16 votes
Accepted

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

The primary factor to consider is the directivity of the parabolic antenna. It is given as: $$d=\frac{(\pi D)^2}{\lambda^2} \tag 1$$ where D is the diameter of the dish and $\lambda$ is the ...
Glenn W9IQ's user avatar
  • 18.5k
14 votes

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

You can use a satellite TV dish antenna for amateur radio use but how you use it depends on what frequency you want to operate on. The satellite dish antenna is two basic parts, the parabolic ...
progrmr's user avatar
  • 342
12 votes
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Does a receiving antenna need radials?

Most antennas are reciprocal — they have the same properties when receiving as when transmitting. This means that in many ways, a good antenna design makes both a good receiving antenna and a good ...
Kevin Reid AG6YO's user avatar
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10 votes
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Dipole Antenna Current Distribution at any Time Instant

You have aptly discovered why a balun is necessary when feeding a dipole with coax. You are right to think the book is wrong, because it is. With a coax feed and no balun, the current distributions on ...
Phil Frost - W8II's user avatar
10 votes

antenna in the rain

The antenna itself won't be significantly affected by the water. However, waterproofing the coax connection is essential. If this is not done, water will creep inside the coax by capillary action and ...
Phil Frost - W8II's user avatar
10 votes
Accepted

Why are there differences in antennas that depend on electrical component and magnetic component of a radio wave?

In free space, the electric and magnetic fields are always in a fixed ratio, a physical constant called the impedance of free space, about 377 volts per ampere. The two are always in phase (and thus ...
Phil Frost - W8II's user avatar
10 votes

How do VHF antennas compensate for change in frequency in Frequency Modulation?

All modulated signals, not just FM, have a bandwidth. The antenna has a bandwidth, which must be wider than the modulation of the signal you are using. Note that receive bandwidth and transmit ...
user10489's user avatar
  • 5,651
9 votes

Wider wire = picks up more energy, yah?

In short, no. In long, it's really complicated. The wider your wire, the wider the bandwidth, due to the increase in available paths. Wide multi-strand wire does better against skin effect (more ...
DonkeyOaty's user avatar
9 votes

What ways are there to extend an antenna?

You have an SMA connector – use that! You can buy ready-made coax cables with SMA connectors on both ends. As mentioned, what you want is a coax cable. The electromagnetic wave travels within the ...
Marcus Müller's user avatar
8 votes

Aluminum vs copper antenna element lengths

Besides mechanical differences, the primary difference between aluminum and copper in antenna construction is RF resistance. Copper will have slightly less RF resistance for the same surface area. ...
Glenn W9IQ's user avatar
  • 18.5k
8 votes

Will stainless steel bolts work with my copper antenna?

Stainless steel fasteners, lead and tin are compatible with copper. Lead tin solder, however, has poor mechanical strength as you have apparently discovered. Solder can be used to improve conductivity ...
Glenn W9IQ's user avatar
  • 18.5k
8 votes

Wire antenna slightly too long

You should not make any coil in the middle of the antenna as that will greatly change its RF characteristics. Instead, bundle up the wire at the ends in some fashion: One practical solution is to ...
Kevin Reid AG6YO's user avatar
  • 24.4k
8 votes

RigExpert AA-35 - Interpreting The Information

First, a general statement: the antenna analyzer has one set parameter, the frequency, and one measured parameter, the impedance (which is a complex number and therefore requires two real numbers to ...
Kevin Reid AG6YO's user avatar
  • 24.4k
8 votes

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

Apart from using it as a ham radio satellite antenna (eg. for QO-100) or a microwave terrestrial antenna, you can turn it into a VHF slot antenna. Here is an example: https://w6nbc.com/articles/20xx-...
filo's user avatar
  • 181
8 votes

Antenna Basics - Open/Short Circuit & Half-Duplex/Full-Duplex

My Understanding 1 - Antenna is just a piece of a metal conductor. "Antenna is an OPEN CIRCUIT, and not a SHORT CIRCUIT". Is my understanding correct that the Antenna is an open circuit and not a ...
Kevin Reid AG6YO's user avatar
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8 votes
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Connection for Moxon antenna (blank space)

There is no connection in the 17mm space. The wire that sits in the 46x249x46 space is simply a "reflector", and has no connection to the other wires, which are considered the "driven&...
Louis Seaman's user avatar
7 votes
Accepted

What is the attraction of vertical antennas for HF?

Cribbing a few quotes from answers to related questions, here's a start. From https://ham.stackexchange.com/a/195/1362: The primary advantages of vertical antennas are that they are ...
natevw - AF7TB's user avatar
7 votes

Do PCB antennas suit for NOAA and ADS-B?

PCB is an appropriate and useful way of making antennas for higher frequencies, say from 900 MHz and up. My company made thousands of GSM antennas for window mounting (in the days of car-installed ...
tomnexus's user avatar
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7 votes
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RF Antenna - V pole - Should one leg go to ground and the other to signal?

One leg of the antenna goes to the center conductor and the other leg of the antenna goes to the braided shield of the coaxial cable. The terminal block is just a way to make the connections, and it ...
Kevin Reid AG6YO's user avatar
  • 24.4k
7 votes

antenna in the rain

Water has a drastically different relative permittivity $\varepsilon$ than air (water: ca 88, air: pretty much 1); it is, however, pretty non-conductive, just like air (being distilled and all). In a ...
Marcus Müller's user avatar
7 votes
Accepted

3 Band (80-40-20 Meter) Fan Dipole Tuning Question

Before getting to the questions you asked, an observation: the design doesn't appear to include a balun. Adding one is probably a good idea. Is there a way to flatten the SWR in this range [80m] or ...
Phil Frost - W8II's user avatar
7 votes

Magnetic loop antenna : loops vs selectivity

Two factors explain the wider bandwith: Firstly, as the frequency increases, bandwidth will necessarily increase even if the Q factor remains constant. There are a number of ways to define Q factor, ...
Phil Frost - W8II's user avatar
7 votes

How do VHF antennas compensate for change in frequency in Frequency Modulation?

Or does this antenna have a frequency tolerance? This is closest, but the antenna, itself, does not actually have a “frequency tolerance” (more usually called a bandwidth). Rather, the antenna's ...
Kevin Reid AG6YO's user avatar
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7 votes
Accepted

What's the proper way to mount antenna mast to the side of a house?

I know that the gap between the wall and the antenna mast that would be created using the wall mounts you mention is not for lightning damage prevention purposes. If a bolt of lightning can travel ...
rclocher3's user avatar
  • 9,142
7 votes

How do I rewire a simple a.m. loop antenna that became unwound?

There is no special precise construction to these antennas — they are just wire wrapped around an inert plastic frame. It does not matter (significantly) how the turns (wraps) lay next to each other. ...
Kevin Reid AG6YO's user avatar
  • 24.4k
7 votes

Putting up a tower on my residential property

I read it is fine and a city can not limit the height of the tower. They can, but they can't unreasonably limit it. Saying "no structures higher than the house" is unreasonable. What you're ...
hobbs - KC2G's user avatar
  • 11.7k
7 votes

Why don't J-Poles need to be grounded?

There are 3 kinds of ground in radio: Lightning ground Electrical ground Antenna ground Electrical ground is irrelevant for antennas. Antenna ground is a misnomer, it's really just the other half of ...
user10489's user avatar
  • 5,651
6 votes

How to detect common-mode currents or “RF in the shack”?

Another way to detect current on the outside of coax is to run your hand up and down the coax wile an analyzer is connected , if you see a fluctuation on the meter then current is following on the ...
De Bohannan KC5ULU's user avatar
6 votes

Steel Directors with Copper DE

It's probably OK to use a different metal for the directors than the driven element, as long as you don't have dissimilar metals touching that would create a galvanic corrosion problem. But steel is ...
rclocher3's user avatar
  • 9,142
6 votes
Accepted

Hentenna beam...is it possible?

Let me combine the following statements of your question I want to explore (the strange new world of creating a beam antenna) to boldly go where no man has gone before Would the perpendicular rods ...
Edwin van Mierlo's user avatar

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