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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5
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8answers
7k views

How does the length of a metal sleeve around a (shieled) coax cable affect antenna performance?

A post on http://adsbexchange.com/forums/topic/beginners-2-cantenna-easy-diy-antenna-to-improve-rangeplane-count uses a $\frac{\lambda}{4}$ sleeve made of a pop can beneath a $\frac{\lambda}{4}$ wire ...
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2answers
296 views

Tuning an antenna with cold weather

I have a 20m long dipole that starts at 2m above the ground and ends at perhaps 20m above the ground. It was -10 °C here tonight (that's +14 °F), currently around zero (32 °F) and my antenna is out of ...
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0answers
98 views

Antenna Impedance calculation for low frequency [duplicate]

If I have an end fed long wire in free space, say 100 ft, how do I calculate its $R$ & $X$ at different frequencies?
2
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2answers
146 views

Interpretation of NASA design

I'm very interested in replicating a design published by NASA here : https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19670027843.pdf Specifically the arrangement on Page 11. I have a similar ...
2
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2answers
2k views

Does antenna frequency matter when trying to pick up radio waves?

I'm buying the following: https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0129EBDS2/ref=sr_1_3?ie=UTF8&qid=1480215974&sr=8-3&keywords=RTL-SDR to analyze radio waves as ...
1
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1answer
143 views

Utility pit MW/LW omnidirectional antenna

I am looking at antennas for a rather unusual application: mounted under a utility pit lid (manhole cover). The goal is to receive commercial MW/LW stations. The antenna has to be attached to the ...
3
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1answer
173 views

Polarisation loss Dipole antennas

For a school assignment I need to calculate a link budget between two half wave dipole antennas, but I am stuck at calculating the polarisation losses in the antennas. the antennas are ideal and ...
11
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2answers
362 views

What kind of antenna is that one?

Yesterday I saw the following antenna: I am very puzzled, at first glance it seems a simple dish but: The mesh is really wide (low frequency?). It is pointing to Zenith. I think that most dish ...
2
votes
1answer
219 views

Influence of bending and asymetric ground wire on monopole antenna

I'm currently building a rc radio system using the 433mhz RFM69W transceiver, so far everything works fine, but i am not sure about the way i laid out my antenna and how the layout cripples the ...
2
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1answer
106 views

Portable radio antenna measurement

Just purchased a HP 8711A and have "upgraded" the bootrom to enable vector measurements. I am now trying to learn more about how to make better measurements and understand what's going on. One of the ...
3
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2answers
381 views

How does the antenna noise temperature vary with antenna elevation?

I'm using a 14 element cross Yagi antenna in my system. For my link budget calculations, what antenna noise temperature should I consider? How does this vary with elevation?
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4answers
697 views

Is it safe to live close to cellular antenna?

I saw some apartment in my county in a very good location (quite close to the beach), however, the rent is very cheap. The apartment is the highest on that building, on top of this building there is a ...
8
votes
2answers
935 views

cubesat turnstile antenna material selection

My cubesat team is working on our design for rolled whip antennas to deploy in a UHF turnstile configuration based on this design: What I would like advice on is the material for the antennas ...
3
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3answers
589 views

Why does an “electrically small” antenna have narrow bandwidth?

Reading this interesting piece on magnetic loop antennas, the author explains that a magnetic loop has great efficiency even at small size, but the the price you pay is very narrow bandwidth. Why is ...
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2answers
2k views

DIY 433MHz antennas from copper wire

I need to build two minimalistic antennas for RX/TX at ~433MHz. I have insulated solid core copper wire, but I need to make it perfectly straight. I was thinking of using the type of sticks you set ...
5
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3answers
445 views

Mounting my antenna

I just bought a CB and mounted it in my truck. I ran my antenna to the back and was going to stick it to my tool box but it turns out to be aluminum, so I'm thinking of bolting a metal plate to the ...
5
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3answers
5k views

Distance between antenna and radio

I live in a small cottage with an unlevelled terrain. My house was built in the lower part of it (left-side), and in the other half of it there is a hill. On top of the hill there's a fairly good ...
1
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3answers
218 views

How to calculate/estimate the effect of having conductive material nearby an antenna

I have a system with a 1/4 wave whip antenna and above the antenna there is a mess of aluminium they're not connected but are nearby. I would like to figure out what effect this would have on the ...
8
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3answers
2k views

Antenna for a cramped attic

Brand new Ham. I bought a cheapo UV5 right before I got my call sign. I want to set up a decent 2m/70cm station for starters and I realize that a better radio is important but wanted to knock out the ...
1
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1answer
435 views

Best way to make a selfmade Long-Range WiFi Link

What needs to be considered? Which type of antenna(only self-made or reused parts, for example satellite dish) is the best for a long range, high throughput WiFi? How to calculate Antenna size and ...
0
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3answers
2k views

Will two ends of dipole antenna pointing to the same direction cancel out the signal

I am living in a small compartment, considering setting up an antenna indoors. As my room is so small (3m^2), thinking of putting a dipole antenna with soft wire indoors. If two ends of dipole ...
0
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1answer
92 views

Directional antenna overlapping main lobes

In a 2-Rx by 2-Tx directional antenna system, say both transmitters are transmitting concurrently as in Fig. The main lobes from the two transmitters overlap. How does this affect the resultant signal ...
2
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3answers
4k views

Calculating bandwidth of antenna?

Is there a way to calculate bandwidth of an classical dipole antenna having this information: center frequency wire velocity wire diameter I would disregard antenna height, to simplify. I am not ...
3
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3answers
533 views

Which is better in my situation: Balanced dipole, or as much wire as possible in the air?

I'm finally getting to the point of hopefully putting up a HF antenna. The idea is to start with a simple, straight wire dipole using trees as support points. (No traps or coils.) However, with the ...
3
votes
1answer
252 views

How to calculate effective isotropic radiated power apply to lossy antennas

If a band allows one watt EIRP and I have an antenna that is 1% effective could I legally run 100 watts into the antenna because only one watt is radiated? If that same antenna also has a gain would ...
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2answers
219 views

Strange Noise Floor observed in UHF Band

I have a tracking station for UHF band satellites which comprises of a cross yagi of 12 dBi and a wideband LNA of 40 dB Power Gain and 1.3 dB Noise Figure. I observe a Noise floor of about 300 kHz ...
3
votes
2answers
370 views

Combining yagi and J pole for airband

I use a J Pole for air band (122 MHz). I get superb aircraft reception but a very weak signal from my local airport 20 miles away. Is there a way to set up a yagi, or other gainy directional antenna, ...
0
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1answer
142 views

Feed line direction for Quad antenna

I am currently getting my EE degree, and I'm trying to build my first antenna for a weather balloon. I understand with a dipole, you want the feed line perpendicular to the antenna for at least l/4, ...
1
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2answers
363 views

2,4GHz Spectrum Analyzer with wireless card

I am new in the world of Radio Technology and I would build an idea with Bluetooth 4.0 and want to see the frequency for debugging. So I will need a Spectrum Analyzer, but won't buy one of these. ...
0
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2answers
152 views

What type 2 m /70 cm antenna to use when I want to receive a number of spacially separated beams?

So I have a 1.5 m by 1.5 m window. Through it, I have a number of spatially separated ~10 cm wide "beams" coming from local repeaters. It looks something like this: Outside of the marked areas, ...
6
votes
4answers
3k views

Does mounting a ground plane antenna upside down change the takeoff angle?

A typical gain pattern for a quarter wave ground plane antenna is: Image from a similar question and see watermark. For a situation where the signals of interest are below the antenna in elevation (...
0
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2answers
90 views

Acquiring specs on anntenas so as to mathematically model level curves in their transmission feilds

Is there an antenna supplier out there that is particularly well known for publishing enough data on their antennas that one can model their antennas' transmission fields in spherical or cylindrical ...
2
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3answers
2k views

Can VHF/UHF antennas have different orientation

I am communicating about 1000'. Is the orientation of the antennas critical, can a vertical antenna communicate with a horizontal antenna? The equipment is spec'd as VHF 148-174MHz and UHF 400-470MHz.
2
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2answers
895 views

3 way coax split / impedance match

I would like to split a coaxial feed line 3 ways, maintaining 50 Ω impedance. I know how to do this 2 ways; you use 1/4 wavelength 75 Ω coax as matching stubs. I know how to do this 4 ways; you do 2 ...
2
votes
1answer
85 views

tuning trouble - 1/4 wave 8 elevated ground radials 10 meter

It is resonate for 22 Mhz haven't had any luck tuning it for 30 Mhz it is an excellent antenna I feel at the Z is 0 for 22 Mhz I have given up and think I will just buy a Imax 2000 w/ radials?? "10 ...
2
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5answers
488 views

Yaesu FT-950 with G5RV lite antenna auto tune problem on 21Mhz

I am unable to autotune on 21Mhz as the SWR is more than 1:3 which is out side the range of the radio. I would like use it only for digital TX with a max. power of 50 watts. Any solution/s?
1
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2answers
282 views

Scanner radio purchase advice for someone that's nosy but not technological?

If it sounds like a stupid question, it probably is. My mom loves being nosy... When she hears the police siren, an ambulance, firefighters, or something like that, she's the first one to run to the ...
3
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3answers
1k views

Would retrofitting an external antenna to a smartphone be feasible?

I'm not sure if this is the proper StackExchange site, but you guys know RF and I don't know who else would know better. I take the commuter rail to work every day. I have 60-70% cell phone coverage. ...
2
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3answers
337 views

RSSI on both ends of UHF Point to Point network do not match

My understanding of an RSSI reading is that it should equal Tx power - Tx feed loss + Tx antenna gain - pathloss + Rx antenna gain - Rx feed loss. If this is the case, if the radios at either end are ...
4
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1answer
544 views

How to bypass LNA for TX in UHF Antenna?

I want to work with amateur, low power, and/or pico satellites. I would like to use an Eggbeater or Turnstile antenna with my UHF 433 MHz radio, since those antennas are very cheap and easy to build ...
2
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3answers
605 views

Would a 2.4ghz yagi antenna work for Ham Radio?

I am building a miniature yagi antenna that is made for 2.4ghz. Would a 2.4ghz yagi antenna work for Ham Radio?
4
votes
3answers
530 views

Bridging LAN over ~1-2km distance

A friend of mine and I live across a lake from each other, and recently we thought it'd be fun to try and connect our computers together somehow across that distance. Running cable from either side ...
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2answers
4k views

Conductive boom vs non conductive boom: what's the difference on a Yagi?

I designed a Yagi antenna using 4nec2, assuming that I would use a non conductive boom. If I use an aluminum boom but I insulate the elements from the boom, can I keep the same design? How does it ...
1
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3answers
585 views

2.4GHz wifi parabolic antenna frequency response

what happens to the gain of a parabolic antenna, say this, http://www.amazon.com/24dBi-Directional-Booster-Parabolic-Antenna/dp/B00NQGVMSE, for example if I use it in lower or higher frequencies? ...
1
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2answers
134 views

Reproduce ambient EM fields inside a Faraday cage?

I am part of a research team looking at the possible effects of EM fields on psychological function. The experiment calls for participants to perform a series of tests while inside a Faraday tent that ...
6
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4answers
853 views

Why a thousand miles long antenna is not needed to receive LW and MW?

From what I've learnt so far, the longer the wave frequency on which you want to transmit or receive, the longer the antenna needed to do so. However my portable receiver other than SW can also ...
9
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2answers
2k views

Can every antenna be used both for transmit and receive?

Assuming I have an antenna for receiving GPS signals, can I use it also for transmit — to create a repeater in a tunnel (or some place with no reception)?
1
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1answer
114 views

4NEC2 - Antenna outside Pattern

I am very new to 4Nec2 and need to do a simulation of a half-wave dipole antenna for 433 MHz. I've read a couple of tutorials and I understand most of it so far, still, my simulation doesn't make ...
1
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2answers
353 views

What is an adequate antenna for a JRC NRD-545?

I live in an attic apartment, just acquired a JRC NRD-545, and am somewhat limited to what I can put outside (within reason). I have an old folded dipole CB antenna that I might get away with ...
0
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1answer
124 views

Amateur Radio shack/antenna considerations during house construction

We are constructing a house on a tiny 30ft by 55ft plot and the construction uses cement bricks and the roof has embedded iron rods. The house has ground + 2 floors and the top floor mostly has two ...