13
votes
Do these look like amateur radio antennas?
It looks like a fibre or telephone cable strung between buildings.
It sets a good precedent for setting up your antenna though - if you can get access to the other rooftop at night, and a catapault or ...
- 10.5k
11
votes
Accepted
Tuning a wire antenna by folding
Why does this have an influence on the standing wave?
Although there is no electrical connection between the folded sections at DC, that analysis neglects effects that are relevant at RF. Imagine a ...
- 51.6k
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 ...
- 91
9
votes
How would you get an "I'm alive" message to family in another state using amateur radio?
The ARRL NTS (National Traffic System) is the method you would use to send messages to anyone anywhere in North America and in concert with other traffic systems to many parts of the world.
NTS has ...
- 2,988
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 ...
- 15.5k
9
votes
Cheap antenna for new HF HAM
The cheapest antenna you can set up is a speaker wire dipole. A spool of speaker wire long enough to split the conductors and make a center fed half wave dipole ought to cost around ten dollars US (...
- 4,097
9
votes
Accepted
Is it ok to use a length of wire as an RX only antenna to test my new radio?
You are generally correct.
Antenna tuning is primarily about maximizing radiation for the transmission frequency, which is important because power emitted by the final transmitter amplifier stage that ...
- 4,097
8
votes
Accepted
How would you get an "I'm alive" message to family in another state using amateur radio?
When establishing emergency communications in a disaster, the natural choice of band is one that will allow you to communicate out of the disaster zone. Given the scenario you describe, a massive ...
- 9,162
8
votes
If i connect two antennas to one radio using a t connector will it work?
Assuming that both antennas are 50 Ω resistive, they will combine in parallel for a 25 Ω load impedance when transmitting. This will cause the transmitter to see a 2:1 SWR. This is a 0.333 voltage ...
- 18.5k
8
votes
If i connect two antennas to one radio using a t connector will it work?
If I connect two antennas to one radio using a t connector will it work?
That depends on your t-connector.
If your tee really is just a branch in the inner conductor and connected outer conducters, ...
- 15.5k
8
votes
Accepted
Can an antenna be too powerful for certain receivers?
Would the portable ~$40 Tecsun get damaged somehow by a 100-foot antenna because it's designed to work with shorter, portable antennas?
Unless you are within a kilometer or two of a very high power ...
- 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 ...
- 24.4k
8
votes
What is the optimum length for a random longwire on 10m?
A random longwire is just that, a random length. There is no optimum length, by definition. Usually people use random longwires for multi-band operation. Since the design frequency is "a lot of ...
- 51.6k
7
votes
Accepted
Using crocodile clips to make modular QRP antennas? Are there downsides?
If you look up "link dipole" or "linked dipole" you will find several designs that do just that. It works well for QRP or even for 100W. The ones I've seen have used several ...
- 11.8k
7
votes
Are "end-fed" antennas really more multi-band than dipoles?
End fed antennas do work on more bands than centre fed dipoles.
The reason is that end fed antennas are resonant on all harmonics, while normal dipoles only resonate on every other harmonic.
To see ...
- 359
7
votes
Are "end-fed" antennas really more multi-band than dipoles?
It's mostly real.
To a first approximation, a center-fed dipole will have a reasonable impedance on bands where it is an odd multiple of a half wavelength (the fundamental, third harmonic, fifth ...
- 11.8k
6
votes
How would you get an "I'm alive" message to family in another state using amateur radio?
Send an HF-E-Mail addressed to your familymembers using a system like WinLink 2000 (http://www.winlink.org). It uses Radio Message Servers (RMS), which provide a bridge between the Central Message ...
- 61
6
votes
Long Wire Antenna for SWL
First, I believe the 160/6 might refer to the antenna's coverage of the 160 meter band through the 6 meter band, with all other ham bands between included. Only important if you plan to transmit.
...
- 316
6
votes
If i connect two antennas to one radio using a t connector will it work?
For receiving it should work up to a certain level.
However, the impedance will be completely different from that of a single antenna. So the SWR will be too high for transmitting and reception will ...
- 803
6
votes
Accepted
Why long wire antenna length shouldn't be a multiple of λ/2?
A real antenna is more complicated, but I believe the insight you seek can be obtained by learning about a simpler case of transmission line stubs.
Consider what happens when a DC voltage is applied ...
- 51.6k
6
votes
Why can't we use a simple wire for receiving 2.4 GHz signals?
It might be a good idea to start by trying to make a block diagram of what you have inside of each of those controllers...
Namely, the drone controller is most likely some sort of a system on a chip, ...
- 2,873
6
votes
Accepted
Why can't we use a simple wire for receiving 2.4 GHz signals?
A wire will pick up a GHz signal, as well as a ton of other RF signals, all mixed together. Some sort of filtering is required to separate out your desired radio signals. An Arduino has none of ...
- 13.2k
6
votes
Accepted
Electromagnetic signal from spark gap
Don't worry, there have been many researchers before you, and you can borrow some of their work. Your English is fine.
If you do a web search for "lightning spectrum", you will find a ...
- 9,162
6
votes
Accepted
Would it be possible to light up a bulb wired one side to a transmitting antenna?
no, because the current has to flow through the bulb, and the end of the dipole is exactly the point where, through inevitable boundary conditions (end of conductor) the current is always 0.
What you ...
- 15.5k
5
votes
How to produce a NEC antenna file (and what software to use it with)?
It is true that 4nec2 is a bit non-intuitive when it comes to creating a new antenna, but it is easy to start from scratch and create anything, without the need to import.
4nec2 provides 4 different ...
- 51
5
votes
Which is better in my situation: Balanced dipole, or as much wire as possible in the air?
I think in practice you'll find it doesn't make much difference as long as there's a common mode choke or "current balun1" at the feedpoint. In fact, if you get it off-center in just the right place ...
- 51.6k
5
votes
Accepted
Could a weather balloon make a good antenna?
Hoisting a vertical antenna with a balloon seems to be a fairly-common trick for Field Day. A web search for tethered balloon antenna returns many interesting ...
- 9,162
5
votes
Accepted
How to probe a dipole antenna?
First problem is how to connect the transmitter antenna to the signal generator. I will use a 50 ohm coax cable of small length. Since the waveform and directivity is not critical, could I get away ...
- 24.4k
5
votes
Accepted
75Ω Wire FM antenna
In general, impedance mismatches are not very important for receiving. Unlike a transmitter, you cannot damage a receiver with a mismatch. You miss some of the signal power that you could have gotten, ...
- 24.4k
5
votes
Antenna suggestions for 160m band in smallish yard?
Almost any 160 meter antenna is a compromise. With limited space or budget, the compromise tends to be larger.
At first glance, a dipole that is shortened by loading coils might appear quite ...
- 18.5k
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