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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42 votes
7 answers
48k views

Using a balun with a resonant dipole

I am preparing to construct a resonant, center-fed, horizontal dipole. I have seen people use baluns at the feedpoint of the antenna, and some people swear by them, but I have never gotten a ...
W5VO's user avatar
  • 1,901
36 votes
4 answers
57k views

Effect of different metals for antenna elements

Other than rust, corrosion, and other reactions with air that would make the use of a metal unfavorable, how do different metals affect the performance? Let's give Yagi an example: Let's say I use 4 ...
Skyler 440's user avatar
  • 7,600
31 votes
6 answers
40k views

Can I reduce RFI/noise at the antenna?

Recently, the power was out in my neighborhood for an extended period of time. I fired up my HF rig using battery power and was amazed at the lack of noise across the HF bands. When the power grid ...
The Driver's user avatar
28 votes
11 answers
35k views

What's a cost-effective way to boost the range of my cheap 2m/70cm handheld?

I'm a very casual/beginner level ham and as such have mostly avoided committing too much in the way of financial resources - I have a UV-5R for a personal radio, anything else I do I've used others' ...
Amber's user avatar
  • 2,718
27 votes
4 answers
20k views

What is the relationship between SWR and receive performance?

If an antenna analyzer shows 1:1, does that mean it's an ideal receiver as well? And what about the converse, will a well performing receive antenna show a 1:1 SWR? I've wondered this for a while, ...
K9KRB's user avatar
  • 642
26 votes
2 answers
6k views

How do Handheld antennas work without ground?

Dipoles have the 2 wires going to each leg of the antenna completing the circuit. Big AM towers use the second wire as a ground plane But how do handheld rigs transmit and receive with just one wire ...
Skyler 440's user avatar
  • 7,600
24 votes
4 answers
6k views

How does the signal know where the cable ends and the antenna starts?

I know very little about antennas. I know, that for a certain frequency the antenna needs a certain lengths for good sending/receiving conditions. Often the antenna is at the end of a cable. Why doesn'...
flux's user avatar
  • 241
23 votes
2 answers
19k views

What makes a 5/8 wavelength vertical desirable?

An ordinary 1/4 wavelength vertical is smaller and resonant without any loading coil or matching network. What's the advantage to a 5/8 wavelength vertical? Why 5/8 in particular, and not something ...
Phil Frost - W8II's user avatar
23 votes
3 answers
4k views

Can I build a radio telescope out of a parabolic TV satellite dish?

I have the possibility to buy a very inexpensive 2.4m parabolic satellite dish and I would like to build a radio telescope from it. Originally this dish was designed to be a satellite TV antenna. ...
SP5RFD's user avatar
  • 333
22 votes
3 answers
9k views

Why do I need to tune an antenna?

I've heard that when an antenna is set up, it needs to be tuned to reduce reflective power back into the radio. Is this always necessary, and if so how would I go about tuning it?
berry120's user avatar
  • 1,744
21 votes
5 answers
76k views

Good wire for wire antenna?

What properties should I look for in a good wire for building a wire antenna? Could anyone recommend something specific for me?
Timtech's user avatar
  • 2,336
20 votes
10 answers
99k views

What antenna on a BaoFeng UV-5R Pro will give me better reception? [closed]

I am happy with my BaoFeng UV-5R Pro but the local UHV VHF repeater and simplex reception is terrible, even for contacts less than 50 kilometers. I assume that it's because the rubber-ducky antenna on ...
Warren  VE3WPX's user avatar
20 votes
4 answers
16k views

What is the peak voltage at the tips of a dipole antenna?

What is the peak voltage present at the very end tips of half-wave dipole antenna in free space, and how might this peak voltage relate to transmitter type, transmitter power, RF frequency vs. antenna ...
hotpaw2's user avatar
  • 13.3k
19 votes
5 answers
16k views

Why do folded dipoles have greater bandwidth than ordinary resonant dipoles?

This is something I've read in passing, but never encountered an explanation of why. For example, Wikipedia says: Another common place one can see dipoles is as antennas for the FM band; these are ...
Phil Frost - W8II's user avatar
19 votes
3 answers
34k views

How does a mag mount antenna achieve a ground plane?

I've been thinking for some time about magnet mount mobile antennas and wondering how they establish their ground plane. Consider that many mag mount antennas have some kind of protective coating on ...
Peter KB1AVL's user avatar
19 votes
1 answer
5k views

How does moving a feedpoint off-center in a dipole affect the resonant frequency and resistive load?

Specifically, I understand that OCF dipoles change the SWR, but does it do this via reactance or resistance, or both?
Bill - K5WL's user avatar
  • 1,194
18 votes
3 answers
3k views

What is a "random wire antenna"?

Some antenna tuners claim to match any “random wire” to any HF frequency. Can one really use a random wire as a practical antenna system? From everything I have heard, the resonance of the antenna (...
Ron J. KD2EQS's user avatar
17 votes
8 answers
38k views

Should I chose a vertical or a horizontal HF antenna?

If I only have the budget for one HF antenna, should I chose a vertical or a horizontal antenna?
Timtech's user avatar
  • 2,336
16 votes
12 answers
19k views

How can I safely transmit without an antenna tuner or SWR meter?

Just what the title says. An Antenna Tuner, henceforth AT, is almost a de facto piece of equipment in a shack; working the bands without one is tantamount to leaping off the diving board into a ...
VU2NHW's user avatar
  • 2,834
16 votes
8 answers
20k views

Are there any real advantages to an aftermarket NA-701 over the Baofeng stock antenna? [closed]

I have a Baofeng UV-5R HT radio that I have been using for about a month now and I really like it because it was very inexpensive and portable. It currently has the stock antenna on it and I have ...
StompinFlax's user avatar
15 votes
4 answers
5k views

Are there federal laws (US) protecting antenna installation?

Are there any federal laws or FCC guidelines that allow ham radio operators to install antennas? I live in an apartment building in a large city that bans outdoor antennas. I recall reading that the ...
Brad's user avatar
  • 265
15 votes
2 answers
3k views

If I install a G5RV in my attic how could I be certain there are not harmful levels of RF in the shack, or my kids bedroom?

I assume that anyone who has a G5RV or G5RV junior in their attic has done so with ceramic spacers, and has zigzag or dog-leg installations, or otherwise has contorted the antenna to fit up there. My ...
Warren  VE3WPX's user avatar
15 votes
4 answers
6k views

Is a vertical noisier than a dipole, and if so, why?

I've had people tell me, anecdotally, that a vertical is noisier than a dipole. Is this true, and if so, why? If it is true: Is this additional noise, such that SNR is degraded, or is the vertical ...
Phil Frost - W8II's user avatar
14 votes
3 answers
12k views

What is the effect of using different number of radials with ground plane antenna

I'm new to electronics and telecommunication at all, I having trouble with understanding the difference between 2, 3 and 4 radials, as I've searched online I've learned that I can use only 1 radial(...
Aviel Fedida's user avatar
14 votes
5 answers
7k views

How does a folded dipole work?

A folded dipole is like an ordinary dipole, but with the ends extended and folded back, until they meet. Although it looks like a loop, I'm told it behaves similarly to a dipole. How does this thing ...
Phil Frost - W8II's user avatar
14 votes
4 answers
9k views

What does the addition of a shield to a small loop accomplish?

A small shielded loop is an antenna with a loop of wire, smaller than 1/10th of a wavelength in diameter, also surrounded by a shield. Often, they are constructed from coax. There is a gap in the ...
Phil Frost - W8II's user avatar
13 votes
6 answers
33k views

Calculating Antenna Length on the FCC Exam vs. in Reality

I have seen the following formulas for calculating half and quarter wavelength antennas: Formula for $\frac{1}{2}$-wavelength antenna (in free space): \begin{equation} \mathrm{Length~(feet)} = \frac{...
Dan's user avatar
  • 1,754
13 votes
1 answer
2k views

Hanging a dipole from a tree not code compliant?

I just got off the phone with my town's electrical inspector (in Massachusetts), and he informed me that you are not allowed to hang anything electrical from "vegetation". He said if I did ...
kr4sh's user avatar
  • 367
13 votes
3 answers
10k 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 ...
GmodCake's user avatar
  • 233
13 votes
4 answers
3k views

Handheld Dipoles

A problem with handheld devices is poor grounding. I read from someone else's question that dipoles don't need a ground. Why don't they make little handhelds with two antennas instead of one, or a ...
Skyler 440's user avatar
  • 7,600
13 votes
4 answers
4k views

Why does ice on a wire dipole affect the SWR?

We just had snow and ice overnight and my wire dipole was coated in ice. Why does the ice covering negatively affect the SWR of the antenna?
Ron J. KD2EQS's user avatar
12 votes
4 answers
3k views

Are antennas circuits?

For an antenna to work, doesn’t charge have to flow through it? A current must be present. To me it indicates it must be a circuit, but how is a dipole a circuit? If they are not circuits, then how ...
mikew's user avatar
  • 335
12 votes
2 answers
441 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 ...
Seitam's user avatar
  • 223
12 votes
2 answers
10k views

How much RF energy do trees and branches absorb?

For the 20m - 10m and 6m bands, will having my dipoles below the tops of trees (I live in redwood forests) drastically affect the RF power out or radiation patterns of my dipoles if I can still get ...
gdc's user avatar
  • 308
12 votes
3 answers
5k views

Share antenna between receiver and transceiver?

I recently put up a fan dipole for 80/40/20/10. I'm looking for a way to share this antenna with a receive-only SDR and my shack transceiver. Obviously I can just switch this antenna between the two ...
s3c's user avatar
  • 837
12 votes
5 answers
1k views

How does an antenna transform impedances along its length?

If I insert some impedance (like a loading coil, or a trap) at the base of a monopole antenna, the effect on the feedpoint impedance is easy to predict: the impedance is in series with the antenna, so ...
Phil Frost - W8II's user avatar
11 votes
6 answers
48k views

What is a Gamma match in the context of the driven element of a Yagi antenna?

How (and why) does a Gamma match work, when used on the driven element of a Yagi antenna? As shown here: (source: http://www.iw5edi.com/ham-radio/?2-element-yagi-for-10-meters-band,49) The article ...
Ron J. KD2EQS's user avatar
11 votes
6 answers
16k views

Can you use a satellite dish for a ham radio antenna?

Can I use a satellite dish as a ham radio antenna? I was thinking that because there are two unused, working satellite dishes that have all appropriate wires attached conveniently to the roof of my ...
hopefulhacker-Reinstate Monica's user avatar
11 votes
2 answers
758 views

How to determine if my antenna is an effective radiator?

So I build an antenna, tune it with the SWR and make it look great for a 50 ohm load. That does not determine if it is good at getting a signal out or not, it could just be a 50 ohm dummy load. ...
Skyler 440's user avatar
  • 7,600
11 votes
6 answers
3k views

While backpacking, is it worth mounting the antenna to the backpack frame (above my head)?

I am planning a trip with a large group in 6 weeks. We will be spread out in small groups on a trail in a mostly desert plateau landscape perhaps 5 miles apart, but mostly in a straight line. I'm new ...
NL - Apologize to Monica's user avatar
11 votes
1 answer
2k views

How does a "chip antenna" work?

How does a tiny surface-mount "chip antenna" for the 2.x thru 5.x GHz frequency bands work? What allows such a tiny item to radiate or receive RF with some amount of efficiency? What allows a chip ...
hotpaw2's user avatar
  • 13.3k
11 votes
1 answer
421 views

What is body blocking, and does it work with a stock HT on a foxhunt?

I've heard that you might not need a special directional antenna to participate in a foxhunt, that some people are able to use their body to help determine the direction of a signal. How does this ...
Adam Davis's user avatar
  • 12.1k
10 votes
2 answers
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 ...
BarsMonster - R2AYN's user avatar
10 votes
2 answers
855 views

If two antennas of 50 Ω and 377 Ω have VSWR=1:1, then which one is more efficient?

If there are two antennas of 50 Ω and 377 Ω (same as the intrinsic impedance of air) impedance with 0 $\Omega$ ohmic resistance, and they are exactly matched with their transmission line, then which ...
kaka's user avatar
  • 203
10 votes
2 answers
4k 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)?
volatile's user avatar
  • 327
10 votes
2 answers
3k 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 ...
Ryan J.'s user avatar
  • 103
10 votes
3 answers
2k views

What kind of antenna has a spiral connected to a reflector like this picture?

The description on the antenna says it is used for satellite communication, but it was taken in 1984. Is this an antenna style that is still in use? What is it called? What kind of gain should be ...
Jason Petrilla's user avatar
10 votes
2 answers
16k views

Connect two receiving antennas to the same radio

I have built a 1090 MHz ADS-B antenna roughly following some video instructions. It appears to work reasonably. However, because of how it is placed, it captures signals for more or less a half of ...
Giovanni Mascellani's user avatar
10 votes
4 answers
7k views

Real world performance of magnetic loop antennas?

I was investigating about magnetic loop antennas. In a paper about them I found some bold claims: and This almost sounds too good to be true, considering a lot of us hams are surronded by city noise ...
hjf's user avatar
  • 1,199
10 votes
2 answers
4k views

What determines power handling capacity of an antenna?

I just bought a cheap 1/4-wavelength, 2m. mag-mount antenna. The package says it can handle 50 watts. I can think of three things that could limit the capacity: $I^2R$ losses in the connection to the ...
Pete NU9W's user avatar
  • 950

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