All Questions
11 questions
2
votes
3
answers
1k
views
Understanding how antenna mismatch can damage a transmitter
I know it's important to tune an antenna to the same impedance as the transmitter for maximum power transfer. But I've read that if you don't do so, you not only get less radiated power, but you can ...
- 301
2
votes
2
answers
1k
views
What does antenna frequency range mean in practice?
I'm trying to wrap my head around software defined radios and antennas and noticed that lots of antennas are described in terms of a frequency range. For example, this one is described as operating ...
- 123
1
vote
3
answers
158
views
Can a receiving antenna really be "as small as you can imagine"?
I read this antenna theory statement somewhere:
And, for next-step or future thoughts: a receiving antenna can be as small as you can imagine, without loss of signal to noise.
Is this BS or not?
- 27
1
vote
2
answers
104
views
Beam antenna changed directivity
My Hy-Gain TH6DXX antenna has been up on a tower about 20 years, with excellent results. Suddenly, the gain of the antenna is off the side; in other words, when the boom is broadside to the ...
- 11
1
vote
0
answers
65
views
Interpreting the Friis transmission equation [duplicate]
In the Friis transmission equation, can you please explain the significance of the factor
$$\left(\frac{\lambda}{4\pi R}\right)$$
and what it helps us achieve? Specifically in terms of path loss.
- 123
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 ...
- 52.5k
6
votes
2
answers
7k
views
How does a folded balun work?
A folded balun is made from two quarter-wavelength, parallel conductors. A picture is worth a thousand words:
Here are some pictures of an actual construction from Gisela & Joe Noci on diydrones....
- 52.5k
9
votes
1
answer
814
views
Why must twin-lead conductor spacing be small to avoid radiation?
A transmission line does not radiate when the spacing between the two wires is very small when compared to the wavelength, but the transmission line begins to radiate when the spacing between the ...
- 193
5
votes
2
answers
184
views
How is RF a radio receives just not a mishmash of eletromagnetic energy?
So at any given time, electromagnetic waves of many different frequencies are flooding the space around me. I have a little 2 meter radio. Are not all these electromagnetic waves exciting the ...
- 345
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 ...
- 345
19
votes
3
answers
36k
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 ...
- 862