any antenna at a given frequency. With a given antenna gain (dbi) in the direction I want to receive the signal (...
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2answers
341 views

baofeng UV-5RA has issues with j-pole

I have a baofeng UV-5RA which doesn't seem to receive properly with my j-pole antenna. my dad's radio (same model, different firmware) receives without a problem, so it's a radio issue. if I go into ...
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4answers
1k views

Good Hidden Antenna For 2m

I would like to have an antenna outside for 2 meter VHF use but I do not want it to be expensive and I won't be allowed to put it up if it stands out too much. Does anyone know a good antenna to buy ...
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3answers
283 views

How do you keep your vehicle clean with a mobile antenna?

I want to add a V/U antenna to my truck, but my wife started asking about weather proofing and car washes and I had no answer. How do you keep your vehicle clean after installing a new antenna, and ...
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2answers
300 views

dual band j-pole creates connectivity problems when connected all the way

I recently made a "deseret j-pole" dual band antenna for basic 2m and 70cm transmitting and receiving use. I have it on a large metal tube behind my house, connected through a 50 ohm pl-259 cable, and ...
6
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1answer
411 views

What kind of antenna is this?

This was found among some old ham stuff and is believed to have been used on 2 meters. The vertical elements are 17 1/2" long and the connector on the bottom is a standard SO-239. Antenna (left) and ...
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2answers
1k views

How to best connect an FM transmitting GPIO pin to an antenna?

I'm trying to use a RaspberryPi3 as a FM transmitter, using pifm and/or PiFmRds to send audio in 88-108 MHz band. The RPi can then use the GPIO-4 pin to transmit between ...
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1answer
2k views

My Baofeng radio won't recieve but transmit does not work when I hold the MONI button [closed]

My radio won't receive. Help? It literally went dead and I still have the rubber duck antenna
3
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1answer
481 views

Using an HF antenna for VHF scanning

Are there any disadvantages (or advantages) to using a long-wire HF antenna for wide-band VHF reception? Or would feedline losses make that useless compared to a ground level ducky or short whip? (...
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3answers
374 views

High SWR on a Jeep with Spare Tire Mount

I just installed a spare-tire mount and Browning BR-180 dual band antenna on my Jeep JK. Initial SWR testing show nothing higher than 1.4:1 across both bands so I didn't try to tweak it. Then I put ...
4
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1answer
410 views

DAB antenna in roof space

We are setting out our roof-space as an attic, and after decorating, there will be a triangular void under the house ridge, which will be about 36" wide, and 18" high. I can easily fit a standard ...
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1answer
421 views

How to assemble an antenna (impedance matching methods)

I got the following plans off Martin E. Meserve's website. How do I go about assembling the antenna once I have the elements and boom? What is the impedance of the driven element? Do I need baluns ...
4
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1answer
763 views

What is the difference between “Cross Polarized” vs “Circularly Polarized” Antennas?

What is the difference between cross-polarized yagi antennas and circularly polarized antennas?
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1answer
53 views

Transmission Line Model of Co-ax Lines

I have got 2 questions on transmission line. In coax line, the centre wire is Copper, and the outer line is Aluminium, as far as I can see in the coax that I have. I have got couple of questions on ...
3
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3answers
577 views

Unexpected Resonance - Dual-Band Dipole

I tried to make a dual-band (2m/70cm) dipole this morning by following the instructions on this page: http://www.amateurradio.bz/2m-70cm_vertical_dipole_antenna.html, with the rather major significant ...
2
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3answers
405 views

Maximum Thickness for NMO Mounting Surface?

How thick can the metal be for a common NMO antenna mount? I know they're meant for sheet metal but can they go as thick as 1/4"? Edited to add: By "common", I mean NOT the ones designed for extra ...
1
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1answer
215 views

Antenna Ground System

I have a designed an arrayed dipole antenna for transmitting in 200MHz frequency. Where I am confused is, what should be my ground system for both antennas (Transmitting, and Receiving). Say I am ...
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1answer
324 views

What is the directivity of thin dipole antenna of length 1.25λ?

I want to know about the directivity of thin dipole antenna of length 1.25λ for my assignment.Is there any formula related to its length?
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2answers
2k views

Balun and tuner configuration for multiband dipole

I'm putting up a multiband dipole in some tall trees. (Perhaps it's more correct to call it a "dipole-doublet"). The situation I'm imagining looks like this: The legs of the antenna are each 100 ...
2
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1answer
305 views

Rules of thumb for large (“somewhat” full wavelength) loop antennas?

I would like to put up a relatively large loop antenna to cover all the HF bands. I have sloping terrain and geographically in a slight "bowl" with hills and/or ridges in many directions. If I stick ...
1
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1answer
88 views

Ramsey's DDF1 with a SMA connector

Need some help with my Ramsey DDF1. It comes with telescopic antennas and my son has accidentally stepped on and broken one. I'm taking the opportunity to replace them with a SMA connector and ...
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2answers
1k views

Moon->Earth 433MHz link achievable digital bandwidth

Let's assume we have the following situation: Transmitter on moon orbit (distance from earth ~400'000km), around 433Mhz. Transmitter power 1W, antenna gain 10dB, circular polarization. Steered to ...
2
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2answers
2k views

How far does a watt equal in range in the FM band?

How many watts would be needed to cover a 10 mile radius with good sound for music on the 88-108 MHz FM broadcast band? I am an amateur and for fun only.
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2answers
134 views

Serial matching stub combined with RF choke

If I use RG6 coaxial cable in odd multiples of 1/4 wavelength as a serial matching stub, can I also use it, without modifying the length, as a coiled RF choke balun at the antenna feed point?
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1answer
287 views

Mathematica notebook for NEC2 (NEC, Numerical Electromagnics Code)

Are there any open source Mathematica notebooks that interface with NEC2? I am primarily interested in plotting the NEC2 results from Mathematica.
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2answers
5k views

How the Coaxial Collinear Antenna Works?

A length of coaxial cable radiates negligible amount of RF. Same length, if cut into pieces of length (λ/2 * VF), and these pieces joined again cross-connected (i.e. core of a piece to shield of ...