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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3answers
2k views

Running ladder line through window from inside shack to outside dipole antenna - what to watch out for?

For HF operating, I am considering running a ladder line from the ATU just inside a window, through the window (squeezing it between the window and the window frame; not actually through the glass), ...
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1answer
125 views

Can PIM occur with one carrier?

the literature talks about PIM occuring with two or more carriers: can it not happen in a single carrier antenna? e.g. creating second harmonic (2*f)?
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2answers
183 views

Theoretical Wifi antenna not working for the expected range

You buy a "20dBi omni" Wifi antenna, operating in the 2.4-2.5GHz band. You note that the expected range is not achieved from this 300mm long antenna. What could be wrong? Can someone please tell me ...
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2answers
204 views

How can I calculate current distribution on an end-fed dipole antenna in theory?

I understand that in a half-wave center-fed antenna current distribution has a sinusoidal wave approximately, so the current in the center has max value and it has to become zero at the ends of dipole ...
5
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2answers
3k views

Is there good antenna for 160m Band?

I live in Japan. Japanese houses are very narrow, but I want to try 160 m band. Is there good antenna for 160 m band? I want to operate HF (160m~10m) bands. Now I use vertical antenna (40, 30,20,15,...
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4answers
668 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 ...
4
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3answers
217 views

What are these antennas used for?

I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
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4answers
1k views

Can a CB SWR meter be used for HF amateur bands?

I have a basic CB SWR meter, I can’t see any reason why it can’t be used on other HF bands and be at least indicative of what the SWR is, even if the absolute power measurement is inaccurate. Is this ...
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5answers
358 views

Coax cable as antenna for 5 watt handy

For a normal 5 watt handy working in VHF or UHF freq with 50 ohm antenna , is it possible to use a same length coax cable instead of a stub antenna, so as to work like a crude antenna. Will this only ...
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2answers
4k views

Tuning/trimming a ground plane antenna

I've built a ground plane antenna with a 19.5" vertical and 4 20" radials. Currently, at 147.135 MHz my SWR is 3:1, clearly not ideal (and even bad for the transmitter!). I'm reluctant to start ...
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3answers
72 views

What kind of antenna for an automatic high bands monitoring station?

I would like to monitor NCDXF beacons, and WSPR. What kind of antenna would be good for reception in the bands of 6, 10, 12, 15, 17 and 20M? Some antennas I considered: A trapped dipole, with traps ...
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3answers
631 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
850 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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3answers
594 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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4answers
1k views

Counterpoise for telescopic antenna AL-800 as a portable/base antenna on 70cm?

Recently I bought a telescopic antenna, model AL-800: http://www.pryme.com/index.php?l=product_detail&p=2155 It is 863mm (34 inches) long when fully extended. When retracted, it is 785mm long. ...
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3answers
580 views

Height and feedline loss tradeoff for VHF

Currently my 2m antenna is about 3m above the ground inside, my HF antenna is connected to 30m (2db loss) coax and is about 12m up. Since the loss for 2m is a lot more when traveling down such a long ...
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4answers
859 views

Is string trimmer line suitable for supporting antennas?

In searching for suitable materials for a wire antenna, I found a few mentions of using string trimmer line to hold up each end of the antenna. This would be a nice option as it is readily available ...
4
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1answer
211 views

How do I design a dual band LPDA antenna?

Im not sure if this is the best place to ask a question like this but its the best place i could find. My goal is to build a dual band antenna similar to this one. That covers ...
4
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1answer
172 views

Two way ham radio to communicate between two stations

Apologies if this not the right place for this question. I'm into electronics and now endeavouring into radios and communications. Unfortunately I'm not sure what terms to use to find what I'm ...
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2answers
1k views

My Baofeng UV-5RV2+ will receive a signal with rubber duck antenna but not with a new Nagoya

I bought my self a Baofeng UV-5RV2+ as an inexpensive way to introduce myself to the world of ham radio. With all of the stock components everything has been working fine. I wanted to try to increase ...
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2answers
2k views

Ideal antenna type for FM 2 meters?

Clearly, building a Yagi tuned for 2 meters will likely have the best directional performance. Putting that aside, I'm trying to get information on what antenna type will have the best overall ...
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1answer
1k views

How does power received by a dipole relate to electric field intensity?

Let's say there's a transmitter far away, and I'm going to receive the transmitted signal. To keep things simple let's further say the transmitted signal is a pure, unmodulated sine wave. Further, let'...
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2answers
96 views

Basic antenna matching theory?

I'm fairly new to antenna matching, other than having built a base loaded vertical. I'm also new to EZNEC and I tried to simulate an horizontal loop. I arbitrarily chose a 10x10M loop, so I added 4 ...
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4answers
320 views

Partially Collapse Telescoping Antenna to Change Effective Length

I recently purchased a cheap RTL-SDR kit to experiment with SDRs and different frequency bands. This kit came with 23cm and 100cm telescoping antennas. I now wish to use the 100cm antenna to pick up ...
4
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3answers
305 views

Antenna suggestions for 160m band in smallish yard?

I have a decent-sized but not huge yard (roughly 50x100' / 15x30m) and I'd like to get on the 160-metre band. It's hard enough to get out on this band so I'm looking to do something reasonably ...
4
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1answer
940 views

Antenna, input and ground bonding

I'm new to this and am in need of guidance. I am mounting a multi-band antenna on a 50 foot tall 1 1/4" galvanized mast. I plan to drive a ground rod at the base of the antenna and bond the mast to ...
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3answers
164 views

Substitute for Dacron rope in antennas

I am building an antenna that specifies the use of Dacron rope to help support the spreaders, but that is not readily available in Trinidad and Tobago. What will be a good replacement with regards to ...
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1answer
166 views

Using a trap out of its resonance frequency?

I have a vertical antenna, about 7M total length, with a loading coil at 6M height. This is just because aluminium tubing is sold in 6 meter lengths. The loading coil is used to make it resonate at 7....
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2answers
63 views

Setting up an Outdoor Antenna

If I would buy a ham radio with an outdoor antenna, what would I need to do to make it work (e.g can I just stick it outside) especially because I live in Miami and Miami doesn't exactly have the best ...
4
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1answer
89 views

What gain and power are required for successful DX contacts on 2m/70cm bands in CW?

I would like to practice in CW on 2m/70cm bands when and if there will be a tropospheric or sporadic-E propagation. However I don't have mush space for the antenna. There is a possibility to install 3+...
4
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1answer
203 views

Is a ground plane antenna a poor choice to use in a forest?

Some time ago, when I just started with amateur radio, a few more experienced hams told me that an inverted-V works better in the forest than a ground plane, and that it has something to do with the ...
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2answers
129 views

Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?

Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
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1answer
79 views

no contacts with Rockmite

I finished building my Rockmite ][. It's running off of 3x 18650s, or 12v. I connected it to a MFJ-1840T and held the antenna horizontally in the air (also tried vertically) with my hand. I tried ...
4
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1answer
181 views

How does a higher antenna reduce rain static on a lower antenna?

I have operated at several stations - including my own - where a 40m beam is stacked above a tribander. During a rain storm, there is so much QRN on the 40m beam that the band is unusable, but the ...
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3answers
421 views

2m Biquad - Why not?

I'm thinking about putting together an Echolink link node on my local repeater frequency so I can participate in the weekly net when out of town. This seems straightforward as it's simply: Being in ...
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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 ...
4
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2answers
376 views

Resistive impedance with frequency

Full disclosure, I'm a little dyslexic. Concepts that are easy to most people usually seem ambiguous to me. I also have a had time expressing myself through writ so please forgive me if this seems ...
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2answers
8k views

Antennas I can effectively use in an apartment? [closed]

What are some antenna designs that balance manageable size/shape with effectiveness for use in an apartment?
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3answers
136 views

Do resonant antennas actually resonate?

Do resonant antennas actually resonate (in the lumped circuit sense, exchanging stored energy between inductive and capacitive elements at a natural oscillation frequency)? If so, can this resonance ...
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2answers
487 views

How should I mount a mobile antenna on a vehicle with a non-conductive body?

I would like to mount a self tuning antenna, ATAS-120, matched with the FT-857D transceiver. I would like to make this pair function on an ARGO 8x8 amphibious vehicle with a polyethylene body. There ...
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2answers
4k views

Can I ignore the radial elements of a 2m/70cm antenna if it's on a metal roof?

I'm looking for a dual band base station antenna, and find that many of them have short radials around the base. Due to the specifics of my installation, I need to remove them. However, it is being ...
4
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1answer
1k views

Does a larger Biquad antenna give better results?

Consider a biquad antenna used for receiving, not for sending. They are typically built with each side having a length of $\lambda / 4$. If a biquad antenna was built with a side length of $\lambda / ...
4
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1answer
338 views

What is the average fade margin required for proper operation at 2.4 GHz?

I have two radios. Sensitivity is -84 dBm and transmitting EIRP is +30 dBm. How much distance should I expect? I want it to be somewhere near about 2-3 km. Is it possible?
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2answers
2k views

Can an HF antenna be put inside a tree?

There are some trees around with branchy tops that seem wider than half of 10M, maybe even half of 20M, and above the nearby rooftops. Can a wire dipole or a vertical be mounted inside a tree? If so,...
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2answers
1k views

What impedance matching do I need between my 300Ω feedline and Softrock receiver?

I will be assembling a Softrock Ensemble II HF receiver, and I know I'm going to want it on air as soon as I build it, so I'm challenging myself to build an antenna for it first. The plan is to do a ...
4
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1answer
65 views

Voltages in a beam antenna's passive elements?

This question has good answers for the voltages reached in portions of a dipole antenna during transmit. In a beam (Yagi or Yagi-Uda) antenna, do points along passive or parasitic elements (...
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2answers
210 views

100MHz to 1000MHz Antennas for Transmit and Receive

I am building a ground and wall penetrating frequency modulated continuous wave radar. The only components that I have not been able to track down are the antennas. I need two antennas (one for ...
4
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1answer
425 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 ...
4
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1answer
264 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
870 views

Cross Yagi Antenna Design

What will be the effect if I add the insulation between elements and metallic boom of the cross yagi antenna (where elements from outside of the boom, instead of through boom) and in this case boom ...

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